Questions: Respiration in Plants

Q1. Why is respiration called a controlled process while combustion is not?

Answer (English): Respiration releases the energy of glucose in a series of enzyme-catalysed steps at body temperature, and a large part of the energy is captured in ATP. Combustion is a single rapid reaction at high temperature in which the energy is released at once as heat and light and cannot be captured usefully. The control by enzymes also allows the cell to slow or speed the process as needed.

Hinglish: Respiration enzymes ke control mein chhote steps se energy release karta hai aur ATP mein store karta hai, jabki combustion ek dum se high temperature par energy heat aur light mein chhod deta hai.

Q2. What is the net gain of glycolysis and where does it occur?

Answer (English): Glycolysis occurs in the cytoplasm and converts one glucose into two pyruvate molecules. Two ATP are used in the early steps and four ATP are formed later, so the net gain is two ATP. Two NADH are also produced. The ATP comes from substrate level phosphorylation, not from the electron transport chain.

Hinglish: Glycolysis cytoplasm mein hoti hai, ek glucose se do pyruvate bante hain, do ATP kharch aur chaar milte hain, isliye net do ATP aur do NADH milte hain.

Q3. How is NAD+ regenerated in fermentation and why is it needed?

Answer (English): In fermentation the NADH produced in glycolysis reduces pyruvate or its derivative, so NAD+ is regenerated. In yeast, pyruvate is converted to ethanol and CO2, and in muscle pyruvate becomes lactic acid, with NADH oxidised to NAD+ in both cases. The NAD+ is needed because glycolysis cannot continue once the NAD+ pool is exhausted.

Hinglish: Fermentation mein NADH pyruvate ko reduce karke NAD+ wapas bana deta hai. NAD+ ke bina glycolysis ruk jaati hai, isliye yeh step zaroori hai.

Q4. What happens to pyruvate before it enters the citric acid cycle?

Answer (English): Pyruvate enters the mitochondrial matrix and is decarboxylated and dehydrogenated by the pyruvate dehydrogenase complex. One carbon leaves as CO2, the remaining two-carbon acetyl group joins coenzyme A to form acetyl CoA, and one NADH is produced. This link reaction connects glycolysis with the citric acid cycle.

Hinglish: Pyruvate mitochondrion mein jaakar pyruvate dehydrogenase se CO2, acetyl CoA aur NADH deta hai; isi link reaction se pyruvate Krebs cycle mein pahunchta hai.

Q5. List the products of one turn of the citric acid cycle.

Answer (English): One turn oxidises one acetyl group and gives two CO2, three NADH, one FADH2 and one ATP. The ATP is made at the step where succinyl CoA becomes succinic acid, by substrate level phosphorylation. Since one glucose gives two acetyl CoA, the cycle runs twice per glucose and the totals double.

Hinglish: Ek turn mein 2 CO2, 3 NADH, 1 FADH2 aur 1 ATP milti hai. Ek glucose ke liye cycle do baar chalti hai, isliye products double ho jaate hain.

Q6. Where is the electron transport system located and what is its final electron acceptor?

Answer (English): The electron transport system is located on the inner mitochondrial membrane. NADH and FADH2 deliver electrons to the complexes, and oxygen is the final electron acceptor at complex IV, where it accepts electrons and protons to form water. The transfer of electrons also pumps protons into the intermembrane space, building the gradient used for ATP synthesis.

Hinglish: ETS inner mitochondrial membrane par hoti hai aur oxygen final electron acceptor hai, jo paani banata hai. Electron transfer se proton gradient banta hai.

Q7. How does ATP synthase work in the mitochondrion?

Answer (English): The ATP synthase has an F1 headpiece that projects into the matrix and an F0 channel embedded in the inner membrane. Protons flow back from the intermembrane space into the matrix through F0, and this flow drives a conformational change in F1, where ADP and inorganic phosphate are joined to make ATP. The process is called oxidative phosphorylation because the energy comes from the oxidation of carriers.

Hinglish: Proton intermembrane space se F0 channel ke through matrix mein aate hain, isse F1 headpiece ka shape badalta hai aur ADP aur Pi se ATP banti hai; isi ko oxidative phosphorylation kehte hain.

Q8. Define RQ and give its value for carbohydrate, fat and protein.

Answer (English): RQ is the ratio of the volume of CO2 released to the volume of O2 consumed during respiration. A carbohydrate completely oxidised gives an RQ of 1 because the volumes are equal. Fat gives an RQ below 1, and for tripalmitin the calculated value is about 0.7 because the molecule needs a large amount of oxygen from outside. Protein gives about 0.9, and in a living tissue the substrate is a mixture so the measured value lies between these cases.

Hinglish: RQ = CO2 / O2. Carbohydrate ka 1 aur fat ka lagbhag 0.7 hota hai, protein ka lagbhag 0.9 hota hai, aur living tissue mein substrate mix hone se measured value inke beech aati hai.

Q9. Why is the respiratory pathway called amphibolic?

Answer (English): The pathway is mainly catabolic because it breaks down carbohydrate, fat and protein to release energy. It is also anabolic because several intermediates are withdrawn for biosynthesis: fatty acids are degraded to acetyl CoA, glycerol enters as PGAL, and amino acids enter at several points after deamination. Serving both breakdown and building in the same pathway makes it amphibolic.

Hinglish: Respiration catabolic hai kyunki fuels todta hai, lekin iske intermediates biosynthesis mein bhi lagte hain, isliye yeh amphibolic kehlata hai.

Q10. Why does the theoretical 38 ATP figure differ from the real yield?

Answer (English): The 38 ATP figure assumes an orderly pathway, transport of glycolytic NADH into the mitochondrion without cost, no withdrawal of intermediates for other uses and fixed ATP yields for the carriers. In a living cell some energy is spent on shuttling NADH, some protons leak across the membrane and intermediates are used in biosynthesis. The real yield is therefore lower, and it varies with the tissue and its activity. A fair answer on this point states both sides: the balance sheet is useful for comparing stages, and its assumptions are also the reason every textbook number is qualified with the phrase theoretical gain.

Hinglish: 38 ATP ek theoretical hisaab hai jisme NADH transport ka kharch, proton leak aur intermediates ka doosre kaam mein lagna shamil nahi hai. Asli cell mein yield kam hoti hai.

Quiz pointer. A five question chapter quiz follows this page. Attempt it without looking back, and read the explanation for every question you miss, because the quiz retests the ATP counts and the enzyme locations used on this page.