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Bioenergetics > Week 10 - Protein Metabolism > Flashcards

Week 10 - Protein Metabolism Flashcards

1
Q

Define the amino acid pool

A

aa in blood + extracellular fluids

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2
Q

How much protein in kg does the body of a 60kg woman have?

+ how much of free aa (g)

A

60kg woman:

  • 10kg protein

about 170g of free aa

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3
Q

Define non-essential/dispensable aa

A

aa synthesised by liver to make body proteins

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4
Q

Define essential/indispensable aa

A

aa that can’t be synthesised so must be obtained in diet.

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5
Q

Can some non-essential aa become indispensable? why?

A

yes

if they’re not prod at a fast enough rate.

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6
Q

What happens to the aa synthesised in the liver

A

Used in liver or released into blood

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7
Q

Whats left after an aa loses their amino group?

A

Carbon skeleton

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8
Q

What can happen to the carbon skeleton?

A

Oxidised directly

Used to make glucose in gluconeogenesis

Converted into fat for storage

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9
Q

Why do aa need protein transporters to move them?

A

Because of their charged groups

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10
Q

What are the types of protein transporters for aa

A

Sodium ion dependent

Sodium independent

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11
Q

Sodium ion dependent transporters

A

Symport transport system in which aa moves into cell down Na+ conc. grad + can be moved vs their conc. grad

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12
Q

Define transamination

A

1 aa is changed to another by the transfer of an amino group

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13
Q

Can humans use the N in the amino groups as an energy source?

A

NO, so most is excreted.

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14
Q

How are carbon skeletons very valuable?

A

Can become intermediates for the TCA cycle

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15
Q

When will aa undergo constant oxidative degradation?

A

During normal synthesis + degradation of proteins.

When we ingest more aa than our bodies need

During starvation, fasting, dieting or uncontrolled diabetes mellitus

When we overtrain

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16
Q

NUTRITIONALLY NON-ESSENTIAL OR ESSENTIAL

Alanine

A

NUTRITIONALLY NON-ESSENTIAL

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17
Q

NUTRITIONALLY NON-ESSENTIAL OR ESSENTIAL

Histidine

A

ESSENTIAL

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18
Q

NUTRITIONALLY NON-ESSENTIAL OR ESSENTIAL

Leucine

A

ESSENTIAL

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19
Q

What are the 2 major stages of catabolism of ind aa

A
  • Lose N atoms as can’t obtain usable energy from the N groups.
  • Resulting carbon skeletons are fed into specific energy-yielding pathways so that their chemical energy can be retrieved.
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20
Q

What organ removes the amino groups from most aa

A

Liver

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21
Q

What has a significant capacity for deamination of the BCAAs (branched-chain amino acids)

A

Skeletal muscle

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22
Q

What aa can’t undergo transamination reactions?

A

Threonine + lysine

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23
Q

NUTRITIONALLY NON-ESSENTIAL OR ESSENTIAL

Asparagine

A

Non-essential

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24
Q

NUTRITIONALLY NON-ESSENTIAL OR ESSENTIAL

Lysine

A

Essential

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25
Q

NUTRITIONALLY NON-ESSENTIAL OR ESSENTIAL

Glycine

A

Non-essential

26
Q

NUTRITIONALLY NON-ESSENTIAL OR ESSENTIAL

Proline

A

non-essential

27
Q

What vitamin does aminotransferase contain

A

Vitamin B6

28
Q

What is the typical reaction for aminotransferase

A

Transfers an amino group to α-ketoglutarate to make glutamate + a new carbon skeleton in the form of a keto acid:

α-ketoglutarate + aa – (aminotransferase) – > glutamate + α-keto acid.

29
Q

What is vitamin B6 a precursor for?

A

Coenzyme pyridoxal phosphate

30
Q

Are transamination reactions reversible or irreversible?

A

Freely reversible

Their net direction depends on the rel conc of the reactants

31
Q

In deamination, where can the amino groups be shuttled from?

