Amino Acids, Peptides, Proteins

Question 1

amino acids

Answer 1

four groups attached to a central (α) carbon; an amino group, a carboxylic acid group, a hydrogen atom, and an R group 20 appear in the proteins of eukaryotic organisms stereochemistry is L in eukaryotes, D can exist in prokaryotes hydrophobic - w/ long alkyl chains hydrophilic - w/ charges

Question 2

R group

Answer 2

determines chemistry and function of that amino acid

Question 3

cysteine

Answer 3

polar side chain only amino acid with (R) configuration

Question 4

glycine

Answer 4

non-polar, non-aromatic side chain only amino acid that is not chiral has a H atom as its R group

Question 5

non-polar, non-aromatic amino acids

Answer 5

glycine, alanine, valine, leucine, isoleucine, methionine, proline

Question 6

aromatic

Answer 6

tryptophan, phenylalanine, tyrosine

Question 7

polar

Answer 7

serine, threonine, asparagine, glutamine, cysteine

Question 8

negatively charged (acidic)

Answer 8

aspartate, glutamate

Question 9

positively charged (basic)

Answer 9

lysine, arginine, histidine

Question 10

amphoteric

Answer 10

can accept or donate protons amino acids

Question 11

pKa

Answer 11

pH at which half of the species is deprotonated [HA] = [A-]

Question 12

zwitterion

Answer 12

neutral amino acid that exists at pH near the pI of the amino acid

Question 13

isoelectric point (pI)

Answer 13

calculated by averaging the two pKa values of amino acid without a charged side chain

Question 14

formation/breaking of peptide bond

Answer 14

condensation/hydration reaction–one molecule of water released 1. nucleophilic amino group of one amino acid attacks the electrophilic carbonyl group of another amino acid 2. amide bonds are rigid due to resonance hydrolysis reaction–one molecule of water added

Question 15

primary structure

Answer 15

linear sequence of amino acids in a peptide and is stabilized by peptide bonds

Question 16

secondary structure

Answer 16

local structure of neighboring amino acids, and is stabilized by hydrogen bonding between amino groups and nonadjacent carboxyl groups α-helices, ß-pleated sheets

Question 17

α-helices

Answer 17

secondary structure of protein clockwise coils around a central axis

Question 18

ß-pleated sheets

Answer 18

secondary structure of protein rippled strands that can be parallel or antiparallel

Question 19

proline

Answer 19

non-polar, non-aromatic side chain can interrupt secondary structure because of its rigid cyclic structure

Question 20

tertiary structure

Answer 20

three-dimensional shape of a single polypeptide chain, and is stabilized by hydrophobic interactions, acid-base interactions (salt bridges), hydrogen bonding, and disulfide bonds

Question 21

hydrophobic interactions

Answer 21

tertiary structure of protein push hydrophobic R groups to the interior of a protein which increases entropy of the surrounding water molecules and creates a negative Gibbs free energy

Question 22

disulfide bonds

Answer 22

occur when two cysteine molecules are oxidized and create a covalent bond to form cystine

Question 23

quaternary structure

Answer 23

interaction between peptides in proteins that contain multiple subunits

Question 24

prosthetic group

Answer 24

attached molecule of a conjugated protein may be a metal ion, vitamin, lipid, carbohydrate, or nucleic acid

Question 25

denaturation

Answer 25

both heat and increasing solute concentration can lead to loss of three-dimensional protein structure

Question 26

alanine

Answer 26

non-polar, non-aromatic side chain

Question 27

valine

Answer 27

non-polar, non-aromatic side chain

Question 28

leucine

Answer 28

non-polar, non-aromatic side chain

Question 29

isoleucine

Answer 29

non-polar, non-aromatic side chain

Question 30

methionine

Answer 30

non-polar, non-aromatic side chain

Question 31

tryptophan

Answer 31

aromatic side chain

Question 32

phenylalanine

Answer 32

aromatic side chain

Question 33

tyrosine

Answer 33

aromatic side chain

Question 34

serine

Answer 34

polar side chain

Question 35

threonine

Answer 35

polar side chain

Question 36

asparagine

Answer 36

polar side chain

Question 37

glutamine

Answer 37

polar side chain

Question 38

aspartic acid (aspartate)

Answer 38

negatively charged side chain (acidic)

Question 39

glutamic acid (glutamate)

Answer 39

negatively charged side chain (acidic)

Question 40

arginine

Answer 40

positively charged side chain (basic)

Question 41

lysine

Answer 41

positively charged side chain (basic)

Question 42

histidine

Answer 42

positively charged side chain (basic)