Download Document

PowerPoint® Lecture Slides
prepared by
Janice Meeking,
Mount Royal College
CHAPTER
2
Chemistry
Comes Alive:
Part A
Copyright © 2010 Pearson Education, Inc.
Matter
•
Anything that has mass and occupies
space
•
States of matter:
1. Solid—definite shape and volume
2. Liquid—definite volume, changeable shape
3. Gas—changeable shape and volume
Copyright © 2010 Pearson Education, Inc.
Mass and Weight
• the mass of an object is a fundamental property
of the object
• a numerical measure of its inertia
• measure of the amount of matter in the object.
• definitions of mass often seem circular because it
is such a fundamental quantity that it is hard to
define in terms of something else
• the usual symbol for mass is m and its SI unit is
the kilogram
• the weight of an object is the force of gravity on
the object (w = mg)
3
Copyright © 2010 Pearson Education, Inc.
Energy Concepts
• What is energy?
•
The capacity to perform work
• What is the difference between potential and kinetic energy?
•
Stored vs. motion
• Energy is neither created nor destroyed but…
•
Converted from one form to another
•
This property is called the conservation of energy
• What is the usual way in which energy is “lost?”
•
Through heat
• What type of energy is heat?
•
Kinetic due to random motion of atoms
•
Heat is generated by friction (in this example between atoms and air)
• Heat is highly __________ energy and highest amount of _________.
•
Disordered, entropy
• Chemical energy is a form of ____________ energy.
•
Potential
• What is the primary form of chemical energy in living organisms?
•
ATP
• What is cellular respiration? What are the byproducts?
•
Conversion of glucose into ATP through reduction of oxygen forming water and carbon
dioxide
Copyright © 2010 Pearson Education, Inc.
Energy Form Conversions
• Energy may be converted from one form to
another
• Conversion is inefficient because some
energy is “lost” as heat
Copyright © 2010 Pearson Education, Inc.
Major Elements of the Human Body
• Oxygen (O)
• Carbon (C)
• Hydrogen (H)
• Nitrogen (N)
Copyright © 2010 Pearson Education, Inc.
About 96% of body mass
Atomic Structure
• Determined by numbers of subatomic
particles
• Nucleus consists of neutrons and protons
Copyright © 2010 Pearson Education, Inc.
Atomic Structure
• Neutrons
• No charge
• Mass = 1 atomic mass unit (amu)
• Protons
• Positive charge
• Mass = 1 amu
Copyright © 2010 Pearson Education, Inc.
Atomic Structure
• Electrons
• Orbit nucleus
• Equal in number to protons in atom
• Negative charge
• 1/2000 the mass of a proton (0 amu)
Copyright © 2010 Pearson Education, Inc.
Identifying Elements
• Atomic number = number of protons in
nucleus
Copyright © 2010 Pearson Education, Inc.
Identifying Elements
• Mass number = mass of the protons and
neutrons
• Mass numbers of atoms of an element are not
all identical
• Isotopes are structural variations of elements
that differ in the number of neutrons they
contain
Copyright © 2010 Pearson Education, Inc.
Mixtures
• Most matter exists as mixtures
• Two or more components physically
intermixed
• Three types of mixtures
• Solutions
• Colloids
• Suspensions
Copyright © 2010 Pearson Education, Inc.
Solutions
• Homogeneous mixtures
• Usually transparent, e.g., atmospheric air or
seawater
• Solvent
• Present in greatest amount, usually a liquid
• Solute(s)
• Present in smaller amounts
Copyright © 2010 Pearson Education, Inc.
Colloids and Suspensions
• Colloids (emulsions)
• Heterogeneous translucent mixtures, e.g.,
cytosol
• Large solute particles that do not settle out
• Undergo sol-gel transformations
• Suspensions:
• Heterogeneous mixtures (blood)
• Large visible solutes tend to settle out
Copyright © 2010 Pearson Education, Inc.
Solution
Colloid
Suspension
Solute particles are very
tiny, do not settle out or
scatter light.
Solute particles are larger
than in a solution and scatter
light; do not settle out.
Solute particles are very
large, settle out, and may
scatter light.
Solute
particles
Solute
particles
Solute
particles
Example
Example
Example
Mineral water
Gelatin
Blood
Copyright © 2010 Pearson Education, Inc.
Figure 2.4
Mixtures vs. Compounds
• Mixtures
• No chemical bonding between components
• Can be separated physically, such as by
straining or filtering
• Heterogeneous or homogeneous
• Compounds
• Can be separated only by breaking bonds
• All are homogeneous
Copyright © 2010 Pearson Education, Inc.
Chemical Bonds
• Electrons occupy up to seven electron shells
(energy levels) around nucleus
• Octet rule: Except for the first shell which is
full with two electrons, atoms interact in a
manner to have eight electrons in their
outermost energy level (valence shell)
Copyright © 2010 Pearson Education, Inc.
Chemically Inert Elements
• Stable and unreactive
• Outermost energy level fully occupied or
contains eight electrons
Copyright © 2010 Pearson Education, Inc.
(a)
Chemically inert elements
Outermost energy level (valence shell) complete
8e
2e
Helium (He)
(2p+; 2n0; 2e–)
Copyright © 2010 Pearson Education, Inc.
2e
Neon (Ne)
(10p+; 10n0; 10e–)
Figure 2.5a
Chemically Reactive Elements
• Outermost energy level not fully occupied by
electrons
• Tend to gain, lose, or share electrons (form
bonds) with other atoms to achieve stability
Copyright © 2010 Pearson Education, Inc.
(b)
Chemically reactive elements
Outermost energy level (valence shell) incomplete
1e
Hydrogen (H)
(1p+; 0n0; 1e–)
6e
2e
Oxygen (O)
(8p+; 8n0; 8e–)
Copyright © 2010 Pearson Education, Inc.
4e
2e
Carbon (C)
(6p+; 6n0; 6e–)
1e
8e
2e
Sodium (Na)
(11p+; 12n0; 11e–)
Figure 2.5b
Types of Chemical Bonds
• Ionic
• Covalent
• Hydrogen
Copyright © 2010 Pearson Education, Inc.
