Amino Acids: Fate of Amino + Urea Cycle (Dustin)

Question 1

What are 3 situations when amino acids undergo oxidative degradation?

Answer 1

1. Some proteins that have been broken down form amino acids that are not needed for new protein synthesis
2. Protein rich diet -> excess of amino acids. Amino acids cant be stored, so are catabolized instead
3. Starvation -> cellular proteins used as fuels

Question 2

What remains after an amino acid loses its amino group?

Answer 2

the carbon skeleton, which is an alpha keto acid

Question 3

What are the 4 amino acids used in nitrogen metabolism?

Answer 3

1. glutamate
2. glutamine
3. alanine
4. aspartate

Question 4

What amino acid is this?

Answer 4

Glutamate

(5 carbons, only 1 amino group)

Question 5

What amino acid is this?

Answer 5

Glutamine

(5 carbons, 2 amino groups)

Question 6

What molecule is this?

Answer 6

Alpha-ketoglutarate

5 carbons, no amino groups

Exchanges with glutamate/glutamine due to all having 5 carbons

Also, an intermediate in TCA cycle

Question 7

What amino acid is this?

What molecule involved in glycolysis can this become when its nitrogen is removed?

Answer 7

Alanine

Can become Pyruvate

Question 8

What amino acid is this?

What intermediate in the TCA cycle can it be converted into?

Answer 8

Aspartate

Can be converted into Oxaloacetate

Question 9

What two amino acids are considered the “general collection point” for amino groups?

Answer 9

Glutamate and Glutamine

Question 10

What are the 4 forms that Nitrogen may be in when it is excreted from the body by the kidney?

Answer 10

Urea

NH4+

Creatinine

Urate

Question 11

When one is starving, would the nitrogen excreted by greater or less than the nitrogen ingested?

What about during pregnancy or developing children?

Answer 11

Starvation -> more excreted nitrogen than ingested

Pregnancy/child development -> more nitrogen ingested than excreted

Question 12

Which two amino acids may be taken from muscle during starvation to be used for gluconeogenesis in the liver?

Answer 12

Glutamine

Alanine

Question 13

With ingested dietary proteins, what enzymes are responsible for converting the proteins into peptides?

What converts peptides into amino acids?

And what converts amino acids into (still within GI tract) ammonia?

Answer 13

Food proteins converted by proteases to peptides

Peptides converted by peptidases into amino acids

Amino acids converted by bacteria into ammonia

Question 14

What type of proteases are trypsin, chymotrypsin, and elastase?

Answer 14

Serine proteases

Part of the endopeptidases group for digestion of exogenous proteins