Ch. 3.2 Molecules of Life: Macromolecules

Carbohydrates: carbon, hydrogen, and oxygen. 1:2:1 Monomer = monosaccharide (simple sugar) (CH 2 O) n where n = A six-carbon monosaccharide would be C 6 H 12 O 6. 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