Ionic Bonds
• Ions are formed by transfer of valence shell
electrons between atoms
• Anions (– charge) have gained one or more
electrons
• Cations (+ charge) have lost one or more
electrons
• Attraction of opposite charges results in an
ionic bond
Copyright © 2010 Pearson Education, Inc.
Sodium atom (Na)
(11p+; 12n0; 11e–)
Chlorine atom (Cl)
(17p+; 18n0; 17e–)
+
–
Sodium ion (Na+)
Chloride ion (Cl–)
Sodium chloride (NaCl)
(a) Sodium gains stability by losing one electron, and
chlorine becomes stable by gaining one electron.
Copyright © 2010 Pearson Education, Inc.
(b) After electron transfer, the oppositely
charged ions formed attract each other.
Figure 2.6a-b
Formation of an Ionic Bond
• Ionic compounds form crystals instead of
individual molecules
• NaCl (sodium chloride)
Copyright © 2010 Pearson Education, Inc.
CI–
Na+
(c) Large numbers of Na+ and Cl– ions
associate to form salt (NaCl) crystals.
Copyright © 2010 Pearson Education, Inc.
Figure 2.6c
Covalent Bonds
• Formed by sharing of two or more valence
shell electrons
• Allows each atom to fill its valence shell at
least part of the time
Copyright © 2010 Pearson Education, Inc.
Reacting atoms
Resulting molecules
+
Molecule of
Hydrogen
Carbon
methane gas (CH4)
atoms
atom
(a) Formation of four single covalent bonds:
carbon shares four electron pairs with four
hydrogen atoms.
Copyright © 2010 Pearson Education, Inc.
or
Structural
formula
shows
single
bonds.
Figure 2.7a
Reacting atoms
Resulting molecules
+
Oxygen
atom
or
Oxygen
atom
Molecule of
oxygen gas (O2)
(b) Formation of a double covalent bond: Two
oxygen atoms share two electron pairs.
Copyright © 2010 Pearson Education, Inc.
Structural
formula
shows
double
bond.
Figure 2.7b
Reacting atoms
Resulting molecules
+
Nitrogen
atom
or
Nitrogen
atom
Molecule of
nitrogen gas (N2)
(c) Formation of a triple covalent bond: Two
nitrogen atoms share three electron pairs.
Copyright © 2010 Pearson Education, Inc.
Structural
formula
shows
triple
bond.
Figure 2.7c
Covalent Bonds
• Sharing of electrons may be equal or unequal
• Equal sharing produces electrically balanced
nonpolar molecules
• CO2
Copyright © 2010 Pearson Education, Inc.
Copyright © 2010 Pearson Education, Inc.
Figure 2.8a
Covalent Bonds
• Unequal sharing by atoms with different
electron-attracting abilities produces polar
molecules
• H2O
• Atoms with six or seven valence shell
electrons are electronegative, e.g., oxygen
• Atoms with one or two valence shell
electrons are electropositive, e.g., sodium
Copyright © 2010 Pearson Education, Inc.
Copyright © 2010 Pearson Education, Inc.
Figure 2.8b
Copyright © 2010 Pearson Education, Inc.
Figure 2.9
Hydrogen Bonds
• Attractive force between electropositive
hydrogen of one molecule and an
electronegative atom of another molecule
• Common between dipoles such as water
• Also act as intramolecular bonds, holding a
large molecule in a three-dimensional shape
Copyright © 2010 Pearson Education, Inc.
Hydrogen bonds
•
The bonds of a water molecule represent ________ _______ type of bond. Also known as a ________.
•
•
Oxygen has a greater affinity for the electrons and is therefore more _____________. Whereas, hydrogen
has a lesser attraction for electrons is more _____________.
•
•
•
Negative, positive
The attraction between the negative oxygen end of one water compound to the positive hydrogen end of
another water represents a ___________ bond.
•
•
Electronegative, electropositive
The oxygen end of the molecule is therefore slightly more _________ and the hydrogen ends are slightly
more _________.
•
•
Polar covalent, dipole
Hydrogen
Hydrogen bonds are strong bonds. (T/F)
•
False
•
They are easily broken
Hydrogen bonds may inter- or intramolecular. (T/F)
•
True
• The unique properties of water are attributable to hydrogen bonds. Some of the properties
include….
•
Cohesion, high boiling point, why ice floats, high heat of vaporization, high heat capacity
Copyright © 2010 Pearson Education, Inc.
+
–
Hydrogen bond
(indicated by
dotted line)
+
+
–
–
–
+
+
+
–
(a) The slightly positive ends (+) of the water
molecules become aligned with the slightly
negative ends (–) of other water molecules.
Copyright © 2010 Pearson Education, Inc.
Figure 2.10a
Chemical Reactions
• Occur when chemical bonds are formed,
rearranged, or broken
• Represented as chemical equations
• Chemical equations contain:
• Molecular formula for each reactant and
product
• Relative amounts of reactants and products,
which should balance
Copyright © 2010 Pearson Education, Inc.
Examples of Chemical Equations
H + H  H2 (hydrogen gas)
(reactants)
(product)
4H + C  CH4 (methane)
Copyright © 2010 Pearson Education, Inc.
Patterns of Chemical Reactions
• Synthesis (combination) reactions
• Decomposition reactions
• Exchange reactions
Copyright © 2010 Pearson Education, Inc.
Synthesis Reactions
• A + B  AB
• Always involve bond formation
• Anabolic
Copyright © 2010 Pearson Education, Inc.
(a) Synthesis reactions
Smaller particles are bonded
together to form larger,
more complex molecules.
Example
Amino acids are joined together to
form a protein molecule.
Amino acid
molecules
Protein
molecule
Copyright © 2010 Pearson Education, Inc.
Figure 2.11a
Dehydration Synthesis and Hydrolysis
• What is dehydration synthesis?
• Removal of a water molecule to form a new covalent
bond
• What is hydrolysis?
• The addition of a water molecule to break a covalent
bond
• What is anabolism?
• Forming new bonds to build something bigger.
Requires energy (endergonic)
• What is catabolism?
• Breaking bonds to make something smaller. Large
molecules down to subunits.
• Releases energy (exergonic).
