Module 11: Amino Acid Metabolism (Part 01)

Question 1

These are formed through digestion process enters the amino acid pool in the body

Answer 1

Amino Acids

Question 2

This is the total supply of free amino acids available for use in the human body.

Answer 2

Amino Acid Pool

Question 3

The amino acid pool is derived from what three (3) sources?

Answer 3

(1) Dietary protein
(2) Protein turnover
(3) Biosynthesis of amino acids in the liver

Question 4

This is a repetitive process in which the body proteins are degraded and resynthesized

Answer 4

Protein turnover

Question 5

The amino acid pool is used for what?

Answer 5

(1) protein synthesis = 90%
(2) Synthesis of nitrogen containing compounds
(3) gluconeogenesis (fasting)
(4) ketogenesis (fasting)
(5) energy (fed)

Question 6

Why do we oxidize amino acids?

Answer 6

(1) protein turnover
(2) diet is rich in protein
(3) starvation and diabetics

Question 7

This releases amino acids in excess of use in protein synthesis. in this, amino acids are used for energy reservoir and is a source of glucose.

Answer 7

Protein Turnover

Question 8

How are amino acids not used in protein synthesis important

Answer 8

They are oxidized to form glucose because they have no storage unlike fats and carbohydrates. They are known as the spare glucose.

Question 9

The Degradation of amino acids involves what?

Answer 9

removal of the a-amino group and degradation of the remaining carbon skeleton.

Question 10

They act as collection point of amino groups for amino acids.

Answer 10

Glutamate and glutamine

Question 11

This transports amino groups from skeletal muscle and brings it to the liver.

Answer 11

Alanine

Question 12

What happens to excess ammonia in the body?

Answer 12

Excess ammonia in most other tissues is converted to glutamine. Glutamine transports amino groups from brain.

Question 13

Most AA are derived from what

Answer 13

dietary proteins or breakdown of cellular proteins.

Question 14

Most amino acids are metabolized in the _____

Answer 14

liver, where they are either used for biosynthetic pathways or excreted as urea or uric acid.

Question 15

For ammonia generated in extrahepatic tissues, they are brought into the liver by _________(muscle) and ________(muscle, brain and other tissues).

Answer 15

alanine and glutamine

Question 16

Amino acids undergo what?

Answer 16

Amino acids undergo transamination to keto acids. Amino group from amino acid is given to a-ketoglutarate which becomes glutamate. Transamination of alanine (A) forms pyruvate.

Question 17

Glutamine enters the liver and is deaminated to glutamate by what.

Answer 17

glutaminase

Question 18

Amino groups from many amino acids are collected in the liver in the form of ____________.

Answer 18

glutamate.

Question 19

Glutamate from the cytosol goes to the mitochondria where it undergoes what.

Answer 19

undergoes oxidative deamination to a-ketoglutarate (a 5C keto acid) catalyzed by glutamate dehydrogenase

Question 20

This is the state that results when the amount of nitrogen taken into the human body as protein equals the amount of nitrogen excreted from the body in waste materials.

Answer 20

Nitrogen Balance

Question 21

In this form of nitrogen imbalance, protein degradation exceeds protein synthesis. Hence the amount of N in urine exceeds nitrogen consumed.

Answer 21

Negative Nitrogen Balance

Question 22

Where is negative nitrogen balance sprung up?

Answer 22

From tissue wasting, post surgery, advance cancer or diet deficiency

Question 23

This form of nitrogen imbalance is where the rate of protein synthesis (anabolism) is more than protein degradation (catabolism

Answer 23

Positive nitrogen imbalance

Question 24

What triggers positive nitrogen imbalance?

Answer 24

Growth, pregnancy and tissue synthesis

Question 25

The first step in the catabolism of L-amino acids is what

Answer 25

(1) Removal of an alpha amino group by transamination and oxidative deamination

Question 26

What happens in transamination?

Answer 26

The α-amino group of an amino acid is given to α-ketoglutarate which becomes glutamate, while the remaining C skeleton becomes a keto acid.

Question 27

These are confined in the liver. If present in the blood in high concentrations is an indication of liver disease.

Answer 27

TRANSAMINASES, SGPT & SGOT

Question 28

This is the acceptor of amino groups from amino acids.

Answer 28

Glutamate

Question 29

In many aminotransferase reactions, ___________is the amino group acceptor.

Answer 29

a-ketoglutarate

Question 30

All aminotransferases have ______________ as cofactor.

Answer 30

pyridoxal phosphate (PLP)

Question 31

In this, amino acid is converted into the corresponding keto acid by the removal of the amine functional group as ammonia which occurs as ammonium which eventually goes into the urea cycle.

Answer 31

Oxidative deamination

Question 32

In oxidative deamination, alanine forms what

Answer 32

pyruvate (C3) + NH4+

Question 33

In oxidative deamination, glutamate forms what

Answer 33

a-ketoglutarate (C5) ) + NH4

Question 34

In oxidative deamination, aspartate forms what

Answer 34

oxaloacetate (C4) + NH4+

Question 35

What happens to excess ammonia?

