Early Experiments, Site & Pigments — NEET Biology MCQs with Solutions
Free NEET Biology Early Experiments, Site & Pigments MCQs with step-by-step solutions (67 questions). Part of Photosynthesis in Higher Plants. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Early Experiments, Site & Pigments · easy · theory
The most abundant photosynthetic pigment, absorbing chiefly blue and red light and reflecting green, is:
A. Chlorophyll b
B. Xanthophyll
C. Chlorophyll a ✓ Correct
D. Carotene
Solution: Chlorophyll a is the chief pigment (reaction centre); accessory pigments (chl b, carotenoids) widen the absorbed spectrum.
Q2 — Early Experiments, Site & Pigments · easy · theory
Photosynthesis in higher plants takes place in the:
A. Chloroplast (mesophyll) ✓ Correct
B. Cell wall
C. Mitochondrion
D. Nucleus
Solution: The chloroplast is the site: light reactions occur in the thylakoid (grana) and the Calvin cycle in the stroma.
Q3 — Early Experiments, Site & Pigments · medium · theory
Engelmann's experiment, using a filamentous alga and aerobic bacteria, identified the ______ regions of the spectrum as most effective for photosynthesis:
A. Blue and red ✓ Correct
B. Green and yellow
C. Only green
D. Ultraviolet
Solution: Bacteria accumulated where blue and red light fell — the action spectrum peaks matching chlorophyll absorption.
Q4 — Early Experiments, Site & Pigments · medium · theory
Half-leaf experiments and Ruben's isotope studies established that the O₂ released in photosynthesis comes from:
A. Carbon dioxide
B. Glucose
C. The atmosphere directly
D. Water ✓ Correct
Solution: Using H₂¹⁸O, the released ¹⁸O₂ was traced to water — O₂ comes from the photolysis of water, not CO₂.
Q5 — Early Experiments, Site & Pigments · hard · theory
Carotenoids (accessory pigments) are important because they:
A. Release oxygen
B. Are the main reaction-centre pigment
C. Fix carbon dioxide
D. Absorb light at wavelengths chlorophyll cannot and protect chlorophyll from photo-oxidation ✓ Correct
Solution: Carotenoids extend the absorption range and protect chlorophyll from photo-oxidative damage.
Q6 — Early Experiments, Site & Pigments · hard · theory
An action spectrum superimposed on the absorption spectrum of chlorophyll a shows that photosynthesis is highest in blue and red because:
A. These wavelengths are absorbed most by chlorophyll and drive the reaction ✓ Correct
B. Chlorophyll absorbs all colours equally
C. Photosynthesis needs UV light
D. Green is absorbed most
Solution: The close match between action and absorption spectra confirms chlorophyll a as the primary light-harvesting pigment.
Q7 — Early Experiments, Site & Pigments · easy · numerical
Joseph Priestley's bell-jar experiments with a mint plant, a candle and a mouse led him to conclude that plants:
A. take up carbon dioxide only in darkness and release it in light
B. restore to the air whatever breathing animals and burning candles remove from it ✓ Correct
C. release a gas that is chemically identical to the one animals exhale
D. require sunlight in order to purify the surrounding air
Solution: Priestley showed a plant could "restore" air fouled by a candle or a mouse, revealing that plants release oxygen; he had not yet recognised the essential role of light (that was Ingenhousz).
Q8 — Early Experiments, Site & Pigments · easy · numerical
Ingenhousz, using an aquatic plant, added a crucial refinement to Priestley's conclusion by demonstrating that air purification by green plants occurs:
A. only at night, when stomata of the plant are fully open
B. only in sunlight and only from the green parts of the plant ✓ Correct
C. only in the roots, which absorb the impurities from water
D. equally well in light and darkness as long as CO₂ is present
Solution: Ingenhousz showed that bubbles of oxygen formed around the green parts only in sunlight, establishing that light is essential and that only green tissue does the purifying.
Q9 — Early Experiments, Site & Pigments · medium · numerical
The reaction-centre pigment that actually converts light energy into chemical energy in photosynthesis is chlorophyll a, while chlorophyll b, carotenoids and xanthophylls are called accessory pigments because they:
A. replace chlorophyll a as reaction centres when light is very intense
B. absorb light at other wavelengths and hand the energy over to chlorophyll a ✓ Correct
C. store the ATP and NADPH generated so they can be used at night
D. directly split water to release the oxygen during the light reaction
Solution: Accessory pigments widen the range of wavelengths harvested and transfer that energy to chlorophyll a, the only pigment that acts as the reaction centre; they do not themselves drive photochemistry.
