NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions


Which of the following inhibits O2 release in light phase?

  • Zeatin

  • PMA

  • DCMU

  • None of these



DCMU is a very specific and sensitive inhibitor of photosynthesis (photosynthetic inhibitors). It blocks the plastoquinone binding site of photosystem II, disallowing the electron flow from photosystem II to plastoquinone. Thus, it inhibits Hill reaction, by inhibiting release of O2.


When the organic acid is oxidised in respiration, the value of R.Q. becomes

  • zero

  • one

  • less than one

  • more than one


more than one

When an organic acid is oxidised the value of R.Q. in respiration becomes more than one. Because organic acids are rich in O2 and require less O2 for their oxidation. It is clear from the equation given below.

C4H6O5 (Malic acid) + 3O2 4CO2 + 3H2O

R.Q. = Volume of CO2 evolvedVolume of O2 taken = 43

R.Q = 1.3 (more than one)


Bilirubin and biliverdin are

  • enzymes

  • bile salts

  • bile pigments

  • None of these


bile pigments

Bilirubin and biliverdin are the break down products of haemoglobin formed by the liver and secreted in the bile to be stored in the gall-bladder. They are required for digestion and absorption of fats.


ABO blood grouping is controlled by gene I which has three alleles and show co-dominance. There are six genotypes. How many phenotypes in all are possible?

  • Three

  • Six

  • Five

  • Four



The six genotypes are as follows:

IAIA or IAi or IBIB or IBi  or IAIor ii


Auxin was first named by

  • C Darwin

  • FW Went

  • Alexopolus

  • KV Thimann


FW Went

FW Went (1928) was the first person to name auxins. Thimann (1936) isolated IAA from Rhizopus sinus and Avena coleoptiles.


The nitrifying bacteria that convert the ammonia to nitrates are

  • Nitrosomonas and Nitrobacter

  • Azotobacter

  • Rhizobium sp.

  • Thiobacillus denitrificans


Nitrosomonas and Nitrobacter

Nitrification is the phenomenon of conversion of ammonium to nitrate by nitriflying bacteria like Nitrosomonas, Nitrobacter, etc. It occurs in two steps-

2NH3 + 3O2 Nitrosomonas 2NO-2 + 2H+ + 2H2O + Energy

2NO-2 + O2 Nitrobacter 2NO-3 + Energy


Ivan Pavlov performed experiments on

  • origin of life

  • cardiac reflexes

  • simple reflexes

  • conditioned reflexes


conditioned reflexes

Conditioned reflex is an automatic response established by training to an ordinarily neutral stimulus. They were first demonstrated in 1920s by the Russian physiologist I.P. Pavlov. He found that the sight and smell of food reflexly cause flow of saliva in hungry animals.


Marasmus in children is caused by deficiency of

  • protein

  • fats

  • vitamins

  • carbohydrates



Marasmus is a protein energy malnutrition disorder.  It is found in infants due to lack of proper diet of protein and calories. It is also in case of less breast feeding diet. Due to this body become lean and weak, eyes depressed and skin wrinkled.


According to Boyle's law, the product of pressure and volume is a constant. Hence,

  • if volume of lungs is increased, the pressure decreases disproportionately

  • if volume of lungs is increased, the pressure remains the same

  • if volume of lungs is increased, the pressure decreases proportionately

  • if volume of lungs is increased, the pressure also increases proportionately


if volume of lungs is increased, the pressure decreases proportionately

Boyle's law states that the pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature. Hence, if volume of lungs is increased, the pressure decreases proportionately.


Which of the following genotypes does not produce a sugar polymer on the surface of the RBCs?

  • IAIA

  • IAi

  • ii

  • IAIB



Alleles IA and IB produce sugar whereas allele i does not produce any sugar.