Protein Metabolism

Question 1

What are the two main sources of Proteins?

Answer 1

Dietary and Intracellular

Question 2

What are the three main drivers of protein oxidation?

Answer 2

1-Normal synthesis and degradation
2-Protein rich diet
3-Starvation or diabetes mellitus

Question 3

What are the 3 major zymogen proteases released from the pancreas?

Answer 3

1-Trypsinogen (Trypsin)
2-Chymotrypsinogen (chymotrypsin)
3-Procarboxypeptidase A and B (Carboxypeptidase A and B)

Question 4

What two signals from intestinal cells are important for protein degradation?

Answer 4

1-Secretin (stimulate bicarbonate)

2-Cholecystokinin (CCK-stimulate zymogen release)

Question 5

What are the three main fates of amino acids once they are absorbed?

Answer 5

1-Sythesis of other proteins
2-Catabolized for energy
3-Transported to liver and excreted

Question 6

Where does most of protein catabolism take place?

Answer 6

Liver

Question 7

What are the four important “Nitrogen shuttle” amino acids?

Answer 7

1-Glutamate (N acceptor)
2-Glutamine (N acceptor)
3-Aspartate (Amine shifter)
4-Alanine (Amine shifter)

Question 8

Why is ammonia toxic?

Answer 8

Disrupts astrocyte K+ uptake causing high extracellular K+ thus preventing GABA inhibition. Cells are then more excitable and result in hyperactivity, seizures, etc.

Question 9

What are the two common amino acid catabolism reactions?

Answer 9

1-Transaminase rxns (transfer amine group)

2-One-Carbon Transfers

Question 10

How is intracellular ammonia buffered?

Answer 10

Converting Glutamate to glutamine

Question 11

What two ways is nitrogen transported to the liver?

Answer 11

1-Gutamine transport

2-Glucose-Alanine cycle (Nitrogen moves in the form of Alanine)

Question 12

What purpose does the Urea cycle serve?

Answer 12

Excrete liver nitrogen

Question 13

What is the “backbone” amino acid of the Urea Cycle?

Answer 13

Ornithine

Question 14

Glutamine is the form of Nitrogen that typically arrives from the?

Answer 14

Vasculature and other tissues

Question 15

Alanine is the form of Nitrogen that typically arrives from the?

Answer 15

Muscles

Question 16

The conversion of Amino acids into Carbamoyl phosphate takes place where?

Answer 16

Mitochondrial matrix

Question 17

What are the two main ways to regulate the urea cycle?

Answer 17

1-Increase synthesis of the 4 main enzymes of the Urea cycle

2-Allosteric regulation of Carbamoyl phosphate synthetase I

Question 18

What are the 4 main enzymes of the urea cycle?

Answer 18

1-Ornithine Transcarbomoylase
2-Arginosuccinate synthetase
3-Arginosuccinase
4-Arginase

Question 19

What process is an important linker between the Citric and Urea cylcles?

Answer 19

Aspartate-argininosuccinate shunt

Question 20

What three cofactors (Vitamins) are important in one carbon transfer reactions?

Answer 20

1-Biotin
2-Tetrahydrofolate
3-Adenosylmethionine

Question 21

Which 6 amino acids are degraded to pyruvate?

Answer 21

1-Tryptophan
2-Threonine
3-Alanine
4-Cysteine
5-Serine
6-Glycine

Question 22

Which 7 amino acids degrade to acetyl-CoA?

Answer 22

1-Tryptophan
2-Tyrosine
3-Threonine
4-Isoleucine
5-Leucine
6-Lysine
7-Phenylalanine

Question 23

Which five amino acids are degraded to a-ketoglutarate?

Answer 23

1-Glutamate
2-Glutamine
3-Arginine
4-Proline
5-Histidine

Question 24

Which four amino acids are degraded to succinyl-CoA?

Answer 24

1-Valine
2-Isoleucine
3-Threonine
4-Methionine

Question 25

Which two amino acids are degraded to oxaloacetate?

Answer 25

1-Asparagine

2-Aspartate