Here below some basic MCQ’s about “Photosynthesis in higher plants” with answer which is explained in details. Let’s check one by one which is given below.
MCQ 1:
What is the primary pigment involved in photosynthesis in higher plants?
A) Carotenoids
B) Chlorophyll a
C) Xanthophyll
D) Chlorophyll b
Answer: B) Chlorophyll a
Explanation:
Chlorophyll a is the main pigment responsible for capturing light energy during photosynthesis. It absorbs light primarily in the blue and red wavelengths and plays a crucial role in the photosynthetic process.
MCQ 2:
Which of the following processes occurs during the light-dependent reactions of photosynthesis?
A) Conversion of carbon dioxide to glucose
B) Splitting of water molecules
C) Formation of sucrose
D) Calvin cycle
Answer: B) Splitting of water molecules
Explanation:
The light-dependent reactions occur in the thylakoid membranes of chloroplasts and involve the absorption of light energy, which leads to the photolysis (splitting) of water molecules to release oxygen, protons, and electrons.
MCQ 3:
In which part of the plant does photosynthesis primarily take place?
A) Roots
B) Stems
C) Leaves
D) Flowers
Answer: C) Leaves
Explanation:
Photosynthesis primarily occurs in the leaves, which contain chloroplasts rich in chlorophyll. The broad surface area of leaves allows for maximum light absorption.
MCQ 4:
What is the main purpose of the Calvin cycle in photosynthesis?
A) To produce ATP
B) To convert light energy into chemical energy
C) To synthesize glucose from carbon dioxide
D) To release oxygen
Answer: C) To synthesize glucose from carbon dioxide
Explanation:
The Calvin cycle, also known as the light-independent reactions, occurs in the stroma of chloroplasts and is responsible for fixing carbon dioxide and synthesizing glucose using ATP and NADPH produced in the light-dependent reactions.
MCQ 5:
Which of the following factors does NOT affect the rate of photosynthesis?
A) Light intensity
B) Temperature
C) Oxygen concentration
D) Carbon dioxide concentration
Answer: C) Oxygen concentration
Explanation:
While light intensity, temperature, and carbon dioxide concentration significantly affect the rate of photosynthesis, oxygen concentration does not directly impact the process; instead, it is a byproduct of photosynthesis.
MCQ 6:
What is the primary role of the stomata in plants during photosynthesis?
A) Absorb sunlight
B) Store glucose
C) Exchange gases
D) Transport water
Answer: C) Exchange gases
Explanation:
Stomata are small openings on the surface of leaves that allow for the exchange of gases, specifically the intake of carbon dioxide and the release of oxygen, which are crucial for the process of photosynthesis.
MCQ 7:
Which of the following is a byproduct of the light-dependent reactions of photosynthesis?
A) Glucose
B) NADPH
C) ATP
D) Oxygen
Answer: D) Oxygen
Explanation:
Oxygen is released as a byproduct during the photolysis of water in the light-dependent reactions. The other options (NADPH and ATP) are energy carriers used in the Calvin cycle.
MCQ 8:
What is the function of RuBisCO in the Calvin cycle?
A) Converts glucose to starch
B) Fixes carbon dioxide
C) Produces ATP
D) Splits water molecules
Answer: B) Fixes carbon dioxide
Explanation:
RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) is the enzyme that catalyzes the fixation of carbon dioxide in the Calvin cycle, initiating the synthesis of glucose.
MCQ 9:
In higher plants, where are chloroplasts primarily located?
A) In root cells
B) In leaf mesophyll cells
C) In stem cells
D) In flower cells
Answer: B) In leaf mesophyll cells
Explanation:
Chloroplasts are predominantly found in the mesophyll cells of leaves, where they facilitate the photosynthetic process.
MCQ 10:
What is the significance of chlorophyll b in photosynthesis?
A) It absorbs light energy at different wavelengths than chlorophyll a.
B) It is the primary pigment for light absorption.
C) It converts glucose to energy.
D) It helps in oxygen production.
Answer: A) It absorbs light energy at different wavelengths than chlorophyll a.
Explanation:
Chlorophyll b assists chlorophyll a by capturing light energy in different parts of the light spectrum, thereby broadening the range of light that can be used for photosynthesis.
MCQ 11:
Which of the following conditions would likely increase the rate of photosynthesis?