Copyright © 2010 Pearson Education, Inc.
Decomposition Reactions
• AB  A + B
• Reverse synthesis reactions
• Involve breaking of bonds
• Catabolic
Copyright © 2010 Pearson Education, Inc.
(b) Decomposition reactions
Bonds are broken in larger
molecules, resulting in smaller,
less complex molecules.
Example
Glycogen is broken down to release
glucose units.
Glycogen
Glucose
molecules
Copyright © 2010 Pearson Education, Inc.
Figure 2.11b
Oxidation-Reduction (Redox) Reactions
• Decomposition reactions: Reactions in which
fuel is broken down for energy
• Also called exchange reactions because
electrons are exchanged or shared differently
• Electron donors lose electrons and are
oxidized
• Electron acceptors receive electrons and
become reduced
Copyright © 2010 Pearson Education, Inc.
Sodium atom (Na)
(11p+; 12n0; 11e–)
Chlorine atom (Cl)
(17p+; 18n0; 17e–)
+
–
Sodium ion (Na+)
Chloride ion (Cl–)
Sodium chloride (NaCl)
(a) Sodium gains stability by losing one electron, and
chlorine becomes stable by gaining one electron.
Copyright © 2010 Pearson Education, Inc.
(b) After electron transfer, the oppositely
charged ions formed attract each other.
Figure 2.6a-b
Chemical Reactions
• All chemical reactions are either exergonic or
endergonic
• Exergonic reactions — release energy
• Catabolic reactions
• Endergonic reactions — products contain
more potential energy than did reactants
• Anabolic reactions
Copyright © 2010 Pearson Education, Inc.
Chemical Reactions
• All chemical reactions are theoretically reversible
• A + B  AB
• AB  A + B
• Chemical equilibrium occurs if neither a forward nor
reverse reaction is dominant
• Many biological reactions are essentially irreversible
due to
• Energy requirements
• Removal of products
Copyright © 2010 Pearson Education, Inc.
Rate of Chemical Reactions
• Rate of reaction is influenced by:
•  temperature   rate
•  particle size   rate
•  concentration of reactant   rate
• Catalysts:  rate without being chemically
changed
• Enzymes are biological catalysts
Copyright © 2010 Pearson Education, Inc.
PowerPoint® Lecture Slides
prepared by
Janice Meeking,
Mount Royal College
CHAPTER
2
Chemistry
Comes Alive:
Part B
Copyright © 2010 Pearson Education, Inc.
Classes of Compounds
• Inorganic compounds
• Water, salts, and many acids and bases
• Do not contain carbon
• Organic compounds
• Carbohydrates, fats, proteins, and
nucleic acids
• Contain carbon, usually large, and are
covalently bonded
Copyright © 2010 Pearson Education, Inc.
Water
• 60%–80% of the volume of living cells
• Most important inorganic compound in living
organisms because of its properties
Copyright © 2010 Pearson Education, Inc.
Properties of Water
• High heat capacity
• Absorbs and releases heat with little
temperature change
• Prevents sudden changes in temperature
• High heat of vaporization
• Evaporation requires large amounts of heat
• Useful cooling mechanism
Copyright © 2010 Pearson Education, Inc.
Properties of Water
• Polar solvent properties
• Dissolves and dissociates ionic substances
• Forms hydration layers around large charged
molecules, e.g., proteins (colloid formation)
• Body’s major transport medium
Copyright © 2010 Pearson Education, Inc.
+
–
+
Water molecule
Salt crystal
Copyright © 2010 Pearson Education, Inc.
Ions in solution
Figure 2.12
Properties of Water
• Reactivity
• A necessary part of hydrolysis and dehydration
synthesis reactions
• Cushioning
• Protects certain organs from physical trauma,
e.g., cerebrospinal fluid
Copyright © 2010 Pearson Education, Inc.
Salts
• Ionic compounds that dissociate in water
• Contain cations other than H+ and anions
other than OH–
• Ions (electrolytes) conduct electrical currents
in solution
• Ions play specialized roles in body functions
(e.g., sodium, potassium, calcium, and iron)
Copyright © 2010 Pearson Education, Inc.
Acids and Bases
• Both are electrolytes
• Acids are proton (hydrogen ion) donors
(release H+ in solution)
• HCl  H+ + Cl–
Copyright © 2010 Pearson Education, Inc.
Acids and Bases
• Bases are proton acceptors (take up H+ from
solution)
• NaOH  Na+ + OH–
• OH– accepts an available proton (H+)
• OH– + H+  H2O
• Bicarbonate ion (HCO3–) and ammonia
(NH3) are important bases in the body
because of buffering properties
Copyright © 2010 Pearson Education, Inc.
Acid-Base Concentration
• Acid solutions contain [H+]
• As [H+] increases, acidity increases, pH
decreases
• Alkaline solutions contain bases (e.g., OH–)
• As [H+] decreases (or as [OH–] increases),
alkalinity increases, pH increases
Copyright © 2010 Pearson Education, Inc.
pH: Acid-Base Concentration
• pH = the negative logarithm of [H+] in
moles per liter
• Neutral solutions:
• Pure water is pH neutral (contains equal
numbers of H+ and OH–)
• pH of pure water = pH 7: [H+] = 10 –7 M
• All neutral solutions are pH 7
Copyright © 2010 Pearson Education, Inc.
pH: Acid-Base Concentration
• Acidic solutions
•  [H+],  pH
• Acidic pH: 0–6.99
• pH scale is logarithmic: a pH 5 solution has
10 times more H+ than a pH 6 solution
• Alkaline solutions
•  [H+],  pH
• Alkaline (basic) pH: 7.01–14
Copyright © 2010 Pearson Education, Inc.
Concentration
(moles/liter)
Copyright © 2010 Pearson Education, Inc.
