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 Multiple Choice QuestionsMultiple Choice Questions


Starch is insoluble in water, yet it is accumulated in large quantities in potato tuber because :

  • it is useful for storage

  • tubers respire slowly

  • starch is synthesized in tubers

  • translocated sucrose is polymerized here


it is useful for storage

Starch is insoluble in water, yet it is accumulated in large quantities in potato tuber because, it is useful for storage.


Which of the following is not a co-enzyme?

  • NAD

  • NADP

  • FAD

  • ATP



Co-enzymes are organic molecules that acts as co-factors, but unlike prosthetic groups they do not remain attached to the enzyme between reaction. NAD, NADP and FAD are co-enzymes whereas ATP is an energy carrier in cell.


In an experiment freshly hatched larvae of an insect (Khapra beetle) were reared on a basal diet (complete diet without cholesterol) with increasing amounts of cholesterol. Results obtained are shown in the graph given in the table :

The graph indicates that

  • cholesterol is an essential dietary requirement of khapra beetle

  • growth of khapra beetle is directly proportional to cholesterol concentration

  • cholesterol concentration of 2 µg/g diet is the optimum level

  • growth of khapra beetle is inhibited when cholesterol concentration exceeds 5 g/g diet


cholesterol is an essential dietary requirement of khapra beetle

According to the graph, the growth of the insect takes place as the amount of the cholesterol increase and at 6 μg cholesterol/g the growth get static. If the growth rate would have been directly proportional to the cholesterol concentration then the graph would have been straight line.

Option 3 is wrong as the optimum level is 6 µg/g cholesterol concentration.


Which one is antioxidant vitamin?

  • Vitamin- D

  • Vitamin- E

  • Vitamin- B

  • Vitamin- K


Vitamin- E

Antioxidant vitamins are Vitamin C, Vitamin E and β- carotene. They are so called as they inactive oxygen free radicals. Free radicals are highly reactive particles that carry an unpaired electron [e-], they damage cell membranes, DNA, other cellular structures and contribute to formation of artery narrowings and atherosclerosis.


Defect in amino acid metabolism may results in :

  • albinism

  • porphyria

  • Wilson's disease

  • phenylketonuria



Defect in amino acid metabolism is known as phenylketonuria. Children suffering with this disease are unable to breakdown Phenyl Pyruvic acid into Hydroxy phenyl pyruvic acid. Therefore, accumulation of phenyl pyruvic acid results in mental disorder.


An organic substance bound to an enzyme and essential for its activity is called

  • coenzyme

  • holoenzyme

  • apoenzyme

  • isoenzyme



Coenzyme is an organic nonprotein molecule that associates with an enzymes molecule in catalysing biochemical reactions. It usually participates in the substrate-enzyme interaction by donating or accepting certain chemical groups.
Apoenzyme is an inactive enzyme that must associate with a specific cofactor molecule in order to function.
Isoenzyme or isozyme is one of the several forms of an enzyme that catalyse the same reaction but differ from each other in such properties as substrate affinity and maximum rates of enzymes-substrate reaction.



Which is called soluble RNA

  • r-RNA

  • t-RNA

  • m-RNA

  • hn-RNA



tRNA is known as the soluble RNA as they are soluble in 1M-NaCl. Hence they are also known as soluble RNA.


Which one of the following statements regarding enzyme inhibition is correct?

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

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

  • Non-competitive inhibition ofan enzyme can be overcome by adding large amount of substrate

  • None of these


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

In competitive inhibition, an inhibitor that resembles the normal substrate binds to the enzyme, at the active site, and prevents the substrate from binding.

Non-competitive inhibition is a type of enzyme inhibition where the inhibitor reduces the activity of the enzyme and binds equally well to the enzyme whether or not it has already bound the substrate.


Which enzyme is most specific ?

  • Trypsin

  • Pepsin

  • Sucrose

  • Nuclease



Nuclease enzymes are the most specific enzymes.


In DNA, which is absent

  • Adenine

  • Thymine

  • Guanine

  • Uracil



Adenine, Guanine, Cytosine and thymidine are the bases of DNA, while Adenine, Guanine, Cytosine and uracil are the component of RNA.