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Bioenergetics > Week 10 - Protein Metabolism > Flashcards

Week 10 - Protein Metabolism Flashcards

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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
NUTRITIONALLY NON-ESSENTIAL OR ESSENTIAL Glycine
Non-essential
26
NUTRITIONALLY NON-ESSENTIAL OR ESSENTIAL Proline
non-essential
27
What vitamin does aminotransferase contain
Vitamin B6
28
What is the typical reaction for aminotransferase
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
What is vitamin B6 a precursor for?
Coenzyme pyridoxal phosphate
30
Are transamination reactions reversible or irreversible?
Freely reversible Their net direction depends on the rel conc of the reactants
31
In deamination, where can the amino groups be shuttled from?
1 aa to α-ketoglutarate to make GLUTAMATE Glutamate to another keto acid to create a NEW AA
32
Where must the amino group on glutamate be transferred to (if not already there) + what happens to it there
To liver + into the creation of the urea mol.
33
What happens in the glutamate dehydrogenase reaction?
Removes N from glutamate which can then be used to make urea. In the liver
34
Is the glutamate dehydrogenase reaction reversible?
YES, freely reversible
35
Where does the glutamate dehydrogenase reaction take place
In the mit matrix
36
Where can most aminotransferase enzymes be found?
Mit matrix + cytosol
37
What type of reaction is the glutamate dehydrogenase reaction as it proceeds to the right
A deamination reaction as it removes the amino group
38
When does the glutamate dehydrogenase reaction become an oxidative deamination reaction?
NAD+ --> NADH
39
What is the relationship between the prod of ammonium ion + its release from muscle?
Proportional to the intensity of the exercise.
40
What % of the aa pool is glutamine?
60
41
Where does glutamine come from?
Some diet Most synthesised in body from glutamate using glutamine synthetase.
42
What is glutamine fuel for
Gut + immune system
43
Wheres an important site for glutamine synthesis ?
Skeletal muscle But also prod in brain, adipose tissue + heart.
44
What is the reverse reaction of the glutamine synthetase reaction?
Removal of the amino group from the side chain of glutamine.
45
What reaction does glutamine synthetase catalyse?
Glutamate + ATP + NH4+ --> ADP + Pi + Glutamine
46
Where can glutaminase be mainly found
Liver mitochondria
47
What does glutaminase catalyse the reaction of?
Deamination reaction: Glutamine + H20 --> Glutamate + NH4+
48
Give examples of BCAA
Leucine Isoleucine Valine
49
Where are BCAAs metabolised?
Mainly in skeletal muscle but can also be metabolised in liver.
50
After the 1st 3 reactions of the catabolism of BCAAs what happens next?
- 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
What happens in the 1st reaction of the catabolism of the BCAAs
Transamination = in which the amino group is transferred to α-ketoglutarate to make GLUTAMATE.
52
Whats different about the BCAA aminotransferase enzyme compared to the aminotransferase enzyme in transamination reactions
Aminotransferase in freely reversible transamination reactions. BCAA aminotransferase goes only 1 way.
53
Why does BCAA aminotransferase work only one way
Due to products undergoing an oxidative decarboxylation catalysed by BCKAD (Branched-chain ketogenic acid dehydrogenase).
54
What does the alanine aminotransferase enzyme do?
Can transfer the amino groups on the BCAAs rom glutamate to pyruvate
55
What are the 2 safer temporary forms of ammonia
Amino group of glutamate Side chain amide N in glutamine
56
Where is urea formed
Liver
57
Where is urea excreted from
kidney when urine is formed
58
Where does the carbonyl group on urea come from
CO2
59
Urea synthesis req ammonium ions coming from where?
Ammonia taken up by the liver from the blood From glutamine via the glutaminase reaction From glutamate via the glutamate dehydrogenase reaction.
60
Where does aspartate come from?
Transamination reaction = in which oxaloacetate undergoes transamination from glutamate to make aspartate + a-ketoglutarate

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