Q63. Which of the following statements in plant respiration are CORRECT?
P. The oxidative Pentose Phosphate Pathway can accomplish the oxidation of glucose in the stroma of mitochondria
Q. ATP is produced in the reaction step of TCA cycle catalyzed by succinyl-CoA synthetase
R. In addition to Cytochrome c oxidase, an alternative oxidase enzyme resistant to cyanide reduces oxygen molecule in the electron transport system
S. In Glyoxylate cycle acetyl-CoA reacts with citrate to form α-ketoglutarate
P is incorrect because the oxidative Pentose Phosphate Pathway (PPP) oxidizes glucose-6-phosphate primarily in the plastid stroma (chloroplasts in plants) or cytosol, not the mitochondrial stroma.
Q is correct: Succinyl-CoA synthetase in the TCA cycle converts succinyl-CoA to succinate, producing GTP (or ATP via substrate-level phosphorylation).[ from prior context]
R is correct: Plants have cyanide-resistant alternative oxidase (AOX) alongside cytochrome c oxidase; AOX reduces O₂ in the electron transport chain without proton pumping.[ context]
S is incorrect: In the glyoxylate cycle, acetyl-CoA reacts with oxaloacetate (not citrate) via isocitrate lyase (after citrate formation) to form glyoxylate and succinate, bypassing α-ketoglutarate dehydrogenase.[ context]
Answer: (C) Q, R
The oxidative Pentose Phosphate Pathway, TCA cycle, and alternative oxidase play key roles in plant respiration, vital for competitive exams like GATE Life Sciences. This article analyzes Q63 statements on plant respiration to identify correct ones, aiding biochemistry and molecular biology prep.
Statement P Analysis
The oxidative Pentose Phosphate Pathway oxidizes glucose-6-phosphate to ribulose-5-phosphate, generating NADPH mainly in plastid stroma or cytosol. It does not occur in mitochondrial stroma, making P incorrect.
Statement Q Verification
Succinyl-CoA synthetase catalyzes succinyl-CoA + GDP + Pi → succinate + GTP + CoA in the TCA cycle, yielding substrate-level ATP (or GTP equivalent). This confirms Q as correct.
Statement R Explanation
Cytochrome c oxidase (complex IV) is cyanide-sensitive, but plants’ alternative oxidase (AOX) resists cyanide, directly reducing O₂ at ubiquinone level. R is correct.
Statement S Evaluation
Glyoxylate cycle forms citrate from acetyl-CoA + oxaloacetate, then splits isocitrate to glyoxylate + succinate (via isocitrate lyase), not acetyl-CoA with citrate to α-ketoglutarate. S is wrong.
Statement
Key Fact
Correct?
P
PPP in plastid stroma, not mitochondria
No
Q
ATP from succinyl-CoA synthetase
Yes
R
Alternative oxidase cyanide-resistant
Yes
S
Glyoxylate cycle skips α-KG step
No
Exam Tip: Focus on plant-specific pathways like AOX for respiration questions in GATE Life Sciences.
