Complete Photosynthesis in Higher Plants Question Bank & Solutions (24 Questions)
Q1 of 24
NEET NCERT Line-by-Line
The oxygen released during photosynthesis comes from:
(A)
Carbon dioxide
(B)
Water
(C)
Glucose
(D)
Chlorophyll
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Correct Answer: (B) Water
Van Niel showed (and radioisotopes confirmed) that the O₂ released comes from the splitting of water, not CO₂.
Q2 of 24
NEET NCERT Line-by-Line
Priestley's experiments with a candle, mouse and mint plant established that:
(A)
Light is needed for growth
(B)
Plants restore air that burning/breathing fouls
(C)
CO₂ is released by plants
(D)
Chlorophyll absorbs red light
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Correct Answer: (B) Plants restore air that burning/breathing fouls
Priestley concluded plants restore to air whatever breathing animals and burning candles remove.
Q3 of 24
NEET NCERT Line-by-Line
The first action spectrum of photosynthesis was described by:
(A)
Joseph Priestley
(B)
Julius von Sachs
(C)
T.W. Engelmann
(D)
Melvin Calvin
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Correct Answer: (C) T.W. Engelmann
Engelmann split light with a prism onto Cladophora with aerobic bacteria; bacteria gathered in blue & red light.
Q4 of 24
NEET NCERT Line-by-Line
Which is NOT one of the four pigments separated from a leaf?
(A)
Chlorophyll a
(B)
Chlorophyll b
(C)
Phycoerythrin
(D)
Carotenoids
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Correct Answer: (C) Phycoerythrin
The four are chlorophyll a, chlorophyll b, xanthophylls and carotenoids. Phycoerythrin is not among them.
Q5 of 24
NEET NCERT Line-by-Line
The reaction centre chlorophyll of Photosystem I is called:
(A)
P680
(B)
P700
(C)
P870
(D)
P960
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Correct Answer: (B) P700
PS I = P700 (absorption peak 700 nm); PS II = P680 (680 nm).
Q6 of 24
NEET NCERT Line-by-Line
In the chloroplast, the dark reactions (sugar synthesis) occur in the:
(A)
Thylakoid lumen
(B)
Grana membranes
(C)
Stroma
(D)
Outer membrane
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Correct Answer: (C) Stroma
Light reactions occur on the thylakoid membranes; enzymatic sugar synthesis occurs in the stroma.
Q7 of 24
NEET NCERT Line-by-Line
Accessory pigments protect chlorophyll a from:
(A)
Dehydration
(B)
Photo-oxidation
(C)
Carboxylation
(D)
Phosphorylation
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Correct Answer: (B) Photo-oxidation
They widen the usable wavelength range and protect chlorophyll a from photo-oxidation.
Q8 of 24
NEET NCERT Line-by-Line
Splitting of water in photosynthesis is associated with:
(A)
Photosystem I
(B)
Photosystem II
(C)
ATP synthase
(D)
NADP reductase
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Correct Answer: (B) Photosystem II
The water-splitting (oxygen-evolving) complex is associated with PS II, on the inner thylakoid membrane.
Q9 of 24
NEET NCERT Line-by-Line
Cyclic photophosphorylation produces:
(A)
Only NADPH
(B)
Only ATP
(C)
ATP and NADPH
(D)
Only O₂
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Correct Answer: (B) Only ATP
Only PS I is involved; electrons cycle back, producing only ATP (no NADPH, no O₂).
Q10 of 24
NEET NCERT Line-by-Line
In the chloroplast, protons accumulate during the light reaction in the:
(A)
Stroma
(B)
Thylakoid lumen
(C)
Intermembrane space
(D)
Cytoplasm
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Correct Answer: (B) Thylakoid lumen
Unlike mitochondria, here protons accumulate inside the thylakoid lumen, lowering its pH.
Q11 of 24
NEET NCERT Line-by-Line
The primary CO₂ acceptor in the Calvin cycle is:
(A)
PEP (3C)
(B)
OAA (4C)
(C)
RuBP (5C)
(D)
PGA (3C)
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Correct Answer: (C) RuBP (5C)
The acceptor is the 5-carbon RuBP; the first product is 3-carbon PGA.
Q12 of 24
NEET NCERT Line-by-Line
The first stable product of CO₂ fixation in C3 plants is:
(A)
OAA
(B)
RuBP
(C)
PGA
(D)
Malic acid
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Correct Answer: (C) PGA
In C3 plants the first product is 3-phosphoglyceric acid (PGA), a 3-carbon acid.
