Download CHAPTER 3: Basic Introduction to Organic Chemistry

CHAPTER 3: Basic Introduction to Organic Chemistry
1. ORGANIC COMPOUNDS:
A. Originally named because they were found in “living” organisms, however today
these compounds can be synthesized in the lab.
B. These compounds include complex ___________________________ (sugars),
__________________ (fats), _____ __________________, and nucleic acids.
C. All organic molecules contain the element __________________ and at least one
hydrogen atom. Those that contain only hydrogen and carbon are also known as
_________________________________.
D. Due to the atomic structure of carbon and where it is placed on the periodic table,
a carbon atom will form a total of _____ covalent bonds as it forms a molecule,
whereas hydrogen will form ___ covalent bond and oxygen will form ____ bonds.
E. Organic molecules generally consist of a chain of carbon atoms (commonly called
the backbone or skeleton of the molecule) with one atom or a cluster of atoms
covalently bonded to the chain. This atom or group of atoms attached to the
carbon chain are commonly called _____________________ groups.
F. There are a number of ways to represent or draw an organic molecule.
1. MOLECULAR FORMULA: this is the easiest, but only gives which elements
are present in the compound and in what ratio.
Examples include: H2O, CO2, C6H12O6 and C18H36O2
b. STRUCTURAL FORMULA: this takes more time, but not only gives
which elements are present in the molecule but also shows how they are
arranged (connected to each other). Sometimes these formulas are
simplified by ignoring all of the hydrogen atoms, and sometimes even
ignoring the carbon and hydrogen atoms altogether, expecting the student
to recognize that these elements naturally occur in organic molecules. The
following are several examples:
Glucose (dry)
Fructose (dry)
c. Two organic molecules
that have the same molecular
formula but different
structural formulas as in the
case of Glucose and Fructose
seen at the right are called
ISOMERS of each other.
d. As you can see the structural
formula changes for some
substances when they get wet.
Glucose (wet)
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Fructose (wet)
2. Before studying the characteristics of the main biological molecules important in the
structure and function of the human body (which are generally very large and
complex molecules), it is important to study the pieces or “building blocks” that will
be assembled to form these large molecules and how they are connected.
A. The Carbon Chain (also called the “backbone” or “skeleton” of the molecule):
1. The carbon chain is formed by numerous carbon atoms covalently bonded to
each other. Since carbon can have a total of 4 bonds, most carbon atoms in
the carbon chain also have 2 hydrogen atoms attached, except for the end
carbons which will have 3 hydrogen atoms attached.
2. These hydrogen atoms are not able to form hydrogen bonds with other atoms,
so are NOT “attracted” to water molecules. The backbone of organic
molecules therefore does not “like” water and is referred to as being
_________________________ or non-polar. (review from last chapter)
B. Functional Groups:
1. Functional groups are atoms or groups of atoms that are attached to the carbon
backbone (chain) by ________________________ bonds (strong bonds) and
give the entire molecule distinct properties, such as solubility in water or
chemical reactivity.
2. These groups tend to be __________ reactive than the hydrocarbon backbone.
3. Because these groups are generally attached to the side of the carbon chain,
they are also known as “side groups” and structurally have a “dash” which
designates where the group attaches to the carbon chain. The other atoms are
covalently bonded to each other.
4. The following are the functional groups you need to know: For each of these
groups, draw a diagram in the left hand margin.
a. ____________________ (-OH): is commonly found in alcohols and sugar
(carbohydrate) molecules. This group is also part of water (H-OH), which
makes organic molecules with this functional group very soluble in water.
Molecules that “like” water are called ______________________ (polar).
b. ______________________: is a carbon atom with a DOUBLE covalent
bond to an __________________ atom. If it is at the end of the carbon
chain the molecule is called an ALDEHYDE, whereas if the carbon is in
the middle of the chain the molecule is called a ____________________.
This group is commonly found in sugars, proteins and nucleic acids; and it
also likes water (is hydrophilic).
c. ________________________: is a carbon atom with a double covalent
bond to an oxygen atom AND a single covalent bond to a hydroxyl group.
This functional group is also hydrophilic (“likes” water). Due to the
attraction of the oxygen for electrons, the –OH portion of this group tends
to release the hydrogen ion (H+1) to solution, causing this group to act like
an ______________. This group is found in proteins and fatty acids.
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d. ________________________: is a group that contains a nitrogen atom
covalently bonded to several hydrogen atoms. Because of a pair of
electrons on the nitrogen atom, this group tends to attract hydrogen ions
(H+1) and acts as a weak_______________. These electrons on the
nitrogen atom also are what cause this group to be able to form hydrogen
bonds with water molecules, causing molecules with this group to also be
quite soluble in water. This group is found in proteins and nucleic acids.
e. ________________________: is a group that contains a phosphorous
atom covalently bonded to four oxygen atoms. This group is found mainly
in nucleic acids (DNA, RNA and ATP) and to a limited extent in some
protein molecules. All of these oxygen atoms have a large number of
electrons that are not part of a covalent bond (lone pairs) and repel each
other. This is the chemical basis for why ATP is a good energy source for
the cell (This will be discussed in more detail in later chapters.) They also
explain why this group can form hydrogen bonds with water, making this
another group that can be classified as hydrophilic.
f. ________________________: is a group that contains a sulfur atom
covalently bonded to a hydrogen atom. This group is only found in
protein molecules and helps to stabilize the three-dimensional structure of
the protein by forming a di-sulfur bridge (discussed in more detail later).
3. Organic molecules can be described as having a simple structure or a complex
structure. Those with a simple structure tend to be much smaller in size and
serve as “building blocks” (subunits) for making the larger more complex molecules.
A. The smaller subunits are more commonly known as ___________________; and
the larger more complex molecules are known as ________________________.
B. The main “building blocks” or subunits of the major biological molecules include
the following. (you may need to look ahead in the chapter to find these)
1. SIMPLE _______________: join together to form complex carbohydrates
2. FATTY_____________: join together with other molecules to form lipids
(except for cholesterol and other sterols)
3. ______________ ACIDS: join together to form protein molecules
4. _____________________: join together to form nucleic acids
4. All chemical changes that occur in our cells can be classified as one of the following
five types of chemical reactions:
A. ________________________________ TRANSFER: occurs when one molecule
releases a functional group and another molecule accepts (takes) it. A
phosphorylation reaction transfers a phosphate group from one molecule to
another molecule.
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B. ________________________ TRANSFER: occurs when one or more electrons
is removed from one molecule and are donated to another molecule. This process
creates charged particles called ions. As a review from chapter 2:
1. Positive ions are called _________________ and are formed when an
atom or molecule gives away (loses) one or more electrons.
2. Negative ions are called __________________ and are formed when
an atom or molecule takes (accepts) one or more electrons.
C. __________________________: occurs when bonds or functional groups change
positions within a molecule creating a new and different molecule.
D. __________________________: occurs when two monomers combine to form a
larger more complex molecule. This type of reaction generally occurs as one
monomer loses a hydroxyl group (-OH) while another monomer loses a hydrogen
atom (H) and the two join together to form a molecule of _______________. It is
for this reason that this type of reaction is also commonly known as a
DEHYDRATION SYNTHESIS reaction. The diagram below illustrates this type
of reaction
E. ________________________: occurs when a large complex molecule splits into
smaller ones. A common form of this type of reaction is the reverse of a
condensation (dehydration) reaction. In this reaction, a molecule of water is used
to break a covalent bond. The water breaks apart, adding the Hydrogen atom to
one of the monomers and the hydroxyl group to the other monomer. Because
water is used to break the bond, this type of reaction is also commonly known as a
_________________________ reaction. The diagram below illustrates this type
of reaction.
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5. CARBOHYDRATES:
A. These are the most abundant of all the macromolecules found in the body,
however because most of them are small in size, and not stored for long periods of
time, they only make up about 1-3% of the total body weight.
B. These molecules have many hydroxyl groups attached, which makes them very
soluble in water.
C. The main function of carbohydrates in humans is as a source of ______________.
D. There are three main classes of carbohydrates:
1. __________________ SUGARS: these are very small molecules, consisting
of only ONE sugar molecule, therefore they are also known as
_______________________. Some have a five-carbon backbone (ribose and
deoxyribose) the sugars found in the nucleic acid molecules RNA and DNA.
Some have a 6-carbon backbone like glucose (blood sugar) and fructose (fruit
sugar).
2. __________________________ CARBOHYDRATES: these have two or a
“few” sugar molecules connected by covalent bonds.
a. _____________________________: consist of TWO sugar molecules.