A

1 aa to α-ketoglutarate to make GLUTAMATE

Glutamate to another keto acid to create a NEW AA

32
Q

Where must the amino group on glutamate be transferred to (if not already there) + what happens to it there

A

To liver + into the creation of the urea mol.

33
Q

What happens in the glutamate dehydrogenase reaction?

A

Removes N from glutamate which can then be used to make urea.

In the liver

34
Q

Is the glutamate dehydrogenase reaction reversible?

A

YES, freely reversible

35
Q

Where does the glutamate dehydrogenase reaction take place

A

In the mit matrix

36
Q

Where can most aminotransferase enzymes be found?

A

Mit matrix + cytosol

37
Q

What type of reaction is the glutamate dehydrogenase reaction as it proceeds to the right

A

A deamination reaction as it removes the amino group

38
Q

When does the glutamate dehydrogenase reaction become an oxidative deamination reaction?

A

NAD+ –> NADH

39
Q

What is the relationship between the prod of ammonium ion + its release from muscle?

A

Proportional to the intensity of the exercise.

40
Q

What % of the aa pool is glutamine?

A

60

41
Q

Where does glutamine come from?

A

Some diet

Most synthesised in body from glutamate using glutamine synthetase.

42
Q

What is glutamine fuel for

A

Gut + immune system

43
Q

Wheres an important site for glutamine synthesis ?

A

Skeletal muscle

But also prod in brain, adipose tissue + heart.

44
Q

What is the reverse reaction of the glutamine synthetase reaction?

A

Removal of the amino group from the side chain of glutamine.

45
Q

What reaction does glutamine synthetase catalyse?

A

Glutamate + ATP + NH4+ –> ADP + Pi + Glutamine

46
Q

Where can glutaminase be mainly found

A

Liver mitochondria

47
Q

What does glutaminase catalyse the reaction of?

A

Deamination reaction:

Glutamine + H20 –> Glutamate + NH4+

48
Q

Give examples of BCAA

A

Leucine

Isoleucine

Valine

49
Q

Where are BCAAs metabolised?

A

Mainly in skeletal muscle but can also be metabolised in liver.

50
Q

After the 1st 3 reactions of the catabolism of BCAAs what happens next?

A
  • Valine + isoleucine produce succinyl CoA.
  • Leucine catabolises –> acetoacetate + Acetyl CoA which can’t be converted to glucose, so leucine is considered a ketogenic aa.
51
Q

What happens in the 1st reaction of the catabolism of the BCAAs

A

Transamination

= in which the amino group is transferred to α-ketoglutarate to make GLUTAMATE.

52
Q

Whats different about the BCAA aminotransferase enzyme compared to the aminotransferase enzyme in transamination reactions

A

Aminotransferase in freely reversible transamination reactions.

BCAA aminotransferase goes only 1 way.

53
Q

Why does BCAA aminotransferase work only one way

A

Due to products undergoing an oxidative decarboxylation catalysed by BCKAD (Branched-chain ketogenic acid dehydrogenase).

54
Q

What does the alanine aminotransferase enzyme do?

A

Can transfer the amino groups on the BCAAs rom glutamate to pyruvate

55
Q

What are the 2 safer temporary forms of ammonia

A

Amino group of glutamate

Side chain amide N in glutamine

56
Q

Where is urea formed

A

Liver

57
Q

Where is urea excreted from

A

kidney when urine is formed

58
Q

Where does the carbonyl group on urea come from

A

CO2

59
Q

Urea synthesis req ammonium ions coming from where?

A

Ammonia taken up by the liver from the blood

From glutamine via the glutaminase reaction

From glutamate via the glutamate dehydrogenase reaction.

60
Q

Where does aspartate come from?

A

Transamination reaction

= in which oxaloacetate undergoes transamination from glutamate to make aspartate + a-ketoglutarate

Bioenergetics (12 decks)

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