Respiration in Plants: NEET PYQ, 2018–2026

Q1 · Botany · Respiration in Plants

In eukaryotic cells, where is the electron transport system located?

• AOuter mitochondrial membrane
• BInner mitochondrial membrane
• CMitochondrial matrix
• DCytoplasm

Q2 · Botany · Respiration in Plants

How many molecules of NADH are produced per molecule of glucose during glycolysis itself, excluding any NADH formed later when pyruvate is oxidised?

• A1
• B2
• C4
• D8

Q3 · Botany · Respiration in Plants

Fluoride ions inhibit the enzyme enolase, which catalyses the conversion of 2-phosphoglycerate to phosphoenolpyruvate during glycolysis. In a glycolysing cell with this inhibition, which intermediate accumulates just before the block, and what is the consequence for ATP production?

• A2-phosphoglycerate accumulates, phosphoenolpyruvate is not formed, and the substrate-level ATP step at the pyruvate kinase reaction is lost, reducing ATP yield.
• B3-phosphoglycerate accumulates and phosphoglycerate kinase stops working, so ATP yield is unaffected because pyruvate kinase still operates.
• CPhosphoenolpyruvate accumulates because fluoride blocks the conversion of phosphoenolpyruvate to pyruvate, and ATP yield increases through pyruvate kinase.
• DPyruvate accumulates because enolase is the final enzyme of glycolysis, so the ATP yield is not changed.

Q4 · Botany · Respiration in Plants

In one turn of the Krebs cycle, at how many points is NAD⁺ reduced to NADH + H⁺, and at how many is FAD reduced to FADH₂?

• ANAD⁺ at three points and FAD at one point
• BNAD⁺ at one point and FAD at three points
• CNAD⁺ at four points and FAD at one point
• DNAD⁺ at two points and FAD at two points

Q5 · Botany · Respiration in Plants

How many molecules of CO₂ are released in one turn of the Krebs cycle, which starts with one molecule of acetyl CoA?

• A3
• B2
• C6
• D1

Q6 · Botany · Respiration in Plants

Fructose 1,6-bisphosphate is the product of the committed phosphofructokinase step in glycolysis. Which enzyme does this metabolite stimulate allosterically, and what does that feed-forward activation accomplish?

• AIt activates phosphofructokinase, reinforcing its own production so the committed step runs faster.
• BIt activates pyruvate kinase, so the downstream step is accelerated and phosphoenolpyruvate is drained faster into pyruvate.
• CIt activates hexokinase, so that more glucose is phosphorylated and enters the pathway.
• DIt inhibits pyruvate kinase as a product that accumulates, so that flux slows when the early pathway is busy.

Q7 · Botany · Respiration in Plants

ATP is formed by transferring a phosphate group directly from a high-energy substrate molecule to ADP, without involvement of an electron transport chain. What is this process called?

• AOxidative phosphorylation
• BPhotophosphorylation
• CChemiosmosis
• DSubstrate-level phosphorylation

Q8 · Botany · Respiration in Plants

Which enzyme of glycolysis is the main regulated, committed step, and is allosterically inhibited when cellular ATP is high?

• APhosphofructokinase-1, which converts fructose-6-phosphate to fructose-1,6-bisphosphate
• BTriose phosphate isomerase, which interconverts dihydroxyacetone phosphate and glyceraldehyde-3-phosphate
• CEnolase, which converts 2-phosphoglycerate to phosphoenolpyruvate
• DAldolase, which cleaves fructose-1,6-bisphosphate into two triose phosphates

Q9 · Botany · Respiration in Plants

Iodoacetate irreversibly alkylates the free sulfhydryl group of the cysteine residue at the active site of glyceraldehyde-3-phosphate dehydrogenase. A plant tissue is supplied with glucose in the presence of this inhibitor. Which change is expected in the glycolytic pathway, and what happens to the net ATP yield?

• ATriose phosphates accumulate upstream of the block, and the ATP invested at the hexokinase and phosphofructokinase steps is not recovered, so the net ATP balance becomes negative.
• B1,3-bisphosphoglycerate accumulates and phosphoglycerate kinase keeps generating ATP, so the net yield is unchanged.
• CPyruvate accumulates because the inhibitor acts on the final kinase, and the NADH formed is reoxidised by the electron transport system, so ATP yield rises.
• DFructose 1,6-bisphosphate is cleared faster because the aldolase step is activated, so the glucose-to-pyruvate flux is unaffected.

Q10 · Botany · Respiration in Plants

In eukaryotic cells, where do the enzymes of the Krebs cycle lie?

• AIn the mitochondrial matrix
• BIn the cytoplasm, alongside glycolytic enzymes
• CIn the outer mitochondrial membrane
• DIn the thylakoid lumen of chloroplasts