Examples include:
1. Sucrose (also known as table sugar) which consists of a glucose
molecule bonded to a fructose molecule
2. Lactose (also known as milk sugar) which consists of a glucose
bonded to a galactose molecule
3. Maltose (also known as grain sugar) which consists of two glucose
molecules bonded to each other
b. ___________________________: consist of a FEW sugar molecules (the
word few is a very vague term meaning more than two but less than
many). These are found on the surface of cells and serve as antigens (cell
markers) as in determining blood type (A, B, AB or O).
3. ______________________ CARBOHYDRATES: consist of hundreds to
thousands of individual sugar molecules. These may be straight chains or
highly branched structures.
a. _______________________: a structural material that is tough, insoluble
in water and used in plant cells walls for structural strength. This
compound is NOT a source of energy for humans because we lack the
needed enzymes to break the bonds connecting the glucose molecules
together; however it is needed by the body to keep the digestive system
working properly. This compound is commonly called “dietary fiber.
b. _______________________: an un-branched coiled chain of glucose
molecules or highly branched chains of glucose that are easily hydrolyzed
into individual glucose molecules. This complex carbohydrate is used as a
storage form of energy for __________________. Due to a large number
of hydroxyl groups (-OH) it is soluble in water, but due to its large size it
is sometimes difficult to get it to dissolve.
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Starch molecules can be used by humans as an energy source, and due to
their size they can provide energy for a sustained period of time. This is
why marathon runners often eat large amounts of pasta the night before
the race. This practice is called “carbohydrate loading”.
c. ___________________________: a highly branched chain of glucose
molecules used as a storage form of energy by animals. It is found in
highest concentrations in ________________ and _______________cells.
When blood sugar levels drop, the liver cells break down glycogen into
individual glucose molecules and release them into the blood.
E. Complete the following table by entering the name of the carbohydrate class, the
specific carbohydrate, or the main function.
Carbohydrate Class
Specific Carbohydrate
Function
Sucrose
The most plentiful sugar in nature;
also known as table sugar; formed by
joining together glucose and fructose
Monosaccharide
The main energy source for most
organisms; serves as building blocks
(monomers) for larger carbohydrates
Cellulose
Monosaccharide
Structural material of plant cell walls;
formed from long straight chains of
glucose; unable to be used by humans
as a source of energy; also known as
dietary fiber
Ribose
Polysaccharide
Disaccharide
The complex carbohydrate found in
animals, stored especially in liver and
muscle tissue; formed from many
branched glucose chains
Lactose
Starch
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The storage form for sugars produced
by plants using photosynthesis, able to
be used by animals as a source of
energy
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6. LIPIDS:
A. These molecules are greasy or oily to the touch.
B. They are much larger than monosaccharide, contain mostly carbon and hydrogen
with much less oxygen than the carbohydrates and therefore are not able to form
hydrogen bonds with water. This makes lipids resist dissolving in water or in
other words are ________________________ (water fearing).
C. These molecules make up about 12-25% of the total body weight.
D. Oils, fats and waxes are all classified as lipids. Oils tend to be smaller in size and
liquid at room temperature, fats are larger and are “soft” solids at room
temperature, while waxes are much larger and are solids at room temperature.
E. Lipids serve several functions in the body:
1. Reservoire for long-term storage of potential ___________________.
2. _______________________ the body (think of whale blubber).
3. Act as a “shock absorber” (padding around sensitive organs like the kidneys)
and as space fillers (especially around joints).
4. Are a major part of cell ________________________.
5. Some act as hormones (chemical messengers in the body)
F. There are several classes of lipids:
1. ________________________: have a long hydrocarbon backbone of as any
as 36 carbon atoms and a carboxyl group (acid group) attached to the end of
the chain (tail). These molecules can be further divided into two main groups:
a. ___________________________: those that have all single bonds in the
carbon chain, therefore containing the maximum number of hydrogen
atoms possible. When something is full, it is saturated (filled to capacity).
b.
____________________________: those that have at least one double
bond in the carbon chain, therefore containing less hydrogen atoms than
possible without the double bonds. When something is not full, it is
unsaturated (not filled to capacity).
stearic acid
Saturated
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oleic acid
Unsaturated
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linolenic acid
Polyunsaturated
2. ____________ (also known as glycerides): these molecules
have one, two or three fatty acid molecules attached to a
glycerol (3 carbon sugar) backbone by a condensation
(dehydration synthesis) reaction. The triglycerides are the
most plentiful lipid found in the body and are stored in
_______________ tissue. Gram for gram, they provide
more than ______________ the amount of energy when
compared to complex carbohydrates, which is why a high
fat diet tends to cause a person to gain weight. The body
doesn’t use all the energy available, so stores it for later use.
This type of lipid is also used by the body to act as a shock
absorber (padding) to protect organs, and provide thermal insulation.
There are several types of fat:
a. ____________________ FATS: have fatty acids with all single bonds in
the carbon chain. The straight chain allows these molecules to pack tightly
together, making it a good form for storage in adipose tissue of animals
and causes them to be more solid at room temperature. These molecules
tend to be found in animal fat or lard.
b. __________________________ FATS: have at least one double bond in
the carbon chain. The double bond causes the “tail” to bend or kink,
keeping these molecules slightly separated from each other. These
molecules tend to be easier for the body to digest and less likely to lead to
heart or vascular conditions. They tend to be found in plants (olive oil,
safflower oil, vegetable oil, etc.).
c. ______________ FATS: produced by a chemical process called
“hydrogenation” where an unsaturated fat (vegetable oil) are forced to
accept extra hydrogen atoms, breaking the double bonds to form straight
chains. This process causes vegetable oils to pack tightly together,
forming a solid at room temperature. They are unhealthy because the
body treats them like animal fat.
3. ______________________________: are similar to triglycerides except that
one of the fatty acid tails is replaced with a phosphate group and another very
polar group. These groups cause the glycerol portion of the molecule to like
water, so it is often referred to as the _____________________ or polar head.
These molecules are the main component of cell membranes that will be
discussed in more detail in the next chapter.
4. STEROIDS (STEROLS): this class of lipid does
NOT contain any fatty acid molecules, rather it has
a rigid backbone of four fused-together carbon rings.
________________________ is the most common
type found in the body and is modified into various
hormones (estrogen and testosterone), bile salts, as
well as the activated form of vitamin D.
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5. ____________________: have very long fatty acid tails that are tightly
packed together allowing them to be firm yet pliable. They repel water and
therefore act as a good barrier against dehydration and when warmed, serve as
a good lubricant. In the ear canal it serves as a sticky covering trapping dust
and foreign objects before they reach the ear drum.
6. EICOSANOIDS: these are short chain fatty acid molecules that are released
by damaged tissues and function to stimulate nerve endings producing the
sensation of “pain”. They are also released by uterus to initiate labor
contractions and the secretion of various other hormones.
G. Match the correct lipid below with the their descriptions.
A.
B.
C.
D.
E.
F.
G.
saturated fatty acids
unsaturated fatty acids
saturated triglycerides (fats)
unsaturated triglycerides (fats)
phospholipids
waxes
sterols (steroids)
1.
______
provide the richest source of stored energy for the human body
2.
______
these fatty acids have only single bonds between the carbon atoms
in the chain with a maximum of hydrogen atoms attached
3.
______
cholesterol is the most common form of this type of lipid in animal
tissues
4.
______
have three saturated fatty acid tails attached to a glycerol backbone
5.
______
vegetable oil is an example of this type of lipid
6.
______
these type of lipids lack fatty acid tails
7.
______
these lipids are the main component of cell membranes
8.
______
these lipids have a rigid backbone of four fused carbon rings
9.
______
these lipids have one or more double bonds between the carbon
atoms
10. ______
these lipids are the precursors of vitamin D, fat soluble hormones,
and bile salts
11. ______
butter and lard are examples of this type of lipid
12. ______
provides insulation from the cold and acts as a shock absorber to
protect organs
13. ______
these lipids provide protection, lubrication and pliability for hair
and skin
14. ______
these lipids have a hydrophilic “head” and two hydrophobic “tails”
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7. PROTEINS:
A. These are the most diverse of all the macromolecules in the body. There are
estimated to be more than 140,000 different protein molecules in the body, and
they make up more than 50% of the total body weight.
B. Proteins are macromolecules made from joining together _____________ acids
by a condensation (dehydration synthesis) reaction.
A hydrogen atom from the amino group and the hydroxyl
group from the carboxylic acid group form water while the
remaining part of the amino acids form a very strong covalent
bond known as a _______________________ bond.
