13

Q1. The active component of photosystem I is composed of

• Chlorophyll a with absorption peak at 680 nm
• Chlorophyll a with absorption peak at 700 nm
• Chlorophyll h with absorption peak at 680 nm
• Chlorophyll a and h with absorption peak at 700 nm

Solution

The chlorophyll a reaction centre for PS I has an absorption maxima peak at 700 nm.

Q2. A photosystem is composed of

• Reaction centre
• Light-harvesting complex
• Reaction centre and light-harvesting complex
• Granum

Solution

A photosystem is composed of both a reaction centre as well as a light-harvesting complex which are involved in trapping light and synthesising energy-rich molecules like ATP and NADPH.

Q3. The point at which the amount of CO₂ fixed in photosynthesis is equal to the CO₂ evolved in respiration and photorespiration is called

• Concentration point
• Compensation point
• Optimal point
• Balance point

Solution

When the levels of CO₂ is reduced, there comes a point in photosynthesis that the plant stops absorbing CO₂ from the atmosphere, and the amount of CO₂ fixed in the plant is equal to the amount of CO₂ produced by the plant as a result of respiration and photorespiration. This point is called the compensation point or threshold value.

Q4. Energy required for ATP synthesis in PS II comes from  

• Proton gradient  
• Electron gradient  
• Reduction in glucose  
• Oxidation of glucose  

Solution

The proton gradient is formed due to accumulation of protons on the lumen side of the thylakoid. Also, the transport of electrons through the photosystem moves protons from the stroma to the lumen side, decreasing the proton concentration in the stroma and increasing it on the lumen side. This results in the generation of a proton gradient across the thylakoid membrane. The ATPase enzyme breaks down this proton gradient and uses its energy for the synthesis of ATP molecules.  

Q5. Which of the following is an inhibitor of non-cyclic photophosphorylation?  

• Only DCMU  
• Only CMU  
• Only diquat  
• DCMU, CMU and diquat, all inhibit non-cyclic photophosphorylation  

Solution

DCMU, CMU and diquat are herbicides and inhibit plant growth by blocking non-cyclic photophosphorylation.  

Q6. The number of thylakoids in a granum is  

• 5-10  
• 2-100  
• 100-150  
• 150-200  

Solution

The number of thylakoids in a granum can vary from 2 to 100.  

Q7. The first stable compound in C₃ plants is

• PGA
• OAA
• RuBP
• PEP

Solution

3-Phosphoglycerate is the first stable compound which is formed in the C₃ cycle in the carboxylation stage. The reaction uses CO₂ and RuBP, a five-carbon compound, with the reaction being catalysed by RuBP carboxylase.

Q8. Which elements are essential for photophosphorylation?  

• Mg and P  
• Zn and I  
• K and Cl  
• Mn and Cl  

Solution

Mn and Cl are useful for light reactions as they are important for the process of splitting of water.  

Q9. Oxygen in air was discovered by

• Priestley
• Jan Ingenhousz
• Julius von Sachs
• T. W. Engelmann

Solution

Joseph Priestley discovered oxygen in 1774.

Q10. Light saturation point for shade plants is at how much percent of full sunlight?  

• 10%  
• 50%  
• 90%  
• 100%  

Solution

The light intensity at which a plant reaches the maximum photosynthesis rate is known as the light saturation point. This is about 10% of full sunlight for shade plants, 50-70% of full sunlight for C₃ sun plants and up to 200% for C₄ sunplants_.  

Q11. The correct sequence of cell organelles during photo respiration is  

• Chloroplast - Golgi bodies - Mitochondria  
• Chloroplast - Rough endoplasmic reticulum - Dictyosomes  
• Chloroplast - Mitochondria - Peroxisomes  
• Chloroplast - Vacuole - Peroxisome  

Solution

The first stage of photorespiration involves the formation of glycolate in the chloroplasts. Further reactions of the glycolate pathway occur in the mitochondria and peroxisomes, and eventually, a compound is formed which is returned to the chloroplasts, where the process began.  

Q12. Bacteria which live in regions such as hot springs can perform photosynthesis even at

• 35°C
• 48°C
• 12°C
• 70°C

Solution

Bacteria which live in or near hot springs can perform photosynthesis even at 70°C.

Q13. Consider the following statements regarding photosynthesis: A. ATP formation during photosynthesis is termed photophosphorylation. B. Kranz anatomy pertains to leaf. C. Reduction of NADP⁺ to NADPH occurs during the Calvin cycle. D. In a chlorophyll molecule, magnesium is present in the phytol tail Of the above statements,

• A and B are correct.
• C and D are correct.
• A and C are correct.
• A and D are correct.
• B and C are correct.

Solution

ATP and NADPH are formed during the light reaction phase (photophosphorylation), which is used during the dark reactions for the fixation of CO₂ and the synthesis of sugars. Kranz anatomy is a specialised anatomy of the leaves of C₄ plants where the vascular bundle is surrounded by bundle sheath cells, which in turn are surrounded by mesophyll cells.

Q14. Cornelius van Niel demonstrated that photosynthesis is essentially a light-dependent reaction. He based his study on which organism?