Examples
[OH–]
[H+]
pH
100
10–14
14
1M Sodium
hydroxide (pH=14)
10–1
10–13
13
Oven cleaner, lye
(pH=13.5)
10–2
10–12
12
10–3
10–11
11
10–4
10–10
10
10–5
10–9
9
10–6
10–8
8
10–7
10–7
7 Neutral
10–8
10–6
6
10–9
10–5
5
10–10
10–4
4
10–11
10–3
3
10–12
10–2
2
10–13
10–1
1
10–14
100
0
Household ammonia
(pH=10.5–11.5)
Household bleach
(pH=9.5)
Egg white (pH=8)
Blood (pH=7.4)
Milk (pH=6.3–6.6)
Black coffee (pH=5)
Wine (pH=2.5–3.5)
Lemon juice; gastric
juice (pH=2)
1M Hydrochloric
acid (pH=0)
Figure 2.13
Acid-Base Homeostasis
• pH change interferes with cell function and
may damage living tissue
• Slight change in pH can be fatal
• pH is regulated by kidneys, lungs, and
buffers
Copyright © 2010 Pearson Education, Inc.
Buffers
• Mixture of compounds that resist pH changes
• Convert strong (completely dissociated) acids
or bases into weak (slightly dissociated) ones
• Carbonic acid-bicarbonate system
Copyright © 2010 Pearson Education, Inc.
Organic Compounds
• Contain carbon (except CO2 and CO, which
are inorganic)
• Unique to living systems
• Include carbohydrates, lipids, proteins, and
nucleic acids
Copyright © 2010 Pearson Education, Inc.
Organic Compounds
• Many are polymers — chains of similar units (monomers
or building blocks)
• Synthesized by dehydration synthesis
• Broken down by hydrolysis reactions
• How are polymers formed?
• By dehydration synthesis
• What reactions break down polymers into monomers?
• By hydrolysis
• What molecule is essential to this process?
• H2O
Copyright © 2010 Pearson Education, Inc.
(a)
Dehydration synthesis
Monomers are joined by removal of OH from one monomer
and removal of H from the other at the site of bond formation.
Monomer 1
+
Monomer 2
Monomers linked by covalent bond
(b)
Hydrolysis
Monomers are released by the addition of a water molecule, adding OH to one monomer and H to the other.
+
Monomer 1
Monomer 2
Monomers linked by covalent bond
(c)
Example reactions
Dehydration synthesis of sucrose and its breakdown by hydrolysis
Water is
released
+
Water is
consumed
Glucose
Copyright © 2010 Pearson Education, Inc.
Fructose
Sucrose
Figure 2.14
Carbohydrates
• Sugars and starches
• Contain C, H, and O [(CH20)n]
• Three classes
• Monosaccharides
• Disaccharides
• Polysaccharides
Copyright © 2010 Pearson Education, Inc.
Carbohydrates
• Functions
• Major source of cellular fuel (e.g., glucose)
• Structural molecules (e.g., ribose sugar in
RNA)
Copyright © 2010 Pearson Education, Inc.
Monosaccharides
• Simple sugars containing three to seven C
atoms
• (CH20)n n = 3 – 7
• C3H6O3
• C6H12O6
Copyright © 2010 Pearson Education, Inc.
(a) Monosaccharides
Monomers of carbohydrates
Example
Example
Hexose sugars (the hexoses shown
Pentose sugars
here are isomers)
Glucose
Copyright © 2010 Pearson Education, Inc.
Fructose
Galactose
Deoxyribose
Ribose
Figure 2.15a
Disaccharides
• Double sugars
• Too large to pass through cell membranes
Copyright © 2010 Pearson Education, Inc.
(b) Disaccharides
Consist of two linked monosaccharides
Example
Sucrose, maltose, and lactose
(these disaccharides are isomers)
Glucose
Fructose
Sucrose
Copyright © 2010 Pearson Education, Inc.
Glucose
Glucose
Maltose
Galactose Glucose
Lactose
Figure 2.15b
Polysaccharides
• Polymers of simple sugars, e.g., starch and
glycogen
• Not very soluble
Copyright © 2010 Pearson Education, Inc.
• Glycogen is animals main storage form of glucose. Found in high concentrations in the liver and muscles.
• Starch is plants main storage form of glucose.
• Cellulose is a key structural molecule in plants. Not digestible by humans.
(c) Polysaccharides
Long branching chains (polymers) of linked monosaccharides
Example
This polysaccharide is a simplified representation of
glycogen, a polysaccharide formed from glucose units.
Glycogen
Copyright © 2010 Pearson Education, Inc.
Figure 2.15c
Lipids
• Contain C, H, O (less than in carbohydrates),
and sometimes P
• Insoluble in water
• Main types:
• Neutral fats or triglycerides
• Phospholipids
• Steroids
• Eicosanoids
Copyright © 2010 Pearson Education, Inc.
Triglycerides
• Neutral fats — solid fats and liquid oils
• Composed of three fatty acids bonded to a
glycerol molecule
• Main functions
• Energy storage
• Insulation
• Protection
Copyright © 2010 Pearson Education, Inc.
(a) Triglyceride formation
Three fatty acid chains are bound to glycerol by
dehydration synthesis
+
Glycerol
Copyright © 2010 Pearson Education, Inc.
3 fatty acid chains
Triglyceride,
or neutral fat
3 water
molecules
Figure 2.16a
Saturation of Fatty Acids
• Saturated fatty acids
• Single bonds between C atoms; maximum
number of H
• Solid animal fats, e.g., butter
• Unsaturated fatty acids
• One or more double bonds between C atoms
• Reduced number of H atoms
• Plant oils, e.g., olive oil
Copyright © 2010 Pearson Education, Inc.
Phospholipids
• Modified triglycerides:
• Glycerol + two fatty acids and a phosphorus
(P)-containing group
• “Head” and “tail” regions have different
properties (amphipathic)
• Hydrophilic head
• Hydrophobic tail
• Important in cell membrane structure
Copyright © 2010 Pearson Education, Inc.
(b) “Typical” structure of a phospholipid molecule
Two fatty acid chains and a phosphorus-containing group are
attached to the glycerol backbone.
Example
Phosphatidylcholine
Polar
“head”
Nonpolar
“tail”
(schematic
phospholipid)
Phosphoruscontaining
group (polar
“head”)
Copyright © 2010 Pearson Education, Inc.
Glycerol
backbone
2 fatty acid chains
(nonpolar “tail”)
Figure 2.16b
Steroids
• Steroids — interlocking four-ring structure
• Cholesterol, vitamin D, steroid hormones, and
bile salts
Copyright © 2010 Pearson Education, Inc.
