Download Zoology – The Chemical Basis of Animal Life

Zoology – The Chemical Basis of Animal Life
I. Attributes of Living Organisms
A. It would seem a simple thing to define life, but it actually isn’t. Many of the
characteristics of life can be found in nonliving things.
1. It is easier to describe the characteristics of life.
B. Composition and Structure
1. The hierarchy of life. An ascending order of complexity:
a. Cells – the smallest unit of life (e.g. a heart muscle cell)
b. Tissues – cells that have a similar appearance and are organized
together to perform a common function (e.g. the heart muscle)
c. Organs – 2 or more tissues that combine to perform a common
function (e.g. the heart – including muscle, epithelial, nervous, and
connective tissues)
d. Organ systems – 2 or more organs that share a common function (e.g.
the cardiovascular system – the heart & its blood vessels)
e. Organism – there are 11 organ systems in a human being.
C. Growth – changes in size and shape a plant undergoes from origin to adult
1. Growth usually results from the production of new cells.
2. Cell lineages differentiate and become adult tissues.
3. Growth is influenced both by genetics and the environment
D. Reproduction - Organisms produce offspring, which resemble the parents
1. Reproduction can occur sexually or asexually
E. Response to Environmental Stimuli – adapting to their environment
F. Homeostasis – the tendency of an organism or a cell to regulate its internal
conditions, usually by a system of feedback controls, despite outside changing
conditions.
G. Metabolism– all of the biochemical reactions taking place in an organism.
1. Respiration – releasing the energy of carbohydrate (C6H12O6) bonds to
produce carbon dioxide (CO2) and water (H2O). This energy is caught and
used to form ATP (the energy currency of cells).
H. Complexity of Organization
1. Living organisms are made up of far more complex molecules than nonliving
matter.
2. These complex molecules are called macromolecules and include…
a. Carbohydrates which are chains of simple sugars
b. Lipids, which include triglycerides and cholesterol
c. Proteins, which in turn are made up of chains of amino acids
d. Nucleic acids which include DNA and RNA
II. Chemical Basis of Life
A. The Elements – units of matter
1. Matter occupies space, has mass, and is composed of elements.
2. Matter exists in 4 states: solid, liquid, gas, and plasma
B. The Atom: Smallest stable subdivision of an element
1. Atoms have a nucleus where you find the protons and neutrons.
a. Each proton has a positive charge.
2. Circling around the nucleus are electrons.
a. Each electron has a negative charge.
b. The electrons occupy electron (or valence) shells.
c. The shells can only hold a specific number of electrons.
3. Atoms and molecules try to be as electrically stable as possible. Two ways
they can achieve this stability include…
a. Remaining electrically neutral (i.e. the number of electrons must
equal the number of protons). Any atom or molecule with a charge is
an ion.
1) If an atom or molecule has more electrons than protons, it will
become negative.
a) This is an anion. Important anions in biology are
chlorine (Cl-) and bicarbonate (HCO3-).
2) If an atom or molecule has more protons than electrons, it will
become positive.
a) This is a cation. Important cations in biology are
potassium (K+), sodium (Na+), and calcium (Ca++).
b. Filling their outermost electron shells (known as valence shells).
C. Elements can combine to form molecules through chemical bonds.
1. There are 3 types of chemical bonds:
a. Ionic bonds – A bond in which one atom loses an electron to form a
positive ion and the other atom gains an electron to form a negative
ion. (An example is table salt, Na+Cl-)
b. Covalent bonds - a chemical bond that involves sharing a pair of
electrons between atoms in a molecule. (An example is the
phosphoanhydride bonds in ATP which store potential energy.)
c. Hydrogen bonds – A hydrogen atom of one molecule is attracted to
an electronegative atom (especially a nitrogen, oxygen, or fluorine
atom) of another molecule. (An example is the hydrogen bonds
holding complementary base pairs together in DNA.)
D. Acids, Bases, Buffers, and Salts
1. The concentration of ions is
commonly expressed in terms of the pH
scale.
a.The pH scale is measured from
0 to 14.
1) Pure water pH = 7
(neutral)
2) Anything with a pH below
7 is acidic
3) Anything with a pH above
7 is alkaline (basic)
b. The pH scale is a negative
logarithmic scale with a base
number of ten.
1) Thus, a solution with a pH
of 2 is 10 times more
acidic than a solution with
pH of 3
2. Acids - release hydrogen (H+) ions when dissolved in water
3. Bases - release negatively charged hydroxyl (OH-) ions when dissolved in
water
4. Buffers - Substances that enable solutions to resist pH changes when an acid
or base is added.
c. Buffers are very important in helping organisms maintain a relatively
constant pH.
5. Salts – usually crystalline solid compounds that formed, or can be regarded
to have formed, from an acid and a base by replacement of one or more
hydrogen atoms in the acid molecules by positive ions from the base
d. e.g. Table salt, Na+ClIII. The Molecules of Animals
A.
The chemicals that enter into, or are produced by, metabolic reactions are
divided into 2 large groups:
1.
Inorganic molecules – lack carbon atoms
2.
Organic molecules – contain carbon atoms – we are carbon-based life
forms. The important groups of organic molecules in animals include:
a.
Carbohydrates
b.
Lipids
c.
Proteins
d.
Nucleotides
e.
Nucleic acids
B. Living organisms are made up of far more complex molecules than nonliving
matter. Polymers (macromolecules) are formed when 2 or more small monomers
bond together.