• Blue-green algae
• E. coli
• Purple and green bacteria
• Aquatic plants

Solution

Cornelius van Niel based his study on purple and green bacteria and demonstrated that photosynthesis is essentially a light-dependent reaction.

Q15. Stomata of CAM plants

• Are always open
• Open during the day and close at night
• Open during the night and close during the day
• Never open

Solution

The CAM cycle is an adaptation in succulent plants. In plants with the CAM cycle, the stomata remain close during the day and open during the night. This helps in preventing loss of water due to transpiration.

Q16. RuBisCO is the most abundant enzyme in the world and present in very high concentration in chloroplasts. It is required in very high concentration for     photosynthesis because it  

• Is a very slow-acting enzyme  
• Also acts as an oxygenase  
• Catalyses a reversible reaction  
• Is degraded very rapidly  

Solution

RuBisCO is a very slow-acting enzyme as it can capture only a few molecules of CO₂ for fixation; thus, it is produced in large amounts in plants to carry out optimum levels of photosynthesis.  

Q17. Photosynthetically active radiation (PAR) represents which of the following range of wavelength?  

• 500-600 nm  
• 450-950 nm  
• 340-450 nm  
• 400-700 nm  

Solution

400-700 nm wavelength of the electromagnetic spectrum belongs to the visible light region which is the main and only source of light for photosynthesis.  

Q18. Bulk fixation of carbon through photosynthesis takes place in  

• Crop plants  
• Tropical plants  
• Oceans  
• Rain forests  

Solution

Oceans cover a large portion of the earth. The ocean is home to a large amount of organisms which include both producers and consumers. In oceans, microscopic organisms (e.g. cyanobacteria and dinoflagellates) along with multicellular producers (e.g. sea weed and sea grass) account for most of the CO₂ fixation on Earth.  

Q19. The light reaction of photosynthesis occurs in  

• Stroma  
• Grana  
• Endoplasmic reticulum  
• Cytoplasm  

Solution

The granum is the site for light reactions as it contains light-harvesting complexes, and the stroma is the site for dark reactions as it contains all the necessary enzymes required for the fixation of CO₂ and the synthesis of sugars.  

Q20. The type of CO₂ fixation seen in many succulent plant species is  

• C₄ pathway  
• C₂ pathway  
• CAM pathway  
• C₃ pathway  

Solution

Succulent plants are those that live in arid climates or regions with water scarcity. To preserve water in them, they have adapted to the CAM pathway where their stomata remain closed during the day and open at night to prevent the loss of water due to transpiration.  

Q21. Which one does not occur in cyclic photophosphorylation?

• Oxygen is not given off
• Water is not consumed
• Only photosystem I is involved
• NADPH formation

Solution

NADPH formation does not take place in cyclic photophosphorylation. In this pathway, only a single molecule of ATP is synthesised.

Q22. Electrons from an excited chlorophyll molecule of photosystem II are accepted first by  

• Cytochrome-b              
• cytochrome-f     
• quinone  
• ferredoxin  

Solution

Quinine is the first electron acceptor for electrons given out by photosystem II.

Q23. The Calvin cycle is

• Reductive carboxylation
• Oxidative carboxylation
• Reduction
• Oxidation

Solution

The Calvin cycle is a reductive carboxylation process as it involves the carboxylation of RuBP to 3-PGA and the further reduction of 3-PGA by a series of steps which leads to the synthesis of sugars.

Q24. Structurally, chlorophyll a and b are different as  

• Chl a has a methyl group and Chl b has an aldehyde group.  
• Chl a has a carboxyl group and Chl b has an aldehyde group.  
• Chl a has an aldehyde group and Chl b has a methyl group.  
• Chl a has an ethyl group and Chl b has an aldehyde group.  

Solution

Chl a has a methyl group (-CH₃) and Chl b has an aldehyde group (-CHO) in its structure.  

Q25. Blue and red light roughly resemble the absorption spectrum of

• Chlorophyll a
• Chlorophyll b
• Chlorophyll a and b
• Accessory pigments

Solution

Blue and red light roughly resemble the absorption spectrum of chlorophyll a and b.

Q26. Which chlorophyll molecule does not have a phytol tail?  

• Chl a  
• Chl b  
• Chl c  
• Chl d  

Solution

Chlorophyll c is an accessory pigment and forms part of the antennae system. It is different from the rest of the chlorophyll molecules as it lacks a phytol tail. It is generally found in some marine algae (e.g. diatoms).  

Q27. Chloroplast dimorphism is a characteristic feature of

• Plants with the Calvin cycle
• C₄ plants
• All plants
• Only in algae

Solution

C₄ plants are different from C₃ and CAM plants in the sense that they possess two types of chloroplasts, found in two different cell types. The chloroplasts found in mesophyll cells possess grana, while those found in bundle sheath cells are agranal.

Q28. Which of the following statements is true with regard to the light reaction of photosynthesis?

• In PS II, the reaction centre chlorophyll a has an absorption peak at 700 nm and is called P 700.
• In PS I, the reaction centre chlorophyll a has an absorption maxima at 680 nm and is called P 680.
• The splitting of the water molecule is associated with PS I.
• Photosystems I and II are involved in the Z scheme.
• Lamellae of the grana have PS I and PS II, and stroma lamellae membranes have PS II only.

