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NEET Botany

NEET UG MCQ questions — Physics, Chemistry, Botany & Zoology for medical entrance.

276 Q 4 Subjects 12th (PCB)
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Difficulty: All Easy Medium Hard 11–20 of 276
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Q.11 Medium NEET Botany Plant Physiology
Which of the following factors does NOT directly affect photosynthesis?
A Chlorophyll concentration
B Soil pH
C CO2 concentration
D Light wavelength
Correct Answer:  B. Soil pH
EXPLANATION

While soil pH affects nutrient availability, it does not directly affect the photosynthetic process itself. Chlorophyll, CO2, and light wavelength directly influence photosynthesis.

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Q.12 Medium NEET Botany Plant Physiology
In the electron transport chain, which complex pumps the most protons across the inner mitochondrial membrane?
A Complex I
B Complex II
C Complex III
D Complex IV
Correct Answer:  A. Complex I
EXPLANATION

Complex I (NADH dehydrogenase) pumps 4 protons, Complex III pumps 4, Complex IV pumps 2, making Complex I the most significant proton pump.

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Q.13 Medium NEET Botany Plant Physiology
Which statement about transpiration is INCORRECT?
A Cuticular transpiration accounts for 5-10% of total water loss in most plants
B Stomatal transpiration is the major pathway of water loss in mesophytes
C Transpiration is independent of atmospheric humidity
D Transpiration cools the plant through evaporative cooling
Correct Answer:  C. Transpiration is independent of atmospheric humidity
EXPLANATION

Transpiration is highly dependent on atmospheric humidity. Lower humidity increases transpiration rate due to greater water vapor gradient.

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Q.14 Easy NEET Botany Plant Physiology
The Q10 value for enzyme-catalyzed reactions is typically:
A 1.0-2.0
B 2.0-3.0
C 3.0-4.0
D 4.0-5.0
Correct Answer:  B. 2.0-3.0
EXPLANATION

Q10 of 2.0-3.0 indicates that enzyme activity doubles or triples with every 10°C increase in temperature, typical for biological systems.

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Q.15 Medium NEET Botany Plant Physiology
Which of the following statements about respiration is correct?
A Aerobic respiration yields 38 ATP per glucose molecule
B The Krebs cycle directly produces the maximum ATP in cellular respiration
C Anaerobic respiration in plants produces ethanol and CO2 through fermentation
D Glycolysis is an aerobic process occurring in the mitochondrial matrix
Correct Answer:  C. Anaerobic respiration in plants produces ethanol and CO2 through fermentation
EXPLANATION

In plants, anaerobic conditions lead to fermentation producing ethanol and CO2. Aerobic respiration yields ~30-32 ATP; Krebs cycle produces limited ATP directly; Glycolysis is cytoplasmic.

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Q.16 Easy NEET Botany Plant Physiology
In the Calvin cycle, which enzyme catalyzes the fixation of CO2?
A Ribulose-1,5-bisphosphate carboxylase (RuBisCO)
B Phosphofructokinase
C Aldolase
D Transketolase
Correct Answer:  A. Ribulose-1,5-bisphosphate carboxylase (RuBisCO)
EXPLANATION

RuBisCO is the most abundant enzyme on Earth and catalyzes the carboxylation of RuBP with CO2 in the dark reactions.

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Q.17 Medium NEET Botany Plant Physiology
At what light intensity does compensation point occur in a typical C3 plant?
A 50-100 μmol/m²/s
B 500-1000 μmol/m²/s
C 1000-2000 μmol/m²/s
D 2000-3000 μmol/m²/s
Correct Answer:  A. 50-100 μmol/m²/s
EXPLANATION

The light compensation point for C3 plants typically occurs at 50-100 μmol/m²/s where photosynthesis equals respiration rate.

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Q.18 Medium NEET Botany Plant Physiology
Which of the following is the correct sequence of electron carriers in the light-dependent reactions?
A P680 → Plastoquinone → Cytochrome b6f → Plastocyanin → P700
B P700 → Plastoquinone → Cytochrome b6f → Plastocyanin → P680
C P680 → Cytochrome b6f → Plastoquinone → Plastocyanin → P700
D P700 → Cytochrome b6f → Plastoquinone → Plastocyanin → P680
Correct Answer:  A. P680 → Plastoquinone → Cytochrome b6f → Plastocyanin → P700
EXPLANATION

The correct electron flow is: PSII (P680) → Plastoquinone → Cytochrome b6f complex → Plastocyanin → PSI (P700) → NADP+ reductase.

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Q.19 Easy NEET Botany Plant Physiology
During photosynthesis, the splitting of water molecules occurs in which compartment of the chloroplast?
A Stroma
B Thylakoid lumen
C Outer membrane
D Inner membrane
Correct Answer:  B. Thylakoid lumen
EXPLANATION

Water photolysis (photosystem II) occurs in the thylakoid lumen where oxygen is released as a byproduct.

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Q.20 Medium NEET Botany Plant Physiology
In plants experiencing drought stress, stomatal closure occurs primarily due to a decrease in:
A Chlorophyll content
B Turgor pressure in guard cells
C Light availability
D Photosynthetic rate
Correct Answer:  B. Turgor pressure in guard cells
EXPLANATION

During drought, water loss causes cells to lose turgor pressure. ABA accumulation further reduces guard cell turgor by opening K+ efflux channels, closing stomata.

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