protein degradation

Question 1

List amino acids which are ONLY ketogenic

Answer 1

leucine (leu) and lysine (lys)

Question 2

List aa that are both ketogenic and glucogenic

Answer 2

Tyrosine (Tyr), Isoleucine (Iso), Phenylalanine (Phe), Tryptophan (Trp)

Question 3

Which amino acids make up collagen

Answer 3

hydroxyproline and hydroxylysine add strength. Also contains glycin, proline.

Question 4

function of hydroxyproline in collagen and how its made

Answer 4

Is used in collagen for H-bonding that increases collagen strength. Prolyl hydroxylase converts Pro to Hyp (requires Vit C)

Question 5

Function of hydroxylysine in collagen and how its made

Answer 5

Used in collagen for interchain cross-links btw Hyl and lysine. Lysyl hydroxylase converts Lys to Hyl (requires Vit C)

Question 6

Scurvy

Answer 6

Reduced strength of collagen fibrils du to Lack of vitamin C - Prolyl hydroxylase and Lysyl hydroxylase rely on Vit-C (ascorbate) as coenzyme to post-translationally modify proline and lysine to be used in collagen.

Question 7

signs of scurvy

Answer 7

reduced vascular endothelium > hemorrhages > loss of RBCs > swollen gums, bruising, anemia. Pale skin, loss of tetch, sunken eyes

Question 8

What is gamma-carboxyglutamate

Answer 8

G-glytamyl carboxylase converts Glu to Gla (gamma-carboxyglutamate), which is Vit-K dependent. GLA is used to target proteins to membranes via Ca chelation

Question 9

function of ornithine

Answer 9

Post-translationally modified aa used in urea cycle

Question 10

Which aa does prothrombin rely on

Answer 10

g-carboxyglutamate- used to target membranes

Question 11

List methods for protein degradation

Answer 11

1. ubiquitin-proteasome system. 2. lysosomal path. 3. proteases in GI tract

Question 12

Describe ubiquitin degradation

Answer 12

ATP dependent process that is used to cross-link protein to ubiquitin. Ubiquitinated proteins are then sequestered to the proteasome for degradation

Question 13

describe lysosomal degradation

Answer 13

ATP independent process that is used primarily to “engulf” extracellular proteins (or even live pathogens). Proteins are broken down by acid hydrolysis and other lysosomal proteins (i.e. cathepsins).

Question 14

pepsin digestion

Answer 14

hydrolyzes N-terminal side of aromatic residues (Phe,Trp,Tyr)

Question 15

trypsin digestion

Answer 15

hydrolyzes C-terminal side of basic aminod acids (Arg,Lys)

Question 16

chymotrypsin digestion

Answer 16

hydrolyzes C-terminal side of aromatic & some hydrophobic residues (Phe,Trp,Tyr & Leu,Met).

Question 17

carboxypeptidase A digestion

Answer 17

Hydrolyzes C-terminal of hydrophobic amino acids. (Ala, Ile, Leu, Val).

Question 18

carboxypeptidase B digestion

Answer 18

Hydrolyzes C-terminal of basic residues amino acids (Arg, Lys).

Question 19

describe transamination

Answer 19

Aminotransferases: enzymes that transfer amino groups from aa to alpha-keto acid and back. These enzymes “Move Nitrogen”. Keq ~ 1

Question 20

List two aminotransferases

Answer 20

• Alanine aminotransferase (Alt) • Aspartate aminotransferase (Ast)

Question 21

aminotransferases coenzyme

Answer 21

Pyridoxal phosphate (PLP)- Vit B6 derivative. Holds amino group during its transfer. In resting state, PLP forms schiff base with aminotransferase to hold PLP in resting enzyme

Question 22

reaction catalyzed by ALT

Answer 22

alanine + alpha ketoglutarate< > pyruvate + glutamate

Question 23

reaction catalyzed by AST

Answer 23

aspartate + alpha ketoglutarate < > oxaloacetate + glutamate

Question 24

goal of urea cycle

Answer 24

get rid of ammonia by forming less toxic compounds

Question 25

Overall rxn of urea cycle

Answer 25

3ATP + HCO3- + NH4+ + aspartate > 2ADP + AMP + 2Pi + PPi + fumarate + urea

Question 26

Where does urea cycle occur

Answer 26

mitochondria and cytosol

Question 27

which compound is recycled in urea cycle

Answer 27

ornithine

Question 28

Entry points for nitrogen in urea cycle

Answer 28

apartate, or free ammonia (incorporated into carbanoyl phosphate)

Question 29

regulation of transamination

Answer 29

ALT and AST are regulated by relative concentrations of substrates and products

Question 30

signs of hyperammonemia

Answer 30

cerebral edema, coma, death