4. Calcium activates the TCA cycle mainly in:

A. Liver during fasting
B. Brain neurons
C. Muscle during contraction
D. Adipose tissue

5. Accumulation of succinyl-CoA directly inhibits which TCA enzyme?

A. Citrate synthase
B. Isocitrate dehydrogenase
C. α-Ketoglutarate dehydrogenase
D. Malate dehydrogenase

Hello StudentsWe’ve started the TCA cycle and discussed regulation + MCQs.

What’s your comfort level right now?

🔹 Very clear
🔹 Some concepts still confusing
🔹 MCQs are helpful but need more explanation
🔹 Need diagrams before MCQs

Your response helps me plan the next post better.

🔬 TCA Cycle (Citric Acid Cycle) – Exam-Oriented Overview

The TCA cycle is the central hub of metabolism, linking carbohydrates, fats, and proteins to energy production.

📍 Location: Mitochondrial matrix
📍 Entry molecule: Acetyl-CoA
📍 Nature: Amphibolic (catabolic + anabolic)

🎯 Why TCA cycle is important

✔️ Oxidizes acetyl-CoA to CO₂
✔️ Produces NADH & FADH₂ for ETC
✔️ Supplies intermediates for biosynthesis
✔️ Acts as the final common pathway

⚙️ Regulation (High-Yield)

Activated by: ADP, NAD⁺, Ca²⁺

Inhibited by: ATP, NADH

Key control enzymes:
▪️ Citrate synthase
▪️ Isocitrate dehydrogenase
▪️ α-Ketoglutarate dehydrogenase

⚡️ Energy Yield

From 1 acetyl-CoA:

3 NADH

1 FADH₂

1 GTP
👉 ≈ 10 ATP

SAVE THIS | Metabolism in One View

Glycolysis → Pyruvate
Pyruvate → Acetyl-CoA
Acetyl-CoA → TCA
TCA → NADH/FADH₂
NADH/FADH₂ → ETC → ATP

📌 If this made sense, you’re studying the right way.

🔑 Exam One-Liner
TCA cycle is amphibolic because it provides both energy and biosynthetic intermediates.

Attempt this one -ETC stops when oxygen is absent because:

A. ATP synthase stops
B. NADH accumulates
C. Electron flow halts
D. Proton gradient collapses

✍️ Scientific Writing Tip for UG & PG Students

Good science can lose marks if it is not written clearly.

📌 One simple rule for scientific writing:

One idea = one paragraph

When writing:
✔️ Start with a topic sentence
✔️ Support it with logic or data
✔️ End with a clear conclusion

This improves:

Assignments

Project reports

Review articles

Exam answers

👩‍🔬 – Megha Gupta
(9+ research publications | Academic & scientific writing)

Here are MIXED METABOLIC CYCLES exam-oriented MCQs

Exams reward understanding, not memorization.
Focus on concepts — marks will follow.

Concept Alert "Which pathway produces ATP by substrate-level phosphorylation?" MCQ me maine PPP (Pentose Phosphate Pathway) mark kar diya tha —
thank you jis student ne explanation poocha 👏

👉 Correction + Concept clarity below ⬇️

❌ Why PPP is NOT the correct answer?

Pentose Phosphate Pathway:

❌ ATP produce nahi karta

❌ Substrate-level phosphorylation nahi hota

✅ Produces NADPH (reducing power)

✅ Produces Ribose-5-phosphate (nucleotide synthesis)

✅ Correct answer: Glycolysis

ATP by Substrate-Level Phosphorylation is produced in:

🔹 Glycolysis

1️⃣ 1,3-Bisphosphoglycerate → 3-Phosphoglycerate
2️⃣ Phosphoenolpyruvate → Pyruvate

👉 Dono steps me direct ATP formation hota hai

🔹 One step in TCA Cycle

Succinyl-CoA → Succinate

Produces GTP (→ ATP)

🧠 Exam-Oriented Takeaway (GATE | CSIR | ICMR)

PPP = NADPH pathway, not ATP pathway
SLP = Glycolysis (+ one TCA step)

🙌 Why I’m happy this doubt came

Science me:

Questions = learning

Corrections = clarity

Discussions = growth

Aise doubts hi real understanding banate hain 💯

— Megha Gupta

If today’s post helped even a little, you’re on the right track.
Drop a 👍 if you’re studying consistently.

✍️ Scientific Writing Help by Megha Gupta

Struggling with assignments, abstracts, or project reports?
Don’t worry — I can help you make it clear, concise, and exam-ready.

What I offer:
✔️ Short notes & summaries
✔️ Concept clarity guides
✔️ MCQs integrated for learning
✔️ Abstracts & review writing help

💡 Tip: Good writing = half the marks won!

📩 DM me if you want guidance or notes.
Let’s turn confusion into clarity ✨