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Metabolism > Proteins > Flashcards

Proteins Flashcards

1
Q

What is creatinine?

A

A breakdown product of creatine and creatine phosphate which is usually produced at a constant rate.

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2
Q

What is the creatinine urine excretion proportional to?

A

Muscle mass

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3
Q

What is a positive nitrogen balance and when is this normal?

A

Intake of nitrogen exceeds output therefore there is an increase in total body protein.
Normal during growth, pregnancy or in an adult recovering from malnutrition.

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4
Q

What is a negative nitrogen balance?

A

The intake of nitrogen is less then the output of nitrogen therefore there is a net loss of body protein.
This is never normal.

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5
Q

What can cause a negative N balance?

A

trauma, infection and malnutrition

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6
Q

What does the protein turnover refer to?

A

Proteins are constantly being synthesised and broken down

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7
Q

Name the 2 ketogenic amino acids

A

Lysine and leucine

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8
Q

Give 2 examples of amino acids that are keto and glucogenic

A

Tyrosine

Phenylalanine

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9
Q

How does cortisol affect proteins?

A

Increases degradation and decreases synthesis

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10
Q

Name the nitrogen containing compounds of the body

A

amino acids, proteins, purines and pyrimidine, haem, creatine, neurotransmitters, catecholamine hormones

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11
Q

What happens to protein in skin in Cushing’s syndrome?

A

Excess cortisol leads to increased breakdown of protein. This weakens skin structure and causes striae to form.

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12
Q

Which amino acids are essential to children and pregnant women on top of the 9 already essential amino acids?

A

arginine, tyrosine and cysteine

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13
Q

Where do the carbon atoms for the synthesis of amino acids come from?

A

intermediates of glycolysis, pentose phosphate pathway and the Krebs cycle

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14
Q

Which molecules are synthesised using tyrosine?

A

catecholamines, melanin, thyroid hormones, dopamine

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15
Q

What is arginine needed for?

A

Nitric oxide synthesis which is required for vasodilation

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16
Q

What do we require glycine to make?

A

purines, haem, creatine, glutathione

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17
Q

What kind of enzymes are used for transamination?

A

aminotransferase enzymes

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18
Q

The cofactor for the aminotransferase enzymes is a derivative of which vitamin?

A

Vitamin B6

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19
Q

Which amino acids can be fed into the urea cycle?

A

Glutamate

Aspartate

20
Q

Which is the role of alanine aminotransferase?

A

Conversion of alanine to glutamate using alpha-ketoglutarate.

21
Q

What is the role of aspartate aminotransferase?

A

To convert glutamate to aspartate using oxaloacetate.

22
Q

What do we measure as part of a liver function test?

A

ALT and AST levels in the plasma

23
Q

When are AST and ALT levels high?

A

When the functioning of the liver is problematic

24
Q

What are the deamination enzymes?

A

amino acid oxidases, glutaminase and glutamate dehydrogenase

25
Q

What are the features of urea?

A

high nitrogen content, water soluble, chemically inert, non-toxic

26
Q

Where does the urea cycle occur?

A

mitochondria and cytoplasm of hepatocytes

27
Q

What other molecules does the urea cycle require?

A

carbon dioxide

water

28
Q

Does the urea cycle require energy?

A

Yes

29
Q

How many enzymes are involved in the urea cycle?

A

5 enzymes

30
Q

Which inheritance pattern do defects in the urea cycle follow?

A

Autosomal recessive

31
Q

What does a deficiency in one of the enzymes of the urea cycle lead to?

A

hyperammonaemia and accumulation/excretion of urea cycle intermediates

32
Q

What are the symptoms of defects in the urea cycle?

A

vomiting, lethargy, irritability, seizures, mental retardation

33
Q

What is the management for defects in the urea cycle?

A

low protein diet and replace amino acids in diet with keto acids

34
Q

What are some of the toxic effects of ammonia?

A

interference with amino acid transport and protein synthesis, increase in pH, alteration of blood brain barrier, interference with TCA cycle

35
Q

What are the 2 ways that ammonia can be transported safely?

A

combine with glutamate for transportation as glutamine or combine with pyruvate for transportation as alanine

36
Q

What does the heel prick test for?

A

sickle cell disease, cystic fibrosis, congenital hypothyroidism and inborn errors of metabolism

37
Q

What is phenylketonuria?

A

The most common inborn error of amino acid metabolism due to a deficiency in phenylalanine hydroxylase. Phenylalanine accumulates in tissues to phenylketones will be present in the urine. This prevents the formation of tyrosine by the body.

38
Q

Which pattern of inheritance does PKU follow?

A

Autosomal recessive

39
Q

What is the treatment for PKU?

A

low phenylalanine diet, avoid artificial sweeteners, avoid high protein foods

40
Q

What is the major problem with PKU?

A

No tyrosine can be made and therefore we cannot make many other molecules.
eg. dopamine, adrenaline, thyroxine, melanin

41
Q

What are the symptoms of PKU?

A

developmental delay, intellectual disability, microcephaly (small head), seizures, hypopigmentation

42
Q

What causes homocystinurias?

A

There is a problem breaking down methione and therefore an excess of homocysteine. Most commonly due to a defect in cystathionine beta-synthase.

43
Q

Which pattern of inheritance do homocystinurias follow?

A

autosomal recessive

44
Q

What is the treatment for homocystinurias?

A

low methione diet, avoid high protein foods, avoid nuts, take vitamin supplements

45
Q

What is elevated homocysteine shown to be associated with?

A

Increased risk of cardiovascular disease

Metabolism (17 decks)

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