Amino Acids (Zhao L1)

Question 0

What gives each amino acid its unique properties?

Answer 0

The side chain.

Question 1

Amino acids are ______ at physiologic pH.

Answer 1

dipolar

NH3+
COO-

Question 2

What is the bond between two adjacent amino acids in a polypeptide?

Answer 2

peptide bond

between the O on the N-terminal aa and the N on the C-terminal aa

Question 3

What 5 major classes of aa’s are there?

Answer 3

1. Nonpolar - aliphatic
2. Polar - uncharged
3. Negatively charged (acidic)
4. Positively charged (basic)
5. Aromatic

Question 4

Which aa. can form disulfide bridges within a polypeptide?

Answer 4

Cysteine

-CH2-SH

Question 5

What are the aromatic amino acids?

Answer 5

Phenylalanine
Tyrosine
Tryptophan

Question 6

What are the negatively charged amino acids?

Answer 6

Aspartate

Glutamate

Question 7

What are the positively charged amino acids?

Answer 7

Lysine
Arginine
Histidine

Question 8

What are the polar uncharged amino acids?

Answer 8

Serine
Threonine
Cysteine
Asparganine
Glutamine

Question 9

What are the nonpolar amino acids?

Answer 9

Glycine
Proline
Alanine
Valine
Leucine
Isoleucine
Methionine

Question 10

What aa. modification is vitamin K essential for?

Answer 10

gamma-carboxylation of glutamate —> carboxyglutamate

Question 11

What aa. modification is Scurvy related to?

Answer 11

Hydroxyproline

Question 12

What tissue type is hydroxyproline found in?

Answer 12

Collagen

promotes collagen stability
allows “sharp twisting” in the collagen helix

Question 13

What vitamin is required for hydroxylation of proline?

Answer 13

Vitamin C

Question 14

Lack of vitamin C can lead to…

Answer 14

lack of hydroxyproline necessary for collagen

—> scurvy

Question 15

In what common physiological response pathway is carboxyglutamate found?

Answer 15

The clotting cascade

Question 16

What vitamin is required to induce the gamma-carboxylation of clotting factors (at their glutamate residues)?

Answer 16

Vitamin K

Question 17

What is the pI of a protein?

Answer 17

The pH where the protein will have no net charge.

Question 18

Where is Histidine often found and why?

Answer 18

pKa of His is 6.5
very close to physiological pH
can switch from neutral to + charged easily under phys. pH

Is often found in the active sites of enzymes

Question 19

When pH<pKa which form of the aa dominates?

Answer 19

The protonated form.

Think about what low pH means…high [H+]
Think of pKa as the aa’s tolerance level for resisting protonation.

Question 20

Henderson-Hasselbach eqn

Answer 20

pKa = pH + log[Acid]/[Base]

pH = -log[H+]
pKa = -log( [Base] / [Acid][H+] )

standard prod/react business

Question 21

Name three aa’s that are typically glycosylated (cell surface proteins) and what type of glycosylation linkage each has.

Answer 21

1. Ser: O-linked
2. Thr: O-linked
3. Asn: N-linked

Question 22

Give an example of the clinical relevance of glycosylation of cell surface proteins.

Answer 22

CDG: Congenital disorder of glycosylation
abnormal N-linked glycosylation pathway (Asparagine)

Giant range of symptoms and severity

Question 23

Give an example of a protein that has a lot of post-translational acetylation and methylation.

Answer 23

Histones.

Question 24

What does vorinostat do?

Answer 24

Inhibits histone deacetylases (HDAC)

Used in cancer treatments

Question 25

Where can you generally phosphorylate / dephosphorylate amino acids post-translation?
Which aa’s receive this post-transl. modification?

Answer 25

On -OH groups

Ser -CH2-OH
Thr -CH(OH)-CH3
Tyr -C-(Ph)-OH

Question 26

What does Ubiquination of a protein signal?

Answer 26

Marks the protein to be sent to the proteosome to be degraded.

Question 27

What does Velcade do?

Answer 27

Inhibits ubiquintination and the proteosome.

Used to treat Multiple Myeloma