Mcat Biochemistry Chapter 1

Front 1

stereochemistry for alpha-carbon in chiral amino acids in eukaryotes

Back 1

L

Front 2

stereochemistry for prokaryotic amino acids

Back 2

either L or D

Front 3

configuration of all chiral amino acids is _____, except for ______

Back 3

S, cysteine

Front 4

which amino acid is non-chiral

Back 4

glycine (hydrogen atom as R group)

Front 5

nonpolar, nonaromatic amino acids (7)

Back 5

glycine, alanine, valine, leucine, isoleucine, methioning, proline

Front 6

aromatic amino acids (3)

Back 6

tryptophan, phenylalanine, tyrosine

Front 7

negatively charged (acidic) amino acids (2)

Back 7

glutamic acid, aspartic acid (glutamate, aspartate)

Front 8

positively charged (basic) amino acids (3)

Back 8

lysine, arginine, histidine

Front 9

polar amino acids (5)

Back 9

glutamine, asparagine, cysteine, threonine, serine

Front 10

amphoteric

Back 10

they can accept or donate protons. amino acids are amphoteric

Front 11

pKa

Back 11

pH at which half of the species is deprotonated

[HA] = [A-]

Front 12

state of amino acid in low pH (acidic):

at pH near pI of AA:

at high (alkaline) pH:

Back 12

fully protonated

neutral (zwitterion)

fully deprotonated

Front 13

zwitterion

Back 13

neutral amino acid, at pH near the pI of the amino acid

Front 14

isoelectric point (pI)

Back 14

average the pKa values of the amine and the carboxylic acid (positive and negative) of the AA

Front 15

titration curve at pHa values of AA

Back 15

nearly flat

Front 16

titration curve at pI of AA

Back 16

nearly vertical

Front 17

how to calculate pKa of charged side-chain amino acids

Back 17

averaging the two pKa values that correspond to protonation and deprotonation of the zwitterion

Front 18

pI of:

1. AA without charged side chains

2. acidic AA

3. basic AA

Back 18

1. around 6

2. well below 6

3. well above 6

Front 19

dipeptides

Back 19

two amino acid residues

Front 20

tripeptides

Back 20

3 amino acid residues

Front 21

oligopeptides

Back 21

few amino acid residues (<20)

Front 22

polypeptides

Back 22

many amino acid residues (>20)

Front 23

forming a peptide bond is:

Back 23

a condensation or dehydration reaction (releasing one molecule of water)

Front 24

how is a peptide bond formed

Back 24

nucleophilic amino group of one amino acid attacks the electrophilic carbonyl group of another amino acid

Front 25

breaking a peptide bond is a _____ reaction

Back 25

hydrolysis

Front 26

why are amide bonds rigid

Back 26

resonance

Front 27

primary protein structure

Back 27

linear sequence of amino acids in a peptide, stabilized by peptide bonds

Front 28

secondary protein structure

Back 28

local structure of neighbouring amino acids, stabilized by hydrogen bonding between amino groups and nonadjacent carboxyl groups