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Nutrition & Metabolism > W6 - Protein Metabolism > Flashcards

W6 - Protein Metabolism Flashcards

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1
Q

What are proteins metabolised to in the stomach?

A

Polypeptides

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2
Q

Where do the polypeptides from the stomach travel to?

A

Small intestine

–where peptidases (secreted from the pancreas + intestinal wall) break them down to:

  • aa, di peptidases + tri peptidases.
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3
Q

What happens to the aa in the small intestine?

A

Absorbed into blood

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4
Q

aa after eating - fed state

A

⬆️ insulin in blood

aa arrive at liver from the hepatic portal vein

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5
Q

aa after eating - fed state

What do the aa do once arrived at the liver

A

Used for protein synthesis

Transported to other tissues

Storage - TAG / Glycogen

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6
Q

aa when not having eaten for a while - fasted state

A

Body needs to make energy

aa broken down as body is in a catabolic state

Glucagon in blood

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7
Q

What are the 2 ways aa can be classified?

A

Glucogenic

Ketogenic

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8
Q

Fate of ketogenic aa

A

Will be converted to AcetylCoA or Acetoacetyl CoA

Then enter TCA cycle if in catabolic situation

OR

Converted back to be stored as fat.

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9
Q

Fate of glucogenic aa

A

Feed into TCA cycle:

  • Used for energy if in catabolic state.

OR

  • If taken in excess aa, store them as CHO
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10
Q

Difference between aa + a-keto acid

A

a-keto acid is an aa but with the N group removed

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11
Q

What happens to the aa that aren’t used for protein synthesis or synthesis of any N containing compounds?

A

Metabolised by transamination or deamination

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12
Q

What is the most common way to remove N from an aa?

A

By transaminating it

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13
Q

How does transamination work/.

A

N group on aa is transferred to an a-keto acid

= Interchangeable reaction

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14
Q

How is deamination carried out?

A

W/ dehydrogenase

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15
Q

What does deamination result in?

A

a-keto acid

NH3

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16
Q

What is transamination important for?

A

Production of non-essential aa

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17
Q

Transaminases are freely reversible but what do they depend on?

A

Substrate availability

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18
Q

Where does transamination occur?

A

Most tissues including the muscle

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19
Q

What do main transamination reactions involve?

A

Alanine

Aspartate

Glutamate

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20
Q

What does the liver do during exercise in regards to alanine?

A

Increases its uptake by about 50%

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21
Q

Why does the liver increase the uptake of alanine during exercise?

A

As it can be converted to pyruvate.

  • Pyruvate can go through gluconeogenesis OR can be oxidised to give energy
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22
Q

Why is aspartate important for nitrogen excretion?

A

Plays a part in the urea cycle

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23
Q

When can transamination be heavily utilised?

A

During periods of starvation or prolonged exercise

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24
Q

Where does oxidative deamination occur?