A) High levels of oxygen
B) Low carbon dioxide concentration
C) Optimal light intensity
D) High humidity
Answer: C) Optimal light intensity
Explanation:
Photosynthesis increases with light intensity up to a certain point. After reaching saturation, other factors (such as CO₂ and temperature) will then limit the rate.
MCQ 12:
During which part of the photosynthesis process is ATP produced?
A) Calvin cycle
B) Photolysis
C) Light-dependent reactions
D) Dark reactions
Answer: C) Light-dependent reactions
Explanation:
ATP is produced in the light-dependent reactions of photosynthesis through the process of photophosphorylation.
MCQ 13:
Which structure in the chloroplasts is responsible for capturing light energy?
A) Stroma
B) Thylakoid
C) Outer membrane
D) Inner membrane
Answer: B) Thylakoid
Explanation:
Thylakoids are the membrane-bound structures within chloroplasts where the light-dependent reactions take place, capturing and converting light energy.
MCQ 14:
What is the main role of NADPH in photosynthesis?
A) Energy storage
B) Electron transport
C) Carbon fixation
D) Synthesis of glucose
Answer: B) Electron transport
Explanation:
NADPH serves as an electron carrier, transferring electrons and protons during the Calvin cycle to help reduce carbon compounds, ultimately leading to glucose synthesis.
MCQ 15:
Which of the following statements about photosynthesis is true?
A) It occurs only in green plants.
B) It is a process that releases carbon dioxide.
C) It converts light energy into chemical energy.
D) It occurs in the roots of plants.
Answer: C) It converts light energy into chemical energy.
Explanation:
Photosynthesis is the process by which plants convert light energy into chemical energy stored in glucose, primarily occurring in leaves.
MCQ 16:
What effect does increasing temperature have on the rate of photosynthesis, up to a certain limit?
A) It always decreases the rate.
B) It has no effect.
C) It generally increases the rate.
D) It causes chlorophyll to degrade.
Answer: C) It generally increases the rate.
Explanation:
As temperature increases, the rate of photosynthesis generally increases due to enhanced enzyme activity, up to an optimal temperature. Beyond this, the rate may decrease due to enzyme denaturation.
MCQ 17:
What is the role of water in photosynthesis?
A) It provides carbon.
B) It is the source of electrons.
C) It absorbs light.
D) It acts as a nutrient.
Answer: B) It is the source of electrons.
Explanation:
Water molecules are split during the light-dependent reactions to provide electrons, which are crucial for the formation of ATP and NADPH.
MCQ 18:
In which phase of photosynthesis is carbon dioxide fixed?
A) Light-dependent reactions
B) Calvin cycle
C) Photolysis
D) Glycolysis
Answer: B) Calvin cycle
Explanation:
The Calvin cycle is where carbon dioxide is fixed into organic molecules, eventually leading to glucose synthesis.
MCQ 19:
What is photophosphorylation?
A) The production of glucose from carbon dioxide.
B) The synthesis of ATP using light energy.
C) The conversion of oxygen into glucose.
D) The splitting of water molecules.
Answer: B) The synthesis of ATP using light energy.
Explanation:
Photophosphorylation refers to the process of ATP synthesis driven by light energy during the light-dependent reactions of photosynthesis.
MCQ 20:
Which of the following statements is true regarding C4 plants?
A) They use the Calvin cycle for carbon fixation only.
B) They are more efficient in hot and dry environments.
C) They do not require sunlight for photosynthesis.
D) They primarily photosynthesize at night.
Answer: B) They are more efficient in hot and dry environments.
Explanation:
C4 plants have a specialized mechanism that allows them to fix carbon dioxide efficiently in high temperatures and low moisture, reducing photorespiration.
MCQ 21:
What is the role of the enzyme ATP synthase in photosynthesis?
A) Fixing carbon dioxide
B) Splitting water molecules
C) Synthesizing ATP
D) Converting glucose to starch
Answer: C) Synthesizing ATP
Explanation:
ATP synthase is an enzyme that synthesizes ATP from ADP and inorganic phosphate, using the proton gradient generated during the light-dependent reactions.
MCQ 22:
Which gas is primarily absorbed by plants during photosynthesis?
A) Oxygen
B) Nitrogen
C) Carbon dioxide
D) Hydrogen
Answer: C) Carbon dioxide
Explanation:
Plants absorb carbon dioxide from the atmosphere through stomata, which is essential for the photosynthesis process to produce glucose.