C. Proteins perform numerous functions in the body:
1. Structural support (especially at the cellular level): within most cells is a
cytoskeleton made of protein fibers. (Collagen & Elastin)
2. Movement: muscle contraction is caused by protein fibers sliding against
each other. (Actin & Myosin)
3. Transport: especially of substances that do not dissolve in water like fats and
most of the oxygen is transported in the blood attached to a protein called
hemoglobin. (High & Low Density Lipoproteins: HDL & LDL)
4. Enzymes: protein molecules that help regulate chemical reactions
(metabolism) in the body. (Lipase & Protease)
5. Hormones (chemical messengers): released by cells and travel throughout the
body signaling cells to modify their activities. (Insulin)
6. Antibodies: one mechanism used by the body for protection against foreign
pathogens (disease causing substances or organisms). (Gammaglobulins)
7. Buffering the blood: proteins help to stabilize the pH of the blood.
D. With this many and very different functions to perform, there must be more than
one kind of amino acid and proteins must have a very complex structure. When a
cell needs to make a protein, enzymes in the cell join together one amino acid
after another forming a long chain of amino acids, also known as a
__________________________ chain.
E. There are _______ different amino acids, however each one
has an amino group (-NH2), a carboxyl or acid group (-COOH)
and one or more atoms called its “R” group (for the “rest” of
the molecule). All three “side groups” are covalently bonded
to a central carbon atom. Each amino acid has only one R group,
but it is the characteristic of the “R Group” that determines the
overall characteristic of each amino acid molecule. The vast
majority of amino acids are neutral, but some are acidic and some
are basic, some are hydrophilic and some are hydrophobic.
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F. For each of the following diagrams, circle the “R” group part of the amino acid.
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G. The structure of protein molecules is divided into four levels of complexity.
1. _______________________ STRUCTURE: gives the specific sequence
(order) of amino acids in the polypeptide chain. In other words, it identifies
which of the 20 amino acids is used and in which order they are connected to
each other.
a. This structure is stabilized by __________________bonds (very strong
covalent bonds) that are difficult to break.
b. If this structure is broken, the protein will fail to function, and the cell will
begin to break it down and recycle the amino acids, using them to make
new protein molecules. It is not clear why, but this structure can NOT be
repaired when damaged; however the cell will reuse the amino acids.
c. Some protein molecules stop at this level of organization. The
polypeptide chains arranged in strands or sheets, similar to a rope or sheet
of burlap. Proteins with this structural arrangement are common in
muscle, bone, ligaments, and tendons and are called _________________
proteins.
2. ________________________ STRUCTURE: refers to the coiling or
“pleating” (sheet-like arrangement) of the protein strand.
a. This structure is stabilized by _____________________bonds between the
amino group and carboxyl group of amino acids separated by 3 or 4 amino
acids.
b. Because these bonds are relatively easy to break, this structure can break
and reform repeatedly without damage to the protein chain.
c. This structure allows some proteins to and “elastic” quality or allows the
protein to have various forms, kind of like an “ON” and “OFF” form,
especially noticed in enzyme activity.
3. _________________________ STRUCTURE: refers to the folding of the
coiled protein chain on itself forming a three dimensional “ball” or “blob”.
a. This is due to the attraction between some of the “R groups” of the amino
acids. Those that are hydrophilic are attracted to each other, and those that
are hydrophobic are attracted to each other.
b. Many of the “R groups” have a + or – charge and are therefore attracted to
each other, forming __________________bonds. Once formed, the
structure is further stabilized by many additional hydrogen bonds.
c. Because the chance of the exact same + and – ions finding each other a
second time is unlikely, if this structure is destroyed, the protein can NOT
be repaired, and must be broken down so the amino acids can be used to
form other proteins.
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4. ___________________________ STRUCTURE: describes the complex
structure that forms as two or more different protein molecules join together.
The forces that cause the proteins to join together are the same as those in the
tertiary structure, so this structure is also not repairable, but the individual
amino acids can be recycled to make new proteins.
a. Hemoglobin (found in red blood cells) is a good example of a protein with
a quaternary structure.
b. Lipoproteins (proteins with a lipid molecule attached) and glycoproteins
(proteins with a carbohydrate molecule attached) are also classified as
quaternary proteins.
c. Proteins with this level of organization are arranged in compact, rounded
shapes (like a “blob”) are commonly called _________________ proteins.
Most enzymes, hormones and transporter molecules in the blood have this
structural arrangement.
H. ____________________________ is any process that disrupts or destroys the
hydrogen bonds or the overall three-dimensional shape of a protein molecule, and
thereby changes the overall function of the protein. In most cases the process is
irreversible and the protein is destroyed. This process can be caused by changing
the _______________________ or the _______(acidity) of the cell.
I. Match the following descriptions with the most appropriate term related to
proteins and protein structure.
1. ___ amino acid
9. ___ quaternary structure
A. A coiled or pleated structure caused by
regular intervals of hydrogen bonds
B. Three or more amino acids joinded in a linear
chain
C. Proteins with oligosaccharides covalently
bonded to them
D. Folding of a protein molecule due to
interactions between the “R” groups of the
amino acids in the protein chain
E. Proteins with cholesterol or phospholipids
covalently bonded to them
F. Another name for a covalent bond between
two amino acids
G. The globular protein hemoglobin with four
protein chains is an example of a protein with
this level of organization
H. Breaking of protein bonds therby changing
the shape and function of the protein
I. Formed by joining together two amino acids
10. ___ secondary structure
J.
2. ___ denaturation
3. ___ dipeptide
4. ___ glycoproteins
5. ___ lipoproteins
6. ___ peptide bond
7. ___ polypeptide chain
8. ___ primary structure
11. ___ tertiary structure
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The linear arrangement or sequence of amino
acids in a protein molecule
K. The monomer of all proteins, composed of an
amino, phosphate and “R” group.
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8. NUCLEIC ACIDS:
A. These macromolecules are made of “building blocks” (monomers) known as
_____________________________ that consist of three parts.
1. A five carbon _________________ (ribose or deoxyribose)
2. A _________________________ group (PO4)
3. A _____________________________ base (a single or double ring structure
that contains a few nitrogen atoms)
a. There are five different nitrogenous bases used to make nucleotides.
(See chapter 13, section 13.2 for details)
1. Two of these are called Purines and have a double ring structure:
_____________________ (A) and _____________________ (G)
found in DNA and RNA
2. Three of them are called Pyrimidines and have a single ring structure:
__________________ (T) and _________________(C) found in DNA
and ____________________(U) only found in RNA
Example of a Pyrimidine
Example of a Purine
Adenine
Cytosine
B. Nucleic acids perform several functions in the body:
1. DNA (deoxyribonucleic acid): stores the genetic information needed for
survival.
2. RNA (ribonucleic acid): carries the “working copy” of the genetic
information and instructs the production of specific protein molecules.
3. __________ (adenosine triphosphate): the energy form used by cells to
drive specific cellular reactions or activities.
4. _________ (nicotinamide adenine dinucleotide) and _________(flavin
adenine dinucleotide): act as coenzymes in metabolic reactions.
5. ___________ (cyclic adenosine monophosphate): acts as a chemical
messenger within the cell.
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C. DNA and RNA structure:
1. These are very large molecules made of many nucleotides connected to each
other by strong covalent bonds forming long strands. Since they contain
many nucleotides, they are also called _____________________________.
2. The covalent bonds form between the sugar group of one nucleotide and the
phosphate group of the next nucleotide, forming a “backbone” of the
molecules with alternating sugar and phosphate groups.
3. RNA is a molecule that has a _______________strand of nucleotides.
4. DNA is a molecule that has a ________________ strand of nucleiotides.
a. The sugar-phosphate backbone forms the side chains (like the legs of a
ladder)
b. The two “backbones” (legs of the ladder) are connected to each other by
forming _____________________ bonds between the nitrogenous bases
(like the steps on a ladder). Remember that these bonds are weak bonds
however when there are many of them working together they are quite
strong.
D. Review the structure and function of nucleic acids by matching each of the
phrases on the right with a word or phrase from the list on the left. Answers may
be used more than once.
_____ 1. Sugar found in RNA
_____ 2. Describes the overall structure of DNA
_____ 3. Short for ribonucleic acid
_____ 4. Genetic material passed on from parent to
offspring
_____ 5. Nitrogenous bases found in RNA
_____ 6. Sugar found in DNA
_____ 7. Nitrogenous bases found in DNA
_____ 8. Short for deoxyribonucleic acid
_____ 9. Some act as intermediates that contain proteinbuilding instructions
_____ 10. Nucleotides contain a 5-carbon sugar, a
phosphate group, and a _______________
_____ 11. The sugar of one nucleotide bonds to the
_____________ of the next nucleotide in the
chain, forming the backbone of a nucleic acid.
