Photosynthesis – Site and Pigments Involved in Photosynthesis: NEET MCQs with Answers

15 free questions on Photosynthesis – Site and Pigments Involved in Photosynthesis for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

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Question 1

Previous-year question
Within the plastid, the dark reaction and the light reaction take place, respectively, in the: [NEET 2021 (Paper-2)]
  1. Grana and stroma respectively
  2. Grana and matrix respectively
  3. Matrix and grana respectively
  4. Stroma and grana respectively
Show answer
Answer: (D) Stroma and grana respectively
Explanation: The membrane system (grana/thylakoids) traps light energy and carries out the light reaction, while the enzymatic dark reaction (Calvin cycle) occurs in the stroma. 'Matrix' is used for mitochondria, not chloroplasts.

Question 2

Previous-year question
Water-soluble pigments found in plant cell vacuoles are [NEET 2016]
  1. xanthophylls
  2. chlorophylls
  3. carotenoids
  4. anthocyanins
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Answer: (D) anthocyanins
Explanation: Anthocyanins are water-soluble flavonoid pigments dissolved in the cell sap of the vacuole, and they give red, purple and blue colours to flowers and fruits. Chlorophylls, carotenoids and xanthophylls are lipid-soluble and are confined to the plastids.

Question 3

Previous-year question
Chromatophores take part in [AIPMT 2015]
  1. growth
  2. movement
  3. respiration
  4. photosynthesis
Show answer
Answer: (D) photosynthesis
Explanation: Chromatophores are the pigment-bearing membranous structures of photosynthetic bacteria, which lack organised chloroplasts. They house the bacterial photosynthetic pigments and are the sites of the light reaction in these prokaryotes.

Question 4

Previous-year question
The structures formed by the stacking of organised flattened membranous sacs in the chloroplast are [AIPMT 2015]
  1. grana
  2. stroma lamellae
  3. stroma
  4. cristae
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Answer: (A) grana
Explanation: Flattened membranous sacs called thylakoids are arranged in stacks known as grana, which are connected to one another by the stroma lamellae. Cristae are the infoldings of the inner membrane of a mitochondrion.

Question 5

Previous-year question
The dimensions of a chlorophyll molecule are approximately [AIPMT 1988]
  1. head 15 × 15 Å, tail 25 Å
  2. head 20 × 20 Å, tail 25 Å
  3. head 15 × 15 Å, tail 20 Å
  4. head 10 × 12 Å, tail 25 Å
Show answer
Answer: (C) head 15 × 15 Å, tail 20 Å
Explanation: A chlorophyll molecule has two parts: a porphyrin head measuring about 15 × 15 Å and a phytol tail about 20 Å long. The porphyrin head is hydrophilic and acidic, while the phytol tail is hydrophobic and alcoholic — this amphipathic nature anchors the molecule in the thylakoid membrane.

Question 6

Previous-year question
The dark reactions of photosynthesis take place in the [AIPMT 1991]
  1. granal thylakoid membranes
  2. stromal lamellae membranes
  3. stroma outside the photosynthetic lamellae
  4. periplastidial space
Show answer
Answer: (C) stroma outside the photosynthetic lamellae
Explanation: The light reaction occurs on the granal thylakoid membranes, while the dark reaction (Calvin cycle) occurs in the stroma — the matrix lying outside the photosynthetic lamellae — where all the carbon-fixation enzymes are dissolved.

Question 7

Previous-year question
Most plants appear green in colour because [AIPMT 1991]
  1. the atmosphere filters out all colours of the visible spectrum except green
  2. green light is the most effective wavelength region of sunlight for photosynthesis
  3. chlorophyll is least effective in absorbing green light
  4. green light permits maximum photosynthesis
Show answer
Answer: (C) chlorophyll is least effective in absorbing green light
Explanation: Chlorophyll absorbs strongly in the blue-violet and red regions but absorbs green light poorly. The unabsorbed green wavelengths are reflected and transmitted, and it is this reflected light that reaches our eyes, making leaves look green.
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Question 8

Previous-year question
In chloroplasts, the photosynthetic pigments are located in the [AIPMT 1991]
  1. thylakoid membranes
  2. plastoglobules
  3. matrix
  4. chloroplast envelope
Show answer
Answer: (A) thylakoid membranes
Explanation: Chlorophylls and carotenoids are embedded within the thylakoid membranes, where they are organised into protein–pigment complexes called photosystems. These complexes carry out the absorption of light during the light-dependent reactions.

