1

### AIPMT 2001

Which of the following is correct about H-bonding in nucleotide?
A
A $-$ T, G $-$ C
B
A $-$ G, T $-$ C
C
G $-$ T, A $-$ C
D
A $-$ A, T $-$ T

## Explanation

Guanine G is linked to cytosine C by three hydrogen bonds and adenine A is linked with thymine T by two hydrogen bonds. It is abbreviate as : G ≡ C and A = T
2

### AIPMT 2000

Which one is responsible for production of energy in bio-reaction?
A
Thyroxine
B
C
Oestrogen
D
Progesterone

## Explanation

It is a hormone secreted from thyroid gland. It controls various biochemical reactions involving burning of proteins, carbohydrates, fats to release energy.
3

Mg is present in
A
chlorophyll
B
haemoglobin
C
vitamin-D
D
vitamin-B

## Explanation

Chlorophyll is an organometallic complex with Mg as central metal. It’s formula is C55H72MgN2O6.
4

### AIPMT 2000

$\alpha$ -$D$-glucose and $\beta$-$D$-glucose are
A
epimers
B
anomers
C
enantiomers
D
diastereomers

## Explanation

Here 1st carbon atom becomes asymmetric giving two isomers which differ in the configuration of the asymmetric carbon. These two isomers are called as anomers.