_____ 12. Is a monomer (building block) of nucleic acids
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A. Phosphate group
B. Deoxyribose
C. A, T, C, G
D. DNA
E. Nucleotide
F. A, U, C, G
G. Double helix
H. Ribose
I. Nitrogenous base
J. RNA
9. As you have seen in this chapter, there are four main classes of macromolecules.
Most are polymers, assembled from smaller monomers (building blocks) in a process
called a condensation reaction or dehydration synthesis. Water is produced as a biproduct of these reactions. The process by which the large polymers are broken back
down into monomers is called a cleavage reaction or hydrolysis. This process
requires that water also be broken down and its parts (the H– and –OH) be used to
satisfy the bonds that are broken in the polymer. State whether each of the following
statements relates to dehydration synthesis reactions (D) or hydrolysis reactions (H).
____ 1.
Connects monomers to form a polymer
____ 2.
Produces water as a by-product
____ 3.
Breaks up polymers, forming monomers
____ 4.
Water is used to break bonds between monomers
____ 5.
Joins amino acids to form a protein
____ 6.
Glycerol and fatty acids combine this way to form a fat.
____ 7.
Occurs when polysaccharides are digested to form monosaccharides
____ 8.
―H and ―OH groups are removed, forming a water molecule
____ 9.
Nucleic acid breaks up to form nucleotides.
____ 10. Water breaks up, forming ―H and ―OH groups on separate monomers.
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Sample Test Questions for Chapter 3 and Lab #7:
1. The four main categories of macromolecules in a cell are
a. proteins, DNA, RNA and steroids
b. RNA, DNA, proteins and carbohydrates
c. monosaccharides, lipids, polysaccharides and proteins
d. nucleic acids, carbohydrates, monosaccharides and proteins
e. proteins, nucleic acids, carbohydrates and lipids
2. Of the following molecules, which are the only ones that contain phosphorous?
a. fatty acids
b. saccharides
c. proteins
d. DNA
e. all of the above
3. Proteins are built from how many different kinds of amino acids?
a. 4
b. 10
c. 20
d. 30
4. In a hydrolysis reaction, _____________, and in this process water _________.
a. a polymer breaks up to form monomers…………is consumed
b. a polymer breaks up to form monomers……….. is produced
c. a monomer breaks up to form polymers…………is produced
d. monomers are assembled to produce a polymer…….is consumed
e. monomers are assembled to produce a polymer……..is produced
5. Proteins are to amino acids as _____________ are to glucose.
a. fatty acids
b. lipids
c. starches
d. nucleic acids
e. monosaccharides
6. When dehydration synthesis takes place what is happening?
a. water has been added to break the polymer into monomers
b. chemical takes up excess hydrogen ions
c. water is removed to link monomers into polymers
d. two amino acids are joining together
e. more than one of the above
7. Lipids are:
a. commonly known as fats
b. hydrophobic
c. molecules that mostly have carbon and hydrogen, very little oxygen
d. include molecules known as triglycerides
e. all of the above
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8. TRUE or FALSE: A functional group is generally more reactive than the rest of the
molecule.
9. What are the three parts that make up a nucleotide?
a. five carbon sugar, phosphate group, and a double helix
b. phosphate group, nitrogenous base, and a double helix
c. five carbon sugar, nitrogenous base, and enzymes
d. phosphate group, nitrogenous base, and five carbon sugar
10. Which of the following protein structures is (are) reversible?
a. primary
b. secondary
c. tertiary
d. quarternary
e. more than one of the above
11. A molecule with a formula C18H38O is probably a
a. monosaccharide
b. polysaccharide
c. protein
d. fat
e. nucleic acid
12. A major type of lipid found in the cell membrane is
a. steroid
b. triglyceride
c. phospholipid
d. glycerol
13. Peptide bonds
a. hold the polypeptide chains of complex proteins together
b. form between fatty acids
c. are formed by a hydrolysis reaction
d. link amino acids together
e. none of the above
14. What sugar is it that we humans cannot digest?
a. glycogen
b. starch
c. cellulose
d. glucose
15. Depakene 0.75 grams is prescribed by a physician. The bottle of Depakene syrup is
labeled 250 mg per 5 ml. How many ml should be given the patient?
a. 1 ml
b. 2 ml
c. 3 ml d. 5 ml e. 15 ml
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CHAPTER 4: Cell Structure and Function
1. General Organization of a Cell:
A. Most cells in the human body have the following three features:
1. ______________ Membrane( Cell Membrane): forms an outer boundary of
the cell. It has a phospholipid ______________ arrangement (like an
Oreo cookie). The outer surface and inner surface
has the phosphate heads that like water
(are ______________________) while the middle of
the two layers is made up of the fatty acid tails that
do not like water (are ________________________).
2. ___________________: a membrane-bound “sac” that stores the genetic
information (DNA) for most cells. Bacteria do NOT have a nucleus, rather
the DNA is found in a region called the “nucleoid”.
3. ______________________: the space inside the cell between the cell
membrane and the nucleus. The space is filled with a semi-fluid liquid called
the cytosol and numerous organelles that carry out specific functions.
B. There are two types of cells that will be covered in this class:
1. _______________________ Cells: are those that have a clearly defined
nucleus and numerous organelles. Animals and plants that are multicellular
organisms have this type of cells.
2. _______________________ Cells: are those that do NOT have a nucleus
(although they do have DNA) and NO organelles. An example would be
Bacteria, that are unicellular (1 cell) organisms.
C. What determines the size of a cell?
1. If a cell is too ______________, there may not be enough space to hold all the
organelles needed by the cell to survive.
2. If a cell is too _________________, the surface area may not be large enough
to keep up with the increased volume, so parts of the cell may not get enough
of the needed nutrients from the surrounding environment and will die. Also
the cell may not be able to excrete (get rid of) waste products fast enough and
the cell will die.
3. As a cell grows, the volume increases faster than the surface area.
a. The formula for Volume of a cell = length x width x height
b. The formula for Surface area of a cell = length x width
c. The volume (cm3) of a cell increases by a power of 3 (cubed) whereas the
surface area (cm2) increases by a power of 2 (squared) so the volume
increases faster than the surface area as a cell grows in size.
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2. Introduction to Microscopes:
A. ___________________ Microscope:
1. These were first used around the mid-1600’s
2. This type of microscope uses light to see the sample and lenses to magnify the
image seen.
3. These have a maximum magnification of about ________ times; beyond that
level of magnification the image gets fuzzy or blurry.
4. These microscopes make it is possible to see plant and animal cells, the
nucleus, and the largest of the organelles (mitochondria and chloroplasts) as
well as most bacteria, but NOT viruses.
5. This type of microscope is the best choice for studying living cells.
B. ____________________Microscope:
1. These were first used around the mid-1950’s
2. This type of microscope uses a beam of electrons to create an image that is
captured by receptors and stored on a monitor or computer screen.
3. These have a maximum magnification of about ___________________ times.
4. These microscopes make it possible to see even the smallest organelles,
viruses and macromolecules like DNA and proteins.
5. A limitation to this type of microscope is that the sample must be frozen, and
held in a vacuum. In other words the sample must be DEAD!
6. There are two types of electron microscopes:
a. __________________________ Electron Microscope:
This microscope works by passing a stream of electrons through the slide
and specimen to show ______________________ details of cell structure.
b. __________________________ Electron Microscope:
This microscope works by passing a beam of electrons back and forth
across the surface of a specimen coated with a very thin layer of metal.
This microscope shows the _____________________details of cells,
organisms and molecules, providing a three dimensional (3-D) image.
C. Match each description with the correct type of microscope.
1. ____ compound light
microscope
2. ____ scanning electron
microscope
3. ____ transmission electron
microscope
BIOL 160: Module 2
A. A narrow beam of electrons pass
through a cell to form an image of
internal structures.
B. Glass lenses bend light rays to form an
enlarged image of a specimen.
C. A narrow beam of electrons moves back
and forth across the surface of a
specimen coated with a thin layer of
metal creating an image of external
structures.
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D. Identify which type of microscope would best be used in each of the following
situations.
1. ____ examining the fine structural
details within cell organelles
2. ____ observing how a cell changes
shape as it moves
3. ____ studying the tiny bumps on the
surface of a cell or virus
4. ____ filming changes in the nucleus as
a cell prepares to divide
A. compound light microscope
B. scanning electron microscope
C. transmitting electron microscope
3. Introduction to PROKARYOTIC Cells: (Bacteria)
A. These cells are structurally the simplest cells known to exist.
B. These cells lack a clearly defined, membrane bound nucleus; the DNA is simply
found in an area called the ___________________ region.
C. The CELL _____________________ (plasma membrane) is selectively
permeable and regulates or monitors what gets into and out of the cell.
D. The CELL _____________ (seen in some of these cells) helps to maintain the
shape of the cell and provides added protection.
