Chapter 5: The Structure and Function of Macromolecules
Polymer: large molecule consisting of many identical or similar subunits connected together.
Monomer: subunit molecules of a polymer.
Macromolecule: Large organic polymer. There are four classes of macromolecules: carbohydrates, lipids,
proteins and nucleic acid.
The structural variation of macromolecules leads to diversity.
There are only 40-50 monomers needed to make a macromolecule, which leads to unity among them.
Polymerization reactions: linking 2 or more small molecules to form larger molecules with repeating subunits.
Condensation synthesis (dehydration synthesis): Polymerization rxn where for every 2 monomers covalently
bonded together, the removal of a water molecule occurs.
1.
2.
3.
4.
one monomer loses -H, the other loses -OH.
this rxn requires energy
this rxn requires catalysts or enzymes for regulation.
an example of this is photosynthesis.
Hydrolysis: Rxn where covalent bonds between monomers are broken by adding a water molecule.
1.
2.
3.
I.
one monomer gains -H, the other gains -OH.
this rxn releases energy.
an example of this is digestion or respiration
Carbohydrates:
A.
Monosaccharides: single sugar molecule made of only C, H, O in ratio of CH2O
1.
2.
3.
4.
5.
6.
major nutrients for cells especially glucose.
made by autotrophs (plants) in photosynthesis.
storage of energy in chemical bonds.
joined to form disaccharides/ polysaccharides.
Characteristics: -OH attached to each C except one with =O. There are aldehyde or
ketone sugars.
Size of C skeleton is 3-7 carbons usually.
a.
b.
Triose= glyceraldehyde
pentose= ribose
Chapter 5: The Structure and Function of Macromolecules
7.
8.
9.
B.
c.
hexose= glucose
sugars usually end in -ose.
stereoisomers exist around an asymmetric carbon in hexose (glucose = C6H12O6). This
affects the molecular shape an
sugars form rings in aqueous solutions.
Dissacharides: two monosaccharides joined by a covalent bond (called glycosidic linkage).
1.
2.
Dehydration synthesis joins monosaccharides.
ie: glucose + glucose  maltose (beer sugar)
glucose + galactose  lactose (milk sugar)
glucose + fructose  sucrose (table sugar &
transport sugar in plants)
C.
3.
Polysaccharides: made of a few 100 or 1000 monomers of sugar.
1.
2.
uses dehydration synthesis.
important energy storage (starch & glycogen).
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II.

a. starch (glucose polymer) found in plants.
b. amylose (simplest form) is unbranched.
c. amylopectin (branched form) more common.
d. is digestible (wheat, corn, rice, potato)
e. glycogen (glucose polymer) found in animals
f. more highly branched
g. stored in muscle and liver cells
h. cellulose (linear unbranched polymer of D-glucose)
i. part of plant cell walls forming fibrils
j. different likages than starch
k. different properties than starch
l. not digestible by humans
m. is digestible by bacteria, protozoa, fungi
n. chitin (polymer of amino sugars
o. forms exoskeleton of arthropods and cell walls of fungi.
 Lipids: compounds that are insoluble in water and dissolve in nonpolar solvents (ether, chloroform,
benzene). Lipids are fats, phospholipids and steroids.
A.
Fats:
1.
2.
3.
4.
5.
composed of 3 fatty acids & a glycerol (triacylglycerol
COOH group @ one end, hydrocarbon tail @ other end
hydrocarbon chains are nonpolar & hydrophobic
ester linkage bonds glycerol & 3 fatty acids.
functions:
a.
energy storage (2x better than starch)
Chapter 5: The Structure and Function of Macromolecules
b. compact storage (starch is bulky)
c. cushions vital animal organs
d. insulates against heat loss
Saturated fats
no double bonds
max. # of H atoms
solid @ room temp
animal fat
B.
C.
Unsaturated fats
double bonds present
C=C kinks lacking H atoms
liquid @ room temp
plant fat (vegetable oil)
phospholipids:
1.
2.
3.
4.
composed of one glycerol & 2 fatty acids plus a phosphate group
tails are hydrophobic, heads are hydrophilic
major components of cell membranes forming lipid bilayers
Steriods:
1.
2.
lipids with 4 fused carbon rings
cholesterol is a precursor to hormones and present in the cell membrane
III.
Proteins: polymers of amino acids linked by peptide bonds. They compose 50% of the dry weight of
organisms.
A.
B.
Functions of Proteins:
1.
2.
3.
4.
5.
6.
7.
8.
structural report (collagen, elastin, keratin)
storage of amino acids
transport (hemoglobin)
signaling (insulin- a chemical messenger)
cellular response to chemical stimuli (receptors)
movement (contractile protein: actin, myosin (in muscle), & dynein (cilia and sperm))
defense (antibodies)
catalysts in rxns. (enzymes)
Amino acids: the building blocks of proteins
1.
2.
3.
4.
composed of asymmetric carbon bonded to:
a. one H atom
b. carboxyl group
c. amino group
d. R group (side chain determines chem. And phys. properties of the molecule)
20 amino acids make up proteins
some are polar/nonpolar
form polypeptides by bonding -NH2 group of one amino acid to the -COOH of the next
amino acid
Protein Conformation and Structure:
Chapter 5: The Structure and Function of Macromolecules
Proteins are 3D @ normal temperatures (37 C) enabling them to recognize and bind to another
molecule. This is extremely important!!
The Levels of protein structure:
1.
2.
3.
4.
5.
primary (1) structure: the sequence of amino acids. This is determined by genes. A slight
change can affect the structure and function as in sickle cell anemia.
secondary (2) structure: regular, repeated folding of a protein’s peptide backbone which
stabilizes H bonds. This 2 structure contains an -helices (helix coil of amino acids stabilized by
H bonds) or -sheets (sheet of anti-parallel chains folded and stabilized by H bonds).
tertiary (3) structure: Three dimensional irregular contortions due to H-bonding between polar
side groups (R-chains) and ionic bonds between charged side chains. Hydrophobic regions
interact and stay away from water as well. Sulfur components of proteins form disulfide bridges.
quaternary (4) structure: interaction among several polypeptide chains within a single protein.
Example: collegen has 3 helical components supercoiled into a triple helix for strength.
Hemoglobin has 4 subunits to bond to 4 O2 molecules.
Denaturation: excessive heat, pH or chemicals that disrupt H, ionic and sulfide bonds of a
protein causing it to unravel or lose conformation. This can disrupt biological activity.
IV. Nucleic acids:
A.
B.
DNA:
1.
2.
3.
4.
Can replicate itself
passed from one cell line to the next
found in nucleus of eukaryotic cells
makes up genes which make proteins
RNA:
1.
functions in actual synthesis of proteins coded for by DNA.
C. DNA  RNA  proteins: the central dogma of biology.
D. nucleotides:
1. monomer of nucleic acid polymers
2. composed of 5 C sugar, nitrogenous base and phosphate group.
Ribose is in RNA,
Deoxyribose in DNA.
3.
E.
4.
nitrogenous bases: inside helix, linked by H bonds
a.
b.
purines: A, G
pyrimidines: T, C, U (RNA)
Sugar and phosphates form backbone of DNA or RNA molecule.
Evolution:
1.
similar organisms have similar DNA and protein structures. This is measurable and is
used to create the new 3 kingdom system.