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3-2: Carbs
4 MAJOR CLASSES OF BIOMOLECULES
1. CARBOHYDRATES = sugars and their polymers

Used for ENERGY and CARBON sources

3 Types:
a) Monosaccharides = monomers of sugars in which C, H, and O occur in the ratio
of 1:2:1  (CH2O)n
Ex. C6H12O6
o Major E SOURCE for cells (GLUCOSE is the most common)
o Store energy in their chemical bonds
o Carbon skeletons are raw materials for other organic molecules
o Characteristics:

An –OH group is attached to each C except one, which is doublebonded to an oxygen

Size of the carbon skeleton varies from 3 to 7 carbons

Spatial arrangement around asymmetric carbons may vary

In aqueous solutions, many monosaccharides form rings
b) Disaccharide = a double sugar that is made of 2 monosaccharides monomers
joined by a glycosidic linkage
o Ex. Sucrose = glucose + fructose
c) Polysaccharides = macromolecules that are polymers of a few hundred or
thousand monosaccharides
o Formed by dehydration reactions
o Tend to be linear in shape
o Two Types:

STORAGE Polysaccharides (for energy and carbon)

Starch = storage polysaccharide for glucose in plants
o Most animals have digestive enzymes to break down
starch

Glycogen = storage polysaccharide for glucose in animals
o Stored in the liver and muscle of humans other
vertebrates
o Insulin triggers its creation from glucose molecules,
glucagon causes its breakdown into glucoses

STRUCTURAL Polysaccharides = for cell/body support

Cellulose – structural polysaccharide in plant cells walls
o Is the most abundant organic molecule on Earth
o Cannot be digested by most animals, since they lack the
enzyme that can hydrolyze the β-linkage

Peptidoglycan in bacteria

Chitin – structural polysaccharide of an amino sugar (with a Ncontaining group that replaces a hydroxyl)
o Found in exoskeletons of arthropods and cells walls of
Fungi
2. LIPIDS = diverse group of organic compounds that are insoluble in water
A) Fats and Oils (a.k.a. Triglycerides) = Macromolecules made of:

Glycerol – a 3-C alcohol with three –OH groups attached

3 Fatty Acids
o Hydrocarbon chain has a long C-skeleton usually with an even number
of carbon atoms (most with 16-18 carbons)
o Nonpolar C-H bonds make the chain hydrophobic and not water
soluble
o Attached to the glycerol by an ester linkage = bond formed between a
–OH group and a –COOH group

Variation is in the fatty acid composition
o Fatty acids may all be the same or they may differ
o Fatty acids may vary in length
o Fatty acids may vary in the number and location of double bonds
between C’s
SATURATED FAT
NO double bonds between C’s in fatty acid
UNSATURATED FAT
One or more double bonds…
tails - Bonded to maximum # of H’s
(“saturated”)
Tail kinks at each C=C, so molecules do not
Straight chains
pack closely
Solids at room temperature
Liquids at room temperature
Animal fats (ex. Lard and Butter)
Plant fats (ex. Olive oil)

Functions of Fats:
o Energy storage
o LONG-TERM fuel reservoir

Gram-for-gram, fats store 4x more energy than glycogen
o Cushion vital organs
o Protects against heat loss (ex. Blubber)
B) Phospholipids = glycerol + 2 fatty acids + one phosphate group
o 3rd C of glycerol is joined to a negatively charged phosphate group

Often the phosphate will have additional side groups attached to it
o Shows ambivalent behavior toward water.
o Tails are hydrophobic, but phosphate “head” is polar and hydrophilic
o Are major constituents of cell membranes!!!

Form the Lipid Bilayer
C) Steroids = lipids which have 4 fused C-rings with various functional groups attached
o “Honeycomb, honeycomb, honeycomb, house”
o Cholesterol is an important steroid

Precursor to sex hormones, bile acids, etc.

Common component of animal cell membranes

Can contribute to atherosclerosis
D) Waxes = long-chain fatty acids bonded with long-chain alcohols
o High melting points at normal temperatures (solid)
o Hydrophobic  repel water and resist degradation
o Form a protective cuticle on the outsides of plants, preventing water loss