MCQ 23:
What is the primary product of the Calvin cycle?
A) Glucose
B) Oxygen
C) ATP
D) NADPH
Answer: A) Glucose
Explanation:
The primary output of the Calvin cycle is glucose, which is synthesized from carbon dioxide and the energy carriers ATP and NADPH produced in the light-dependent reactions.
MCQ 24:
Which of the following is a characteristic of light-dependent reactions?
A) They take place in the stroma.
B) They require light energy.
C) They produce glucose directly.
D) They occur in the absence of light.
Answer: B) They require light energy.
Explanation:
Light-dependent reactions occur in the thylakoid membranes of chloroplasts and require light energy to generate ATP and NADPH.
MCQ 25:
In C3 plants, photorespiration is a process that:
A) Enhances photosynthesis.
B) Reduces the efficiency of carbon fixation.
C) Occurs in the presence of high CO₂ levels.
D) Produces more glucose.
Answer: B) Reduces the efficiency of carbon fixation.
Explanation:
Photorespiration occurs when RuBisCO fixes oxygen instead of carbon dioxide, leading to reduced efficiency in carbon fixation in C3 plants.
MCQ 26:
Which of the following factors can limit the rate of photosynthesis?
A) Sufficient light and water
B) High carbon dioxide concentration
C) Extreme temperatures
D) All of the above
Answer: C) Extreme temperatures
Explanation:
While sufficient light and CO₂ can enhance photosynthesis, extreme temperatures can limit the process by denaturing enzymes involved in photosynthesis.
MCQ 27:
The primary light-absorbing pigments in photosynthesis are located in which part of the chloroplast?
A) Stroma
B) Thylakoid membranes
C) Inner membrane
D) Outer membrane
Answer: B) Thylakoid membranes
Explanation:
The thylakoid membranes contain chlorophyll and other pigments that capture light energy during the light-dependent reactions of photosynthesis.
MCQ 28:
What is the significance of the light-harvesting complexes in photosynthesis?
A) They store glucose.
B) They transport water.
C) They capture and transfer light energy to reaction centers.
D) They fix carbon dioxide.
Answer: C) They capture and transfer light energy to reaction centers.
Explanation:
Light-harvesting complexes contain various pigments that absorb light energy and funnel it to the reaction centers where photosynthesis begins.
MCQ 29:
In which part of the chloroplast does the Calvin cycle occur?
A) Thylakoid membranes
B) Outer membrane
C) Stroma
D) Granum
Answer: C) Stroma
Explanation:
The Calvin cycle occurs in the stroma of chloroplasts, where it uses ATP and NADPH produced in the light-dependent reactions to fix carbon dioxide.
MCQ 30:
Which of the following processes occurs in the thylakoid membrane?
A) ATP synthesis
B) Glucose synthesis
C) Carbon fixation
D) Oxygen release
Answer: A) ATP synthesis
Explanation:
ATP synthesis occurs in the thylakoid membrane during the light-dependent reactions through chemiosmosis facilitated by ATP synthase.
MCQ 31:
What role do carotenoids play in photosynthesis?
A) They directly capture light energy.
B) They provide structural support to chloroplasts.
C) They protect chlorophyll from photodamage.
D) They transport glucose.
Answer: C) They protect chlorophyll from photodamage.
Explanation:
Carotenoids serve as accessory pigments that help absorb excess light energy and protect chlorophyll from damage caused by excessive light.
MCQ 32:
In photosynthesis, the term “photolysis” refers to:
A) The breakdown of glucose.
B) The splitting of water molecules.
C) The fixation of carbon dioxide.
D) The synthesis of ATP.
Answer: B) The splitting of water molecules.
Explanation:
Photolysis is the process where light energy is used to split water molecules into oxygen, protons, and electrons during the light-dependent reactions.
MCQ 33:
What is the effect of increased carbon dioxide concentration on photosynthesis?
A) It decreases the rate of photosynthesis.
B) It has no effect.
C) It increases the rate of photosynthesis.
D) It leads to photorespiration.
Answer: C) It increases the rate of photosynthesis.
Explanation:
Higher concentrations of carbon dioxide generally increase the rate of photosynthesis until other factors become limiting.
MCQ 34:
What is the final electron acceptor in the light-dependent reactions of photosynthesis?