E. Many of these cells have a sticky, jellylike coating made of polysaccharides
called a ________________________ that helps them attach and stick to surfaces.
F. _____________ (singular: pilus) are short, hair-like extensions that help these
cells cling to surfaces or in other words anchor bacteria to surfaces.
G. _______________________ are longer hair-like extensions used for movement.
4. Introduction to EUKARYOTIC Cells:
A. These cells are structurally much more complex than prokaryotic cells.
B. These cells have a clearly defined, membrane bound ________________ that
stores and protects the DNA.
C. The CELL _____________________ (plasma membrane) is selectively
permeable and regulates or monitors what gets into and out of the cell.
D. These cells contain other membrane bound sacs called _____________________,
each with a specific structure and function. There are numerous benefits or
advantages to having these structures in the cell.
1. Having separate organelles surrounded by their own membranes allows a cell
to carry out very different activities at the same time. One organelle may be
synthesizing (making) a protein while another organelle may be breaking
down proteins.
2. Having organelles also greatly increases the membrane surface area, where
chemical reactions frequently occur and allow the cell to maintain the needs of
the cell while staying relatively small in size.
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5. The following is a list of the main organelles and non-membranous structures
commonly found in Eukaryotic cells and a description of their primary functions:
A. CELL MEMBRANE (_________________ Membrane): outer surface of the cell
1. Is called a plasma membrane because it is rather “fluid-like”, NOT rigid.
2. The membrane is described as being selectively permeable, which means it
acts like a gatekeeper, controlling what enters and what exits the cell.
B. _______________________: generally found near center of the cell
1. Stores DNA (genetic information).
2. Is surrounded by a membrane similar to the cell membrane but it is a double
membrane, also known as the nuclear _______________________, with small
openings (nuclear pores) to allow small molecules to enter and leave easily.
3. It contains ___________________, which is a total collection of all the DNA
molecules, unraveled into long strands and scattered throughout the nucleus
with their associated proteins. Each individual strand of DNA is known as a
_________________________ (humans have 46, 23 from each parent) and it
is normally not visible under a microscope unless the cell is preparing to
undergo division.
4. It contains one or several darkened areas called a ___________________
(plural = nucleoli ) which is the location where RIBOSOMES are made.
C. __________________________: seen as little dots throughout the cell
1. This is the site of protein synthesis.
2. This organelle makes the ___________________structure of the protein,
linking together the correct amino acids in the correct order with very strong
covalent bonds called peptide bonds.
3. Some are scattered throughout the cytoplasm and are called “free” whereas
others are attached to the surface of other organelles and are called “fixed”.
a. Those that are “free” produce proteins that remain in the cell cytoplasm.
b. Those that are “fixed” produce proteins that will become part of the cell
membrane or be secreted from the cell to be used by other cells.
D. _______________________ RETICULUM (ER): network of interconnected sacs
(like a maze) that primarily function as “storage sheds”. There are two types:
1. ________________ ER:
a. is generally found near the nucleus (or continuous with it) and has what
appears to be many tiny dots (ribosomes) on the surface when viewed
under a transmission electron microscope.
b. the primary function is to begin to
modify the protein structure (forming
the 2o and 3o structures) and storing the
protein made by the ribosomes
c. this organelle begins the process of
forming the proteins that will become
part of the cell (plasma) membrane
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2. _________________ER:
a. found anywhere in the cell, but does NOT have the dots (ribosomes) on
the surface.
b. synthesizes and stores lipids (fats) and
then modifies them into fatty acids,
phospholipids and steroids
c. it makes the lipid molecules that become
part of the cell membrane.
d. in some cells, the smooth ER stores other substances:
- calcium in muscle cells (for help in muscle contractions)
- enzymes in liver cells (for detoxifying blood)
E. TRANSPORT VESICLES: small round “sacs” scattered throughout the cell
that are designed to move substances from one organelle to another (especially
from the rER and sER to the Golgi Complex).
F. ________________BODY (or COMPLEX or APPARATUS): a stack of
flattened sacs (like plates) that are NOT connected to each other.
1. This organelle further modifies molecules produced
in the rough and smooth endoplasmic reticulum. For
example a protein or carbohydrate coat may be added
to a lipid molecule, forming a lipoprotein or a glycolipid.
2. As the molecule is “improved”, it moves from one
chamber to the next until it is finally released from the
complex.
G. SECRETORY VESICLES: these are similar to transport vesicles except the final
destination is the cell membrane, so the contents can be released (secreted) from
the cell, or the membrane of the vesicle can become part of the cell membrane.
H. ____________________: these are similar to transport vesicles, but are generally
larger in size and they stay inside the cell. These organelles contain enzymes for
digesting macromolecules or destroying bacteria that enter the cell, or cell parts
(damaged organelles) found within the cell. In a sense, they are like the cells
“garbage disposal”.
I. ____________________: these are also similar to transport vesicles, and they also
stay within the cell. They contain enzymes that break down ____________ acids,
______________ acids and ___________________________(a toxic substance
produced by the metabolism of some proteins and fatty acids). These organelles
are found in a higher number in liver and kidney cells where their primary
function is to break down ____________________ and other toxins (drugs).
BIOL 160: Module 2
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J. __________________________: a kidney bean shaped organelle with an inner
chamber that has a large surface area by folding in
on itself forming finger-like projections called cristae.
1. This organelle is the site of energy production.
as it converts glucose into __________.
2. There may be several of them depending on the
energy demands of the cell.
K. ______________________: small “sacs” that store water or food substances.
These are not so clearly visible in animal cells, however because plants can not
relocate to find water, they tend to have a very large, central vacuole for water
storage.
L. CYTOSKELETON: a network of protein fibers of various sizes, scattered
throughout the cell cytoplasm.
1. ____________________________: these are the smallest of the fibers and
are typically found just under the surface of the cell membrane forming the
cell cortex and reinforce the membrane. It helps with maintaining and
changing the shape of a cell.
2. ________________________ FILAMENTS: as the name implies are in
between in size. These are scattered throughout the cytoplasm (like a net) and
help to stabilize the cell as well as helping organelles remain in position
(especially the nucleus).
3. ____________________________: these are the largest of the fibers and
providing rigidity to the cell, and form “tracks” for organelles to follow as
they move about inside the cell
M. _______________________: long extensions from the cell membrane, generally
few in number, that acts like a “tail” or “whip” and moves the cell in the
surrounding area. The sperm cell is the only cell in the human that has this
structure.
N. _________________: short “hair-like” structures on the surface of the cell and
are responsible for moving substances along the surface of the cell (out with old,
in with new). The cells that line the respiratory tract and fallopian tubes (in
women) have many of these structures.
7. Circle one of two possible answers given between the parentheses in each statement.
1. ( Protein Carbohydrate ) subunits form the basic components of microtubules.
2. ( Microtubules Microfilaments ) mechanically supports cell membrane and helps
the cell change its shape.
3. Sperm and many other free-living cells use ( flagella cilia ) as whip-like tails for
movement from one location to another.
4. The human respiratory tract is lined with beating ( flagella
BIOL 160: Module 2
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cilia ).
8. Review the various organelles by matching each phrase on the right with a structure
from the list on the left. Answers can be used more than once and some require more
than one answer.
A. Nucleus
B. Transport vesicle
C. Secretory vesicle
D. Smooth ER
E. Lysosome
F. Golgi apparatus
G. Rough ER
H. Fixed Ribosomes
I. Free Ribosomes
J. Peroxisomes
K. Mitochondria
_____ 1. Lipids are manufactured, modified or stored here
_____ 2. Forms the primary structure of a protein molecule
that is probably going to be used by the cell
_____ 3. Contains chromatin
_____ 4. Contain enzymes that break down large molecules
or pathogens, or in other words carry out
intracellular digestion
_____ 5. Carries secretions for export from cell
_____ 6. Breaks down drugs and alcohol in liver
_____ 7. Makes the phospholipid part of cell membranes
_____ 8. Cell control center
_____ 9. Numerous ribosomes on its surface give it its name
_____ 10. Performs the final modifications of substances that
will become part of the plasma membrane or other
organelles, or be exported outside the cell
_____ 11. Deliver proteins, lipids and other substances from
the ER to Golgi apparatus
_____ 12. Buds off from the Golgi apparatus and migrates to
the cell membrane
_____ 13. Forms the primary structure of proteins that are
probably going to be secreted from the cell
_____ 14. Acts like the “power plant” for the cell, producing
large amounts of ATP
_____ 15. Takes in transport vesicles from the ER and
performs the final modification of their contents
_____ 16. Surrounded by a double layer membrane with
pores, often called an “envelope”
BIOL 160: Module 2
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9. One more time, match each phrase with a structure from the list on the right.
