Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

Assertion: Smoking causes oxygen deficiency in the body.

Reason: Carbon monoxide when inhaled while smoking, combines with haemoglobin to form chemically stable compound.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


22.

Assertion: The immune responses of old persons become weak.

Reason: Thymus is degenerated in old individuals resulting in a decreased production of thymosin

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


23.

Assertion: The enlarged Q and R waves indicate myocardial infarction.

Reason: The QRS complex represents ventricular repolarisation.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


24.

Assertion: The leaves in gymosperms are well adapted to with stand extremes of temperature, humidity and wind.

Reason: Unlike bryophytes and pteridophytes, in gymnosperms the male and female gametophytes do not have an independent free-living existence.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


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25.

Assertion: Glucose is the favoured respiratory substrate.

Reason: When glucose is used as respiratory substrate and is completely oxidized, the RQ is 1.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


26.

Assertion: Human heart is myogenic.

Reason: The contraction is initiated by a specialized patch of modified heart muscles without requiring stimulation from nerve cells.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


27.

Assertion: In basidiomycetes, basidiospores are produced endogenously in the basidium.

Reason: In ascomycetes, ascospores are produced exogenously in ascus.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


28.

Assertion: In a pivot joint, rounded or pointed bone fits into a shallow depression in another bone.

Reason: Pivot joints are present between the metacarpals and phalanges of the fingers.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


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29.

Assertion: Deficiency symptoms of N, K and Mg are first visible in the senescent leaves.

Reason: Biomolecules containing these elements are broken down in the older leaves, making these elements available for mobilising to younger leaves.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


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30.

Assertion: Photorespiration interferes with the successful functioning of Calvin cycle.

Reason: Photorespiration oxidises ribulose1,5 biphosphate which is an acceptor of CO2 in Calvin cycle.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


A.

If both assertion and reason are true and reason is the correct explanation of assertion.

In the 1920s, the German biochemist Otto Warburg (1883-1970) discovered that plants consumed oxygen at a higher rate when they were illuminated. He also found that this increased rate of oxygen consumption inhibited photosynthesis. Stimulation of oxygen consumption by light is now referred to as photorespiration. Biochemical studies indicate that photorespiration consumes ATP and NADPH, the high-energy molecules made by the light reactions. Thus, photorespiration is a wasteful process because it prevents plants from using their ATP and NADPH to synthesize carbohydrates.

RuBISCO, the enzyme which fixes carbon dioxide during the Calvin cycle, is also responsible for oxygen fixation during photorespiration. In particular, carbon dioxide and oxygen compete for access to RuBISCO. RuBISCO's affinity for carbon dioxide is much higher than its affinity for oxygen. Thus, fixation of carbon dioxide typically exceeds fixation of oxygen, even though atmospheric carbon dioxide levels are about 0.035% whereas oxygen is about 21%.


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