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BioChem Exam 2 > Metabolism III: Protein > Flashcards

Metabolism III: Protein Flashcards

1
Q

Can amino acids be synthesized de novo?

A

Yes, but nitrogen has to come from the environment

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2
Q

Where are all AAs derived from?

A

intermediates in:
glycolysis
CAC
PPP-pyruvate

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3
Q

Nitrogen enters the pathways by way of…

A

glutamate and glutamine

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4
Q

How many AAs can plants and bacteria synthesize?

A

all of them

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5
Q

How many AAs can mammals synthesize?

A

only about half of them

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6
Q

What are the fates of carbon skeletons?

A
  • ketogenic AAs
  • Glycogenic AAs
  • Gluco- and ketogenic AAs
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7
Q

How can AAs be classified?

A
  • essential vs nonessential
  • fate of C skeleton
  • hydrophobic vs hydrophilic
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8
Q

AAs as a source of energy

A

humans derive a small fraction of their oxidative energy from the catabolism of AAs

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9
Q

What are the three AA metabolic states?

A
  • protein turnover
  • dietary protein
  • during starvation and uncontrolled diabetes
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10
Q

What happens to AAs during protein turnover?

A

Was released from breakdown of cellular proteins

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11
Q

What happens to AAs during dietary protein?

A
  • Surplus AAs undergo oxidative degradation

- they cannot be stored

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12
Q

What happens to AAs during starvation?

A

Muscle protein broken down to release AAs

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13
Q

What happens to AAs in uncontrolled diabetes?

A

Carbohydrates are not properly utilized

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14
Q

The AAs lose their amino groups to form what during metabolism?

A

a-keto acids (the carbon skeletons of AAs_

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15
Q

What are the two metabolic fates of a-keto acids?

A
  • undergo oxidation (Krebs) to CO2 and H2O

- provide 3 and 4 carbon units that can be converted by gluconeogenesis into glucose

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16
Q

Where do the processes of AA degradation converge?

A

Krebs cycle

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17
Q

What four AAs play a central role in AA metabolism?

A
  • glutamate (a-KG)
  • glutamine (a-KG)
  • alanine (pyruvate)
  • aspartate (oxaloacetate
18
Q

What are the two major biochemical processes that occur during AA catabolism?

A
  • transamination

- deamination

19
Q

What is the enzyme involved in the process of alanine-glucose cycle?

A

alanine aminotransferase

20
Q

What is the enzyme involved in the process between a-KG and glutamate?

A

valine aminotransferase

21
Q

Where does transamination of alanine-glucose cycle occur?

A
  • muscle

- Cytosol of liver

22
Q

What AA metabolism occurs during transamination in the muscle?

A

alanine- glucose cycle

23
Q

What is the reaction that occurs during alanine-glucose cycle?

A

Glutamate + pyruvate –> alanine + aKG (pyruvate)

24
Q

What does the alanine do in the alanine-glucose cycle?

A
  • alanine transports ammonia from skeletal muscle to liver
25
Q

What is the alanine-glucose cycle in concert with?

A

Cori cycle

26
Q

What happens to pyruvate and lactate during the alanine-glucose cycle?

A
  • transported to liver for gluconeogenesis
  • ammonia converted to urea in liver
  • energetic burden is imposed on liver and not muscle
27
Q

Where does deamination occur?

A

mitochondria of liver

28
Q

What is the reaction of deamination?

A

glutamate –> Ammonia + aKG

29
Q

Where does the ammonia in deamination go?

A

urea cycle

30
Q

Where does aKG go in deamination?

A

Krebs cycle

gluconeogenesis

31
Q

What enzyme is used in the conversion of glutamate + ammonia to glutamine?

A

Glutamin synthetase

32
Q

What is the enzyme used in the conversion of glutamine to glutamate?

A

Glutaminase

33
Q

What organ is more susceptible to ammonia toxicity?

A

Brain

34
Q

What occurs during the mechanisms of ammonia?

A

molecular mechanism is unclear

35
Q

What are the terminal states of ammonia intoxication in humans characterized by?

A
  • comatose state
  • cerebral edema
  • increased cranial pressure
36
Q

What is the major acceptor of ammonia?

A
  • glutamate (forms glutamine)

- this will deplete glutamate

37
Q

Glutamate and its derivative (gamma-aminobutyrate) are important …

A

NTs

38
Q

What happens to the free ammonia produced in the extra-hepatic tissues?

A

converted to a non-toxic product

39
Q

What AA is affected in albinism

A

melanin synthesis from tyrosine

40
Q

What AA is affected in alkaptonuria?

A

Tyr degradation

41
Q

What AA is affected in maple syrup disease?

A

(branched chain ketoaciduria)

Iso, Leu, Val degradation

42
Q

What AA is affected in phenylketonuria?

A

conversion of Phe to Tyr

BioChem Exam 2 (6 decks)

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