Answers can be used more than once and some require more than one answer.
1.
_____ Assembles the primary structure of
polypeptide chains
2.
_____ Assembles and stores lipids in the cell
3.
_____ Stores and protects the DNA
instructions for building polypeptide
chains
4.
_____ Initiates protein modification following
assembly of polypeptide chains
5.
_____ Location where proteins and lipids take
on their final form
6.
_____ Process that transport substances out of
the cell cytoplasm
7.
_____ Process that transports substances into
the cell cytoplasm
8.
_____ Special vesicles budding from the
Golgi body that contain enzymes that
break down fatty acids and amino
acids, forming hydrogen peroxide
9.
_____ Special vesicles budding from the
Golgi body that become organelles of
intracellular digestion
10. _____ Transport unfinished proteins to the
Golgi body for final modification
11. _____ Transport finished cellular products to
the plasma membrane for export from
the cell
12. _____ Sorts and packages lipids and proteins
for transport to their proper destinations
following modification
13. _____ Transport unfinished lipids to the Golgi
body for final modification
BIOL 160: Module 2
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A. spaces within the smooth
membranes of ER
B. nucleus
C. Golgi body
D. vesicles budding from the
Golgi body
E. vesicles budding from the
rough ER
F. endocytosis with vesicles
G. exocytosis with vesicles
H. spaces within rough ER
I. ribosomes in the cytoplasm
J. vesicles budding from smooth
ER
K. lysosomes
L. peroxisomes
10. The ENDOMEMBRANE SYSTEM:
Some of the organelles mentioned are closely connected to each other forming a
“pathway” from the center of the cell to the surface for secreting products made
within the cell, and replacing or expanding the cell membrane, or in some cases for
creating storage areas for enzymes and molecules (lysosomes, peroxisomes and
vacuoles). To be a member of this system, the structure must have a membrane and
must be part of the pathway; just having a membrane is not enough!
A. Included in the endomembrane system, in their correct order from inside out:
Smooth and Rough ENDOPLASMIC RETICULUM, TRANSPORT VESICLES,
GOLGI COMPLEX, SECRETORY VESICLES, CELL MEMBRANE, (also the
LYSOSOMES, PEROXISOMES and VACUOLES if they are not producing a
substance to be released from the cell).
B. Not included in the endomembrane system:
RIBOSOMES (because they do not have a membrane) and
MITOCHONDRIA (because it is not synthesizing or modifying a substance to be
exported or used by the cell)
11. CELL JUNCTIONS: connections that hold cells in close proximity to each other
A. _______________ JUNCTIONS: bind cells together forming a leak-proof
barrier, preventing substances from sliding between the cells, kind of like a
zipper, (seen in the stomach and intestinal lining)
B. _______________________ (Anchoring) JUNCTIONS: anchor cells together
and to surfaces (like a “spot weld” or roots of a tree in the ground) protein fibers
attach to the cytoskeleton inside the cell membrane.
C. _____________ (Communicating) JUNCTIONS: canals (openings) in the cell
membrane that allow cells to function as a unit.
12.
Choose the most appropriate description for each type of junction.
1. _____ adhering or
anchoring junctions
2. _____ gap or
communicating junctions
3. _____ tight junctions
BIOL 160: Module 2
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A. Link the cells of epithelial tissues lining
the body’s outer surface, inner cavities,
and organs to prevent substances from
“leaking” between the cells.
B. Link the cytoplasm of neighboring cells,
forming an opening for cellular contents
to move back and forth freely between
the cells.
C. Link the cells in tissues of the skin,
heart, and other organs that are subject to
stretching, holding them firmly together.
BIOL 160: Module 2
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Sample Test Questions for Chapter 4 and Lab #8:
1. Which of the following clues would help you identify if a cell is a prokaryotic or
eukaryotic cell?
a. the presence of a rigid cell wall
b. the cell contains DNA
c. the cell carries out cellular metabolism
d. the cell has a clearly defined nucleus
e. all of the above
2. True or False: The nucleus is located in the cytoplasm.
3. Which of the following is not part of the endomembrane system?
a. Secretory Vesicle
b. Golgi apparatus (complex)
c. Smooth Endoplasmic Reticulum
d. Rough Endoplasmic Reticulum
e. Mitochondria
4. Most of the protein used by a cell is produced in the
a. Ribosomes
b. Smooth endoplasmic reticulum
c. Nucleus
d. Mitochondria
e. Golgi apparatus (complex)
5. Cellular organelles and structures seen in the cell can be divided into specific groups
based on their functions. Which of the following is a function carried out by acellular
organelle or structure?
a. manufacture large molecules from smaller fragments
b. break down large molecules into smaller fragments
c. produce ATP for energy
d. allow for movement of the cell
e. all of the above are functions performed by organelles
6. You would expect a cell with a large amount of smooth endoplasmic reticulum to
a. make a lot of lipids
b. move about actively in it’s surroundings
c. secrete a lot of protein from the cell
d. produce a large amount of ATP for energy
7. It is essential for skin cells to remain tightly bound to each other to maintain the
integrity of the skin. The cell junctions that would best allow this are called
a. anchoring (adhering) junctions
b. tight junctions
c. communicating (gap) junctions
BIOL 160: Module 2
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8. Most hormones are proteins that are secreted into the bloodstream to help activities in
the body. Which of the following best describes the correct order of organelles the
hormone might pass through from its production to its exit from the cell? (not all
structures are listed)
a. rough ER, transport vesicle, Golgi apparatus, ribosomes, cell membrane
b. smooth ER, ribosomes, transport vesicle, Golgi apparatus, lysosome, cell
membrane
c. ribosomes, rough ER, transport vesicle, Golgi apparatus, secretory vesicle, cell
membrane
d. ribosome, smooth ER, Golgi apparatus, transport vesicle, lysosome, cell
membrane
e. rough ER, ribosomes, Golgi apparatus, transport vesicle, cell membrane
9. The ribosomes are formed by the
a. rough endoplasmic reticulum
b. smooth endoplasmic reticulum
c. Golgi apparatus
d. Mitochondria
e. Nucleoli
10. TRUE or FALSE: As a cell grows in size, the surface area increases at the same rate
as the volume of the cell.
11. TRUE or FALSE: On a light microscope, the shortest ocular has the lowest
(smallest) power of magnification.
12. A scientist wants to magnify a pollen grain 5000 times to better examine the
organelles inside the cell. Which of the following microscopes would be best to use
in this situation?
a. light microscope
b. scanning electron microscope
c. transmission electron microscope
d. all of the above
13. When working with a microscope, if the slide is moved to the right and away from
you, how will the image viewed through the eye piece move?
a. to the right and away from you
b. to the left and away from you
c. to the right and toward you
d. to the left and toward you
BIOL 160: Module 2
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CHAPTER 5: Organization of the Cell Membrane
1. Cell Membrane Structure:
A. There are many different molecules including, phospholipids, glycolipids,
cholesterol, proteins and glycoproteins in the cell membrane. This is why the
membrane is often described as having a “mosaic” appearance.
B. The most abundant part of the cell membrane is___________________________
molecules that are arranged in two layers.
1. The central portion is composed of fatty acid tails and cholesterol and is
therefore “water fearing” (______________________ or non-polar)
2. The outer and inner surfaces have the “head” of the phospholipid molecules
that contain a glycerol backbone (sugar), a phosphate group and hydroxyl
groups that are all “water loving” (_____________________ or polar)
C. The unsaturated phospholipid tails of the membrane have a slight bend that helps
to keep the molecules from packing too tightly together, and helps keep it more
“fluid-like”.
D. The lipid molecule cholesterol is more rigid and helps to stabilize the “fluid-like”
phospholipid bilayer at normal body temperature providing some stability and
rigidity to the membrane.
E. The many different protein molecules that are part of the cell membrane have just
as many different functions (described below).
F. The membrane is described as being SELECTIVELY PERMEABLE, which
means that some substances may cross the membrane easily, some must pass
through special protein channels, and still others may not cross at all.
1. non-polar or lipid soluble molecules cross directly through the phospholipid
part of the membrane easily
2. polar or water soluble molecules can only cross through specific protein
channels found in the phospholipid membrane
G. The cell membrane is originally produced at the endoplasmic reticulum, portions
“bud-off” to become transport vesicles that move to the Golgi body, where the
protein molecules are further modified. Secretory vesicles then move to the cell
membrane and fused with it in a process called exocytosis.
2. The membrane proteins serve several different functions. Some of these were
introduced in chapter four.
A. ANCHORING or _______________________ Proteins: help cells of the same
type stick together to form tissues. They serve as attachment points for the
phospholipid membrane to the internal cytoskeleton and external fibers, or to
neighboring cells. These are typically found in tissues that must be able to stretch
as an organ fills, such as in the walls of the stomach, heart, and urinary bladder.
