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Science for Medicine > Nitrogen > Flashcards

Nitrogen Flashcards

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1
Q

Why is nitrogen highly unreactive?

A

Triple bond requires lots of energy to break.

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2
Q

What is the nitrogen triple bond usually broken by?

A 
Lightning (natural)
Haber process (synthetic)
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3
Q

What enzyme does nitrogen fixation require?

A

Nitrogenase.

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4
Q

What is nitrogenase?

A

An enzyme required for nitrogen fixation.

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5
Q

What conditions does nitrogenase exist in why?

A

Anaerobic conditions- inactivated by oxygen.

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6
Q

Why does nitrogenase exist in anaerobic conditions?

A

It is inactivated by oxygen.

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7
Q

What molecule allows the flow of nitrogen in the body from NH4+ to other biomolecules?

A

Glutamate.

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8
Q

What does glutamate do?

A

Allows the flow of nitrogen in the body from NH4+ to other biomolecules.

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9
Q

What is glutamate produced by?

A

Alpha-ketoglutarate.

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10
Q

What is alpha-ketoglutarate?

A

Citric acid cycle intermediate which produces glutamate.

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11
Q

Why is nitrogen conserved in organisms?

A

Because most organisms cannot fix it themselves.

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12
Q

What is assimilation?

A

Nitrogen assimilation is the process by which nitrogen is conserved in organisms.

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13
Q

What is nitrogen transamination?

A

Transamination is the transfer of amino groups between different molecules in order for nitrogen to be conserved.

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14
Q

Is there a net gain/loss of nitrogen in transamination?

A

No net gain or loss because the same amount is just transferred between molecules.

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15
Q

Is transamination reversible?

A

Yes- the process is readily reversible.

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16
Q

What is often one of the 2 substrate pairs within transamination?

A

Glutamate.

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17
Q

What do transaminases often participate in due to amine reversibility?

A

Amino acid synthesis and degradation.

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18
Q

What enzyme is required in transamination?

A

Aminotransferases.

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19
Q

What do aminotransferases rely on?

A

PLP cofactor.

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20
Q

What is PLP?

A

Pyridoxal phosphate cofactor- transfers the amino group during transamination.

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21
Q

Why is PLP relied on by aminotransferases?

A

It is the cofactor that actually transfers the amino groups.

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22
Q

What accepts amino groups?

A

Alpha-ketoglutarate

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23
Q

What can act as a temporary store of amino groups?

A

L-glutamine.

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24
Q

What can donate the nitrogen group when needed for amino acid biosynthesis?

A

L-glutamine.

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25
Q

What does alpha-ketoglutarate do?

A

Accepts amino groups.

Also produces glutamate.

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26
Q

What does L-glutamine do?

A

Acts as a temporary store of amino groups and can donate the nitrogen group when required for amino acid biosynthesis.

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27
Q

Where do aminotransferases exist?

A

Intracellullar.

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28
Q

What does the presence of aminotransferases in the plasma indicate?

A

Cell damage as they are an intracellular enzyme.

29
Q

Do all organisms use amino acids as a source of energy?

A

No- primary source within carnivores but herbivores rarely use them.

30
Q

When are amino acids oxidised?

A

When they are in excess, in starvation (when proteins have been broken down), and when dietary amino acids are degraded.

31
Q

What gives a steady flow of amino acids?

A

Digestion of proteins in the intestine and degradation of proteins in cells.

32
Q

How are amino acids freed in the stomach?

A

Acidic environment and enzymes.

33
Q

How are amino acids further degraded in the intestine?

A

Aminopeptidases degrade them further (membrane-bound proteins).

34
Q

How do humans excrete ammonia?

A 
Urea (from amino acids)
Uric acid (from purines)
35
Q

Where does urea come from?

A

Amino acids.

36
Q

Where does uric acid come from?

A

Purines.

37
Q

How is ammonia transported in the bloodstream?

A

Glutamine.

