Q.8 Identify the correct sequence of the given intermediates fonned during glycolysis
A. Fnrctose 1,6-biphosphate
B. Fructose 6 phosphate
C. Lactate
D. Phosphoenolpynrcate
Answer: B → A → D → C (Fructose 6-phosphate → Fructose 1,6-bisphosphate → Phosphoenolpyruvate → Lactate).
This follows glycolysis sequence: F6P (step 2) → F1,6BP (step 3) → PEP (step 10) → lactate (anaerobic endpoint from pyruvate).
Option Analysis
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A. Fructose 1,6-bisphosphate: Formed from F6P by phosphofructokinase-1 (PFK-1, step 3); splits into DHAP + G3P.
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B. Fructose 6-phosphate: From glucose-6-P isomerization (step 2); PFK-1 substrate.
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C. Lactate: End product under anaerobic conditions; pyruvate reduced by LDH (post-glycolysis).
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D. Phosphoenolpyruvate: Formed from 2-phosphoglycerate (step 9); pyruvate kinase substrate yielding pyruvate + ATP (step 10).
Correct Sequence Logic: Glycolysis energy investment phase (B→A), payoff phase (A→D via GAP→1,3BPG→3PG→2PG→PEP), anaerobic fermentation (D→pyruvate→C).
Glycolysis intermediates sequence is foundational for GATE Life Sciences biochemistry. The correct order among given options: Fructose 6 phosphate (B) → Fructose 1,6-bisphosphate (A) → Phosphoenolpyruvate (D) → Lactate (C).
Glycolysis 10-Step Pathway with Key Intermediates
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Glucose → G6P (hexokinase)
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G6P → Fructose 6-phosphate (B) (phosphoglucose isomerase)
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Fructose 6P → Fructose 1,6-bisphosphate (A) (PFK-1, committed step)
4-5. F1,6BP → 2 G3P
6-8. G3P → 3PG → 2PG -
2PG → Phosphoenolpyruvate (D) (enolase)
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PEP → Pyruvate (pyruvate kinase)
Anaerobic: Pyruvate → Lactate (C) (LDH)
Sequence Position Table
| Intermediate | Step # | Enzyme | Phase |
|---|---|---|---|
| B. F6P | 2 | Isomerase | Investment |
| A. F1,6BP | 3 | PFK-1 | Investment |
| D. PEP | 10 | Pyruvate kinase | Payoff |
| C. Lactate | Post-10 | LDH | Fermentation |
GATE Life Sciences tip: Memorize PFK-1 (F6P→F1,6BP) as rate-limiting; PEP has high-energy phosphate for ATP yield. Glycolysis intermediates sequence mastery = guaranteed biochemistry scores.
