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Y1 Nutrition & metabolism > Protein metabolism > Flashcards

Protein metabolism Flashcards

1
Q

Protein digestion & absorption (overview)

A

Stomach - proteins to polypeptides (HCL, Pepsin)

Pancreas (peptidases)

SI - polypeptides to amino acids (peptidases

absorbed as amino acids

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2
Q

What happens to amino acid pools

A

constantly synthesises into body proteins and then broken down again

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3
Q

what happens to excess amino acids

A

made into CHO or Fat

amine group comes off and is excreted as urea through urine/sweat

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4
Q

Amino acid structure

A

C H O N w/ specific R group

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5
Q

What effect does increase insulin have on amino acids

A

It arrives at the liver and is synthesised into protein and transport to tissues or is stored as CHO/Fat

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6
Q

What happens to amino acids when fasted (catabolic)

A

Amino acids/proteins broken down (amine group removed) to give CHO for energy

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7
Q

How do proteins enter the TCA cycle (ketogenic & Glucogenic)

A

Ketogenic - made into acetyl-CoA

Glucogenic - feed into all different parts of the cycle depending on the AA

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8
Q

name of AA wo/ nitrogen group (amine)

A

Alpha keto - acids

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9
Q

What does Transamination do

A

Transfers amino group from AA to alpha ketoacid in the presence of a transaminase

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10
Q

Why is transamination important

A

needed for non essential amino acid production in body - & is reversable

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11
Q

where does transamination occur

A

most tissues including muscle

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12
Q

2 common transamination examples

A

Alanine + a-Keto glutamate = pyruvate + Glutamate

Aspartate + a-Keto glutamate = oxaloacetate + Glutamate

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13
Q

why is alanine transamination important during exercise

A

can be transaminated into pyruvate in liver for energy

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14
Q

why is aspartate transamination important

A

for urea cycle function

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15
Q

How does oxidative deamination work

A

ammonia group is removed

eg Glutamate to A-ketoglutarate

Is reversible & dependant on substrate availability/requirements

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16
Q

where does oxidative deamination occur

A

in the mitochondria matrix of the liver

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17
Q

Why is Glutamine synthesis important

A
  • Has 2 nitrogen’s (can remove 2 ammonia groups at once)
  • the most abundant free AA in blood
  • Gluconeogenic precursor
  • Fuels GI & immune systems
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18
Q

How is nitrogen (ammonia) removed from the body

A
  • small amounts are excreted rest enters the urea cycle (energy & enzyme regulated)
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19
Q

AA - Urea link

A

^ AA = ^ Urea

Flux is dependant on substrate supply

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20
Q

How does the urea cycle work (carbamoyl production)

A

Ammonia + Co2 = Carbamoyl phosphate (enzyme = carbamoyl phosphate synthetase)

Irreversible

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21
Q

How does the urea cycle work (the cycle)

A

Carbamoyl phosphate combined with aspartate to produce urea - uses energy (fumarate side product for TCA cycle)

Urea out via sweat/urine

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22
Q

Branched chain amino acids (BCAA) examples & importance

A
  • Leucine, Isoleucine, Valine

Can be oxidised in skeleton muscle mitochondria

important for muscle protein synthesis

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23
Q

BCAA oxidation overview

A

each pathway is specific w/ enzymes

Vitamin B12 and biotin required in pathways

Products are fed into TCA cycle

24
Q

How does glycogen get back into the blood from muscle (Glucose-Alanine cycle work)

A

Glycogen -> G-6-P -> Pyruvate -> Alanine (transamination) -> released by muscle into blood

25
Q

What happens to alanine once in the blood (Glucose-Alanine cycle work)

A

enters the liver and undergoes transamination w/ a-ketoglutarate forming pyruvate and glutamate

Pyruvate undergoes gluconeogenesis producing glucose

26
Q

What happens to glucose/glutamate produced in the liver (Glucose-Alanine cycle work)

A

Glucose - it is release back into the blood and transported to muscle/brain

Glutamate deaminated (ammonia excreted)

27
Q

Muscle protein synthesis definition

A

Building up of amino acids into functioning muscle

28
Q

Muscle protein breakdown definition

A

Degradation of polypeptide chains within a muscle

29
Q

net balance definition

A

relationship between synthesis and breakdown

30
Q

Turnover defintion

A

constant use and restoration of protein

31
Q

Protein synthesis (PS) - protein breakdown (PB) = ?

A

net protein balance

32
Q

PB > PS = ?

A

negative protein balance (protein loss)

33
Q

PS > PB = ?

A

positive protein balance (protein gain)

34
Q

What % of basal energy expenditure is used for RNA formation

A

20%

35
Q

why do some proteins have short half-lives

A

enzymes only needed for a short period of time

36
Q

What does selective gene expression do

A

determines structural and functional characteristics of various cell types

37
Q

How do genes & proteins differ

A

genes may be expressed but proteins must be activated, modified or converted

38
Q

Protein synthesis process order

A
  • transcription
  • translation
  • post translational modification & protein activation
39
Q

Transcription process overview

A

copying DNA strand to mRNA (complementary base pair)

Enzyme = RNA polymerase

40
Q

How is transcriptional controlled (3 groups)

A

Activators - bind to enhancer sites promoting transcription

Coactivator proteins - correctly position RNA polymerase

Repressors - bind to silencer sites

41
Q

How is RNA polymerase regulated?

A

general factors - set base rate
specific factors - interact to modulate rate

hormones

  • specific (steroids) - modulate process
  • Secondary messenger (cAMP) - bind to cell membrane
42
Q

What does aminoacyl tRNA synthetase do?

A

catalyses binding of AA to appropriate tRNA (w/ ATP)

is able to proofread before releasing tRNA

43
Q

3 steps of translation

A

Initiation

Elongation

Termination

44
Q

What is translation initiation

A

40S + 60S ribosomal subunits + mRNA molecule building new DNA molecule

(signally proteins eg eIF2 control this process)

45
Q

Common start and stop codons

A

Start - Met

Stop - Aug

46
Q

What is translation elongation

A

adds AA to carboxyl terminal end of PP chain

(because anticodon of aminoacyl-tRNA recognises second codon on mRNA)

Peptide bond forms

47
Q

What is translation termination

A

When a stop codon is reached a release factor releases the complete PP chain from the last tRNA (addition of water)

ribosomal units separate

48
Q

what do the 3 tRNA sites do (A P E)

A

A - landing site

P - Second binding site

E - Exiting site

49
Q

what does post-translational modification do

A
  • Continue folding to make the protein functional

- Transportation

50
Q

What do molecular chaperones do

A

help build protein 3D shape (eg heat shock proteins HSP)

51
Q

What do scaffolding proteins do

A

take proteins across mitochondrial membrane

52
Q

Why do we breakdown proteins

A

Quality control - remove mutants, damaged

Turnover - short life, not required

Provision of AA - energy
(a-ketoacids) , protein synthesis

53
Q

How does Ubiquitin-proteosome breakdown proteins

A

marks a specific protein for degradation

54
Q

How doe lysosomal breakdown proteins

A

endocytosis

55
Q

How does caspases breakdown proteins

A

programmed cell death

56
Q

how does matrix metalloproteinases

A

removes extracellular matrix breakdown proteins

57
Q

Why is calpain used to breakdown protein in muscles

A

because it is calcium activated

Y1 Nutrition & metabolism (11 decks)

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