38
Q

Where is excess glutamine produced?

A

Intestines, liver, kidney.

39
Q

How does glutamate act on pyruvate?

A

Glutamate can donate ammonia to pyruvate which produces alanine. This prevents the build-up of lactic acid and reduces muscle pain and fatigue.

40
Q

What does the conversion of pyruvate to alanine require?

A

Donation of ammonia from glutamate.

41
Q

What does the conversion of pyruvate to alanine result in?

A

Reduced build-up of lactic acid and decreased fatigue/muscle pain.

42
Q

What happens to alanine`?

A

Direct transport for metabolism in the liver.

43
Q

Why are amino acids travelling in the bloodstream as glutamine/alanine converted back into glutamate?

A

Glutamine and alanine have no charge whereas glutamate is negatively charged so glutamine/alanine are used to permeate the membranes.

44
Q

What charge does glutamate have?

A

Negative.

45
Q

What charge do glutamine/alanine have?

A

No charge- can permeate the cell membrane.

46
Q

Where is excess glutamate metabolised?

A

Mitochondria of hepatocytes.

47
Q

What is the first nitrogen-acquiring reaction?

A

Recapture of ammonia through synthesis of carbamoyl phosphate.

48
Q

The synthesis of what product allows the recapture of ammonia in the first nitrogen-acquiring reaction?

A

Carbamoyl phosphate.

49
Q

What is the second nitrogen-acquiring reaction?

A

The nitrogen from carbamoyl phosphate enters the urea cycle as aspartate.

50
Q

What does the nitrogen from carbamoyl phosphate enter the urea cycle as?

A

Aspartate.

51
Q

What are carbon skeletons?

A

Carbon skeletons are the bit of the amino acid left when amino nitrogen group is removed.

52
Q

What happens to carbon skeletons?

A

They are either converted into glucose or oxidised as part of the citric acid cycle.

53
Q

How are carbon skeletons converted into glucose?

A

Feed back into gluconeogenesis- produce glucose or glycogen in the liver.

54
Q

What are carbon skeletons that feed back into gluconeogenesis called?

A

Gluconeogenetic.

55
Q

How are carbon skeletons oxidised as part of the citric acid cycle?

A

Feed into acetoacetate or acetyl CoA-

56
Q

What are carbon skeletons that feed into the citric acid cycle for oxidation called?

A

Ketogenic.

57
Q

Can ketogenic carbon skeletons contribute to gluconeogenesis?

A

No- this is because the pyruvate > acetyl CoA is reversible.

58
Q

What are inherited metabolic disorders?

A

Inherited metabolic disorders are groups of individual diseases involving metabolic defects.

59
Q

Are inherited metabolic disorders common?

A

They are individually rare but collectively quite common.

60
Q

What are inherited metabolic disorders caused by?

A

Single gene defects.

61
Q

How do inherited metabolic disorders present clinically?

A

Clinically severe symptoms, typically present in childhood.

62
Q

What type of inheritance do inherited metabolic disorders usually show?

A

Autosomal recessive inheritance.

63
Q

What do inherited metabolic disorders often show defects in?

A

Enzyme defects.

64
Q

What clinical features do enzyme defects within IMDs usually show?

A

Acidosis, failure to thrive, vomiting, irritability, feed refusal, CNS dysfunction, hypoglycaemia, unusual order.

65
Q

What characterises urea cycle defects?

A

More common in X-linked inheritance, rare, characterised by hyperammonaemia (elevated ammonia in blood).

66
Q

What is PKU?

A

Amino acid disorder in which there is an absence or deficiency in phenylalanine hydroxyls which breaks down phenylalanine.

67
Q

What does high phenylalanine lead to?

A

Developmental issues.

68
Q

How is PKU treated?

A

Reduced protein diet supplemented with tyrosine.

69
Q

What does treatment of inherited metabolic disorders require?

A

Integration of clinician and laboratory.

Science for Medicine (19 decks)

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