A

Mit matrix of liver

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25
What happens when there's a shortage of substrates during oxidative deamination in the liver?
Glutamate is broken down to give: - NADH (can enter ETC) - a-ketoglutarate (can enter TCA cycle)
26
Which aa is the only aa to contain 2 nitrogens?
Glutamine
27
What can be used to make glutamine? How?
Glutamate Glutamate + NH4 + ATP --> Glutamine + ADP
28
Which aa is the most abundant free aa in the skeletal muscle + blood?
Glutamine
29
What is glutamine really important for?
Ammonia transport Gluconeogenic precursor Helps transfer C + N between skeletal muscle + kidneys Fuel for GI tract + immune system
30
What is meant by glutamine being a gluconeogenic precursor?
If amino group is lost from glutamine = glutamate If another is lost = a-ketoglutarate (can enter TCA cycle) Then can go round + back up through gluconeogensis OR can be used for oxidation.
31
Example of a cataplerotic loss
Losing glutamine from muscles
32
Where does the urea cycle happen?
Liver
33
UREA CYCLE - STEP 1 (Before actually entering cycle) NH3 + CO2 + 2ATP---> By what enzyme?
Carbamoyl P + 2ADP By Carbamoyl P synthetase IRREVERSIBLE
34
What is carbamoyl P synthetase stimulated by?
N-acetylglutamate
35
How does carbamoyl P enter the urea cycle?
By combining w/ L-ornithine --> citrulline
36
UREA CYCLE Citrulline --> L-argininosuccinate
Citrulline + ATP + N from aspartate--> L-argininosuccinate + AMP
37
UREA CYCLE What happens to the fumarate produced between L-argininosuccinate --> L-arginine
Leaves + enters TCA cycle
38
In which part of the urea cycle is urea released into the blood?
Between L-arginine + L-ornithine
39
What must happen to get the a-keto acid from BCAAs
Must be transaminated w/ a-ketoglutarate to get glutamate + the a-ketoacids of BCAAs Enzyme = BCAT
40
What happens to the glutamate produced from BCAA oxidation?
Transaminates to form alanine Alanine leaves muscle + taken up by liver
41
What then happens to the a-ketoacids of BCAAs?
Undergo dehydrogenation by BCKDH Where H group is removed so they have their own specific dehydrogenase.
42
What does valine make after the BCAA oxidation?
Succinyl CoA - Glucogenic aa
43
What does isoleucine make after the BCAA oxidation?
Succinyl CoA - Glucogenic aa Also creates acetyl-CoA - Ketogenic
44
What does leucine make after the BCAA oxidation?
Acetyl CoA + Acetoacetyl CoA - Ketogenic
45
Where does glycogenolysis occur?
Muscle
46
What does glycogenolysis result in?
G-6-P which can go further through glycolysis to create pyruvate.
47
Glucose-Alanine cycle Pyruvate created from G-6-P in glycogenolysis. What can happen to it?
Can transaminate w/ an aa to form Alanine in the muscle. Released into blood. Taken up by liver Undergoes transamination w/ a-ketoglutarate --> glutamate + pyruvate.
48
What can happen with the pyruvate formed from the glucose-alanine cycle when in the liver?
Can go through gluconeogenesis. Glucose can be released back into blood + transported to wherever needed.
49
Glucose alanine cycle What happens to the glutamate in the liver?
Deaminated NH3 lost through urea OR used to make plasma proteins.
50
How is net protein balance calculated?
Protein synthesis - Protein breakdown
51
Transcription How is it controlled?
By: Transcription factors Coactivator proteins Repressors
52
Transcription How is it controlled? What comes under transcription factors?
Activators Enhancer sites
53
Transcription How is it controlled? What comes under coactivator proteins?
Signals
54
Transcription How is it controlled? What comes under repressors?
Silencer
55
Role of tRNA
Brings aa to mRNA
56
What catalyses the binding of aa to the appropriate tRNA
Aminoacyl tRNA synthetase
57
3 stages of translation
Initiation Elongation Termination
58
What does the process of initiation of translation involve?
40s + 60s ribosomal units mRNA mol Initial aminoacyl-tRNA (tRNA mol w/ methionine attached) Protein factors to control initiation process Energy from GTP
59
Examples of the protein factors to control the initiation process of translation
p70s6 kinase
60
What does elongation in translation involve?
Addition of aa to carboxyl terminal end of polypeptide chain
61
Why does elongation in translation occur?
Anticodon of aminoacyl-tRNA recognises 2nd codon on mRNA
62
Elongation in translation Where does the peptide bond occur?
Between carboxyl group of MET + 2nd aa (still attached to tRNA)
63
Termination in translation What does the termination / release factor do?
Releases the complete polypeptide chain from the last tRNA 80s dissociates to its 2 x 40s + 60s subunits.
64
Post-translational control of protein function What is it regulated by?
- Chaperones | - Scaffolding proteins
65
What are the 5 main pathways in which protein can be broken down?
Ubiquitin-proteosome Lysosomal proteolysis Caspases Matrix metalloproteases Calpain
66
How can muscle protein synthesis + breakdown be measured?
By looking at: Fractional synthetic rate (FSR) OR Fractional breakdown rate (FBR)
67
How is fractional synthetic rate typically measured?
Biopsies and Isotopes
68
At rest what is greater? - Muscle protein synthesis or muscle protein breakdown
Muscle protein breakdown
69
When taking a muscle biopsy, what muscle protein fractions do you separate out?
Collagen Myofibrillar proteins Mitochondria proteins Sarcoplasmic proteins
70
Which of the muscle proteins is more associated with resistance type exercise?
Myofibrillar proteins
71
Which of the muscle proteins is more associated with endurance type exercise?
Mitochondrial proteins
72
What does exercise do to net muscle protein balance?
Improves it but still no positive values are reached.
73
Availability of substrates in the human body. Where can the CHO be?
Plasma glucose Liver glycogen Muscle glycogen
74
Availability of substrates in the human body. Where can the fats be?
Plasma FAs Plasma TAGs Muscle TAGs Adipose tissue
75
How does the VO2 max test step protocol work in the fat max test?
Start at low intensity at 60W on a bike. ⬆️W by 35 every 3 mins.
76
When collecting data for the VO2 max test step protocol in the fat max test, which data do you collect and disregard?
Disregard = 1st min of each workload Calculate = Average of final 2 mins
77
Where can BCAA be oxidised?
Kidneys + muscle
78
What happens to net balance following resistance exercise ONLY
⬆️ but remains -ive
79
When BCAAs are oxidised, what is their N group generally used to form?
Glutamate + then alanine
80
Where does the decarboxylation of a-ketoacids involving branched chain a-keto acid dehydrogenase occur?
In the mit
81
Which protein breakdown system is most likely to be used in the muscle following exercise?
Calpain system
82
Which amino acid is always the first in a polypeptide chain?
Methionine

Nutrition & Metabolism (17 decks)

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