Solution

The Z scheme of photophosphorylation involves both PS I and PS II with the electrons moving from PS II to PS I and from water to PS II.

Q29. Which hormone(s) is/are responsible for an increase in the rate of photosynthesis?  

• Cytokinin  
• Auxin  
• Gibberellin  
• Both cytokinin and gibberellin  

Solution

Hormones affect the rate of photosynthesis. Cytokinin and gibberellin increase the rate of photosynthesis, whereas abscisic acid reduces the rate of photosynthesis.  

Q30. In PS-II, the first known electron acceptor is  

• Cytochrome  
• PQ  
• FRS  
• Pheophytin  

Solution

Pheophytin is the primary electron acceptor for PS II. It picks up the electron given out by P₆₈₀ and passes it to the next electron acceptor plastoquinone, which further passes it to the cytochrome complex.  

Q31. Which range of wavelength (in nm) is called photosynthetically active radiation (PAR)?

• 100-390
• 390-430
• 400-700
• 760-10,000

Solution

400-700 nm is the range of visible light in the electromagnetic spectrum. Plants respond to and use only visible light for photosynthesis. 680 nm and 700 nm light wavelengths are the most important for photosynthesis.

Q32. The carbon in CO₂ is radioactively labelled. The product in which this radioactive carbon can be found in C₃ plants is

• PEP
• RuBP
• PGAL
• PGA

Solution

The first stable compound formed from fixation of CO₂ in C₃ plants is 3-PGA. RuBP uses CO₂ to undergo carboxylation to form 2 molecules of 3-PGA with the reaction being catalysed by the enzyme RuBisCO.

Q33. Consider the following statements: (a) The portion of the spectrum between 500 nm and 800 nm is also referred to as photosynthetically active radiation (PAR).   (b) Magnesium, calcium and chloride ions play prominent roles in the photolysis of water.   (c) In cyclic photophosphorylation, oxygen is not released (as there is no photolysis of water) and NADPH is also not produced. Of these statements given above,

• (a) is true, but (b) and (c) are false.
• (a) and (b) are false, but (c) is true.
• (a) and (b) are true, but (c) is false.
• (a) and (c) are true, but (b) is false.

Solution

During cyclic photophosphorylation, only a single molecule of ATP is synthesised and there is no photolysis of water, no release of O₂ and no synthesis of NADPH.

Q34. Chlorophyll in chloroplasts is located in

• Grana
• Pyrenoid
• Stroma
• Both grana and stroma

Solution

Grana are structures present in the chloroplast made of stacks of flattened discs called thylakoids. Thylakoids contain the photosystems within which photosynthetic pigments are present.

Q35. In coniferous plants, photosynthesis can take place at a temperature as low as

• 0°C
• −5°C
• −12°C
• −35°C

Solution

In coniferous plants, photosynthesis can even take place at −35°C.

Q36. In photorespiration, the cell organelles involved are  

• Chloroplast and mitochondrion  
• Chloroplast only  
• Chloroplast, mitochondrion and ribosome  
• Chloroplast, mitochondrion and peroxisome  

Solution

Chloroplast, mitochondrion and peroxisome are the three cell organelles which are involved in photorespiration. Their sequence of involvement is Chloroplast-peroxisome-mitochondrion.  

Q37. The reaction which is responsible for the primary fixation of CO₂ is catalysed by

• RuBP carboxylase
• PEP carboxylase
• RuBP carboxylase and PEP carboxylase
• PGA synthase

Solution

RuBP carboxylase is responsible for the fixation of CO₂ in C₃ plants, while PEP carboxylase fixes CO₂ in C₄ plants. RuBP carboxylase uses ribulose-1, 5- bisphosphate as the CO₂ acceptor for the carboxylation reaction, while PEP carboxylase uses phosphoenol pyruvate as a CO₂ acceptor for carboxylation.

Q38. The scientist awarded the Noble Prize in 1960 for tracing the path of carbon in plants is  

• Hatch  
• Huber  
• Calvin  
• Ruben  
• Blackman  

Solution

Melvin Calvin was awarded the Nobel Prize in 1960 for tracing the path of carbon in plants. This pathway is known as the Calvin cycle or C₃ cycle. He used the radioisotope of carbon ¹⁴C for tracing the path of carbon in algal photosynthesis.  

Q39. A process which makes an important difference between C₃ and C₄ plants is  

• Transpiration  
• Glycolysis  
• Photosynthesis  
• Photorespiration  

Solution

Photorespiration is a process which occurs due to the oxygenase activity of RuBisCO. When the concentration of O₂ is high as compared to CO₂, RuBisCO shows oxygenase activity. C₄ plants have a mechanism by which they can maintain the high concentration of CO₂ at the enzyme site; thus, photorespiration does not occur in C₄ plants.  

Q40. In Priestley’s experiment for photosynthesis, the mouse died in the setup which did not contain the mint plant because of

• Lack of oxygen
• Rise in temperature due to the burning candle
• Starvation
• All the given options are true

Take Another Test