Met 2: Special AAs

Question 1

What special AA’s can be found in collagen?

Answer 1

Hydroxyproline

Hydroxylysine

Question 2

What is one function of hydroxyproline and hydroxylysine?

Answer 2

Hydroxyproline and hydroxylysine create the cross-links between chains in a collagen triple helix

Gives collagen its strength

Question 3

What cofactor is required for hydroxyproline and hydroxylysine synthesis?

What is the disease with deficiency?

What major molecule is affected?

Answer 3

Vitamin C needed to make hydroxyproline and hydroxylysine

Scurvy is insufficient Vitamin C

Collagen is most affected

Question 4

What type of collagen is defective in Ehler’s Danlos?
Osteogenesis Imperfecta?

Answer 4

E-D: Collagen Type 5

OI: Collagen Type 1

Question 5

Vit K is an important cofactor for what AA modification?

Answer 5

Vitamin K needed to carboxylate glutamate

Question 6

Where can carboxy-Glu residues be found?

Answer 6

Carboxy-Glu important in clotting factors

That’s why Vit K (cofactor) deficiency causes bleeding

Question 7

What are the two amino acids with sulfur groups?

Are either essential?

Answer 7

Methionine (essential)

Cysteine (not essential; can be made from Met)

Question 8

Disulfide bonds are 2 ______ residues

in ______ (ox/reduced) state.

Answer 8

Disulfide bonds are 2 cysteine residues in an oxidized state.

Question 9

Name the intermediates involved in cysteine synthesis

Answer 9

Methionine -> SAM -> homocysteine -> cysteine

Question 10

Describe homocysteine recycling

Answer 10

Homocysteine can be converted back to methionine

• Requires B12 and THF

Question 11

Describe the conversion of Methionine into SAM

Answer 11

Methionine -> SAM

• by SAM synthase
• Requires ATP

Question 12

What 2 additional inputs are required for homocysteine to be converted into cysteine?

Answer 12

B6

Serine

Question 13

Name 2 methyl donors

Answer 13

THF

SAM

Question 14

What is the function of THF?

SAM?

Answer 14

• THF acts as methyl donor during synthesis of nitrogenous bases
• SAM acts as methyl donor during synthesis of epi and some nucleotides

Question 15

MOA of methotrexate

Answer 15

Inhibits conversion of folate into THF by Dihydrofolate reductase

This prevents synthesis of nitrogenous bases using THF in cancer cells

Question 16

How does Glutathione deal with ROS?

Answer 16

• Glutathione contains a cysteine that can interconvert between oxidized and reduced form
  
  • acts as a redox buffer

Question 17

Name 3 functions of glutathione

Answer 17

Fight ROS

Help proteins form proper disulfide bonds

Keep RBC Fe in ferrous 2+ state (mops up oxidizing species)

Question 18

What is T4 made from?

Answer 18

Tyrosine

Question 19

Name the 3 aromatic AA’s

Answer 19

Trp, Phe, Tyr

Question 20

Trp can be converted to _________________ to be used for energy.

OR, Trp can be converted to these 3 molecules: ______, __________, __________.

Answer 20

Trp can be converted to acetyl-coA or pyruvate to be used for energy.

OR, Trp can be converted to these 3 signaling molecules: serotonin, niacin, melatonin.

Question 21

What enzymes and cofactor converts Trp into serotonin?

Answer 21

Trp -> serotonin

by aromatic decarboxylase

requires THB

Question 22

What are two possible fates for Phe?

Answer 22

1. Phe can be degraded for energy
2. Phe can be converted to Tyrosine
   
   • This requires THB

Question 23

Name 3 derivatives of tyrosine

Answer 23

Melanin (pigment)

Norepi & Dopamine (catecholamines)

I’m tired of pigs cat-calling me.