Nitrogen and AA Metabolism

Question 1

where does Nitrogen come from?

Answer 1

diet - there is no storage form!

Question 2

in what form is nitrogen released from the kidney ?

Answer 2

as ammonium ions

Question 3

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

Answer 3

urea from the urea cycle

Question 4

what is the amino acid pool?

Answer 4

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

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

Question 5

what 3 things can fill the aa pool?

Answer 5

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

Question 6

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

Answer 6

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]

Question 7

what is dietary essential in children?

Answer 7

arginine

Question 8

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

Answer 8

arginine

Question 9

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

Answer 9

phenylalanine

Question 10

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

Answer 10

methionine

Question 11

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

Answer 11

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

Question 12

what does ubiquitin use for energy?

Answer 12

ATP

Question 13

what is lysosomal degradation independent of?

Answer 13

ATP - does not use!

Question 14

what type of aa have a complex structure?

Answer 14

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

Question 15

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

Answer 15

non-essential - body makes them

Question 16

what food group has the most N?

Answer 16

proteins

Question 17

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

Answer 17

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

Question 18

what happens if one of the aa transporters are deficient?

Answer 18

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

Question 19

how does the liver obtain most of the dietary aa?

Answer 19

portal vein

Question 20

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

Answer 20

aa pool

espicially BCAA

Question 21

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

Answer 21

only hepatocytes

Question 22

how many N does alanine give to liver?

Answer 22

1

Question 23

how many N does glutamine give to liver?

Answer 23

2

Question 24

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

Answer 24

COAL

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

Question 25

what is the most common genetic defect pof aa metabolism?

Answer 25

Cystinuria

Question 26

what is Hartnup's disease?

Answer 26

defect in the transport of large neutral aa - tryptophan

Question 27

what does low levels of tryptophan lead to?

Answer 27

pellagra -like symptoms

Question 28

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

Answer 28

products that can be used for gluconeogenesis pyruvate --> malate = gluconeogenesis

Question 29

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

Answer 29

acetoacetyl CoA or acetyl CoA cannot be used to gluconeogenesis can be used for ketone body synthesis in liver

Question 30

what are the 2 purely ketogenic aa?

Answer 30

leucine and lysine

Question 31

what is transamination?

Answer 31

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.

Question 32

what is deamination?

Answer 32

generates free ammonium ions

Question 33

where is deamination mainly performed?

Answer 33

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

Question 34

What do aminotransferases catalyze?

Answer 34

reversible rxn

Question 35

what do ALT need?

Answer 35

PLP vitamin B6 | 2 substraites = alpha aa and alpha keto acid

Question 36

what aa does ALT use?

Answer 36

alanine

Question 37

what aa does AST use?

Answer 37

aspartate

Question 38

what is the alpha ketoacid for alanine?

Answer 38

pyruvate

Question 39

what is the alpha ketoacid for aspartate?

Answer 39

OAA

Question 40

what is the alpha ketoacid for glutamate?

Answer 40

alpha ketoglutarate

Question 41

what is asparagine demainated to? by what?

Answer 41

aspartate by asparaginase

Question 42

what is aspartate transamination generate?

Answer 42

OAA (TCA cycle)

Question 43

what two aa are used to form asparagine?

Answer 43

aspartate and glutamine

Question 44

what three enzymes use free ammonia for synthesis?

Answer 44

glutamine synthetase glutamate DH carbamoyl phosphate synthase I

Question 45

what is alanine derived from?

Answer 45

pyruvate

Question 46

what is glutamate derived from?

Answer 46

alpha ketoglutarate

Question 47

what is aspartate derived from?

Answer 47

OAA

Question 48

what is cysteine derived from?

Answer 48

methionine

Question 49

what is tyrosine derived from?

Answer 49

from phenalalanine

Question 50

where is arginine formed?

Answer 50

urea cycle

Question 51

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

Answer 51

urea

Question 52

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

Answer 52

dermatitis diarrhea dementia death