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NEET UG

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

904 Q 4 Subjects 12th (PCB)
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Difficulty: All Easy Medium Hard 91–100 of 904
Subjects in NEET UG
Q.91 Hard NEET Botany Plant Physiology
Which statement about ATP synthase is correct?
A It synthesizes ATP using proton gradient energy
B It functions in both photosynthesis and aerobic respiration
C The F0 subunit is embedded in the membrane
D All of the above are correct
Correct Answer:  D. All of the above are correct
EXPLANATION

ATP synthase works in both processes using chemiosmotic gradient; F0 is the membrane-spanning unit; F1 synthesizes ATP from ADP.

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Q.92 Easy NEET Botany Plant Physiology
The phenomenon where plants lose water in liquid form through hydathodes is called:
A Transpiration
B Guttation
C Exudation
D Imbibition
Correct Answer:  B. Guttation
EXPLANATION

Guttation occurs when root pressure forces water out through hydathodes (water pores) as liquid water droplets, typically at night.

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Q.93 Medium NEET Botany Plant Physiology
At saturating light intensity, photosynthesis is primarily limited by:
A Light wavelength
B Photosynthetic pigments
C CO2 concentration
D Chloroplast number
Correct Answer:  C. CO2 concentration
EXPLANATION

When light is saturating, CO2 becomes the limiting factor as RuBisCO activity depends on substrate availability.

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Q.94 Hard NEET Botany Plant Physiology
Which of the following best describes the Pasteur effect?
A Inhibition of photosynthesis by high light intensity
B Inhibition of fermentation by aerobic respiration
C Enhancement of fermentation under anaerobic conditions
D Increased photosynthesis at high CO2 levels
Correct Answer:  B. Inhibition of fermentation by aerobic respiration
EXPLANATION

The Pasteur effect describes how aerobic respiration inhibits the rate of fermentation, as aerobic respiration is more efficient.

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Q.95 Hard NEET Botany Plant Physiology
The rate-limiting step of photosynthesis under normal conditions is:
A Light absorption
B CO2 fixation
C Electron transport
D Water photolysis
Correct Answer:  B. CO2 fixation
EXPLANATION

The carboxylation of RuBP by RuBisCO is typically the slowest step in photosynthesis under normal light conditions.

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Q.96 Medium NEET Botany Plant Physiology
Which organelle is responsible for amino acid synthesis in plants?
A Ribosome
B Chloroplast
C Peroxisome
D Endoplasmic reticulum
Correct Answer:  B. Chloroplast
EXPLANATION

Chloroplasts synthesize amino acids using carbon skeletons from the Calvin cycle and nitrogen from nitrite reduction.

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Q.97 Medium NEET Botany Plant Physiology
In photorespiration, the primary substrate is:
A 3-Phosphoglycerate
B Ribulose-1,5-bisphosphate
C Glyceraldehyde-3-phosphate
D Phosphoenolpyruvate
Correct Answer:  B. Ribulose-1,5-bisphosphate
EXPLANATION

RuBisCO catalyzes oxygenation of RuBP instead of carboxylation under high O2/CO2 ratios, initiating the photorespiratory pathway.

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Q.98 Easy NEET Botany Plant Physiology
The grana in chloroplasts are composed of:
A Stacked thylakoids
B Unstacked thylakoids
C Stroma lamellae
D Cristae
Correct Answer:  A. Stacked thylakoids
EXPLANATION

Grana are stacks of thylakoids arranged vertically, while stroma lamellae are unstacked thylakoids connecting different grana.

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Q.99 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.100 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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