Q13 of 24
NEET NCERT Line-by-Line
To make one glucose, the Calvin cycle must turn:
(A)
3 times
(B)
6 times
(C)
12 times
(D)
18 times
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Correct Answer: (B) 6 times
6 turns fix 6 CO₂; needs 18 ATP and 12 NADPH per glucose.
Q14 of 24
NEET NCERT Line-by-Line
ATP and NADPH consumed per CO₂ fixed in the Calvin cycle:
(A)
2 ATP + 2 NADPH
(B)
3 ATP + 2 NADPH
(C)
2 ATP + 3 NADPH
(D)
3 ATP + 3 NADPH
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Correct Answer: (B) 3 ATP + 2 NADPH
Per CO₂: 3 ATP and 2 NADPH. (2 ATP + 2 NADPH in reduction, plus 1 ATP in regeneration.)
Q15 of 24
NEET NCERT Line-by-Line
The enzyme RuBisCO can bind both CO₂ and:
(A)
N₂
(B)
O₂
(C)
H₂O
(D)
NADP⁺
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Correct Answer: (B) O₂
Its active site binds both CO₂ (carboxylase) and O₂ (oxygenase) — hence photorespiration in C3 plants.
Q16 of 24
NEET NCERT Line-by-Line
'Kranz anatomy' is characteristic of:
(A)
C3 plants
(B)
C4 plants
(C)
CAM only
(D)
All plants
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Correct Answer: (B) C4 plants
C4 plants have large bundle-sheath cells in a wreath ('Kranz') arrangement.
Q17 of 24
NEET NCERT Line-by-Line
In C4 plants the primary CO₂ acceptor and enzyme are:
(A)
RuBP and RuBisCO
(B)
PEP and PEPcase
(C)
OAA and PEPcase
(D)
PGA and RuBisCO
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Correct Answer: (B) PEP and PEPcase
In mesophyll cells, PEP + CO₂ →(PEP carboxylase) OAA. Mesophyll lacks RuBisCO.
Q18 of 24
NEET NCERT Line-by-Line
In C4 plants, the Calvin cycle takes place in the:
(A)
Mesophyll cells
(B)
Bundle-sheath cells
(C)
Guard cells
(D)
Epidermis
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Correct Answer: (B) Bundle-sheath cells
Calvin cycle occurs only in bundle-sheath cells of C4 plants (in all mesophyll cells of C3 plants).
Q19 of 24
NEET NCERT Line-by-Line
Photorespiration in C3 plants results in:
(A)
More ATP
(B)
Synthesis of sugar
(C)
No sugar, no ATP, CO₂ released
(D)
More NADPH
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Correct Answer: (C) No sugar, no ATP, CO₂ released
It produces no sugar, no ATP/NADPH; it releases CO₂ and wastes ATP.
Q20 of 24
NEET NCERT Line-by-Line
Blackman's Law of Limiting Factors states the rate is set by the factor that is:
(A)
Highest
(B)
Nearest its minimal value
(C)
Most variable
(D)
Internal only
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Correct Answer: (B) Nearest its minimal value
The factor in shortest supply (nearest minimum) limits the overall rate.
Q21 of 24
NEET NCERT Line-by-Line
Light saturation in photosynthesis occurs at about:
(A)
1% of full sunlight
(B)
10% of full sunlight
(C)
50% of full sunlight
(D)
Full sunlight
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Correct Answer: (B) 10% of full sunlight
Light saturation occurs near 10% of full sunlight; light is rarely limiting except in shade.
Q22 of 24
NEET NCERT Line-by-Line
The major limiting factor for photosynthesis in nature is usually:
(A)
Light
(B)
Water
(C)
CO₂ concentration
(D)
Temperature
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Correct Answer: (C) CO₂ concentration
CO₂ is the major limiting factor (only 0.03–0.04% of the atmosphere).
Q23 of 24
NEET NCERT Line-by-Line
RuBisCO is notable for being:
(A)
The fastest enzyme
(B)
The most abundant enzyme in the world
(C)
Found only in C4 plants
(D)
Light-activated only
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Correct Answer: (B) The most abundant enzyme in the world
RuBisCO (RuBP carboxylase-oxygenase) is the most abundant enzyme in the world.
Q24 of 24
NEET NCERT Line-by-Line
The Z-scheme describes the path of:
(A)
Protons
(B)
Electrons
(C)
CO₂
(D)
Water
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Correct Answer: (B) Electrons
It traces electron flow from PS II uphill, down the ETS to PS I, then to NADP⁺.