Biochemistry

Question 1

Chiral

Answer 1

AKA stereogenic center Has four different groups attached to carbon Optically active

Question 2

Nonpolar amino acids

Answer 2

Glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptophan

Question 3

Polar amino acids

Answer 3

Tyrosine, serine, threonine, cysteine, asparagine, glutamine

Question 4

Acidic amino acids

Answer 4

Aspartate and glutamate

Question 5

Basic amino acids

Answer 5

Lysine, arginine, histidine

Question 6

Catalytic triad

Answer 6

Found in chymotrypsin The histidine residue in its active site removes a proton from the -COOH group in an aspartic acid residue, which can then deprotonate a serine residue.

Question 7

Amphoteric species

Answer 7

Can either accept a proton or donate a proton

Question 8

pKa

Answer 8

The pH at which, on average, half of the molecules of that species are deprotonated. [HA]=[A-] If pH < pKa then majority protonated If pH > pKa then majority deprotonated

Question 9

Amino acid deprotonation

Answer 9

pKa1 = pKa for carboxyl group = 2 pKa2 = usually amino group = 9-10

Question 10

Zwitterions

Answer 10

At pH 7.4, you will have zwitterion COO- and NH3+ Overall charge is neutral

Question 11

Isoelectric point (pI)

Answer 11

The pH at which the molecule is electrically neutral.

(pka1 + pKa2)/2 = pI of neutral aa

average of two lowest pKa’s for acidic aa

average of two highest pKa’s for basic aa

Question 12

Oligopeptide

Answer 12

A relatively small peptide, up to about 20 residues

Question 13

Peptide bond

Answer 13

Joins residues in peptides together. Forms between the COO- of one group and the NH3+ of another. Forms through dehydration or condensation reaction. Has partial double bond character from resonance.

Question 14

Hydrolytic enzymes

Answer 14

Catalyze hydrolysis of peptides. Trypsin and chymotrypsin. Break apart amide bond by adding a hydrogen atom to the amide nitrogen and an OH group to the carbonyl carbon.

Question 15

Question 16

Lactose

Answer 16

Question 17

Sucrose

Answer 17

Question 18

Glycogen

Question 19

Starch

Question 20

Cellulose

Answer 20

Question 21

Secondary Structure

Answer 21

H-bonds between amino hydrogens and carboxyl oxygen atoms of backbone.

Alpha helixes and Beta sheets

Question 22

Tertiary structure

Answer 22

Interaction of side chains (hydrophobic interactions, VDW forces, ionic bonds, and H bonds)

Question 23

Competitive Inhibition

Answer 23

Inhibitor competes with substrate to bind to active site

Can be overcome by increasing the concentration of substrate

Vmax does not change

Km increases

Question 24

Noncompetitive Inhibition

Answer 24

Inhibitor binds to allosteric site that causes conformational change of active site and prevents substrate from binding. Can bind to enzyme or enzyme-substrate complex.

Km does not change

Vmax decreases

Question 25

Uncompetitive Inhibition

Answer 25

Inhibitor binds to enzyme-substrate complex (can’t bind to enzyme alone) and prevents substrate from being released. Allosteric site is opened only after substrate binds to enzyme Km is lowered Vmax is lowered

Question 26

Acetylation

Answer 26

Euchromatin DNA less tightly bound Chromatin is more active

Question 27

Methylation

Answer 27

heterochromatin