Other Lipids in the Body
• Other fat-soluble vitamins
• Vitamins A, D, E, and K
• Lipoproteins
• Transport fats in the blood
Copyright © 2010 Pearson Education, Inc.
Proteins
• Polymers of amino acids (20 types)
• Joined by peptide bonds
• Contain C, H, O, N, and sometimes S and P
Copyright © 2010 Pearson Education, Inc.
Amine
group
Acid
group
(a) Generalized
structure of all
amino acids.
Copyright © 2010 Pearson Education, Inc.
(b) Glycine
is the simplest
amino acid.
(c) Aspartic acid
(an acidic amino acid)
has an acid group
(—COOH) in the
R group.
(d) Lysine
(a basic amino acid)
has an amine group
(–NH2) in the R group.
(e) Cysteine
(a basic amino acid)
has a sulfhydryl (–SH)
group in the R group,
which suggests that
this amino acid is likely
to participate in
intramolecular bonding.
Figure 2.17
Dehydration synthesis:
The acid group of one
amino acid is bonded to
the amine group of the
next, with loss of a water
molecule.
Peptide
bond
+
Amino acid
Amino acid
Dipeptide
Hydrolysis: Peptide
bonds linking amino
acids together are
broken when water is
added to the bond.
Copyright © 2010 Pearson Education, Inc.
Figure 2.18
Amino acid
Amino acid
Amino acid
Amino acid
Amino acid
(a) Primary structure:
The sequence of amino acids forms the polypeptide chain.
Copyright © 2010 Pearson Education, Inc.
Figure 2.19a
a-Helix: The primary chain is coiled
to form a spiral structure, which is
stabilized by hydrogen bonds.
b-Sheet: The primary chain “zig-zags” back
and forth forming a “pleated” sheet. Adjacent
strands are held together by hydrogen bonds.
(b) Secondary structure:
The primary chain forms spirals (a-helices) and sheets (b-sheets).
Copyright © 2010 Pearson Education, Inc.
Figure 2.19b
Tertiary structure of prealbumin
(transthyretin), a protein that
transports the thyroid hormone
thyroxine in serum and cerebrospinal fluid.
(c) Tertiary structure:
Superimposed on secondary structure. a-Helices and/or b-sheets are
folded up to form a compact globular molecule held together by
intramolecular bonds.
Copyright © 2010 Pearson Education, Inc.
Figure 2.19c
Quaternary structure of
a functional prealbumin
molecule. Two identical
prealbumin subunits
join head to tail to form
the dimer.
(d) Quaternary structure:
Two or more polypeptide chains, each with its own tertiary structure,
combine to form a functional protein.
Copyright © 2010 Pearson Education, Inc.
Figure 2.19d
Fibrous and Globular Proteins
• Fibrous (structural) proteins
• Strandlike, water insoluble, and stable
• Examples: keratin, elastin, collagen, and
certain contractile fibers
Copyright © 2010 Pearson Education, Inc.
Fibrous and Globular Proteins
• Globular (functional) proteins
• Compact, spherical, water-soluble and
sensitive to environmental changes
• Specific functional regions (active sites)
• Examples: antibodies, hormones, molecular
chaperones, and enzymes
Copyright © 2010 Pearson Education, Inc.
Protein Denaturation
• Shape change and disruption of active sites
due to environmental changes (e.g.,
decreased pH or increased temperature)
• Reversible in most cases, if normal conditions
are restored
• Irreversible if extreme changes damage the
structure beyond repair (e.g., cooking an egg)
Copyright © 2010 Pearson Education, Inc.
Enzymes
• Biological catalysts
• Lower the activation energy, increase the
speed of a reaction (millions of reactions per
minute!)
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chap
ter2/animation__how_enzymes_work.html
Copyright © 2010 Pearson Education, Inc.
Enzymes
WITHOUT ENZYME
WITH ENZYME
Activation
energy
required
Less activation
energy required
Reactants
Reactants
Product
Copyright © 2010 Pearson Education, Inc.
Product
Figure 2.20
Characteristics of Enzymes
• Often named for the reaction they catalyze;
usually end in -ase (e.g., hydrolases,
oxidases)
• Some functional enzymes (holoenzymes)
consist of:
• Apoenzyme (protein)
• Cofactor (metal ion) or coenzyme (a vitamin)
Copyright © 2010 Pearson Education, Inc.
Substrates (S)
e.g., amino acids
+
Active site
Enzyme (E)
Copyright © 2010 Pearson Education, Inc.
Enzyme-substrate
complex (E-S)
1 Substrates bind
at active site.
Enzyme changes
shape to hold
substrates in
proper position.
Figure 2.21, step 1
Substrates (S)
e.g., amino acids
+
Energy is
absorbed;
bond is
formed.
Water is
released.
H2O
Active site
Enzyme (E)
Copyright © 2010 Pearson Education, Inc.
Enzyme-substrate
complex (E-S)
1 Substrates bind
2
Internal
at active site.
rearrangements
Enzyme changes
leading to
shape to hold
catalysis occur.
substrates in
proper position.
Figure 2.21, step 2
Substrates (S)
e.g., amino acids
+
Product (P)
e.g., dipeptide
Energy is
absorbed;
bond is
formed.
Water is
released.
H2O
Peptide
bond
Active site
Enzyme (E)
Copyright © 2010 Pearson Education, Inc.
Enzyme-substrate
complex (E-S)
Enzyme (E)
1 Substrates bind
2
Internal
Product is
at active site.
rearrangements 3
released. Enzyme
Enzyme changes
leading to
returns to original
shape to hold
catalysis occur.
shape and is
substrates in
available to catalyze
proper position.
another reaction.
Figure 2.21, step 3
Enzymes
• What is an enzyme?
• Protein
• Biologic catalyst
• What is a catalyst
• Substance that speeds up a reaction
• What is Ea?
• Energy of activation
• Enzymes do what to a reaction?
• Lower energy of activation (heat, mechanical, chemical, etc)
• Speeds up rxn
• On what does an enzyme act?
• Its substrate
• Enzymes are __________ for their substrates?
