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Biochemistry > Module 11: Amino Acid Metabolism (Part 01) > Flashcards

Module 11: Amino Acid Metabolism (Part 01) Flashcards

1
Q

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

A

Amino Acids

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2
Q

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

A

Amino Acid Pool

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3
Q

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

A

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

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4
Q

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

A

Protein turnover

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5
Q

The amino acid pool is used for what?

A

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

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6
Q

Why do we oxidize amino acids?

A

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

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7
Q

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.

A

Protein Turnover

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8
Q

How are amino acids not used in protein synthesis important

A

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

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9
Q

The Degradation of amino acids involves what?

A

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

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10
Q

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

A

Glutamate and glutamine

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11
Q

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

A

Alanine

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12
Q

What happens to excess ammonia in the body?

A

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

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13
Q

Most AA are derived from what

A

dietary proteins or breakdown of cellular proteins.

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14
Q

Most amino acids are metabolized in the _____

A

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

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15
Q

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

A

alanine and glutamine

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16
Q

Amino acids undergo what?

A

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.

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17
Q

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

A

glutaminase

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18
Q

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

A

glutamate.

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19
Q

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

A

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

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20
Q

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.

A

Nitrogen Balance

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21
Q

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

A

Negative Nitrogen Balance

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22
Q

Where is negative nitrogen balance sprung up?

A

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

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23
Q

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

A

Positive nitrogen imbalance

24
Q

What triggers positive nitrogen imbalance?

A

Growth, pregnancy and tissue synthesis

25
Q

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

A

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

26
Q

What happens in transamination?

A

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.

27
Q

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

A

TRANSAMINASES, SGPT & SGOT

28
Q

This is the acceptor of amino groups from amino acids.

A

Glutamate

29
Q

In many aminotransferase reactions, ___________is the amino group acceptor.

A

a-ketoglutarate

30
Q

All aminotransferases have ______________ as cofactor.

A

pyridoxal phosphate (PLP)

31
Q

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.

A

Oxidative deamination

32
Q

In oxidative deamination, alanine forms what

A

pyruvate (C3) + NH4+

33
Q

In oxidative deamination, glutamate forms what

A

a-ketoglutarate (C5) ) + NH4

34
Q

In oxidative deamination, aspartate forms what

A

oxaloacetate (C4) + NH4+

35
Q

What happens to excess ammonia?

A

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

36
Q

Explain the glucose alanine cycle

A

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.

37
Q

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

A

Oxidative Deamination

38
Q

What is the goal of oxidative deamination?

A

To regenerate alpha ketoglutarate

38
Q

Where dies oxidative deamination occur?

A

Liver and kidney

39
Q

Why is glutamate unique?

A

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

40
Q

What is the net effect of amino acid degradation?

A

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

41
Q

What happens to ammonium ion?

A

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)

42
Q

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

A

Ureotelic

43
Q

This transports ammonia from skeletal muscles.

A

Alanine

44
Q

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.

A

Glutamine

45
Q

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.

A

urea

46
Q

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

A

Urea Cycle

47
Q

This the fuel for urea cycle

A

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

48
Q

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.

A

Carbamoyl phosphate synthetase

49
Q

Explain the Urea Cycle begins in the liver mitochondria

A

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

50
Q

This is produced is used in citric acid cycle

A

Fumarate

51
Q

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

A

Aspartate

52
Q

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

A

glucogenic amino acids

52
Q

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

A

glucogenic amino acids

53
Q

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

A

ketogenic amino acids

53
Q

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

A

ketogenic amino acids

54
Q

Interrelationships among Metabolic Pathways

A

(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).

Biochemistry (16 decks)

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