Assertion A: Yeast fermentation continues whatever the alcohol level in the medium. Reason R: Yeasts poison themselves to death when the alcohol level reaches about 13 per cent. Choose the correct answer.

A is not correct but R is correct

Both A and R are correct and R is the correct explanation of A

A is correct but R is not correct

Both A and R are correct but R is not the correct explanation of A

Respiration in Plants

9 NEET-UG practice questions on Respiration in Plants, part of Botany. The first 9 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
Arrange these Krebs' cycle intermediates in the order of their formation, starting after acetyl CoA joins oxaloacetic acid. A. α-ketoglutaric acid B. Malic acid C. Citric acid D. Succinic acid
1. AC, A, B, D
2. BC, A, D, B
3. CC, D, A, B
4. DA, C, D, B
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Answer: B · C, A, D, B
Acetyl CoA and oxaloacetic acid condense to form citric acid (6C). Citric acid gives α-ketoglutaric acid (5C), then succinyl CoA and succinic acid (4C), then malic acid, which forms oxaloacetic acid again.
- A: Malic acid forms after succinic acid, on the way to oxaloacetic acid.
- C: This places a 4C acid before the 5C acid.
- D: Citric acid is the first product, before α-ketoglutaric acid.
Remember this
Carbon count falls 6C, 5C, 4C; oxaloacetic acid is regenerated and joins the next acetyl CoA.
Mnemonic: Citrate Is Krebs' Starting Substrate For Making Oxaloacetate (citrate, isocitrate, α-ketoglutarate, succinyl-CoA, succinate, fumarate, malate, oxaloacetate).
Question 2 · Medium
Assertion A: Yeast fermentation continues whatever the alcohol level in the medium. Reason R: Yeasts poison themselves to death when the alcohol level reaches about 13 per cent. Choose the correct answer.
1. ABoth A and R are correct and R is the correct explanation of A
2. BA is correct but R is not correct
3. CA is not correct but R is correct
4. DBoth A and R are correct but R is not the correct explanation of A
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Answer: C · A is not correct but R is correct
Yeast cells die once alcohol reaches about 13 per cent, so fermentation cannot continue at any level. R is a true fact, and it contradicts A.
- A: A is false, so R cannot explain it.
- B: This reverses the truth of A and R.
- D: A is false, so both cannot be correct.
Remember this
Fermentation is self-limiting in yeast at about 13 per cent alcohol, and yields under 7 per cent of glucose energy.
Question 3 · Medium
In a respirometer, a germinating seed uses 20 mL of O₂ and gives out 18 mL of CO₂ in the same time. What are its respiratory quotient and its most likely respiratory substrate?
1. A0.9; fat
2. B1.11; protein
3. C0.9; protein
4. D1.0; carbohydrate
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Answer: C · 0.9; protein
RQ = volume of CO₂ evolved / volume of O₂ consumed = 18/20 = 0.9. Proteins give an RQ of about 0.9, whereas fats give about 0.7 and carbohydrates give exactly 1.
- A: The value is right, but fats give about 0.7.
- B: This divides O₂ by CO₂, inverting the formula.
- D: An RQ of 1 needs equal volumes of the two gases.
Remember this
RQ is CO₂ out divided by O₂ in; carbohydrate is 1, protein about 0.9, fat about 0.7.
Question 4 · Medium
Match List-I with List-II. List-I (ETS complex) A. Complex I B. Complex II C. Complex III D. Complex V List-II (name or role) I. Cytochrome bc₁ II. ATP synthase III. NADH dehydrogenase IV. Passes reducing equivalents of FADH₂ to ubiquinone
1. AA-III, B-IV, C-I, D-II
2. BA-III, B-I, C-IV, D-II
3. CA-II, B-IV, C-I, D-III
4. DA-IV, B-III, C-I, D-II
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Answer: A · A-III, B-IV, C-I, D-II
NADH is oxidised at complex I, NADH dehydrogenase. FADH₂ feeds ubiquinone through complex II. Ubiquinol passes electrons to cytochrome c through complex III, cytochrome bc₁. Complex V, with F₁ and F₀, makes ATP.
- B: This swaps complexes II and III.
- C: This swaps complexes I and V.
- D: This swaps the NADH and FADH₂ entry points.
Remember this
FADH₂ enters after complex I, so it yields 2 ATP compared with 3 from NADH.
Question 5 · Easy
In the electron transport system of plant mitochondria, electrons finally pass to
1. Acytochrome c
2. BNAD⁺
3. Coxygen
4. Dubiquinone
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Answer: C · oxygen
Electrons travel through the complexes and reach cytochrome c oxidase, which passes them to oxygen. Oxygen, with protons, forms water.
- A: Cytochrome c is a mobile carrier before complex IV.
- B: NAD⁺ brings electrons to the chain as NADH, and is not the final acceptor.
- D: Ubiquinone is a mobile carrier in the middle of the chain.
Remember this
Oxygen is the terminal electron acceptor, so removing it stops the whole ETS and its ATP supply.
Question 6 · Medium
Study these statements on the respiratory pathway. A. Glycerol enters after conversion to PGAL. B. Fatty acids enter after breakdown to acetyl CoA. C. Amino acids can enter only through glycolysis. D. The pathway is amphibolic because its intermediates can also be withdrawn for synthesis. Which of these are correct?
1. AA, C and D only
2. BB, C and D only
3. CA, B and D only
4. DA and B only
Answer and explanation in LearnFree account
Question 7 · Easy
Which stage of the aerobic breakdown of glucose takes place in the cytoplasm?
1. ALink reaction
2. BElectron transport system
3. CKrebs' cycle
4. DGlycolysis
Answer and explanation in LearnFree account
Question 8 · Hard
Given below are two statements: Statement I: During glycolysis, four ATP are formed directly and two are used per glucose, giving a net gain of two ATP. Statement II: The NADH of glycolysis is formed when phosphoenol pyruvate changes to pyruvic acid. Choose the correct answer.
1. AStatement I is incorrect but Statement II is correct
2. BBoth Statement I and Statement II are incorrect
3. CStatement I is correct but Statement II is incorrect
4. DBoth Statement I and Statement II are correct
Answer and explanation in LearnFree account
Question 9 · Hard
Take 3 ATP per NADH and 2 ATP per FADH₂. How many ATP are formed when one pyruvic acid is fully oxidised in the mitochondrion, counting the link reaction and Krebs' cycle?
1. A14
2. B30
3. C12
4. D15
Answer and explanation in LearnFree account

