Chapter 5
The Structure and Function of Macromolecules


Concept #1


Most macromolecules are polymers
-polymers are large molecules consisting of many
identical or similar building blocks.
-subunits are called monomers
-monomers are connected through condensation
reactions (also called dehydration synthesis)
-polymers are broken down by hydrolysis
-a limitless variety of polymers can be built from a
small set of monomers.


Concept #2
Organisms use carbohydrates for fuel and building material
-Carbohydrates include sugars and their polymers
monosaccharides = single sugars
disaccharides = double sugars
polysaccharides = many sugars (a few hundred to a few
thousand)
-Storage polysaccharides
starch (1-4 linkage) plants
glycogen (1-4 linkage) animals
-Structural polysaccharides
cellulose (plants)
chitin (animals)


Concept #3
Lipids are mostly hydrophobic molecules with diverse functions
-the structure of fat consists of one molecule of glycerol and
chains of fatty acids (16-18 carbons long)
-saturated and unsaturated fats relates to the presence of
double bonds in the carbon chains of fatty acids
-phospholipids are structurally related to fats but only have
two fatty acids important in the structure of cell membranes
-steroids are lipids composed of rings of carbons
different steroids have different functional groups
which define their functions.
Examples: cholesterol


Concept #4
Proteins are the molecular tools for most cellular functions
-proteins account for 50% of dry weight of most cells
- 8 important functions
*structural proteins - support
ex. collagen
*storage proteins
ex. ovalbumin (egg white)
*transport proteins
ex. hemoglobin
* hormonal proteins
ex. insulin
*receptor proteins
built into membrane of nerve cells
react to neurotransmitters
* contractile proteins
ex. myosin (in muscles)
* defensive proteins
antibodies
* enzymatic proteins
ex. amylase


Concept #5
A polypeptide is a polymer of amino acids connected in a specific
sequence.
-amino acids
organic chemicals containing both carboxyl and amine
functional groups
- 20 total amino acids
held together in a chain when the carboxyl group on one
is adjacent to the amine group on another.
The result is a peptide bond.
-N-C-N-C-N-C-N-C-N-C = peptide backbone


Concept #6
A proteins’s function depends on its specific conformation.
“Polypeptide chain” is not the same as “protein”.
A protein’s specific conformation determines how it works.
The function of a protein depends on its ability to recognize
and bind to some other molecule.

There are 4 levels of protein structure:

*Primary structure - the unique sequence of amino acids.
*Secondary structure - coils and folds of the peptide chain
which are the result of hydrogen bonds at regular intervals
along the peptide backbone.
*Tertiary structure - irregular contortions from bonding
between side chains of various amino acids. Hydrophobic
interaction is one such factor.Conformation of a protein can be strengthened by disulfide
bonds.
*Quaternary structure - the overall protein structure that
results from the aggregation os two or more polypeptide
chains.
Any environmental factor that causes a protein to unravel and
become biologically inactive is said to have denatured the
protein.

 


Concept #7


Nucleic acids store and transmit hereditary information.
The primary structure of a protein is coded for by a unit of
inheritance called a gene (a section of a nucleic acid chain).
Two types of nucleic acids: DNA (deoxyribonucleic acid)
RNA (ribonucleic acid)
* Nucleic acids are polymers made of monomers called
nucleotides
2 groups of nucleotides -purines (A&G) and pyrimidines
(C&T)
Inheritance is based on the precise replication of DNA which is
a double helix.
Evolution occurs because the replication of DNA is not perfect.