One turn of the helix in a B-form DNA is approximately

1. 0.34 nm

2. 3.4 nm

3. 2 nm

4. 20 nm

Which of the following statements regarding enzyme inhibition is correct?

1. Competitive inhibition is seen when a substrate competes with an enzyme for binding to an inhibitor protein

2. Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme

3. Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate

4. Non-competitive inhibitors often bind to the enzyme irreversibly 

If DNA percentage of thymine is 20. What is the percentage of guanine?                         [2002]

1. 20%

2. 40%

3. 30%

4. 60%

Which is wrong about nucleic acids?                                 [1993]

1. DNA is single stranded in some viruses

2. RNA is double stranded occasionally

3. Length of one helix is 45 Å in B-DNA

4. One turn of Z-DNA has 12 bases

Cellulose, the most important constituent of plant cell wall is made of                     [1998]

1. Unbranched chain of glucose molecules linked by $\mathrm{\alpha }$ 1, 4-glycosidic bond

2. Branched chain of glucose molecules linked by $\mathrm{\beta }$ 1, 4-glycosidic bond in straight chain and $\mathrm{\alpha }$, 1, 6-glycosidic bond at the site of branching

3. Unbranched chain of glucose molecules linked by $\mathrm{\beta }$ 1, 4-glycosidic bond

4. Branched chain of glucose molecules linked by $\mathrm{\alpha }$ 1, 6-glycosidic bond at the site of branching

The most abundant element present in plants is                               [2004]

1. Carbon

2. Nitrogen

3. Manganese

4. Iron

Transition state structure of the substrate formed during an enzymatic reaction is

1. Transient but stable

2. Permanent but unstable

3. Transient but unstable

4. Permanent and stable

Which one of the following is a non-reducing carbohydrate?                                [2014]

1. Maltose

2. Sucrose

3. Lactose

4. Ribose-5-phosphate

In the DNA molecule

1. The total amount of purine nucleotides and pyrimidine nucleotides is not always equal

2. There are two strands which run parallel in 5'$\to$3' direction

3. The proportion of adenine in relation to thymine varies with the organism

4. There are two strands which run antiparallel one in 5'$\to$3' direction and other in 3'$\to$5' direction 

The major portion of the dry weight of plants comprises of                  [2003]

1. Carbon, nitrogen and sulphur

2. Carbon, nitrogen and oxygen

3. Nitrogen, phosphorous and potassium

4. Calcium, magnesium and sulphur