B. COMMUNICATING or __________ Junction Proteins: form an open channel
between two cells allowing chemicals and “messages” to pass quickly from cell to
cell so they may function more effectively as a group. These are expecially
common in the walls of the heart.
BIOL 160: Module 2
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C. ________________________ Proteins: serve as a kind of “identification tag” for
a cell, allowing antibodies and white blood cells to detect who “belongs” and who
must be “destroyed” because they do not belong in the body. These also are
responsible for the various blood types (A, B, AB, etc.)
D. _________________________ Proteins: serve as binding sites for signaling
molecules (hormones) that will trigger a change in the activities of the cell. This
is why some cells respond to a specific chemical (hormone) while others do not.
E. ENZYME Proteins: assist the cell by speeding up essential chemical reactions.
They are generally found attached to either the outer or inner surface of the
membrane.
F. __________________________ Proteins: help move water and water soluble
(polar) substances across the phospholipids membrane. These protein molecules
have an internal channel and tend to be very specific (selective) for the substance
moving through them. There are two main types of these proteins:
1. ____________________Transporters: do not require energy for activation
2. ____________________ Transporters: do require energy for activation
3. There are several “driving forces” that influence the movement of substances
across the cell membrane:
A. __________________________ of a Solution: this is defined as the density of a
particular substance in a given area (volume). ______________________ is
defined as the comparative solute concentration of two solutions on either side of
a selectively permeable membrane.
1. There are essentially three “types” of solutions when discussing the movement
of substances across a membrane:
a. _______________________SOLUTION (“strong”): one with a high
concentration of solutes, therefore one with relatively less water.
b. _______________________ SOLUTION (“weak”): one with a low
concentration of solutes, therefore one with relatively more water.
c. _______________________ SOLUTIONS: those where the concentration
of solutes is the same on both sides of the membrane, therefore the relative
amount of water is the same also.
2. Because the cell membrane is selectively permeable, there is a tendency for
some molecules to have a greater concentration on one side of the membrane
than the other. The composition of the intracellular fluid is quite different
from the composition of the extracellular fluid surrounding the cells in the
body. For most cells in the body, there is a higher concentration of protein
molecules, ATP and potassium ions (K+1) inside the cell than outside the cell.
There is also a higher concentration of everything else outside the cell,
especially sodium ions (Na+1) and chloride ions (Cl-1).
BIOL 160: Module 2
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3. The difference in composition on each side of a cell membrane is called a
__________________________ GRADIENT. There is a natural tendency for
molecules to move ____________from the side of the membrane with a high
concentration and ________________ the side of the membrane with a low
concentration (DOWN their concentration gradient) if at all possible.
B. Because there are many ions in solution, one side of the membrane will often be
more positive and one side more negative, which creates an unequal charge
distribution. Thcharge differences also tend to influence the movement of ions
across the membrane. Remember that ions that have the same charge tend to
________________ each other while those with opposite charges tend to
_________________ each other. Differences in electrical charges on each side of
a cell membrane is called an ELECTRICAL _______________________.
C. Because there are numerous gases dissolved in the body (especially O2 and CO2)
there is typically a gradient that influences the movement of gases across
membranes throughout the body, especially between the lungs and the blood
vessels within the lungs. As the concentration of a gas in solution increases, so
does the pressure of the gas. Differences in gas pressure on each side of a
membrane is called a _______________________ GRADIENT.
4. Substances move across a cell membrane by two main processes:
A. ACTIVE TRANSPORT involves the movement of molecules or ions across a
membrane from the side with a _____________ concentration to the side with
a ______________ concentration. In other words, the molecules are moving
___________ their concentration gradients. This process requires that the cell
use energy (ATP) to accomplish this action and the substance is described as
being “pumped” across the membrane.
1. If the transporter protein “pumps” two substances at the same time and in the
same direction, they are called SYMPORTERS.
2. If the transporter protein “pumps” two substances at the same time in opposite
directions, they are called ANTIPORTERS. The most common example of
this type is the sodium-potassium pump (found in nerve and muscle cells).
B. PASSIVE TRANSPORT involves the movement of molecules and ions across a
membrane from the side with a _______________concentration to the side with a
_______________ concentration, or in other words, the molecules are moving
_____________their concentration or pressure gradients. This process does not
need the cell to supply additional _______________ (ATP) to move the substance
across the membrane.
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5. There are three main mechanisms that use the passive transport process:
A. __________________________: the natural tendency for particles to spread out
from an area of high concentration to an area of low concentration.
1. Remember that the cell membrane is selectively permeable. Lipid soluble
(__________________ or hydrophobic) molecules can pass directly through
the cell membrane as though it is not there. This is also how fat soluble
vitamins and dissolved gases like oxygen (O2) and carbon dioxide (CO2) cross
the cell membrane.
2. There are several factors that will increase diffusion rates across cell
membranes or other membranes in the body:
a. Greater the difference in concentration of solutes on each side of the
membrane, ________________ the rate of diffusion
b. Warmer the temperature of a solution, the ______________ molecules are
moving about in the solution
c. Larger the size of the molecules, the ______________ they move
d. Ions of opposite charges (+ and -) _____________ each other, whereas
those that have the same charges _________________ each other.
e. An increase in pressure of a gas on one side of a membrane causes
molecules to try to move to an area with less pressure.
f. Larger surface area available for diffusion will _________________ the
rate of diffusion. This is especially important in the lungs and intestines.
g. The shorter the distance to diffuse, the ________________ diffusion
occurs. This doesn’t apply to cell membranes as they are all the same
thickness (phospholipid bi-layer), however when the lungs fill with fluid,
it is harder for the oxygen to diffuse into the blood because it must move
through the liquid as well as through the membrane.
B. __________________________ DIFFUSION: the movement of water molecules
and water soluble (polar or _____________________) particles from the side of a
selectively permeable membrane with a higher concentration of the molecule that
is moving to the other side with the assistance (help) of a membrane protein.
1. Some of these protein channels are always open (leakage channels), but only
allow specific molecules to pass through. Many animal and plant cells have
channels called aquaporins that are always open and allow ______________
to cross the membrane easily to help maintain a proper fluid balance.
2. Some channels must change their _________________to allow a molecule to
pass through and therefore can regulate when and if a substance gets through
or not. These proteins are said to be “________________” and can open or
close in response to stimuli like a specific chemical, pressure or changes in
membrane electrical gradients.
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C. ______________________: the diffusion of water across a selectively permeable
membrane. Water like any other substance diffuses from an area of ___________
water concentration to an area of _________ water concentration.
1. The direction of movement of water across a membrane is sometimes difficult
to keep straight because solutions are described by the concentration (amount)
of the solutes dissolved in the water, not by the amount of the water.
2. Water molecules move across a selectively permeable membrane from the
solution that is __________TONIC to the solution that is __________TONIC.
A hypotonic solution has relatively more water compared to a hypertonic
solution, and water moves from the solution where there is “more of it” to the
solution where there is “less of it”.
2%
sucrose
water
Hypotonic
Solution
10% sucrose
Hypertonic
Solution
2% sucrose
Isotonic
Solution
6. There area several additional forces that influence the movement of WATER across
membranes:
A. ________________________ PRESSURE: is the force generated by the flow of a
fluid against a membrane. In the circulatory system the heart pumps blood, which
when under pressure tends to push the fluid through openings in membranes,
carrying with it all small substances dissolved in the blood. This is the driving
force behind how the kidneys filter the blood
B. ______________________ PRESSURE: is the force needed to prevent water
from flowing across a membrane, down the concentration gradient for the water.
This is the driving force behind how the capillaries (very small blood vessels)
“pull” tissue fluid back into the circulatory system.
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7. There are several process that are used to move large quantities of substances or
molecules or substances that are too “large” to cross the cell membrane through the
protein channels:
A. _________________________: this is the process the cell uses to expel or export
large molecules produced inside the cell. Transport vesicles fuse with the
membrane and the contents “spill out” of the cell. This is also the way the
membrane is replaced with a “new and improved” membrane each time a
substance is exported from the cell.
B. ___________________________: this is the process the cell uses to take in
large molecules for use by the cell or to be destroyed by the cell in the case of
white blood cells. This is also the way worn-out membrane is repaired by the cell
as sections are pulled into the cell and broken down by fusing with lysosomes.
.
There are three basic forms of Endocytosis:
1. _______________________________ ENDOCYTOSIS: receptors on the
surface of the cell membrane bind to very specific substances (hormone,
vitamin, mineral, etc.), then the membrane folds in on itself forming a vesicle.