A) Carbon dioxide
B) Oxygen
C) NADP⁺
D) ATP
Answer: C) NADP⁺
Explanation:
NADP⁺ acts as the final electron acceptor in the light-dependent reactions, forming NADPH which is used in the Calvin cycle.
MCQ 35:
Which of the following statements is true about CAM plants?
A) They fix carbon dioxide during the day.
B) They open their stomata at night to minimize water loss.
C) They perform the Calvin cycle only at night.
D) They are adapted to cold environments.
Answer: B) They open their stomata at night to minimize water loss.
Explanation:
CAM (Crassulacean Acid Metabolism) plants open their stomata at night to absorb carbon dioxide and store it as malic acid, minimizing water loss during the day.
MCQ 36:
What is the primary role of the mesophyll cells in leaves?
A) To transport nutrients
B) To store water
C) To perform photosynthesis
D) To protect the plant from herbivores
Answer: C) To perform photosynthesis
Explanation:
Mesophyll cells are the main sites of photosynthesis in leaves, containing chloroplasts that capture light energy.
MCQ 37:
In which part of photosynthesis is glucose produced?
A) Light-dependent reactions
B) Light-independent reactions
C) Glycolysis
D) Krebs cycle
Answer: B) Light-independent reactions
Explanation:
Glucose is synthesized during the light-independent reactions (Calvin cycle) of photosynthesis using ATP and NADPH generated in the light-dependent reactions.
MCQ 38:
Which of the following light wavelengths is least effective in driving photosynthesis?
A) Red light
B) Blue light
C) Green light
D) Yellow light
Answer: C) Green light
Explanation:
Chlorophyll reflects green light, making it the least effective wavelength for photosynthesis compared to red and blue light, which are absorbed efficiently.
MCQ 39:
What is the primary source of energy for photosynthesis?
A) Heat energy
B) Chemical energy
C) Light energy
D) Electrical energy
Answer: C) Light energy
Explanation:
Photosynthesis relies on light energy from the sun to drive the conversion of carbon dioxide and water into glucose and oxygen.
MCQ 40:
In plants, which component is crucial for the synthesis of ATP during photosynthesis?
A) RuBisCO
B) Chlorophyll
C) Proton gradient
D) Glucose
Answer: C) Proton gradient
Explanation:
The proton gradient created across the thylakoid membrane during the light-dependent reactions drives ATP synthesis via chemiosmosis.
MCQ 41:
Which of the following is NOT a phase of the Calvin cycle?
A) Carbon fixation
B) Reduction
C) Regeneration of RuBP
D) Photophosphorylation
Answer: D) Photophosphorylation
Explanation:
Photophosphorylation refers to the generation of ATP using light energy during the light-dependent reactions, not a phase of the Calvin cycle.
MCQ 42:
What is the primary function of the light-dependent reactions of photosynthesis?
A) To fix carbon dioxide
B) To generate ATP and NADPH
C) To produce glucose
D) To store water
Answer: B) To generate ATP and NADPH
Explanation:
The primary function of the light-dependent reactions is to capture light energy and convert it into chemical energy in the form of ATP and NADPH for use in the Calvin cycle.
MCQ 43:
In which type of plants does the enzyme PEP carboxylase play a crucial role?
A) C3 plants
B) C4 plants
C) CAM plants
D) All of the above
Answer: B) C4 plants
Explanation:
PEP carboxylase is critical in C4 plants for fixing carbon dioxide into a four-carbon compound before it enters the Calvin cycle.
MCQ 44:
Which of the following is true regarding the energy conversion in photosynthesis?
A) Light energy is converted to chemical energy.
B) Chemical energy is converted to light energy.
C) Heat energy is converted to electrical energy.
D) None of the above.
Answer: A) Light energy is converted to chemical energy.
Explanation:
Photosynthesis converts light energy from the sun into chemical energy stored in glucose.
MCQ 45:
What is the main advantage of C4 photosynthesis over C3 photosynthesis?
A) Higher oxygen production
B) More efficient water use in hot environments
C) Faster glucose production
D) Ability to thrive in low light
Answer: B) More efficient water use in hot environments
Explanation:
C4 photosynthesis allows plants to minimize water loss during photosynthesis, making it more efficient in hot and dry conditions.
