Top 50 Important MCQs on photosynthesis



Photosynthesis is the process used by plants, algae and certain bacteria to harness energy from sunlight and turn it into chemical energy. Here, we describe the general principles of photosynthesis and highlight how scientists are studying this natural process to help develop clean fuels and sources of renewable energy.

There are two types of photosynthetic processes: oxygenic photosynthesis and anoxygenic photosynthesis.

Oxygenic photosynthesis functions as a counterbalance to respiration by taking in the carbon dioxide produced by all breathing organisms and reintroducing oxygen to the atmosphere.

On the other hand, anoxygenic photosynthesis uses electron donors other than water. The process typically occurs in bacteria such as purple bacteria and green sulfur bacteria, which are primarily found in various aquatic habitats.

Oxygenic photosynthesis is written as follows:
6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O

Similarly, the various anoxygenic photosynthesis reactions can be represented as a single generalized formula:
CO2 + 2H2A + Light Energy → [CH2O] + 2A + H2O

Photosynthesis takes place in the chloroplast. The chlorophyll present in the chloroplast traps the light from the sun and carries out the process.

Photosynthesis MCQs

1. Photosynthesis occurs in___
a) Chloroplast
b) Golgi body
c) Endoplasmic reticulum
d) Nucleus

Answer : a

2. Rate of photosynthesis does not depend upon:
a) Quality of light
b)  Intensity of Light
c) Duration of Light
d) Temperature

Answer: C

3. For photosynthesis green plants require:
a) Chlorophyll only
b) Light
c) Carbon dioxide and water
d) All of the above

Answer : D

4. The optimum temperature for photosynthesis is

a) 25-35℃
b) 10-15℃
c) 35-40℃
d) 20-25℃

Answer : d

5. Photosynthesis is a _____ process.
a) Catabolic
b) Anabolic
c) Exothermic
d) Metabolic

Answer : B


6. Photorespiration occurs in____
a) Four cell organelles
b) Two cell organelles
c) One cell organelle
d) Three cell organelle

Answer : d

7. Name the pigment which is responsible for absorption of light in plants?
a) Chlorophyll
b) Stoma
c) Xylem
d) Phloem

Answer: A

8. Reduction of NADP occurs in
a) Oxidative photophosphorylation
b) Cyclic photophosphorylation
c) Non cyclic photophosphorylation
d) None

Answer : c

9. In bacteria name the colour of light which is responsible for photosynthesis?
a) Ultra-Violet
b) Blue
c) Red
d) None of the above

Answer: C

10. Kranz anatomy is found in the leaves of
a) Wheat
b) Mustard
c) Potato
d) Sugarcane

Answer : d

11. Quantasomes are found in:
a) Cristae of mitochondria
b) Thylakoid membrane of chloroplasts
c) Nucleus membrane
d) Lysosome

Answer : B

12. Peroxisomes are involved in which type of reactions
a) Calvin cycle
b) Glyoxylate cycle
c) Glycolytic cycle
d) Bacterial photosynthesis

Answer : c

13. Name the metal present in chlorophyll ‘a’ and ‘b’?
a) Iron
b) Copper
c) Magnesium
d) Manganese

Answer : C

14. Photorespiration involves oxidation of
a) PGA
b) RuBP
c) Chlorophyll a
d) Both a and b

Answer : b

15. Name the structural unit of photosynthesis?
a) Thylakoid
b) Grana
c) Stroma
d) Chlorophyll

Answer : A

16. C3 and C4 plants differ with respect to___
a) Number of ATP molecules consumed
b) First product
c) Substrate which accepts carbon dioxide
d) All

Answer : d

17. Which of the following statements are true regarding Photosystems?
a) Photosystems are arrangements of chlorophyll and other pigments packed into thylakoids.
b) Many Prokaryotes have only one photosystem.
c) Both A and B are correct.
d) Only A is correct.

Answer : C

18. In Calvin cycle, 1 molecule of glucose is formed from
a) 6CO2 + 30ATP + 12NADPH
b) 6CO2 + 12ATP
c) 6CO2 + 18ATP + 12NADPH
d) 6CO2 + 18ATP + 30NADPH

Answer : c

19. Name the physiochemical process in which chemical energy is produced by light energy with the help of a photosynthetic organism?
a) Photosynthesis
b) Respiration
c) Oxidative decarboxylation
d) Oxidative phosphorylation

Answer : a

20. Where does light reaction take place?
a) Grana
b) Stroma
c)Cytoplasm
d) Endoplasmic reticulum

Answer : a

21. Classification of organisms as oxygenic or anoxygenic during photosynthesis is based on ______
a) The presence of Co2
b) The generation of oxygen
c) The presence of light
d) The presence of water