Answer 35

Excess ammonia in tissues is added to glutamate to form glutamine (glutamate synthase). It is then transported in the blood and enters the liver. Inside it is deaminated to glutamate by the enzyme glutaminase

Question 36

Explain the glucose alanine cycle

Answer 36

Alanine serves as a carrier of ammonia and of the carbon skeleton of pyruvate from skeletal muscle to liver. The ammonia is excreted and the pyruvate is used to produce glucose, which is returned to the muscle.

Question 37

This is catalyzed by glutamate dehydrogenase in which glutamate is converted into alpha-ketoglutarate with the release of an ammonium ion, ion (NH4+)

Answer 37

Oxidative Deamination

Question 38

What is the goal of oxidative deamination?

Answer 38

To regenerate alpha ketoglutarate

Question 38

Where dies oxidative deamination occur?

Answer 38

Liver and kidney

Question 39

Why is glutamate unique?

Answer 39

Glutamate is unique because it is the only amino acid that undergoes rapid oxidative deamination by glutamate dehydrogenase

Question 40

What is the net effect of amino acid degradation?

Answer 40

The net effect of amino acid degradation is the production of ammonium ion which is toxic.

Question 41

What happens to ammonium ion?

Answer 41

It is converted to urea (relatively non-toxic compound) in the liver via urea cycle. It is toxic because it depletes the brain of ATP. It combines with a-ketoglutarate, removing it from the Krebs cycle. (cataplerotic)

Question 42

This is the form of ammonium ions when it is converted to urea and is excreted by terrestrial animals

Answer 42

Ureotelic

Question 43

This transports ammonia from skeletal muscles.

Answer 43

Alanine

Question 44

This, in the muscles, liver and nervous system. Conversion to glutamine is the major mechanism for the removal of ammonia in the brain. Circulating glutamine is taken by the liver and kidneys then deaminated by glutaminase to glutamate.

Answer 44

Glutamine

Question 45

This is made in the liver, goes to blood, to the kidneys then secreted in the urine. This is the excretory form of amino nitrogen in man.

Answer 45

urea

Question 46

This is almost exclusive to hepatocytes. This reaction uses HCO3 that is a byproduct mitochondrial respiration.

Answer 46

Urea Cycle

Question 47

This the fuel for urea cycle

Answer 47

Carbamoyl P is the fuel of urea cycle which requires 2 ATP

Question 48

This converts ammonium and bicarbonate into carbamoyl phosphate. This is the rate-limiting step in the urea cycle. This reaction requires two ATP and occurs in the mitochondria.

Answer 48

Carbamoyl phosphate synthetase

Question 49

Explain the Urea Cycle begins in the liver mitochondria

Answer 49

Stage 1: Carbamoyl group transfer The carbamoyl group of carbamoyl phosphate is transferred to ornithine to form citrulline Stage 2: Citrulline-aspartate condensation Citrulline is transported into the cytosol, citrulline reacts with aspartate to produce arginosuccinate utilizing ATP In this reaction the second of two nitrogen atoms of urea is introduced into the cycle (One nitrogen comes from carbamoyl phosphate and the other from aspartate -- original source of both is glutamate) Two ATP equivalents are used in this step Stage 3: Argininosuccinate cleavage: Argininosuccinate is cleaved to arginine and fumarate by the enzyme argininosuccinate lyase

Question 50

This is produced is used in citric acid cycle

Answer 50

Fumarate

Question 51

This is produced through transamination of oxaloacetate is used in step 2 of the urea cycle as donor of second N of urea.

Answer 51

Aspartate

Question 52

An amino acid that has a carbon-containing degradation product that can be used to produce glucose via gluconeogenesis.

Answer 52

glucogenic amino acids

Question 52

This amino acids converted to pyruvate and citric acid cycle intermediates can serve as glucose precursors

Answer 52

glucogenic amino acids

Question 53

The amino acids converted to acetyl CoA or acetoacetyl CoA can serve as fatty acids and/or ketone body precursors

Answer 53

ketogenic amino acids

Question 53

An amino acid that has a carbon-containing degradation product that can be used to produce ketone bodies

Answer 53

ketogenic amino acids

Question 54

Interrelationships among Metabolic Pathways

Answer 54

(1) Feasting (over eating): Causes the body to store a limited amount as glycogen and the rest as fat. (glu ->glycogen, fat -> body fat, Amino group (AA) -> urea (2) Fasting (no food ingestion): The body uses its stored glycogen (glu for brain) and fat for energy. (3) Starvation (not eating for a prolonged period): Glycogen stores are depleted, Body protein is broken down to amino acids to synthesize glucose. Fats are converted to ketone bodies (used for energy).