Q10 — Early Experiments, Site & Pigments · medium · numerical
The chemical experiment of Cornelius van Niel, based on his study of purple and green sulphur bacteria that use H₂S instead of water, predicted that in green plants:
A. hydrogen sulphide can substitute for water in all green plants
B. no oxygen is released when carbon dioxide is the sole carbon source
C. the O₂ evolved comes from carbon dioxide, not from water
D. the O₂ evolved comes from water, not from carbon dioxide ✓ Correct
Solution: Van Niel reasoned that since sulphur bacteria produce sulphur (not O₂) from H₂S, the oxygen from plants must come from the hydrogen donor water — later confirmed by Ruben and Kamen using ¹⁸O.
Q11 — Early Experiments, Site & Pigments · medium · numerical
Which statement correctly distinguishes the absorption spectrum from the action spectrum of photosynthesis?
A. Both plot the rate of photosynthesis, but at different light intensities
B. The absorption spectrum plots light absorbed by a pigment; the action spectrum plots the rate of photosynthesis at each wavelength ✓ Correct
C. Both plot light absorption, one for chlorophyll a and one for chlorophyll b
D. The absorption spectrum plots the rate of photosynthesis; the action spectrum plots light absorbed by a pigment
Solution: An absorption spectrum shows how much light a pigment absorbs at each wavelength, whereas an action spectrum shows the effectiveness of each wavelength in driving photosynthesis; their close match implicated chlorophyll as the main pigment.
Q12 — Early Experiments, Site & Pigments · easy · numerical
A chloroplast is bounded by a double membrane; the flattened sacs stacked into grana and the fluid surrounding them are, respectively, the sites of:
A. thylakoids — carbon fixation; stroma — water splitting
B. thylakoids — light reaction; stroma — dark (biosynthetic) reaction ✓ Correct
C. stroma — light reaction; thylakoids — dark (biosynthetic) reaction
D. grana — sugar storage; stroma — pigment synthesis
Solution: The membrane-bound thylakoids house the light-harvesting machinery and light reactions, while the enzymatic (carbon-fixing) reactions of the Calvin cycle occur in the stroma.
Q13 — Early Experiments, Site & Pigments · medium · numerical
Assertion (A): Leaves generally appear green to the human eye. Reason (R): Chlorophyll strongly absorbs light in the green region of the visible spectrum.
A. Both A and R are true but R is not the correct explanation of A
B. A is true but R is false ✓ Correct
C. A is false but R is true
D. Both A and R are true and R is the correct explanation of A
Solution: Leaves look green precisely because chlorophyll absorbs blue and red but reflects (does not absorb) green light; R states the opposite of the truth, so R is false.
Q14 — Early Experiments, Site & Pigments · easy · numerical
When chlorophyll a and chlorophyll b are separated by paper chromatography of a leaf extract, the two can be told apart because chlorophyll a and chlorophyll b differ mainly in that:
A. chlorophyll a is a carotenoid whereas chlorophyll b is a xanthophyll
B. chlorophyll a lacks magnesium whereas chlorophyll b contains it
C. chlorophyll a absorbs only green light while chlorophyll b absorbs only blue
D. chlorophyll a is blue-green and chlorophyll b is yellow-green ✓ Correct
Solution: Chlorophyll a appears bright/blue-green and chlorophyll b yellow-green; both are Mg-porphyrin pigments (neither is a carotenoid), differing by a side group.
Q15 — Early Experiments, Site & Pigments · medium · numerical
Engelmann built the first action spectrum by illuminating a filamentous alga with a prism-split spectrum and watching aerobic bacteria cluster where O₂ was released. This clustering pattern demonstrated that:
A. photosynthesis is most efficient in the green and yellow regions of the spectrum
B. oxygen is consumed rather than released in the blue and red regions
C. bacteria move towards regions of highest light intensity regardless of oxygen
D. photosynthesis is most efficient in the blue and red regions of the spectrum ✓ Correct
Solution: The oxygen-seeking bacteria gathered where the alga released most O₂ — the blue and red bands — giving an action spectrum that peaks in blue and red, matching chlorophyll absorption.
Q16 — Early Experiments, Site & Pigments · easy
Chlorophyll is the
A. Green pigment of root of all plants
B. Red pigment of leaf of all plants
C. Blue pigment of leaf of all plants
D. None of these ✓ Correct
Solution: Chlorophyll is the green pigment of the leaf. Since the given options describe it wrongly, 'None of these' is correct.
Q17 — Early Experiments, Site & Pigments · medium
In the below-mentioned experiment, when a part of the leaf is enclosed in a test tube containing KOH-soaked cotton exposed to light, it will
A. Test negative for starch due to inability to absorb light inside test tube
B. Test positive for starch
C. Test negative for starch due to inability to absorb CO2 ✓ Correct
D. Test negative for starch due to absence of water
Solution: KOH absorbs CO2, so the enclosed leaf part cannot carry out photosynthesis and forms no starch, testing negative for starch.
