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Biochemistry Post Midterm > Nitrogen and AA Metabolism > Flashcards

Nitrogen and AA Metabolism Flashcards

1
Q

where does Nitrogen come from?

A

diet - there is no storage form!

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2
Q

in what form is nitrogen released from the kidney ?

A

as ammonium ions

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3
Q

in what form is N released from the liver - major!?

A

urea from the urea cycle

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4
Q

what is the amino acid pool?

A

all the free amino acids in cells, blood and extracellular fluid.

Its the center of whole body N metabolism = 100 g of aa

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5
Q

what 3 things can fill the aa pool?

A
  1. dietary amino acids
  2. synthesized nonessential amino acids
  3. amino acids generated by body protein degradation.
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6
Q

What are the aa in the aa pool taken out and used for?

A
  1. for body protein synthesis
  2. for synthesis of specialized products derived by conversion of amino acids
  3. for eventual degradation for energy metabolism in all cells or for synthesis of glucose or ketone bodies in hepatocytes [glucogenic and ketogenic amino acids]
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7
Q

what is dietary essential in children?

A

arginine

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8
Q

what is semi-essential or conditionally non-essential in adults?

A

arginine

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9
Q

The deficiency of which amino acid makes tyrosine an essential amino acid?

A

phenylalanine

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10
Q

The deficiency of which amino acid makes cysteine an essential amino acid?

A

methionine

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11
Q

Name three concepts how humans can synthesize non-essential amino acids.

A
  1. aminotransferase rxns
  2. amidation rnxs
  3. other aa as precursors (cysteine+tyrosine)
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12
Q

what does ubiquitin use for energy?

A

ATP

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13
Q

what is lysosomal degradation independent of?

A

ATP - does not use!

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14
Q

what type of aa have a complex structure?

A

essential aa - can’t make - aren’t close to glycolysis or TCA cycle intermediates in terms of structure

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15
Q

what type of aa have a close structure to those of glycolysis or TCA cycle intermediates?

A

non-essential - body makes them

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16
Q

what food group has the most N?

A

proteins

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17
Q

How are dietary amino acids transported into the intestinal mucosal cells?

A

Amino acids during digestion are transported against a concentration gradient by secondary active co-transport with sodium ions into the intestinal mucosal cell

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18
Q

what happens if one of the aa transporters are deficient?

A

that transporter is deficient in the intestinal mucosal cell and in the kidney

leads to less up take of the respective group of aa into intestinal mucosal cells and leads to higher urinary levels than normal of aa as reuptake by the kidney is also deficient

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19
Q

how does the liver obtain most of the dietary aa?

A

portal vein

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20
Q

where do the aa go that are not being used by the liver?

A

aa pool

espicially BCAA

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21
Q

what perform the complete urea cycle and generate urea in cytosol?

A

only hepatocytes

22
Q

how many N does alanine give to liver?

A

1

23
Q

how many N does glutamine give to liver?

A

2

24
Q

Which transporter is defective in patients with cystinuria? What is the function of it?

A

COAL

needed for transport of cystine
and dibasic aa - ornithine, arginine, lysine

25
Q

what is the most common genetic defect pof aa metabolism?

A

Cystinuria

26
Q

what is Hartnup’s disease?

A

defect in the transport of large neutral aa - tryptophan

27
Q

what does low levels of tryptophan lead to?

A

pellagra -like symptoms

28
Q

what do glucogenic amino acid leads to a degradation product of?

A

products that can be used for gluconeogenesis

pyruvate –> malate = gluconeogenesis

29
Q

what do ketogenic amino acid leads to a degradation product of?

A

acetoacetyl CoA or acetyl CoA

cannot be used to gluconeogenesis
can be used for ketone body synthesis in liver

30
Q

what are the 2 purely ketogenic aa?

A

leucine and lysine

31
Q

what is transamination?

A

a “safe” way to transfer the α-amino nitrogen from one amino acid to an α−ketoacid which generates another amino acid. Transamination does not generate free ammonium ions which can be toxic. It transfers the nitrogen from the α-amino group to the respective α-ketoacid and verse visa.

32
Q

what is deamination?

A

generates free ammonium ions

33
Q

where is deamination mainly performed?

A

in the liver and kidney, where the ammonium ions are used for the urea cycle or are released into urine.

34
Q

What do aminotransferases catalyze?

A

reversible rxn

35
Q

what do ALT need?

A

PLP vitamin B6

2 substraites = alpha aa and alpha keto acid

36
Q

what aa does ALT use?

A

alanine

37
Q

what aa does AST use?

A

aspartate

38
Q

what is the alpha ketoacid for alanine?

A

pyruvate

39
Q

what is the alpha ketoacid for aspartate?

A

OAA

40
Q

what is the alpha ketoacid for glutamate?

A

alpha ketoglutarate

41
Q

what is asparagine demainated to? by what?

A

aspartate

by asparaginase

42
Q

what is aspartate transamination generate?

A

OAA (TCA cycle)

43
Q

what two aa are used to form asparagine?

A

aspartate and glutamine

44
Q

what three enzymes use free ammonia for synthesis?

A

glutamine synthetase
glutamate DH
carbamoyl phosphate synthase I

45
Q

what is alanine derived from?

A

pyruvate

46
Q

what is glutamate derived from?

A

alpha ketoglutarate

47
Q

what is aspartate derived from?

A

OAA

48
Q

what is cysteine derived from?

A

methionine

49
Q

what is tyrosine derived from?

A

from phenalalanine

50
Q

where is arginine formed?

A

urea cycle

51
Q

what is the major aa that the kidney excretes in urine?

A

urea

52
Q

what are the 4 D’s associated with Hartnup’s disease or pellagra disease>

A

dermatitis
diarrhea
dementia
death

Biochemistry Post Midterm (24 decks)

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