Week 3 Amino Acid Catabolism Flashcards Preview

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Flashcards in Week 3 Amino Acid Catabolism Deck (37)
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1
Q

before an amino acid can be utilized for energy producition what must it be stripped of?

A

nitrogen content

2
Q

The first step of AA catbolism is what?

A

transfer of the amino group (transamination) to alpha-ketogluterate to form Glutamate

3
Q

what enzyme class facilitates the amino group transfer?

A

transaminases or aminotransferases

4
Q

after Glu is made via transamination, what is its fate (2)

A

recycled to support new amino acid synthesis

deaminated and ammonium is formed

5
Q

why is the released ammonia bad?

A

ammonia is a neurotoxin (can cross blood-brain barrier)

6
Q

what is hyperammonemia

A

abnormal elevation of blood ammonia levels (can cause coma or death)

7
Q

what is our bodies solution to limiting ammonia in our bodies?

A

ammonia is converted to non-toxic metabolites

8
Q

how is ammonia “carried” in peripheral tissue?

A

ammonia is wither incorporated into precursor molecules to form glutamine or alanine

9
Q

what enzyme is present in the liver and kidneys that converts glutamine (a carrier of ammonia) back to glutamate and ammonia?

A

glutaminase

10
Q

where is the ultimate site of ammonia detoxification?

A

the liver

11
Q

what is the detoxified form that ammonia is converted to in the liver? what is this biochemical pathway callled

A

urea. urea cycle

12
Q

why is urea a good product for excretion?

A

no net charge, highly water soluble (very polar)

13
Q

if there is little free AA, what happens to the urea cycle? why?

A

urea cycle decreases. AA allosterically regulate the urea cycle such that if there is not sufficient free AA, the cycle (and related protein degradation) does not occur

14
Q

how much ATP is consumed for every molecule of Ammonia in the urea cycle?

A

3 ATP/ammonia

15
Q

what is the strucutre of urea. where do the atoms come from?

A

NH2NH2CO (Carbon from CO2, N from ammonia, N from Asp)

16
Q

other than urea, what is produced during urea cycle?

A

fumerate, this can be used for intermediary metabolism (including gluconeogenesis)

17
Q

what is uremia?

A

an increase in Blood Urea Nitrogen (BUN) correlated with renal failure

18
Q

what organ is responsible for excretion of urea from the blood?

A

kidneys

19
Q

what causes hyperammonemia?

A

defect in liver fxn leading to failure to detoxify ammonia. can be congenital or acquired

20
Q

what are some symptoms of hyperammonemia?

A

ammonia crosses blood-brain barrier and results in tremors, slurred speech, vomiting, coma, death

21
Q

what is a congenital defect?

A

a defect present from birth

22
Q

what is a potential cause of congenital hyperamonemia?

A

a genetic defect in any of the FIVE urea cycle enzymes

23
Q

how many enzymes are used in the urea cycle

A

5

24
Q

Symptoms of Congenital Urea Cycle Disorders (UCDs) tend to be more severe when which enzymes are affected? when do symptoms arise?
why?

A

more severe when enzymes earlier in the urea cycle are impacted (CPSI), symptoms arise 24 to 48 hours after birth, urea cycle is not needed in utero

25
Q

how would you treat hyperammonemia? 2

A

restrict protein and supplement essential AA

create an alternative pathway for ammonia excretion

26
Q

what is the alternate pathway for ammonium excretion?

A

oral Na benzoate or Na phenylbutyrate can complex with Gly or Glu (respecitvely) to form readily excretable water soluble adducts

27
Q

how can hyperammonemia be acquired?

A

liver damage: alcohol abuse, hepatitis, fatty liver disease

28
Q

what is hepatic encaphalopathy?

A

a condition caused by acquired hyperammonemia. neurolopsychiatric alterations and coma. seen in half of liver damage cases.

29
Q

what is urease?

A

a protein produced by certain bacteria that converts urea to ammonia. this is problematic because it can result in kidney stones due to UTI

30
Q

carbon skeletons of degraded AA (AA-Amino group) are classified as what?

A

ketogenic or glucogenic

31
Q

what can glucogenic AA feed into?

A

feed into TCA, gluconeogenesis, non-essential AA synthesis

32
Q

what can ketogenic AA feed into?

A

form Ac-CoA which can only feed into TCA, FA or ketone body synthesis (starvation)

33
Q

every acetyl-CoA that feeds into the TCA cycle produces how much ATP

A

12 (this compensates for the 3 ATP needed to produce urea in urea cycle

34
Q

Most non-essential AA are…why might this be?

A

glucogenic. probably an evoluiton advantage becuase all these AA can be readily enter intermidiary metabolis in a single step

35
Q

what are the 6 wholly or partly ketogenic AA?

A

Leu, Lys (wholly)

Ile, Phe, Trp, Tyr

36
Q

the ketogenic AA typically are broken down to…

A

Acetyl-CoA (cant be converted to pyruvated, enters TCA)

37
Q

what are some metabolites that glucogenic AA are converted to?

A

pyruvate, oxaloacetate (NOT Acetyl-CoA)

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