• Specific
Copyright © 2010 Pearson Education, Inc.
Nucleic Acids
• DNA and RNA
• Largest molecules in the body
• Contain C, O, H, N, and P
• Building block = nucleotide, composed of Ncontaining base, a pentose sugar, and a
phosphate group
Copyright © 2010 Pearson Education, Inc.
Deoxyribonucleic Acid (DNA)
• Four bases:
• adenine (A), guanine (G), cytosine (C), and
thymine (T)
• Double-stranded helical molecule in the cell
nucleus
• Provides instructions for protein synthesis
• Replicates before cell division, ensuring
genetic continuity
Copyright © 2010 Pearson Education, Inc.
Phosphate
Sugar:
Deoxyribose
Base:
Adenine (A)
Thymine (T)
Adenine nucleotide
Sugar
Phosphate
Thymine nucleotide
Hydrogen
bond
(a)
Sugar-phosphate
backbone
Deoxyribose
sugar
Phosphate
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
(b)
Copyright © 2010 Pearson Education, Inc.
(c) Computer-generated image of a DNA molecule
Figure 2.22
Ribonucleic Acid (RNA)
• Four bases:
• adenine (A), guanine (G), cytosine (C), and
uracil (U)
• Single-stranded molecule mostly active
outside the nucleus
• Three varieties of RNA carry out the DNA
orders for protein synthesis
• messenger RNA, transfer RNA, and ribosomal
RNA
Copyright © 2010 Pearson Education, Inc.
Adenosine Triphosphate (ATP)
• Adenine-containing RNA nucleotide with two
additional phosphate groups
Copyright © 2010 Pearson Education, Inc.
High-energy phosphate
bonds can be hydrolyzed
to release energy.
Adenine
Phosphate groups
Ribose
Adenosine
Adenosine monophosphate (AMP)
Adenosine diphosphate (ADP)
Adenosine triphosphate (ATP)
Copyright © 2010 Pearson Education, Inc.
Figure 2.23
Function of ATP
• Phosphorylation:
• Terminal phosphates are enzymatically
transferred to and energize other molecules
• Such “primed” molecules perform cellular
work (life processes) using the phosphate
bond energy
Copyright © 2010 Pearson Education, Inc.
Solute
+
Membrane
protein
(a)Transport work: ATP phosphorylates transport
proteins, activating them to transport solutes
(ions, for example) across cell membranes.
+
Relaxed smooth
muscle cell
Contracted smooth
muscle cell
(b) Mechanical work: ATP phosphorylates
contractile proteins in muscle cells so the
cells can shorten.
+
(c)Chemical work: ATP phosphorylates key
reactants, providing energy to drive
energy-absorbing chemical reactions.
Copyright © 2010 Pearson Education, Inc.
Figure 2.24
PowerPoint® Lecture Slides
prepared by
Janice Meeking,
Mount Royal College
CHAPTER
3
Cells: The
Living Units:
Part A
Copyright © 2010 Pearson Education, Inc.
Cell Theory
• The cell is the smallest structural and
functional living unit
• Organismal functions depend on individual
and collective cell functions
• Biochemical activities of cells are dictated by
their specific subcellular structures
• Continuity of life has a cellular basis
Copyright © 2010 Pearson Education, Inc.
Developmental Aspects of Cells
• All cells of the body contain the same DNA but are
not identical
• Chemical signals in the embryo channel cells into
specific developmental pathways by turning some
genes off
• Development of specific and distinctive features in
cells is called cell differentiation
• Elimination of excess, injured, or aged cells occurs
through programmed rapid cell death (apoptosis)
followed by phagocytosis
Copyright © 2010 Pearson Education, Inc.
Theories of Cell Aging
• Wear and tear theory: Little chemical insults
and free radicals have cumulative effects
• Immune system disorders: Autoimmune
responses and progressive weakening of the
immune response
• Genetic theory: Cessation of mitosis and cell
aging are programmed into genes. Telomeres
(strings of nucleotides on the ends of
chromosomes) may determine the number of
times a cell can divide.
Copyright © 2010 Pearson Education, Inc.
Generalized Cell
• All cells have some common structures and
functions
• Human cells have three basic parts:
• Plasma membrane—flexible outer boundary
• Cytoplasm—intracellular fluid containing
organelles
• Nucleus—control center
Copyright © 2010 Pearson Education, Inc.
Plasma Membrane
• Bimolecular layer of lipids and proteins in a
constantly changing fluid mosaic
• Plays a dynamic role in cellular activity
• Separates intracellular fluid (ICF) from
extracellular fluid (ECF)
• Interstitial fluid (IF) = ECF that surrounds cells
Copyright © 2010 Pearson Education, Inc.
Extracellular Materials
• Body fluids (interstitial fluid, blood plasma,
and cerebrospinal fluid)
• Cellular secretions (intestinal and gastric
fluids, saliva, mucus, and serous fluids)
• Extracellular matrix (abundant jellylike mesh
containing proteins and polysaccharides in
contact with cells)
Copyright © 2010 Pearson Education, Inc.
Extracellular fluid
(watery environment)
Polar head of
phospholipid
molecule
Cholesterol
Glycolipid
Glycoprotein
Carbohydrate
of glycocalyx
Outwardfacing
layer of
phospholipids
Integral
proteins
Filament of
cytoskeleton
Peripheral
Bimolecular
Inward-facing
proteins
lipid layer
layer of
containing
phospholipids
Nonpolar
proteins
tail of
phospholipid
Cytoplasm
molecule
(watery environment)
Copyright © 2010 Pearson Education, Inc.
Figure 3.3
Copyright © 2010 Pearson Education, Inc.
Functions of Membrane Proteins
1. Transport
2. Receptors for signal transduction
3. Attachment to cytoskeleton and extracellular
matrix
Copyright © 2010 Pearson Education, Inc.
(a) Transport
A protein (left) that spans the membrane
may provide a hydrophilic channel across
the membrane that is selective for a
particular solute. Some transport proteins
(right) hydrolyze ATP as an energy source
to actively pump substances across the
membrane.
Copyright © 2010 Pearson Education, Inc.
Figure 3.4a
Signal
Receptor
Copyright © 2010 Pearson Education, Inc.
