The true statement about 'green-house effect' is that it is

• caused only by CO₂

• caused by CO₂, CFCs, CH₄ and NO₂ gases

• caused by combination of many gases

• none of the above

72.

In C₄ plants, CO, fixation is done by

• mesophyll cells

• guard cells

• sclerenchyma

• chlorenchyma and hypodermis

C₄ plants have better productivity because

• C₄ plants absorb more light

• C₄ plants absorb more CO₂

• C₄ plants lack photorespiration

• all of these

Assertion: Photorespiration is a wasteful process where there is no synthesis of ATP energy.

Reason: RuBisCO is present in mesophyll cells of C₄ plants hence they show more productivity.

• 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.

The 1st CO₂ fixation product of C₄ plant is

• Oxaloacetic acid

• ribulose biphosphate

• phosphoenolpyruvate

• phosphoglyceric acid.

Photosynthesis in C₄ plants is relatively less limited by atmospheric CO₂ levels because

• there is effective pumping of CO₂ into bundle sheath cells

• RuBisCO in C4 plants has higher affinity for CO₂

• six carbon acids are the primary initial CO₂ fixation products

• the primary fixation of CO₂ is mediated via PEP carboxylase.

The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes that adenosine triphosphate (ATP) is formed because

• a proton gradient forms across the inner mitochondrial membrane

• there is a change in the permeability of the inner mitochondrial membrane towards adenosine diphosphate (ADP).

• high energy bonds are formed in mitochondrial proteins

• ADP is pumped out of the matrix into the intermembrane space

Carbon dioxide is necessary for photosynthesis. The chemical used to remove this gas most effectively from entering a control apparatus is

• calcium oxide

• distilled water

• potassium hydroxide solution

• sodium carbonate.

Assertion: In light reaction of photosynthesis, light is required for the functioning of PS I and PS II, and production of NADPH and ATP.

Reason: Dark reaction does not occur in light.

• 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.

Assertion : CAM plants lack structural compartmentation of leaf as found in C₄ plants.

Reason : Stomata of CAM plants are open during the day.

• 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