Chapter 3-Amino Acids and Peptides

Question 1

How many amino acids are found in proteins?

Answer 1

20

Question 2

General structure of an amino acid consists of:

Answer 2

amino group and carboxyl group that are both bonded to the alpha carbon

Question 3

amino group

Answer 3

NH2 group

Question 4

carboxyl group

Answer 4

-COOH functional group that dissociates to give -COO minus and H ion

Question 5

sterochemistry

Answer 5

branch of chemistry that deals with the three d shape of molecules

Question 6

side chain group

Answer 6

portion of amino acid that determines its identity

Question 7

chiral

Answer 7

non-superimposable mirror images

Question 8

what is the amino acid that lacks a chiral center (aka achiral)

Answer 8

glycine

Question 9

stereoisomers

Answer 9

molecules that differ from each other only in their configuration (3D shape); aka optical isomers

Question 10

L- and D-amino acids

Answer 10

amino acids whose stereochemistry is the same as the stereochemical standards L- and D-glyceraldehyde

L- amino on left
D- amino on right

Question 11

What form are the amino acids in proteins?

Answer 11

L

Question 12

List the non polar hydrophobic amino acids.

Answer 12

Methionine 
Tryptophan
Phenylalanine
Isoleucine 
Leucine 
Proline
Alanine
Valine 
Glycine

Question 13

List the polar uncharged amino acids.

Answer 13

Threonine 
Cysteine 
Tyrosine
Serine
Asparagine
Glutamine

Question 14

List the acidic amino acids.

Answer 14

aspartic acid

glutamic acid

Question 15

List the basic amino acids.

Answer 15

Histidine
Lysine
Arginine

Question 16

alipathic

Answer 16

absence of benzene ring or related structure

Question 17

proline is often called

Answer 17

imino acid

Question 18

is an indole ring aromatic?

Answer 18

yes

Question 19

which is a stronger acid: phenol or alipathic alcohol

Answer 19

phenol

Question 20

what forms disulfides

Answer 20

thiol groups in cysteine

Question 21

disulfide bridges are formed in what type of reaction

Answer 21

oxidation reduction

Question 22

when a carboxyl group loses a proton what forms

Answer 22

carboxylate anion

Question 23

hydroxyproline and hydroxylysine are found in

Answer 23

collagen

Question 24

thyroxine

Answer 24

• differs from tyrosine in that it has an extra iodine containing aromatic group on the side chain
• produced by thyroid gland only
• formed by post-translational modification of modification of tyrosine residues in thyroglobulin

Question 25

zwitterion

Answer 25

electrically neutral (equal positive and negative charges)

Question 26

neutral amino acids do not exist in the form....

Answer 26

without charged groups

Question 27

what does a titration curve indicate?

Answer 27

the reaction of each function group with hydrogen ion

Question 28

diprotic

Answer 28

two protonated groups

Question 29

electrophoresis

Answer 29

method for separating molecules on the basis of ratio charge to size

Question 30

isoelectric pH (pI)

Answer 30

- a pH at which the molecule has no net charge | - molecule will not migrate an electric field

Question 31

pI equation

Answer 31

=pKa1 + pKa2 _________ 2

Question 32

what type of bond links amino acids (very general)

Answer 32

covalent

Question 33

residues

Answer 33

portions of monomer units included in polymers after splitting out water between the linked monomers

Question 34

peptide bond

Answer 34

amide bond between amino acids in a protein steps: - two amino acids - water removal - formation of CO-NH bond

Question 35

peptides

Answer 35

molecules formed by linking two to several dozen amino acids by amide bonds

Question 36

amide

Answer 36

name for a compound formed by the reaction between an amino group and a carboxyl group

Question 37

polypeptide chain

Answer 37

backbone of protein; formed by linking amino acids by peptide bonds

Question 38

the _____ of the peptide bond lead to a planar group

Answer 38

resonance structures (because of the double bond in the resonance structure there really is no significant rotation)

Question 39

direction of a peptide chain

Answer 39

N---->C

Question 40

peptides can play a role in?

Answer 40

hormones

Question 41

non polar side chains contain:

Answer 41

mostly alipathic or aromatic hydrocarbons

Question 42

amino acids that have electrically neutral polar side chains containing of

Answer 42

electronegative atoms: sulfure, oxygen & nitrogen

Question 43

which two amino acids have carboxyl groups in their side chains?

Answer 43

glutamic acid and asparatic acid