Answer : b

22. Electrons from the excited chlorophyll molecules of PS-II are first accepted by___
a) Pheophytin
b) Ferredoxin
c) Cytochrome f
d) Cytochrome b

Answer : a

23. Which of the following is not a lipid-soluble photosynthetic pigment?
a) Phycobilins
b) Carotenoids
c) Chlorophyll
d) Xanthophylls

Answer : A

24. Non cyclic photophosphorylation results in the production of___
a) NADH
b) NADPH
c) ATP
d) ATP and NADPH

Answer : d

25. Which of these features are not of chlorophyll?
a) It has Mg2+ as the central metal ion
b) It has cyclopentanone ring fused with a pyrrole ring
c) It has a planer tetrapyrrole ring structure
d) It is water-soluble pigment

Answer : d

26. DCMU inhibits
a) PS-I
b)PS-II
c) Oxidative phosphorylation
d) It destroys chloroplast

Answer : b

27. Name the pigment which is responsible for the yellow color of leaves in autumn and orange color of carrots?
a) Phycobilins
b) Chlorophylls
c) Carotenoids
d) Bacteriochlorophyll

Answer :  C

28. Maximum photosynthesis occurs in
a) Blue light
b) Red light
c) White light
d) Green light

Answer : b

29. The first acceptor of CO2 in C4 plants is
a) Aspartic acid
b) Malic acid
c) Oxaloacetic acid
d) Phosphoenolpyruvate

Answer : d

30. Name the mechanism which prevents photo-oxidative damage in plants?
a) Photosynthesis
b) Photorespiration
c) Photoprotection
d) Phytoprotection

Answer : C

31. The first product of C4 pathway is
a) PGA
b) DHAP
c) Oxaloacetate
d) Phosphoenolpyruvate

Answer : c

32. Name the photosynthetic pigment which is structurally similar to bile pigment bilirubin?
a) Chlorophyll
b) Carotene
c) Xanthophyll
d) Phycobilins

Answer : d

33. The two pigment system theory of photosynthesis was proposed by
a) Aron
b) Blackman
c) Hill
d) Emerson

Answer : d

34. What is the location of photosynthetic pigment in an oxygenic photosynthetic organism?
a) Plasma membranes
b) Thylakoid membranes
c) Chromatophores
d) Chlorosome

Answer : b

35. H2 donor during photosynthesis is
a) ATP
b) NADP
c) NADPH
d) NADH

Answer : c

36. What is the absorption spectrum?
a) The graph produced by absorption of light
b) The graph shows the photochemical reaction
c) The graph produced by absorption of oxygen
d) The graph shows oxygen evolution at a different wavelength

Answer : a

37. The minerals involved in spitting reaction during photosynthesis is
a) Potassium and manganese
b) Magnesium and chlorine
c) Potassium and chlorine
d) Manganese and chlorine

Answer : d

38. Name the filamentous fungi which are used in Engelmann’s experiment to show photosynthetic activity?
a) Rhizopus stolonifer
b) Penicillium
c) Cyanobacteria
d) Spirogyra

Answer : d

39. Water-soluble photosynthetic pigment is
a) Chlorophyll a
b) Xanthophyll
c) Anthocyanin
d) Chlorophyll b

Answer :  c

40. Which of the following term defines the production of heat and light when excited molecule returns to its original state?
a) Fluorescence
b) Luminescence
c) Intersystem crossing
d) Phosphorescence

Answer : a

41. In photosynthesis dark reaction, is called so because-
a) It occurs in dark.

b) It does not require light energy.

c) It cannot occur during daytime.

d) It occurs more rapidly at night.

Answer : B

42. What is resonance energy transfer?
a) Transfer of electrons between the molecules
b) The transfer of energy as well as electrons
c) The transfer of electrons but not the energy
d) The transfer of energy but not the electron

Answer : d

43. How many photons are absorbed to produce one molecule of oxygen?
a) Two
b) Ten
c) Twelve
d) Eight

Answer : d

44. Which of the following is a Hill reagent?
a) Sugar
b) Chlorophylls
c) 2, 6- dichlorophenolindophenol
d) Nicotinamide adenine dinucleotide phosphate

Answer : c

45. What is red drop phenomenon?
a) Falling of red color in the spectrum
b) Drop in quantum yield in the red region of the spectrum
c) Drop in quantum yield in the far-red region of the spectrum
d) Falling of far-red color in the spectrum

Answer : C

46. Which of the following correctly defines the yield of oxygen by the no. of photons absorbed?
a) Emerson enhancement effect
b) Quantum requirement
c) Photochemical reaction
d) Quantum Yield

Answer : d