Chapter 3

Question 1

All amino acids have a chiral carbon and are stereoisomers except:

Answer 1

glycine

Question 2

Although amino acids are stereoisomers, only…

Answer 2

L stereoisomers are found in proteins

Question 3

all amino acids have:

Answer 3

• carboxyl group
• amino group
• alpha carbon
• R group (side chain)

Question 4

Which amino acid is often found at turns of polypeptides?

Answer 4

proline, in combination with glycine

Question 5

Which two amino acids have a sulphur group within its side chain?

Answer 5

Methionine and Cysteine

Question 6

The non-polar amino acids are…

Answer 6

hydrophobic and buries in the core of a protein

Question 7

Aromatics have…

Answer 7

ring groups

Question 8

Biggest amino acid

Answer 8

Tryptophan

Question 9

Smallest amino acid

Answer 9

glycine

Question 10

Phosphorylation

Answer 10

introduces a phosphate group to a compound; central mechanism to regulate protein function

Question 11

Post Translational Modification

Answer 11

• an often reversible modification where phosphoric groups are added by kinases to specific hydroxyl-group containing amino acids
• changes property –> activity

Question 12

How can post translational modification be reversed?

Answer 12

adding phosphatases (removes phosphate group)

Question 13

What amino acids can undergo phosphorylation?

Answer 13

Tyrosine
Serine
Threonine

Question 14

How are disulfide bonds formed?

Answer 14

form through the oxidation of sulfhydryl groups of two Cysteine residues (covalent linkage)

Question 15

What do disulfude bonds do?

Answer 15

help stabilize the structures of protein

Question 16

Which amino acids ALWAYS have a positive charge?

Answer 16

Lysine and Arginine

Question 17

Which amino acid has a potential to carry a positive charge?

Answer 17

Histidine

Question 18

Glutamate is responsible for….

Answer 18

umami taste

Question 19

Aspartate and Glutamate have….. in their side chains

Answer 19

carboxyl groups

Question 20

amphoteric

Answer 20

can act as both weak acids and bases (amino acids for ex.)

Question 21

zwitterion

Answer 21

one group has a positive charge, one groups has a negative

Question 22

diprotic

Answer 22

• has 2 groups that accept and donate protons (carboxyl and amino groups)
• 2 buffering regions

Question 23

triprotic

Answer 23

3 buffering regions

Question 24

triprotic amino acids

Answer 24

• have ionizable groups

- Lys, Arg, His, Asp, Glu, Cys, Tyr

Question 25

at pKa…

Answer 25

there is equal numbers of protonated and unprotonated forms (where that groups changes protonation state)

Question 26

pH below pKa

Answer 26

protonated form dominates (HA, weak acid)

Question 27

pH above the pKa

Answer 27

unprotonated form dominates (A-, conjugate base)

Question 28

isoelectric point (pI)

Answer 28

the average of the pKa’s on either side where the net charge is zero

Question 29

pI equation

Answer 29

pI = (pKa1 + pKa2)/2

Question 30

Diprotic amino acids all have similar….

Answer 30

titration curves and isoelectric points

Question 31

peptide bond

Answer 31

covalently links amino acids

Question 32

How do peptide bonds form

Answer 32

by condensation/dehydration reactions (loss of water molecule) between carboxyl of one amino acid and the amino group of another.

Question 33

How to break peptide bonds

Answer 33

just add water!!

Question 34

Map this shit

Answer 34

amino acids —> peptide chains —>proteins

Question 35

N-terminus

Answer 35

amino

Question 36

C-terminus

Answer 36

carboxyl

Question 37

What direction do you read amino acid chain sequences?

Answer 37

N-terminus to C-terminus

Question 38

Which functional groups have a charge?

Answer 38

• carboxyl
• phosphoryl
• phosphoanhydride

Question 39

Which functional groups have 2 R groups?

Answer 39

• carbonyl (ketone)

- disulfide