Respiration in Plants

Arrange these Krebs' cycle intermediates in the order of their formation, starting after acetyl CoA joins oxaloacetic acid. A. α-ketoglutaric acid B. Malic acid C. Citric acid D. Succinic acid

Assertion A: Yeast fermentation continues whatever the alcohol level in the medium. Reason R: Yeasts poison themselves to death when the alcohol level reaches about 13 per cent. Choose the correct answer.

In a respirometer, a germinating seed uses 20 mL of O₂ and gives out 18 mL of CO₂ in the same time. What are its respiratory quotient and its most likely respiratory substrate?

Match List-I with List-II. List-I (ETS complex) A. Complex I B. Complex II C. Complex III D. Complex V List-II (name or role) I. Cytochrome bc₁ II. ATP synthase III. NADH dehydrogenase IV. Passes reducing equivalents of FADH₂ to ubiquinone

In the electron transport system of plant mitochondria, electrons finally pass to

Which stage of the aerobic breakdown of glucose takes place in the cytoplasm?

Given below are two statements: Statement I: During glycolysis, four ATP are formed directly and two are used per glucose, giving a net gain of two ATP. Statement II: The NADH of glycolysis is formed when phosphoenol pyruvate changes to pyruvic acid. Choose the correct answer.

Take 3 ATP per NADH and 2 ATP per FADH₂. How many ATP are formed when one pyruvic acid is fully oxidised in the mitochondrion, counting the link reaction and Krebs' cycle?