Ch. 3.2 Molecules of Life: Macromolecules

Carbohydrates: carbon, hydrogen, and oxygen. 1:2:1

• Monomer = monosaccharide (simple sugar) (CH2O)n where n = 3 - 8. A six-carbon monosaccharide would be C6H12O6. Most common examples:– glucose: main source of energy in cells– fructose: fruit sugar and the sweetest– galactose: milk

• Because all of the simple sugars (say, 6C sugars) have the same chemical formula but different structural formulas (built differently) they have slightly different chemical properties and are called isomers.

• Disaccharides: double sugar

• Polysaccharides: several to hundreds of simple sugars put together.– glycogen: animal sugar storage (short-term) in

liver and muscles for quick use.– starch: plant sugar storage– cellulose: support

Proteins: carbon, hydrogen, oxygen, and nitrogen

• Monomer = amino acids (20 different) works like our alphabet to create variation.– Each A.A. has an amino group and a carboxyl

group. They differ in their side chains.• dipeptides and polypeptides and created by

condensation reactions. see “Large Carbon Molecules” above. The resulting bond is a peptide bond.

• Enzymes: are biological catalysts– most are protein– Induced-fit model (fig 3-9; p.57)• substrate• active site• optimal conditions• lose shape/lose function

Lipids: do not dissolve in water (polar) so they are nonpolar. “Like dissolves like”.

• Lipids store more energy per gram than other macromolecules.

• Fatty acids: long, straight chains of carbon and hydrogen with a functional group at one end.

• If the carbons have all single bonds then it is saturated with hydrogen: a saturated fat.

• If the carbons have any double bonds then it is unsaturated fat.

• Triglycerides: glycerol + 3 fatty acid chains. – If it contains saturated fatty acids then it is

saturated fat like meat fat or butter (animal fat). – Unsaturated triglycerides are oil (plant fat).

• Phospholipids: glycerol + 2 fatty acid chains + phosphate group.– phosphate head is polar like water– lipid tails are nonpolar and repel water.– phospholipids bilayer see p. 59

• Waxes: structural lipid: long fatty acid chain + long alcohol chain. Protects plants from drying out and ear wax for protection from microorganisms.

• Steroids: four fused carbon rings + various functional groups attached to the rings.– cholesterol is starting point to make testosterone,

estradiol (sex hormones)– needed for nerve cells– cell membrane component

Nucleic Acids: DNA, RNA

• Monomer: nucleotides (phosphate, sugar, base)

• DNA: heredity, cell control• RNA: messenger, transport, organization.• see fig 3-12, p.60