Amino Acids (Lecture 24)

Question 1

What are the effects of a urea cycle disorder?

Answer 1

Urea cycle disorders arise from deficiencies of certain enzymes in the urea cycle and may result in hyperammonemia and nerve damage.

Question 2

what is maple syrup urine disease?

Answer 2

deficiency of branched chain alpha keto acid dehydrogenase causes elevated branched chained aa/keto acids, which may lead to neurological damage and death

Question 3

what do amino acids contribute to compounds?

Answer 3

nitrogen

Question 4

glycine can be used to produce…

Answer 4

heme
purine rings
creatine

Question 5

which amino acid is used to make hormones and neurotransmitters?

Answer 5

tyrosine

Question 6

how is nitrogen incorporated into the body?

Answer 6

fixation and assimilation

Question 7

how can diazotrophs fixate nitrogen

Answer 7

they express nitrogenase that fixes the atmospheric nitrogen into the soil and then into the food we eat. The nitrogenase uses 16 ATP and produces ammonia (NH3)

Question 8

how is industrial nitrogen fixation accomplished

Answer 8

Haber-Bosch reaction (high temperature and high pressure)

Question 9

how do plants complete the nitrogen assimilation cycle?

Answer 9

plants express glutamine synthethase, which converts NH3 into glutamine

Question 10

what is the difference between fixation and assimilation?

Answer 10

fixation is the incorporation of nitrogen, (N to ammonia)

assimilation is the incorporation of ammonia into other molecules.

Question 11

explain the steps involved in the dietary uptake of amino acids? (7)

Answer 11

1. mechanical break down of proteins via chewing in the mouth
2. chemical digestion of proteins in the stomach via HCl and pepsin
3. poolypeptides broken down to aa in small intestines (via pancreatic enzymes)
4. transport proteins move the products of protein digestion into the mucosal cell.
5. di/tri-peptides enter the mucosal cell and are broken down into single aa once they enter
6. aa pass from the mucosal cell into the blood and travel to the liver. the liver regulates the distribution of aa
7. some aa are lost in the feces

Question 12

pepsin cleaves…

Answer 12

protein to polypeptides (long chains of aa)

Phe, Leu, Trp, Tyr

Question 13

(pancreatic enzyme) trypsin cleaves…

Answer 13

polypeptides to peptides

Arg and Lys

Question 14

(pancreatic enzyme) chymotrypsin cleaves…

Answer 14

polypeptides to peptides

Phe, Trp and Tyr

Question 15

(pancreatic enzyme) amino peptidase carboxypeptidase A cleaves…

Answer 15

peptides to aa (non-specific)

Question 16

what are the main transporter of the bush border and what to they transport?

Answer 16

PEPT1/PEPT2

they transport dipeptides, tripeptides and peptidomimetics

Question 17

how does PEP1/2 uptake peptides?

Answer 17

symport activity. PEPT1/2 will uptake H+ with the peptides. the hydrogen ions gradient (furnished by the Na/H pump) will drive the symport because the excessive H found outside of the cell will be imported into the cell via PEPT to satisfy the gradient

(symport coupled wit anti port )

Question 18

how do neonatal mammals uptake amino acids?

Answer 18

since the neonatal mammals do not express some of the transporters, the milk proteins will incorporate whole milk proteins by either digest the proteins via a lysosome and secrete aa OR transport intact protein via an endoscope.

Question 19

what is the stereochemistry of amino acids?

Answer 19

L enantiomer (side chain tot he left)

Question 20

when is ammonia produced ?

Answer 20

amino acid break down, hence why it must be detoxified

Question 21

glutamate dehydrogenase uses ____ + ____ to generate glutamate.

Answer 21

alpha Ketoglutarate

NAD(P)H

Question 22

Glutamine and Asparagine synthetase uses ____ +_____ to make glutamine/ asparagine

Answer 22

glutamate + ATP to prime for the addition of NH3

aspartate + ATP to prime for the addition of NH3

Question 23

carbamoyl phosphate synthetase nitrogen assimilation reaction uses ____+_____+____ to make carbonyl phosphate

Answer 23

2ATP
HCO3- (CO2)
NH3

Question 24

how is ammonia carried from various tissues to the liver ?

Answer 24

nitrogen assimilation reactions:

• glutamate dehydrogenase
• glutamine/asparagine synthetase

Question 25

explain the amino acid metabolism

Answer 25

ammonia produced via the breakdown on amino acids after contraction

NH3 is incorporated into glutamate to form glutamine via glutamine synthetase

glutamine can then be transported into the blood and then to the liver

glutamine will release NH3 via glutaminase

NH3 will generate urea in the urea cycle, which will then one excreted via the kidneys

Question 26

other than glutamine, what is another aa that carried NH3

Answer 26

Alanine

Question 27

which two enzymes regulate the amino acid pool

Answer 27

glutaminase (liver) and glutamine synthetase (tissues)