(b) Receptors for signal transduction
A membrane protein exposed to the
outside of the cell may have a binding
site with a specific shape that fits the
shape of a chemical messenger, such
as a hormone. The external signal may
cause a change in shape in the protein
that initiates a chain of chemical
reactions in the cell.
Figure 3.4b
(c) Attachment to the cytoskeleton
and extracellular matrix (ECM)
Elements of the cytoskeleton (cell’s
internal supports) and the extracellular
matrix (fibers and other substances
outside the cell) may be anchored to
membrane proteins, which help maintain
cell shape and fix the location of certain
membrane proteins. Others play a role in
cell movement or bind adjacent cells
together.
Copyright © 2010 Pearson Education, Inc.
Figure 3.4c
Functions of Membrane Proteins
4. Enzymatic activity
5. Intercellular joining
6. Cell-cell recognition
Copyright © 2010 Pearson Education, Inc.
(d) Enzymatic activity
Enzymes
Copyright © 2010 Pearson Education, Inc.
A protein built into the membrane may
be an enzyme with its active site
exposed to substances in the adjacent
solution. In some cases, several
enzymes in a membrane act as a team
that catalyzes sequential steps of a
metabolic pathway as indicated (left to
right) here.
Figure 3.4d
(e) Intercellular joining
Membrane proteins of adjacent cells
may be hooked together in various
kinds of intercellular junctions. Some
membrane proteins (CAMs) of this
group provide temporary binding sites
that guide cell migration and other
cell-to-cell interactions.
CAMs
Copyright © 2010 Pearson Education, Inc.
Figure 3.4e
(f) Cell-cell recognition
Some glycoproteins (proteins bonded
to short chains of sugars) serve as
identification tags that are specifically
recognized by other cells.
Glycoprotein
Copyright © 2010 Pearson Education, Inc.
Figure 3.4f
Membrane Transport
• Plasma membranes are selectively permeable
• Some molecules easily pass through the
membrane; others do not
Copyright © 2010 Pearson Education, Inc.
Types of Membrane Transport
• Passive processes
• No cellular energy (ATP) required
• Substance moves down its concentration
gradient
• Active processes
• Energy (ATP) required
• Occurs only in living cell membranes
Copyright © 2010 Pearson Education, Inc.
Passive Processes
•
What determines whether or not a
substance can passively permeate a
membrane?
1. Lipid solubility of substance
2. Channels of appropriate size
3. Carrier proteins
PLAY
Animation: Membrane Permeability
Copyright © 2010 Pearson Education, Inc.
Passive Processes
• Simple diffusion
• Carrier-mediated facilitated diffusion
• Channel-mediated facilitated diffusion
• Osmosis
Copyright © 2010 Pearson Education, Inc.
Passive Processes: Simple Diffusion
• Nonpolar lipid-soluble (hydrophobic)
substances diffuse directly through the
phospholipid bilayer
PLAY
Animation: Diffusion
Copyright © 2010 Pearson Education, Inc.
Extracellular fluid
Lipidsoluble
solutes
Cytoplasm
(a) Simple diffusion of fat-soluble molecules
directly through the phospholipid bilayer
Copyright © 2010 Pearson Education, Inc.
Figure 3.7a
Passive Processes: Facilitated Diffusion
• Certain lipophobic molecules (e.g., glucose,
amino acids, and ions) use carrier proteins or
channel proteins, both of which:
• Exhibit specificity (selectivity)
• Are saturable; rate is determined by number of
carriers or channels
• Can be regulated in terms of activity and
quantity
Copyright © 2010 Pearson Education, Inc.
Facilitated Diffusion Using Carrier Proteins
• Transmembrane integral proteins transport
specific polar molecules (e.g., sugars and
amino acids)
• Binding of substrate causes shape change in
carrier
Copyright © 2010 Pearson Education, Inc.
Lipid-insoluble
solutes (such as
sugars or amino
acids)
(b) Carrier-mediated facilitated diffusion via a protein
carrier specific for one chemical; binding of substrate
causes shape change in transport protein
Copyright © 2010 Pearson Education, Inc.
Figure 3.7b
Facilitated Diffusion Using Channel
Proteins
• Aqueous channels formed by transmembrane
proteins selectively transport ions or water
• Two types:
• Leakage channels
• Always open
• Gated channels
• Controlled by chemical or electrical signals
Copyright © 2010 Pearson Education, Inc.
Small lipidinsoluble
solutes
(c) Channel-mediated facilitated diffusion
through a channel protein; mostly ions
selected on basis of size and charge
Copyright © 2010 Pearson Education, Inc.
Figure 3.7c
Passive Processes: Osmosis
• Movement of solvent (water) across a
selectively permeable membrane
• Water diffuses through plasma membranes:
• Through the lipid bilayer
• Through water channels called aquaporins
(AQPs)
Copyright © 2010 Pearson Education, Inc.
Water
molecules
Lipid
billayer
Aquaporin
(d) Osmosis, diffusion of a solvent such as
water through a specific channel protein
(aquaporin) or through the lipid bilayer
Copyright © 2010 Pearson Education, Inc.
Figure 3.7d
Passive Processes: Osmosis
• Water concentration is determined by solute
concentration because solute particles
displace water molecules
• Osmolarity: The measure of total
concentration of solute particles
• When solutions of different osmolarity are
separated by a membrane, osmosis occurs
until equilibrium is reached
Copyright © 2010 Pearson Education, Inc.
(a)
Membrane permeable to both solutes and water
Solute and water molecules move down their concentration gradients
in opposite directions. Fluid volume remains the same in both compartments.
Right
Left
compartment:
compartment:
Solution with
Solution with
lower osmolarity greater osmolarity
Both solutions have the
same osmolarity: volume
unchanged
H2O
Solute
Membrane
Copyright © 2010 Pearson Education, Inc.
Solute
molecules
(sugar)
Figure 3.8a
(b)
Membrane permeable to water, impermeable to solutes
Solute molecules are prevented from moving but water moves by osmosis.
Volume increases in the compartment with the higher osmolarity.
