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MEH > Protein + Amino Acid Metabolism > Flashcards

Protein + Amino Acid Metabolism Flashcards

1
Q

Name four major N containing compounds

A

Amino acids
Proteins
Purine + Pyrimidines (RNA/DNA)
Creatine phosphate

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2
Q

What is the breakdown product of creatine and creatine phosphate?

A

Creatinine

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3
Q

Where is creatine and creatine phosphate broken down?

A

The muscle

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4
Q

What is the creatinine excretion in the urine proportional to?

A

Muscle mass

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5
Q

What is creatinine excretion in the urine also an indicator of?

A

Renal function

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6
Q

What does a positive N balance mean?
What does it indicate about body protein?
When does it occur?

A

Intake>output
Increase in total body protein
Growth, pregnancy, recovering from malnutrition

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7
Q

What does a negative N balance mean?
What does it indicate about body protein?
When does it occur?

A

Intake<output
Net loss of body protein
Not normal - trauma, infection, malnutrition

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8
Q

When does mobilisation of protein reserves occur?

A

Extreme stress - starvation

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9
Q

What is the mobilisation of protein reserves controlled by?
Give three examples

A

Hormones

Insulin, growth hormones, glucocorticoids

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10
Q

Which hormones increase protein synthesis and decrease protein degradation?
Vice versa

A

Insulin and growth hormones

Glucocorticoids

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11
Q

What is the syndrome that there is excessive breakdown of proteins?

A

Cushing’s syndrome

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12
Q

What is formed in Cushing’s syndrome?

A

Striae

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13
Q

What does it mean when amino acids are conditionally essential?

A

Can synthesise but may need to consume when demands increase

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14
Q

Where do C atoms come from for amino acid synthesis?

A

Glycolysis
Pentose phosphate pathway
Krebs cycle

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15
Q

Where can an amino group be sourced by other amino acids? (2)

A

Transamination - transfer of an amino acid from one molecule to another

From ammonia

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16
Q

What are the two things that could happen to N once removed?

A

Incorporated into other compounds
Excreted as urea

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17
Q

What are the two main pathways that facilitate the removal of N from amino acids?

A

Transamination
Delaminating

18
Q

Why does an amine group sometimes need to be removed from an amino acid?

A

So the C skeleton can be used to give energy

19
Q

Why does amine need to be excreted?

A

Otherwise it will produce ammonia

20
Q

Describe Transamination

A

Amine group swapped for a keto group

21
Q

What enzyme is used is Transamination?

A

Aminotransferase

22
Q

What do aminotransferase enzymes used to funnel an amino group to glutamate?

A

Alpha ketoglutarate

23
Q

What do aminotransferases require?
What is it derived from?

A

Coenzyme pyridoxal phosphate
Vitamin B

24
Q

Name two key aminotransferases

A

ALT - alanine aminotransferase
AST - aspartate aminotransferase

25
Q

What does plasma ALT and AST levels show?

A

Liver function

26
Q

What does ALT do?

A

Catalyses inter conversion of alanine and alpha-ketogluratate to pyruvate and glutamate

27
Q

What does AST do?

A

Catalyses inter conversion of aspartate and alpha-ketoglutarate to oxaloacetate and glutamate

28
Q

What occurs in deamination?
Where does it occur?

A

Liberates amino group as free ammonia

Liver and kidneys

29
Q

Why is deamination important?

A

Keto acids can be utilised for energy

30
Q

Why is ammonia removed?
How?

A

Very toxic

Converted to urea or excreted directly in urine

31
Q

Describe ureas:
N content
Toxicity
Solubility
Reactivity

A

High
Non-toxic
Water soluble
Inert

32
Q

What happens to urea?

A

Excreted in urine

Osmotic role in kidney tubules

33
Q

Where does the urea cycle occur?
Using how many enzymes?

A

Liver
Five

34
Q

What increases and decreases levels of the urea cycle?

A

High protein diet - induces enzymes

Low protein diet or starvation - represses enzymes

35
Q

What causes a defect in the urea cycle?

A

Autosomal recessive genetic disorder
Deficient in one of the enzymes

36
Q

What can defects in the urea cycle cause?

A

Hyperammonaemia
Accumulation of urea cycle intermediates

37
Q

Symptoms of defects in the urea cycle

A

Vomiting
Lethargy
Irritability
Mental retardation
Seizures
Coma

38
Q

How do you manage defects in the urea cycle?

A

Low protein diet

Replace amino acids in diet with keto acids

39
Q

What are some protential toxic effects of ammonia?

A

PH effects
Interferes with amino acid transport and protein synthesis
Alteration of blood brain barrier

40
Q

What are two molecules that allow ammonia to be transported safely?

A

Glutamate
Alanine

41
Q

Describe how glutamate assists the transport of ammonia

A

Ammonia combined with glutamate - forms glutamine
Glutamine transported in blood to liver or kidneys
Glutamine cleaved by glutaminase - reforms ammonia and glutamate
Liver - ammonia into urea cycle
Kidneys - excreted in urine

42
Q

Describe how alanine is involved in ammonia transport

A

Ammonia combined with pyruvate - forms alanine
Alanine transported in the blood to the liver
Alanine converted back by transamination
Amino group into urea cycle

MEH (10 decks)

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