2. ___________________________: this is the process the cell uses to
“engulf” large microorganisms or “food particles” that happen to be in the
extracellular fluid. This process is also thought of as “cellular eating”
3. ________________________ ENDOCYTOSIS: this process is much less
selective and is used primarily to remove excess membrane that forms as
exocytosis occurs, or to remove sections of worn-out membrane. This process
is sometimes known as PINOCYTOSIS or is thought of as “cellular drinking”,
as some of the extracellular fluid is brought into the cell in the process.
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8. Hydrophilic (polar) substances cross the cell membrane with the assistance of
transport proteins. For each of the following, choose one of the mechanisms of
protein-mediated transport listed. Some descriptions below require active transport,
some indicate passive transport is required, while other descriptions do not provide
enough information to definitively chose one or the other, so may apply to either
active or passive transport.
A. active transport
B. passive transport
C. may apply to either active or passive transport
1.
____ The calcium channel pump uses this method to transport calcium
2.
____ The transport protein channel changes shape
3.
____ Involves a transport protein that is not energized
4.
____ A transport protein is specific to only one type of substance
5.
____ Solute molecules move across the membrane from the side with a higher
concentration to the side with a lower concentration of the solute molecule
6.
____ The transport protein must receive an energy boost, usually from ATP.
7.
____ Binding of ATP to a transporter protein leads to changes in protein shape
8.
____ The sodium-potassium pump uses this mechanism of transport
9.
____ Net movement of solutes will be down the solute’s concentration gradient
using this method of transport.
10. ____ A solute is pumped across the cell membrane against its concentration
gradient.
11. ____ The solute binding site improves when ATP donates energy to the
transport protein to allow a better chemical fit.
12. ____ Passive two-way transport will continue until solute concentrations
become equal on both sides of the membrane.
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9. Osmosis is an important process that has many effects on living things. Test your
understanding of osmosis by predicting in each of the following cases whether water
will enter the cell (In) or leave the cell (Out), or whether there will be no net
movement of water (None). Assume that the plasma membrane is permeable to water
but not to the solutes.
_________ 1. A cell is exposed to a hypertonic solution.
_________ 2. A cell is placed in a salt solution whose concentration is greater than
that of the cell contents.
_________ 3. Due to disease, the solute concentration of the body fluid outside the
cell is less than the solute concentration of the cytoplasm.
_________ 4. The cell is in an isotonic solution.
_________ 5. A single-celled organism is placed in drop of pure water for
examination under microscope.
_________ 6. A cell is immersed in solution of sucrose and glucose whose combined
concentration is greater than the concentration of solutes in the
cytoplasm.
_________ 7. The solute concentration of the cell cytoplasm is greater than the
solute concentration of fluid surrounding the cell.
_________ 8. A cell is exposed to a hypotonic solution.
_________ 9. The concentration of solutes in the cytoplasm is equal to the solute
concentration of the extracellular fluid.
_________ 10. The cytoplasm of a cell is more dilute than the surrounding solution
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10. Choose the most appropriate answer for each.
1. _____ bulk flow
2. _____ osmosis
3. _____ tonicity
4. _____ hypotonic solution
5. _____ hypertonic solution
6. _____ isotonic solutions
7. _____ hydrostatic pressure
8. _____ osmotic pressure
9. _____ plasmolysis
A. Refers to the relative solute concentrations of two
fluids
B. Having the same solute concentrations
C. Mass movement of one or more substances in
response to pressure, gravity, or other external
force
D. The amount of force that prevents further increase
in a solution’s volume
E. The fluid on one side of a membrane that contains
more solutes than the fluid on the other side of the
membrane
F. The diffusion of water in response to a water
concentration gradient between two regions
separated by a selectively permeable membrane
G. Osmotically induced swellingh of a cell until it
ruptures
H. The fluid on one side of a membrane that contains
fewer solutes than the fluid on the other side of the
membrane
I. A fluid force exerted against a cell wall and/or
membrane enclosing the fluid
11. If the statement is true, write a T in the blank. If the statement is false, make it
correct by changing the underlined word(s) and writing the correct word(s) in the
answer blank.
___________ 1. Because membrane exhibits selective permeability, concentrations
of dissolved substances can increase on one side of the membrane
or the other.
___________ 2. A water concentration gradient is influenced by the number of
solute molecules present on both sides of the membrane.
___________ 3. The relative concentrations of solutes in two fluids are referred to
as tonicity.
___________ 4. An animal cell placed in a hypertonic solution would swell and
perhaps burst.
___________ 5. Physiological saline is 0.9 percent NaCl; red blood cells placed in
such a solution will not gain or lose water; therefore, one could
state that the fluid in red blood cells is hypertonic.
___________ 6. A solution of 80 percent water, 20 percent solute is more
concentrated than a solution of 70 percent water, 30 percent solute.
___________ 7. The mass movement of one or more substances in response to
pressure, gravity, or some other external force is called osmosis.
___________ 8. Animal cells placed in a hypotonic solution will swell.
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12. Review the function of cell membranes by matching each of the phrases on the right
with the appropriate mechanisms from the list on the left. Answers may be used more
than once and some questions require more than one answer.
A.
B.
C.
D.
E.
F.
G.
H.
Diffusion
Active transport
Osmosis
Phagocytosis
Passive transport
Facilitated diffusion
Pinocytosis
Receptor-mediated
endocytosis
I. Exocytosis
_____ 1. Movement of substances across a biological
membrane directly through the phospholipids bilayer
_____ 2. Moves solutes against concentration gradient
_____ 3. Any spread of molecules from area of higher
concentration to area of lower concentration
_____ 4. Movement of substances across a membrane down
the concentration gradient with the help of a
transport protein
_____ 5. Three types of endocytosis where substances enter
the cell and are contained within vesicles.
_____ 6. Engulfing of fluid in membrane vesicles
_____ 7. Diffusion of water across selectively permeable
membrane, from hypotonic to hypertonic solution
_____ 8. Transport molecules use ATP to function better
_____ 9. Enables cell to engulf bulk quantities of very specific
large molecules that bind to surface proteins
_____ 10. How oxygen and carbon dioxide enter and leave
cells
_____ 11. Two examples of passive transport through a protein
channel in the membrane
_____ 12. Engulfing of large particle in membrane vesicle
_____ 13. Fusion of membrane-bound vesicle with membrane,
and dumping of contents outside cell
_____ 14. How a cell might capture a bacterium
_____15. A general term used to represent the movement of
substances down their concentration gradient through
a protein channel without the use of ATP energy.
BIOL 160: Module 2
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Sample Test Questions for Chapter 5:
1. The cell membrane consists mostly of a
a. protein bilayer with phospholipids scattered throughout the membrane
b. carbohydrate bilayer with proteins scattered throughout the membrane
c. phospholipid bilayer with proteins scattered throughout the membrane
d. protein bilayer with carbohydrates scattered throughout the membrane
2. The phospholipids molecules of most membranes have
a. a hydrophobic head and a hydrophilic tail
b. a hydrophobic head and a hydrophobic tail
c. a hydrophilic head and two hydrophilic tails
d. a hydrophilic head and two hydrophobic tails
3. In an attempt to describe the membrane as a “fluid mosaic model”, we would describe
the ________ as floating in a sea of ______________.
a. lipid…….protein
b. phospholipids………carbohydrates
c. proteins……….phospholipids
d. lipids……….water
4. Oxygen and carbon dioxide pass through the membrane by which of the following
processes?
a. osmosis
b. diffusion
c. active transport
d. facilitated diffusion
e. receptor mediated endocytosis
5. Movement of molecules against their concentration gradient occurs by which of the
following processes?
a. osmosis
b. diffusion
c. active transport
d. facilitated diffusion
e. receptor mediated endocytosis
6. A red blood cell placed in a hypotonic solution would
a. shrink
b. swell
c. stay the same size
d. become a substrate
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7. Osmosis is similar to passive transport in that both:
a. always involve the diffusion of water
b. do not require the cell to expend ATP energy
c. involve diffusion down the concentration gradient
d. rely on transport proteins
e. both B and C
8. A cell that neither gains nor loses water when it is immersed in a solution is
a. isotonic to its environment
b. hypertonic to its environment
c. hypotonic to its environment
d. metabolically inactive
9. Which of the following pieces of evidence would prove that a substance enters a cell
by active transport rather than passive transport?
a. the substance is moved across the cell membrane by a carrier protein
b. the substance enters the cell when its concentration is higher outside the cell than
inside
c. the breakdown of ATP is needed for the transport to occur
d. all of the above
e. both A and C only
10. Phagocytosis is to eating as __________ is to drinking.
a. osmosis
b. exocytosis
c. pinocytosis
d. diffusion
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