Left
compartment
Right
compartment
Both solutions have identical
osmolarity, but volume of the
solution on the right is greater
because only water is
free to move
H2O
Membrane
Copyright © 2010 Pearson Education, Inc.
Solute
molecules
(sugar)
Figure 3.8b
Importance of Osmosis
• When osmosis occurs, water enters or leaves
a cell
• Change in cell volume disrupts cell function
PLAY
Animation: Osmosis
Copyright © 2010 Pearson Education, Inc.
Tonicity
• Tonicity: The ability of a solution to cause a
cell to shrink or swell
• Isotonic: A solution with the same solute
concentration as that of the cytosol
• Hypertonic: A solution having greater solute
concentration than that of the cytosol
• Hypotonic: A solution having lesser solute
concentration than that of the cytosol
Copyright © 2010 Pearson Education, Inc.
(a)
Isotonic solutions
Cells retain their normal size and
shape in isotonic solutions (same
solute/water concentration as inside
cells; water moves in and out).
Copyright © 2010 Pearson Education, Inc.
(b)
Hypertonic solutions
Cells lose water by osmosis and
shrink in a hypertonic solution
(contains a higher concentration
of solutes than are present inside
the cells).
(c)
Hypotonic solutions
Cells take on water by osmosis until
they become bloated and burst (lyse)
in a hypotonic solution (contains a
lower concentration of solutes than
are present in cells).
Figure 3.9
PowerPoint® Lecture Slides
prepared by
Janice Meeking,
Mount Royal College
CHAPTER
3
Cells: The
Living Units:
Part B
Copyright © 2010 Pearson Education, Inc.
Membrane Transport: Active Processes
• Two types of active processes:
• Active transport
• Vesicular transport
• Both use ATP to move solutes across a living
plasma membrane
Copyright © 2010 Pearson Education, Inc.
Active Transport
• Requires carrier proteins (solute pumps)
• Moves solutes against a concentration
gradient
• Types of active transport:
• Primary active transport
• Secondary active transport
Copyright © 2010 Pearson Education, Inc.
Primary Active Transport
• Energy from hydrolysis of ATP causes shape
change in transport protein so that bound
solutes (ions) are “pumped” across the
membrane
Copyright © 2010 Pearson Education, Inc.
Primary Active Transport
• Sodium-potassium pump (Na+-K+ ATPase)
• Located in all plasma membranes
• Involved in primary and secondary active transport of
nutrients and ions
• Maintains electrochemical gradients essential for
functions of muscle and nerve tissues
Copyright © 2010 Pearson Education, Inc.
Extracellular fluid
Na+
Na+-K+ pump
Na+ bound
K+
ATP-binding site
Cytoplasm
1 Cytoplasmic Na+ binds to pump protein.
P
ATP
K+ released
ADP
6 K+ is released from the pump protein
and Na+ sites are ready to bind Na+ again.
The cycle repeats.
2
Binding of Na+ promotes
phosphorylation of the protein by ATP.
Na+ released
K+ bound
P
Pi
K+
5 K+ binding triggers release of the
phosphate. Pump protein returns to its
original conformation.
3 Phosphorylation causes the protein to
change shape, expelling Na+ to the outside.
P
4 Extracellular K+ binds to pump protein.
Copyright © 2010 Pearson Education, Inc.
Figure 3.10
Extracellular fluid
Na+
Na+-K+ pump
ATP-binding site
K+
Cytoplasm
1 Cytoplasmic Na+ binds to pump protein.
Copyright © 2010 Pearson Education, Inc.
Figure 3.10 step 1
Na+ bound
P
ATP
ADP
2
Binding of Na+ promotes
phosphorylation of the protein by ATP.
Copyright © 2010 Pearson Education, Inc.
Figure 3.10 step 2
Na+ released
P
3 Phosphorylation causes the protein to
change shape, expelling Na+ to the outside.
Copyright © 2010 Pearson Education, Inc.
Figure 3.10 step 3
K+
P
4 Extracellular K+ binds to pump protein.
Copyright © 2010 Pearson Education, Inc.
Figure 3.10 step 4
K+ bound
Pi
5 K+ binding triggers release of the
phosphate. Pump protein returns to its
original conformation.
Copyright © 2010 Pearson Education, Inc.
Figure 3.10 step 5
K+ released
6 K+ is released from the pump protein
and Na+ sites are ready to bind Na+ again.
The cycle repeats.
Copyright © 2010 Pearson Education, Inc.
Figure 3.10 step 6
Secondary Active Transport
• Depends on an ion gradient created by
primary active transport
• Energy stored in ionic gradients is used
indirectly to drive transport of other solutes
Copyright © 2010 Pearson Education, Inc.
Secondary Active Transport
• Cotransport—always transports more than one
substance at a time
• Symport system: Two substances transported in same
direction
• Antiport system: Two substances transported in
opposite directions
Copyright © 2010 Pearson Education, Inc.
Extracellular fluid
Na+-K+
pump
Cytoplasm
1 The ATP-driven Na+-K+ pump
stores energy by creating a
steep concentration gradient for
Na+ entry into the cell.
Copyright © 2010 Pearson Education, Inc.
Figure 3.11 step 1
Extracellular fluid
Glucose
Na+-K+
pump
Na+-glucose
symport
transporter
loading
glucose from
ECF
Na+-glucose
symport transporter
releasing glucose
into the cytoplasm
Cytoplasm
1 The ATP-driven Na+-K+ pump
stores energy by creating a
steep concentration gradient for
Na+ entry into the cell.
Copyright © 2010 Pearson Education, Inc.
2
As Na+ diffuses back across the
membrane through a membrane
cotransporter protein, it drives glucose
against its concentration gradient
into the cell. (ECF = extracellular fluid)
Figure 3.11 step 2
Vesicular Transport
• Transport of large particles, macromolecules,
and fluids across plasma membranes
• Requires cellular energy (e.g., ATP)
Copyright © 2010 Pearson Education, Inc.
Vesicular Transport
• Functions:
• Exocytosis—transport out of cell
• Endocytosis—transport into cell
• Transcytosis—transport into, across, and then
out of cell
• Substance (vesicular) trafficking—transport
from one area or organelle in cell to another
Copyright © 2010 Pearson Education, Inc.