Q18 — Early Experiments, Site & Pigments · medium
________ from a suitable oxidisable compound reduces CO2 to carbohydrates.
A. Hydrogen ✓ Correct
B. Oxygen
C. Carbon
D. Both (1) and (2)
Solution: Van Niel showed that hydrogen from a suitable oxidisable compound reduces CO2 to carbohydrates.
Q19 — Early Experiments, Site & Pigments · easy
Cladophora is
A. Red algae
B. Green algae ✓ Correct
C. Green bacteria
D. Purple and green bacteria
Solution: Cladophora, used in Engelmann's experiment, is a green filamentous alga.
Q20 — Early Experiments, Site & Pigments · medium
Statement A: O2 evolved by the green plant comes from H2O, not from carbon dioxide.
Statement B: This was proved by using radio-isotopic techniques.
Choose the correct option.
A. Both Statement A and B are wrong
B. Both Statement A and B are correct ✓ Correct
C. Statement A is wrong and Statement B is right
D. Statement A is wrong and Statement B is correct
Solution: The O2 released comes from water (not CO2), and this was demonstrated using radioisotope (O-18) techniques; both statements are correct.
Q21 — Early Experiments, Site & Pigments · medium
Match the experiment objective with the scientist who performed it:
i. Priestley
ii. Julius von Sachs
iii. Jan Ingenhousz
I. Production of glucose in photosynthesis
II. Role of sunlight in photosynthesis
III. Role of air in photosynthesis
Select the correct match in the order (i), (ii), (iii).
A. I, III, II
B. II, III, I
C. III, I, II ✓ Correct
D. II, I, III
Solution: Priestley showed the role of air (III), Sachs showed glucose production (I), and Ingenhousz showed the role of sunlight (II).
Q22 — Early Experiments, Site & Pigments · medium
Who performed a series of experiments that revealed the essential role of air on the growth of green plants and when?
A. Joseph Priestley (1770) ✓ Correct
B. T. Engelmann (1756)
C. Both (1) and (2)
D. Cornelius van Niel (1787)
Solution: Joseph Priestley in 1770 performed experiments revealing the essential role of air in the growth of green plants.
Q23 — Early Experiments, Site & Pigments · medium
Who discovered oxygen and when?
A. T. Engelmann (1770)
B. Jan Ingenhousz (1787)
C. Joseph Priestley (1774) ✓ Correct
D. Elvis Priestley (1770)
Solution: Joseph Priestley discovered oxygen in 1774.
Q24 — Early Experiments, Site & Pigments · easy
Who showed that sunlight is essential to the plant?
A. Jan Ingenhousz ✓ Correct
B. Joseph Priestley
C. T. Engelmann
D. Cornelius van Niel
Solution: Jan Ingenhousz showed that sunlight is essential for the plant process that purifies air.
Q25 — Early Experiments, Site & Pigments · easy
Who showed that it is the green part of the plants that could release oxygen?
A. Joseph Priestley
B. None of these
C. T. Engelmann
D. Jan Ingenhousz ✓ Correct
Solution: Jan Ingenhousz demonstrated that only the green parts of plants release oxygen in sunlight.
Q26 — Early Experiments, Site & Pigments · medium
________ were used to detect the sites of O2 evolution.
A. Virus
B. Bacteria ✓ Correct
C. Fungi
D. Algae
Solution: Engelmann used aerobic bacteria (which accumulate where O2 is released) to detect the sites of O2 evolution.
Q27 — Early Experiments, Site & Pigments · medium
Cornelius van Niel studied ____ to demonstrate that photosynthesis is essentially a light-dependent reaction.
A. Both 1 and 2
B. Cladophora
C. Red algae
D. Purple and green bacteria ✓ Correct
Solution: Van Niel studied purple and green (sulphur) bacteria to establish that photosynthesis is a light-dependent reaction in which hydrogen reduces CO2.
Q28 — Early Experiments, Site & Pigments · easy
Sugar is synthesized
A. Enzymatically in grana
B. Enzymatically in stroma ✓ Correct
C. Non-enzymatically in stroma
D. Non-enzymatically in grana
Solution: Sugar synthesis (dark reaction) occurs enzymatically in the stroma of the chloroplast.
Q29 — Early Experiments, Site & Pigments · easy
Which of the following is correct?
A. Dark reaction depends on light reaction ✓ Correct
B. Both of the above
C. Light reaction depends on dark reaction
D. None of the above
Solution: The dark reaction uses the ATP and NADPH produced by the light reaction, so it depends on the light reaction.
Q30 — Early Experiments, Site & Pigments · medium
If a plant is kept in dark for a long time
A. None of these ✓ Correct
B. NADPH will be synthesized in chloroplast but no starch
C. Starch will be synthesized in chloroplast
D. ATP will be synthesized in chloroplast but no starch
Solution: In prolonged darkness there is no light reaction, so no ATP or NADPH is made and no starch is synthesized; hence none of the given options is correct.