Nitrogen Metabolism

Question 1

Can amino acids be stored?

Answer 1

No.

Question 2

The Urea Cycle takes place in what organ?

Answer 2

Liver

Question 3

The first step in breaking down amino acids will give what two products?

Answer 3

NH4+ (ammonium), Carbon skeleton

Question 4

Ammonium (NH4+) can be converted into _____ before entering the Urea Cycle

Answer 4

Carbamoyl Phosphate

Question 5

The carbon skeletons will be converted into ____ before entering the Citric Acid Cycle?

Answer 5

Alpha-Keto acids

Question 6

The Aspartate-arginino-succinate shunt of citric acid cycle is what?

Answer 6

A connection between the Citric acid cycle and Urea cycle

Question 7

Amino group catabolism has the A-amino group of most amino acids transferred to _____

Answer 7

Alpha-ketoglutarate

Question 8

Amino group catabolism forms two products. They are:

Answer 8

1. Glutamate

2. The A-keto acid of the original amino acid

Question 9

Amino-transferase’s are _____ dependent

Answer 9

PLP (Pyridoxal phosphate)

Question 10

Pyridoxine is what vitamin?

Answer 10

B6

Question 11

Alpha-Amino group transfer occurs in what part of the liver cells?

Answer 11

Cytosol

Question 12

The glutamate formed during A-amino group transfer is transported into what part of the cell?

Answer 12

Mitochondria

Question 13

In the mitochondria, glutamate goes through oxidative deamination to form: (2)

Answer 13

1. Alpha-ketoglutarate

2. NH4+ (ammonium)

Question 14

In extrahepatic tissues NH4+ is combined with glutamate (with the help of ATP) to form _____

Answer 14

Glutamine

Question 15

In skeletal muscle under anaerobic conditions _____ builds up

Answer 15

Pyruvate

Question 16

In skeletal muscle, the amino groups are transferred to pyruvate to form ____

Answer 16

Alanine

Question 17

In skeletal muscle, once alanine is formed it is transported to the liver. Explain what happens next to complete the cycle

Answer 17

1. Transamination leads back to pyruvate
2. Pyruvate can be used for gluconeogenesis
3. Glucose is transported back to skeletal muscle

Question 18

What are the two exclusively ketogenic amino acids?

Answer 18

Leucine

Lysine

Question 19

How many ATP are used to convert ammonium into carbamoyl phosphate (for Urea cycle)

Answer 19

2

Question 20

Name the order of products in the Urea cycle starting with Carbamoyl phosphate. (5 main)

Answer 20

1. Carbamoyl phosphate
2. Citrulline
3. Argininosuccinate
4. Arginine (and Fumarate)
5. Ornithine (and Urea)

Question 21

How many ATP are used in the Urea cycle? (Hint: conversion of citrulline to intermediate)

Answer 21

1

Question 22

Name the six common metabolites of amino acid breakdown

Answer 22

1. Pyruvate
2. Acetyl-CoA
3. A-Ketoglutarate
4. Succinyl-CoA
5. Fumarate
6. Oxaloacetate

Question 23

Of the six common metabolites of amino acid breakdown, which three are alpha-keto acids?

Answer 23

1. Pyruvate
2. A-ketoglutarate
3. Oxaloacetate

Question 24

Oxaloacetate is transaminated into ____

Answer 24

Aspartate

Question 25

Name the four common metabolites as precursors for amino acid synthesis (production)

Answer 25

1. 3-Phosphoglycerate 2. Pyruvate 3. A-Ketoglutarate 4. Oxaloacetate

Question 26

Name the essential non-metabolic precursor of amino acid synthesis and what can be made from it

Answer 26

Phenylalanine --> Tyrosine

Question 27

Name the two amino acids that are the major providers of Nitrogen for the synthesis of amino acids

Answer 27

Glutamate | Glutamine

Question 28

Name the 9 essential amino acids

Answer 28

1. Histidine 2. Isoleucine 3. Leucine 4. Lysine 5. Methionine 6. Phenylalanine 7. Threonine 8. Tryptophan 9. Valine

Question 29

Name the conditionally amino acid that is essential as a young human and later not synthesized in adequate amounts

Answer 29

Arginine

Question 30

Name the two normal conditionally essential amino acids

Answer 30

1. Cysteine | 2. Tyrosine

Question 31

Name the amino acid precursor of the Catecholamines - Dopa, Dopamine, epinephrine, and norepinephrine

Answer 31

Tyrosine

Question 32

The amino acid precursor for GABA is ____

Answer 32

Glutamate

Question 33

The amino acid precursor for Serotonin is ____

Answer 33

Tryptophan

Question 34

The amino acid precursor for Histamine is ____

Answer 34

Histidine