Question 9

Previous-year question
Chlorophyll-a is present in [AIPMT 1992]
  1. all photosynthetic autotrophs
  2. all higher plants
  3. all oxygen-liberating autotrophs
  4. all plants except fungi
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Answer: (C) all oxygen-liberating autotrophs
Explanation: Chlorophyll-a (C₅₅H₇₂O₅N₄Mg) is the universal photosynthetic pigment and the reaction-centre pigment of every organism that evolves oxygen. Anoxygenic photosynthetic bacteria contain bacteriochlorophyll instead, so it is not present in all photosynthetic autotrophs — only in all oxygen-liberating ones.

Question 10

Previous-year question
Maximum solar energy is trapped by [AIPMT 1993]
  1. planting trees
  2. cultivating crops
  3. growing algae in tanks
  4. growing grasses
Show answer
Answer: (C) growing algae in tanks
Explanation: Algae capture the greatest amount of solar energy per unit area because their water-soluble accessory pigments (such as phycocyanin) let them harvest a wider range of wavelengths, and their CO₂-concentrating mechanisms and antenna systems give them higher photosynthetic efficiency than higher plants. Grown in tanks, their light-capturing surface per unit volume is also very high.

Question 11

Previous-year question
Roughly nine-tenths (85–90%) of the world's photosynthesis is performed by [AIPMT 1994]
  1. large trees with millions of branches and leaves
  2. algae of the ocean
  3. chlorophyll-containing ferns of the forest
  4. scientists in laboratories
Show answer
Answer: (B) algae of the ocean
Explanation: Nearly 90% of global photosynthesis is carried out by aquatic plants, principally algae — about 80% in the oceans and 10% in freshwater. Terrestrial plants account for only about 10% of the total. Marine phytoplankton therefore form the largest single photosynthetic system on Earth.

Question 12

Previous-year question
In a chlorophyll-a molecule, the carbon atom at position 3 of pyrrole ring-II bears which of the following groups? [AIPMT 1996]
  1. Aldehyde group
  2. Methyl group
  3. Carboxyl group
  4. Magnesium
Show answer
Answer: (B) Methyl group
Explanation: Chlorophyll consists of a tetrapyrrole porphyrin head with a central non-ionic Mg atom, plus a long-chain phytol tail. In chlorophyll-a a methyl group (—CH₃) is attached at carbon 3 of pyrrole ring-II, whereas chlorophyll-b carries a formyl (aldehyde, —CHO) group at that same position. This single substitution accounts for their different absorption properties.

Question 13

Previous-year question
Protochlorophyll differs from chlorophyll in that it lacks [AIPMT 1998]
  1. 2 hydrogen atoms in one of its pyrrole rings
  2. 2 hydrogen atoms in two of its pyrrole rings
  3. 4 hydrogen atoms in one of its pyrrole rings
  4. 4 hydrogen atoms in two of its pyrrole rings
Show answer
Answer: (A) 2 hydrogen atoms in one of its pyrrole rings
Explanation: Protochlorophyll is the immediate precursor of chlorophyll and differs from it by lacking two hydrogen atoms in one of its pyrrole rings. In the presence of light it is reduced and then esterified with a phytol group to form chlorophyll.

Question 14

Previous-year question
Which of the following absorbs light energy for photosynthesis? [AIPMT 2002]
  1. Chlorophyll
  2. Water molecule
  3. O₂
  4. RuBP
Show answer
Answer: (A) Chlorophyll
Explanation: Chlorophyll is the principal light-absorbing pigment of photosynthesis. Water molecules act as the electron and H⁺ donor (supplying electrons after photolysis), O₂ is a by-product, and RuBP is the CO₂ acceptor in the Calvin cycle catalysed by RuBisCO — none of these absorbs light.

Question 15

Previous-year question
Which fractions of the visible solar spectrum are chiefly absorbed by the carotenoids of higher plants? [AIPMT 2003]
  1. Violet and blue
  2. Blue and green
  3. Green and red
  4. Red and violet
Show answer
Answer: (A) Violet and blue
Explanation: Carotenoids are yellow, orange and red accessory pigments with absorption peaks in the blue-violet region of the spectrum. Besides harvesting light energy and transferring it to chlorophyll-a, they protect chlorophyll from photo-oxidative damage under intense illumination.

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