Amino Acids & Peptides (Module 1 Lecture 2)

Question 1

Name the Non-Polar Amino Acids.

Answer 1

1. Glycine (H side group)
2. Alanine (methyl side group)
3. Valine (isopropyl side group)
4. Leucine (tert-butyl side group)
5. Isoleucine (methyl propyl side group)
6. Proline (3 carbon, 1 nitrogen ring side group)
7. Methionine (2 C’s, 1S, 1 C side group)
8. Cysteine (CH2 and SH at end) ?

Question 2

Name the Aromatic Amino Acids.

Answer 2

1. Phenylalanine (benzyl side group)
2. Tyrosine (phenol size group)
3. Tryptophan (double ring side group)

Question 3

Name the Charged Amino Acids.

Answer 3

1. Aspartate - acidic, net negative charge (C & carboxylic acid side group)
2. Glutamate - acidic, net negative charge (2C’s & carboxylic acid side group)
3. Lysine - basic, net positive charge (4C’s & amino side group)
4. Arginine - basic, net positive charge (3C’s and 3 amino groups surrounding last C)
5. Histidine (sometimes) - protonated form increases at acidic pH

Question 4

Name the Polar Amino Acids.

Answer 4

1. Serine (methyl and alcohol side group)
2. Threonine (chiral C with H, CH3, and OH side group)
3. Tyrosine (phenol aromatic side group)
4. Asparagine (CH3 and C with =O and amine side group)
5. Glutamine (2 CHs’s and C with =O and amine side group)

Question 5

What Amino Acid Forms Disulfide Bridges?

Answer 5

Cysteine

Question 6

How is a Disulfide Bridge Formed?

Answer 6

Via oxidation of Cysteine’s sulfhydryl (SH) group to form -S-S-, which releases 2H+’s and 2e-‘s.

Question 7

What is Vasopressin?

Answer 7

A small peptide hormone made of nine amino acids with a disulfide bond between the two cysteine residues. The hormone stimulates water reabsorption in the kidney to prevent dehydration.

Question 8

What is Insulin?

Answer 8

A large polypeptide hormone that has two disulfide bridges holding each polypeptide chain together and holding the A chain to itself. The hormone stimulates entry of glucose through the cell membrane and helps cell growth.