Exam 3 Protein Metabolism

Question 1

Daily protein intake

Answer 1

15-22% of total energy

0.8-1 g/kg

Question 2

Protein storage pool

Answer 2

Not actual storage pool like lipids

Used for structural/signaling fxn

Question 3

Post-translationally modified amino acids

Answer 3

Hydroxy-proline and hydroxy-lysine (collagen, Vit C)
Gamma carboxyglutamate (prothrombin, Vit K)
Ornithine (urea cycle)

Question 4

Two pathways of protein degradation

Answer 4

Ubquination

Lysosomal

Question 5

Transamination - overview

Answer 5

Removal of the N group to use in gluconeogenesis
Bidirectional
Mainly liver (some kidney, intestine, muscle)
Need Vit B6 (PLP)

Question 6

Transamination - enzyme and mech

Answer 6

Aminotransferase
N transferred to a-ketoglutarate
Released as NH3 - regenerating a-ketoglutarate

Question 7

Sulfur containing amino acids

Answer 7

Cysteine

Methionine

Question 8

Ketogenic amino acids (essential)

Answer 8

Leucine

Lysine

Question 9

Both keto/glucogenic (essential)

Answer 9

Tyrosine
Phenyl-alanine
Tryptophan
Isoleucine

Question 10

Vitamins C, K, B6 important rxns

Answer 10

C= Prolyl hydroxylase and lysyl hydroxylase activity (collagen, schiff base formation)
K= Gamma glutamyl carboxylase (prothrombin)
B6= Transamination, PLP holds N (schiff base formation)

Question 11

Control points for protein catabolism

Answer 11

1. Directionality of transamination
2. N-Acetylglutamate activation of CPS-1
3. Directionality of GluDH
4. Energy feedback on GluDH

Question 12

Glucogenic amino acids (essential)

Answer 12

Metionine
Valine
Histadine
Threonine

Question 13

Carbamoyl phosphate synthetase I

Answer 13

Mitochondria
Urea cycle
Ammonia is source of nitrogen
Activator: N-acetyl glutamate

Question 14

Carbamoyl phosphate synthetase II

Answer 14

Cytosol
Pyrimidine synthesis
Glutamine is source of nitrogen
Activator: ATP
Inhibitor: UTP

Question 15

Prolyl hydroxylase vs. lysyl hydroxylase

Answer 15

PH: Pro -> Hyp (important for H bonds?)
LH: Lys -> Hyl (important for covalent bond via lysyl oxidase)
Both hydroxylases require Vit C

Question 16

Tissues and ammonia toxicity/transport

Answer 16

Peripheral tissues: glutamine for transport to liver
Muscle: alanine for transport to liver
Liver: produce urea to Kidney
Kidney: removes urea (liver )and ammonia (glutamine)
Glutamine crosses BBB

Question 17

Glutamate Dehydrogenase

Answer 17

Exists in all tissues
Concentration dependent
Activated by ADP, inhibited by ATP

Question 18

Thyroid hormone synthesis

Answer 18

Thyroglobulin (140 Tyr, few w/ I)
T4 = 4 I
T3 = 3 I (deiodinase)

Question 19

TSH functions

Answer 19

release T3/T4 (bound and transported by TBG)

increase absorption of I

Question 20

Homocysteinuria causes

Answer 20

Defect in methionine synthase
Defect in cystathionine ß synthase
Defect in MTHFR gene (produces THF)

Question 21

Hyperhomocysteinemia consequences

Answer 21

CV disease
Impaired wound healing
Cervical CA

Question 22

Homocysteinuria signs and symptoms

Answer 22

Mental retardation
Osteoporosis
CVD
Marfanoid presentation

Question 23

Cysteinuria causes

Answer 23

Defective PCT transporter of COLA
Cysteine
Ornithine
Lysine
Arginine
Cysteine insoluble in large amounts (Tx. acetazolamide)

Question 24

Purine synthesis basics

Answer 24

Start with sugar -> activate
Add base
Add phosphates

Question 25

Pyrimidine synthesis basics

Answer 25

Start with base
Add sugar
Add phosphates

Question 26

Nucelotide breakdown

Answer 26

Purines -> Uric acid (insoluble, toxic)

Pyrimidines -> TCA intermediates, soluble, non-toxic