Ch 1: Amino Acids, Peptides, Proteins

Question 1

amino acids have 4 groups attached to the central alpha carbon

Answer 1

amino group
carboxylic acid group
hydrogen atom
R group

Question 2

___ amino acids appear in the proteins of eukaryotic organisms

Answer 2

20

Question 3

stereochemistry of alpha carbon for all aa in euk is

Answer 3

L

Question 4

D-amino acids exist in

Answer 4

prokaryotes

Question 5

all aa except ___ have (S) configuration

Answer 5

cysteine

Question 6

all aa except ___ are chiral

Answer 6

glycine

Question 7

nonpolar, nonaromatic

Answer 7

glycine
alanine
valine
leucine
isoleucine
methionine
proline

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Question 8

Aromatic aa

Answer 8

Phenylalanine
Tyrosine
Tryptophan
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Question 9

Polar aa

Answer 9

Serine
Glutamine
Threonine
Asparagine
Cysteine

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Question 10

Positively Charged - basic aa

Answer 10

Lysine
Arginine
Histidine

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Question 11

Negatively Charged - acidic aa

Answer 11

Aspartate
Glutamate

DE

Question 12

pKa of a group is the pH at which half of the species is ____ ; HA = A-

Answer 12

deprotonated

Question 13

aa exist in different forms at diff pH

low acidic pH, aa ___
pH near pI of aa ___
high alkaline pH, aa __

Answer 13

fully protonated

neutral zwitterion

fully deprotonated

Question 14

isoelectric point (pI) of an aa w/o charged group can be calculated by

Answer 14

averaging the 2 pKa values

Question 15

aa can be titrated:

titration curve nearly flat ____

nearly vertical when at the ____

Answer 15

at pKa values of the aa

pI of the aa

Question 16

aa with charged side group can find pI by calculating

Answer 16

the average of two pKas of protonation/deprotonation of zwitterion

Question 17

aa w/o charged sides have pI around

Answer 17

6

Question 18

aa acidic have pI around

Answer 18

well below 6

Question 19

aa basic have pI

Answer 19

well above 6

Question 20

dipeptides have __ aa residues
tripeptides have __
oligopeptides ___
polypeptides __

Answer 20

2
3
less than 20
more than 20

Question 21

forming a peptide bond is a

Answer 21

condensation or dehydration reaction

releasing one molecule of water

Question 22

amide bonds are rigid due to

Answer 22

resonance

Question 23

breaking a peptide bond is a

Answer 23

hydrolysis reaction

Question 24

primary structure

Answer 24

linear seq of aa in a peptide and is stabilized by peptide bonds

Question 25

secondary structure

Answer 25

local structure of neighboring aa, and is stabilized by h bonding between amino groups and nonadjacent carboxyl groups

Question 26

2nd struc: alpha helices

Answer 26

clockwise coils around a central axis

Question 27

2nd struc: beta pleated sheets

Answer 27

rippled strands that can be parallel or anti-parallel

Question 28

proline can interrupt ___ because of rigid ___

Answer 28

2nd structure | cyclic structure

Question 29

tertiary structure

Answer 29

3D shape of a single polypeptide chain and is stabilized by hydrophobic interactions, acid-base interactions (salt bridges), hydrogen bonding, and disulfide bonds

Question 30

(3) hydrophobic interactions push hydrophobic R group to interior of protein which

Answer 30

inc entropy of the surrounding water molecules and creates a neg gibbs free energy

Question 31

disulfide bonds (3)

Answer 31

occur when 2 cysteine molecules are oxidized and create a covalent bond to form cystine

Question 32

quaternary structure is the interaction

Answer 32

between peptides in proteins that contain multiple subunits

Question 33

can lead to denaturation of 3-D protein structure

Answer 33

heat and increasing solute conc

Question 34

proteins w covalently attached molecules are ___ and the attached molecule is a ____ that may be _______

Answer 34

conjugated proteins prosthetic group metal ion, vitamin, lipid, carbohydrate, nucleic acid