34 - AIIMS november 2002 biochemistry mcqs

1q: an alfa helix of a protein is most likely to be disrupted if a missense mutation introduces the following aminoacid with in the alpha helical structure ?

a. alanine
b. aspartic acid
c. tyrosine
d. glycine

answer b . aspartic acid

explanation : alfa helix of a protein can be disrupted due to the introduction of the following aminoacids :

1. proline : the imino group of proline is not geometrically compatible with the right handed spiral of the alpha-helix

2. charged aminoacids : glutamate ,aspartate, lysine, arginine and histidine .

3. aminoacids with bulky side chains : tryptophan

4. aminoacids that branch at the beta-carbon : valine and isoleucine .

33 - AIIMS november 2008 biochemsitry questions

1q: dna without introns is?

A. B dna
b. Z dna
c. C dna
d. Mitochondrial dna

Answer:

2q: all are true about glutathione except?

A. Converts hemoglobin to methemoglobin
b. Decreases free radicals
c. Helps in conjugation reaction
d. Co factor of various enzymes

Answer:



3q: Ribosome has followin enzymatic activity?

A. Peptidyl transferase
b. Amino acyl t rna synthetase
c. Peptidase
d.

Answer:

4q: which enzyme is responsible for carboxylation reaction?

A. Biotin
b.
C.
D. Thiamine pyrophosphate

Answer:

5q: Glowing of firefly is due to?

A. Atp
b. Nadh
c. Gtp
d. Phospho creatinine

Answer:

6q: in carboxylation of clotting factors by vit k which amino acid is carboxylated?

A. aspartate
b. Glutamate
c. Histamine
d. Histidine

answer:

7q: synthesis of a immunoglobulin in membrane bound or independent form is determined by?

A. One turn two turn joining rule
b. Allelic exclusion
c. Class switching
d. Differential rna processing

answer:

8q: phosphorlase b is inhibited by?

A. Atp
b. Amp
c. Glucose
d. Calcium

Answer:

9q: In metabolism of xenobiotics all of the followin reactions occour in phase one except?

A. Conjugation
b. Reduction
c. Hydrolysis
d.oxidation

Answer:

10q: Which is not a second messenger?

A. Amp
b. Guanyl cyclase
c. Dag
d. Ip3

answer:

11q: structure of proteins can be determined by all except?

A. Mass spectrometry
b. Nmr spectrometry
c. Hplc
d.

Answer:

12q: Functions of thiamine?

A. Co enzyme of pyruvate dehydrogenase and alpha keto dehydrogenase
b. Co enzyme of trans ketolase
c.
D.

Answer:

13q: replacing alanine by which amino acid will increase the absorbance of proteins at 280nm?

A. Leucine
b.tryptophan
c. Proline
d. Arginine

Answer: