Chapter 5: Structure and Function of Large Biological Molecules

Macromolecules

Very large molecules or polymers consisting of many smaller structural units linked together or monomers

monomer

a small building-block molecule

Carbohydrates, proteins, and nucleic acids are all…

polymers

Polymer

Large molecule composed of many similar or identical building blocks linked by covalent bonds

How polymers are built

Monomers join through covalent bonds to form polymers

Dehydration reaction (builds polymers)

removes a water molecule, forming a new bond

Hydrolysis reaction (breaks polymers)

Adds water, breaks a covalent bond

Four major classes of biological molecules

Carbohydrates, lipids, proteins, nucleic acids

Why lipids are not true macromolecules

do not have repeating monomers, their components (like glycerol and fatty acids) are not linked in long chains

Carbohydrates

sugar and polymers of sugars; function as fuels and building materials

monomers of carbohydrates

monosaccharides

what monosaccharides contain

one carbonyl group, multiple hydroxyl groups

Glycosidic linkage

covalent bond that joins sugars

structural isomers

glucose and fructose

enantiomers

glucose and galactose

disccharide

two monosaccharides attached by a glycosidic linkage

polysacccharides

macromolecules made from ~100 to ~2000+ monosaccharides joined by glycosidic linkages

example of polysacccharides

glycogen

starch

found in plant tubers and grains

starch monomer and glycosidic bond

α-glucose, α-1,4

starch branching and function

unbranched or branched helical structure, used as an energy storage marcomolecule for plants

Glycogen monomer and glycosidic bond

α-glucose, α-1,6

Glycogen branching and function

branched helical structure, energy storage macromolecule for humans

cellulose

found in the cell wall of plants

cellulose monomer and bond

β-glucose, hydrogen bond

cellulose branching and function

straight, unbranched, structural marcomolecule for plant cell walls, humans do not have enzymes that digest

cellulose is referred to as..

insoluble fiber

monosaccharide

one sugar ring

disaccharide

two sugar rings

polysaccharide

three sugar rings

lipids

a diverse group of hydrophobic compounds

fats (triacylglycerol/triglyceride)

long-term energy storage

fats

Phospholipids

cell membranes

Phospholipids

steroids

hormones, membrane structure

steroids

ester linkage

covalent bond formed between carboxyl group (–COOH) of a fatty acid and the hydroxyl group (–OH) of glycerol

Each fatty acid has a…

carboxyl group (–COOH)

Glycerol has…

three hydroxyl (–OH) groups

A dehydration reaction occurs between…

–OH of glycerol and the –COOH of a fatty acid

dehydration reaction between –OH of glycerol and the –COOH of a fatty acid results in

an ester linkage and releases water

After three ester linkages form, the result is

a triglyceride (fat)

saturated fatty acid

longer shelf life, no double bonds, solid at room temp, increases heart disease (diet high in saturated fats)

unsaturated fats

cis-double bonds (kink) in carbon skeleton, liquid at room temp, healthier

trans fats

artificial double bonds, solid-like, very harmful

unsaturated cis fatty acid to saturated fatty acid

hydrogenated

hydrogenated

adds hydrogen, removes double bond, increases shelf life

side effect of hydrogenation

produces trans fats

Why trans fats are dangerous

Increase LDL (“bad” cholesterol), decrease HDL (“good” cholesterol), raise cardiovascular disease risk

saturated fat

unsaturated fat

trans fat

Phospholipid

Steroid

peptide bond

covalently links carbonxyl group of one AA to amine group of another AA