Question

Can someone please check my answers and aid in #12?

1. The amide nitrogen of glutamine:

A. represents a nontoxic transport form of ammonia.

B. is a major source of ammonia for urinary excretion.

C. is used in the synthesis of asparagine, purines, and pynimidines.

D. can be recovered as ammonia by the action of glutaminase.

E. all of the above are correct.

2- Which of the following statements about glutamate is NOT true:

a It can be synthesized in the transaminase reaction using alanine as a substrate

b It can be synthesized in an aminotransferase reaction using aspartate as a substrate

c It can be synthesized by the glutamate dehydrogenase reaction using alpha-ketoglutarate and free ammonium ion as substrates

d It can transfer it's amino group to oxaloacetate in a one step reaction

e It can transfer it's amino group to citrulline in a one step reaction

3. The products of the catabolism of cysteine are:

a) Serine and phosphate

b) Serine and HCl

c) Pyruvate and sulfate

d) Serine and sulfate

e) Alanine and sulfate

4. The catabolic products of isoleucine, methionine, and valine all enter into the TCA cycle or glycolysis as

A Pyruvate

B Oxaloacetate

C Succinyl CoA

D Acetyl CoA

E Fumarate

5-What is the name of the cofactor for AST, ALT, or any other transamination reaction?

A NAD⁺

B Acetyl CoA

C Pyridoxal phosphate (PLP)

D FADH₂

E NADPH

6. Valine and isoleucine give rise to propionyl CoA, a precursor succinyl CoA. A disease related to a defect in this conversion methylmalonic aciduria. Some patients respond to megadoses of vitamin B Which of the following statements about the conversion of propionyl CoA to succinyl CoA is/are correct?

A. The first step in the conversion is a biotin-dependent carboxylation.

B. Some methylmalonic aciduria patients respond to B12 because the defect in the mutase converting malonyl CoA to succinyl CoA is poor binding of the cofactor.

C. The same pathway of propionyl CoA to succinyl CoA is part oa the metabolism of odd-chain fatty acids.

D. All of the above are correct.

E. None of the above is correct.

7. All of the following are true about the branched-chain amino acids EXCEPT:

A. they are essential in the diet.

B. they differ in that one is glucogenic, one is ketogenic, and one is classified as both.

C. they are catabolized in a manner that bears a resemblance to B-oxidation of fatty acids.

D. they are oxidized by a dehydrogenase complex to branch chain acyl CoAs one carbon shorter than the parent compound.

E. they are metabolized initially in the liver.

8-The most dramatic increases in serum alanine transaminase(SGPT or ALT) levels occur in patients with

A. biliary obstruction.

B. hemolysis.

C. malabsorption of fat-soluble vitamins.

D. inflammatory diseases of the liver.

E. intrahepatic cholestasis.

9. S-Adenosylmethionine:

A. contains a positively charged sulfur (sulfonium) that facilitates the transfer of substituents to suitable acceptors.

B. yields a-ketobutyrate in the reaction in which the methyl is transferred.

C. donates a methyl group in a freely reversible reaction.

D. generates H2S by transsulfuration.

E. provides the carbons for the formation of cysteine.

10-Which of the following compounds serves as a coenzyme for transaminase reactions?

A. pyridoxal phosphate

B. thiamine pyrophosphate

C. nicotinamide adenine dinucleotide

D. flavin adenine dinucleotide

E. coenzyme A

11. In transamination, which amino acid is converted into oxaloacetic acid?
A. Lysine
B. Aspartic
C. Glutamic
D. Threonine
E. Methionine

12.The a -keto acid that is produced by transamination of alanine is:

A. oxalic acid

B. pyruvic acid

C. oxaloacetic acid

D. a -keto butyric acid

E. homocysteine

13- The reactions of the urea cycle take place in

a) the cytosol.

b) the mitochondrion.

c) the nucleus.

d) the cytosol and the mitochondrion.

e) the cytosol and the nucleus.

14- Intermediates in the urea cycle include all of the following except

a) lysine.

b) ornithine.

c) arginine.

d) citrulline.

e) carbamoyl phosphate.

15- The nitrogen atoms in urea are derived directly from

a) ammonia and lysine.

b) ammonia and aspartate.

c) glutamine and glutamate.

d) glycine and ammonia.

e) glycine and asparagine.

16. Carbamoyl phosphate synthetase I:

A. is a flavoprotein.

B. is controlled primarily by feedback inhibition.

C. is unresponsive to changes in arginine.

D. requires N-acetylglutamate as an allosteric effector.

E. requires ATP as an allosteric effector.

17- Which one of the following is synthesized from an essential amino acid?

A. Alanine

B. Glutamate

C. Proline

D. Tyrosine

E. Aspartate

18. The step in porphyrin biosynthesis which is excessively stimulated in the acute porphyrias is the step catalyzed by

A. delta-amino levulinic acid synthase

B. uroporphyrinogen III cosynthase

C. porphobilinogen deaminase

D. coproporphyrinogen III oxidase

E. ferrochelatase

19.In jaundice that accompanies neonatal isoimmune hemolysis the substance most likely to be elevated in   serum is

A. beta-glucuronidase.

B. bilirubin diglucuronide.

C. biliverdin.

D. unconjugated bilirubin.

E. deoxycholic acid.

20. Increased excretion of urobilinogen in the urine is generally the result of

A. acute hemolytic anemia.

B. erythropoetic porphyria.

C. Gilbert’s syndrome.

D. iron deficiency.

E. bile duct obstruction.

Answer 1

Ans 12 : B) pyruvic acid

Alanine transfers its amino group to alpha ketoglutarate and forms pyruvic acid. The reaction is called as transamination reaction , as it involves the transfer of an amino group from the reactant. The reaction is catalysed by aminotransferases enzymes.