1. Bonding between monomers occurs by dehydration synthesis and is
controlled by enzymes.
a.Dehydration synthesis – removal of water in the formation of a bond
1) e.g. Amino acids joining to become a polypeptide (protein).
2) e.g. Monosaccharides joining to form a polysaccharide (starch).
2. Bonds between monomers are broken by hydrolysis
a.Hydrolysis – occurs when a hydrogen becomes attached to one
monomer and a hydroxyl group to the other.
1) e.g. Table salt dissolving in water
2) e.g. ATP  ADP + Pi
b. Energy is released
C. Carbohydrates – animal’s major source of energy, the most abundant organic
compounds in nature. Most animals use mitochondria to release energy stored in
carbon-hydrogen bonds of sugar and starches. This process is called cellular
respiraiton.
1. Carbohydrates are composed of C, H, and O in a ratio of [CH2O]n or 1:2:1
a.e.g. Glucose is C6H12O6. Deoxyribose is C5H10O5.
b. Sugars end with the suffix –ose.
2. There are 3 basic kinds of carbohydrates: monosaccharides, disaccharides,
and polysaccharides.
3. Monosaccharides – simple sugars with backbones of 3 to 7 carbon atoms
a.e.g. Glucose and fructose
4. Disaccharides – formed when two monosaccharides bond together by
dehydration synthesis.
a.e.g. Sucrose (table sugar) = glucose + fructose;
maltose (malt sugar - building block of starch) = glucose + glucose;
lactose (milk sugar) = glucose + galactose
5. Polysaccharides – formed when several to many monosaccharides bond
together.
SUGAR IS ENERGY. WITHOUT ENERGY, CELLS DIE. PROBLEM: SUGARS
CRYSTALLIZE & POP CELLS. CELLS DIE. POLYSACCHARIDES ARE CHAINS OF
SUGARS THAT CANNOT CRYSTALLIZE. ANIMALS STORE SUGARS IN A CHAIN
CALLED GLYCOGEN.
D. Lipids - fatty or oily substances that are insoluble in water. The most common lipids
in animals are fats.
1. Typically store twice as much energy as carbohydrates
a.Important as long term energy reserves and as structural components
of cells. e.g. chloesterol
2. Contain carbon, hydrogen, and oxygen, but have proportionately less oxygen
than carbohydrates
3. Fats and oils are produced from one molecule of glycerol & 3 fatty acid
molecules.
a.Most fatty acids consist of a chain with 16 to 18 carbon atoms.
1) Saturated fats - with hydrogen atoms attached to every
available bonding site on carbons of fatty acid, and with no
double bonds (Solid at room temperature)
2) Unsaturated fats - with fewer hydrogen atoms and with at
least one double bond between carbon atoms (Liquid at room
temperature)
4. Phospholipids – constructed like fats, but one of the fatty acids is usually
replaced by a phosphate group
a.Important components of plasma membranes & other cellular
membranes
E.Proteins, polypeptides, and amino acids
1. Proteins are structural material, energy sources, and regulate chemical
reactions (as enzymes) in cells.
2. Proteins are long chains of amino acids.
a.The amino acids are joined by peptide bonds. Hence, proteins are also
referred to as polypeptides.
b. Each amino acid is composed of:
1) Amino group (-NH2)
2) Carboxyl group (-COOH)
3) R group - can vary from one hydrogen to a
complex ring
a) R groups are distinctive for each of the 20 amino acids
found in living cells.
3. Proteins have complex structures.
a.Primary Structure - Sequence of amino acids fastened together by
peptide bonds
b. Secondary Structure - Formation of an alpha helix or of pleated
sheets due to hydrogen bonding between amino acids
c. Tertiary Structure - Further coiling or
folding maintained by interactions
among R groups (3 dimensional shape)
d. Quaternary Structure - Association
of more than one polypeptide to form a
single functional protein
4. Enzymes – mostly large, complex proteins
that function as biological catalysts under
specific conditions. (A special type of RNA can
also function as an enzyme.)
a.Enzymes do the following:
1) Break bonds and allow new
bonds to form, facilitating
chemical reactions
2) Speed up reaction times
(similar to stirring or heating
sugar to get it to dissolve faster
in tea.)
3) Lower the energy of
activation (the minimal amount of energy needed to cause
molecules to react with one another)
b. Enzymes temporarily bond with a substrate.
1) Substrates fit into the active sites of enzymes.
a) The reaction occurs rapidly & products are released
c. Enzymes remain unchanged in the reaction & usually go on to catalyze
further reactions.
d. Enzyme names end in -ase, e.g., maltase, lactase
F. Nucleic Acids – very large, complex polymers that are vital to internal cellular
communication and cell functioning.
1. There are two types:
a.DNA – deoxyribonucleic acid
b. RNA – ribonucleic acid
2. DNA consists of a double helix of
repeating subunits of nucleotides.
a.Nucleotides are composed of a
nitrogenous base, a five-carbon
sugar and a phosphate.
3. Nucleotides include one of 4
different nitrogenous bases. The bases
pair with hydrogen bonds.
a.Cytosine always pairs with
Guanine.
b. Adenine always pairs with Thymine.
4. DNA forms a double helix.
5. DNA contains genes that code the information that determines the form and
structure of an organism.
a.DNA can be passed on from generation to generation without change.
6. RNA occurs as a single strand and is involved in protein synthesis.
a.The sugar is ribose (as opposed to deoxyribose in DNA)
b. The nitrogenous base Uracil replaces the Thymine found in DNA