Practice questions for test 2

Question 1

Allopurinol is a drug used to treat gout. It acts as a suicide inhibitor of which of the following?

Hypoxanthine
Glycopeptidyl transpeptidase
Uric acid
Xanthine oxidase
Guanine

Answer 1

Xanthine oxidase

Question 2

What does conditionally essential mean?

Answer 2

When Phenylalnine is consumed it is converted to tyrosine. If not enough of Phenyalanine is consumed, tyrosine becomes essential

Question 3

Alanine, aspartate, and glutamate synthesized by transfer of amino group to the alpha acids

pyruvate to Alanine

oxaloacetate to aspartate

alpha ketoglutarate to glutamate

Answer 3

pyruvate to Alanine

oxaloacetate to aspartate

alpha ketoglutarate to glutamate

Question 4

Describe reactions by which serine and glycine are synthesized

Answer 4

Serine is major biosynthetic precursor for both glycine and cysteine.
Serine is synthesized in three steps. Serine is formed by hydrolysis !
Serine comes form glycolysis and grabs a C to form Lysine.
Glycine is formed from serene by removal of a methyl group.
*Cysteine comes from the activated methyl cycle HOMOCYSTEINE!

Question 5

What is a precursor in the biosynthesis of cholesterol?

a. pregnenolone
b. cholic acid
c. progesterone
d. lanosterol
e. malonyl Coa

Answer 5

d. lanosterol

Question 6

Animals fed a high choles. diet exhibit a decreased cholesterol syn by the liver because of the inhibition of what?

a. HMG CoA reductase
b. squalene syn
c. HMG CoA lyase
d. mevalonate kinas
e. HMG coA synthetase

Answer 6

a. HMG CoA reductase

Question 7

Which of the following is correct about plasma lipoproteins

Answer 7

VLDL are precursors of LDL in the circulation

Question 8

pyruvate is

Answer 8

alanine with out amine (think ALT)

Question 9

alpha ketoglutarate is

Answer 9

glutamate with out amine (think ALT)

Question 10

aspartate is

Answer 10

oxaloacetate without amine (think AST)

Question 11

glutamine is

Answer 11

glutamate and amine grp (2 total)

Question 12

Where does the nitrogens broken down amino acids from the urea cycle come from?

Answer 12

They come from the a.a that are broken down in form of glutamate that travel through the blood as glutamine and can be broken down into alpha ketoglutamate and ammonia to ether the cycle.

Question 13

What is the role of alanine in ammonia elimination?

Answer 13

Alanine is formed by transamination of glutamate to pyruvate. roles: 1) carry ammonia to LIVER 2) provide a pyruvate for gluconeogenesis.
***Ammonia is transported from muscle to liver in form of Alanine. *

Question 14

what is the role of glutamine in ammonia elimination?

rxn catalyzed by glutaminase

Answer 14

Glutamine provides a nontoxic storage and transport of ammonia.
It is found in plasma at high concentrations more than other a.a.
Glutamine is alpha ketoglutarate and an amine glutamate. (when you add another you get glutamine)

Question 15

Importance of Fumarate ?

Answer 15

Links the Urea cycle with gluconeogenesis and Transamination of oxaloacetate.

Note: fumarate is converted to oxaloacetate in TCA and then to aspirate by transamination

Question 16

Ammonia toxicity?

Answer 16

Ammonia changes the equilibrium of Glutamate dehydrogenase rxn (so you deplete the CTA and specifically alpha ketoglutarate when doing this!!!

Question 17

How can you acquire hyoerammonemia?

Answer 17

1) acquired hyoerammonemia b/c of liver cirrhosis.
2) hereditary hyoerammonemia
(urea cycle enzyme def.)