MCQ 46:
Which molecule is formed during the splitting of water in photosynthesis?
A) Glucose
B) Oxygen
C) Carbon dioxide
D) Ethanol
Answer: B) Oxygen
Explanation:
The photolysis of water during the light-dependent reactions produces oxygen as a byproduct.
MCQ 47:
Which of the following best describes the relationship between photosynthesis and cellular respiration?
A) They are identical processes.
B) Photosynthesis produces glucose, which is then used in respiration.
C) Respiration occurs in plants only.
D) Photosynthesis and respiration occur in the same organelles.
Answer: B) Photosynthesis produces glucose, which is then used in respiration.
Explanation:
Photosynthesis produces glucose and oxygen, which are used in cellular respiration to generate ATP, thus supporting cellular functions.
MCQ 48:
In photosynthesis, what is the initial acceptor of carbon dioxide?
A) RuBP
B) ATP
C) NADPH
D) G3P
Answer: A) RuBP
Explanation:
In the Calvin cycle, carbon dioxide is initially fixed by the enzyme RuBisCO onto ribulose bisphosphate (RuBP), forming a 6-carbon compound.
MCQ 49:
What is the effect of intense light on the rate of photosynthesis?
A) It always increases the rate.
B) It can lead to photoinhibition.
C) It has no effect.
D) It decreases the rate.
Answer: B) It can lead to photoinhibition.
Explanation:
While increased light can enhance photosynthesis to a point, excessive light intensity can lead to photoinhibition, damaging the photosynthetic machinery.
MCQ 50:
Which of the following processes do NOT occur in the chloroplast?
A) Light-dependent reactions
B) Calvin cycle
C) Krebs cycle
D) Both A and B
Answer: C) Krebs cycle
Explanation:
The Krebs cycle occurs in the mitochondria, not in the chloroplasts, while the light-dependent reactions and Calvin cycle occur in the chloroplasts.
MCQ 51:
What is the primary role of the thylakoid membrane in photosynthesis?
A) To store glucose
B) To synthesize ATP and NADPH
C) To absorb nutrients
D) To transport water
Answer: B) To synthesize ATP and NADPH
Explanation:
The thylakoid membranes are where the light-dependent reactions take place, leading to the synthesis of ATP and NADPH.
MCQ 52:
Which of the following plants typically exhibits Crassulacean Acid Metabolism (CAM)?
A) Wheat
B) Rice
C) Cactus
D) Soybean
Answer: C) Cactus
Explanation:
CAM plants, like cacti, open their stomata at night to minimize water loss and store carbon dioxide for use during the day.
MCQ 53:
The Calvin cycle requires which of the following inputs?
A) Carbon dioxide
B) ATP
C) NADPH
D) All of the above
Answer: D) All of the above
Explanation:
The Calvin cycle requires carbon dioxide, ATP, and NADPH to synthesize glucose from carbon dioxide.
MCQ 54:
What is the main product of the light-dependent reactions that is used in the Calvin cycle?
A) Glucose
B) Oxygen
C) ATP and NADPH
D) Carbon dioxide
Answer: C) ATP and NADPH
Explanation:
ATP and NADPH produced during the light-dependent reactions are essential for driving the reactions of the Calvin cycle.
MCQ 55:
In photosynthesis, which of the following events occurs first?
A) ATP synthesis
B) Water splitting
C) Carbon fixation
D) Oxygen release
Answer: B) Water splitting
Explanation:
The splitting of water molecules occurs early in the light-dependent reactions, providing electrons for the electron transport chain.
MCQ 56:
What do plants primarily use to transport the products of photosynthesis?
A) Xylem
B) Phloem
C) Stomata
D) Chloroplasts
Answer: B) Phloem
Explanation:
Phloem is responsible for transporting the products of photosynthesis (mainly sugars) from the leaves to other parts of the plant.
MCQ 57:
Which pigment primarily absorbs blue and red light?
A) Carotenoids
B) Chlorophyll a
C) Chlorophyll b
D) All of the above
Answer: B) Chlorophyll a
Explanation:
Chlorophyll a primarily absorbs blue and red light, making it the most effective pigment for photosynthesis.
MCQ 58:
Which of the following is a type of non-cyclic photophosphorylation?
A) Photosystem I only
B) Photosystem II only
C) Both Photosystem I and II
D) Neither
Answer: C) Both Photosystem I and II
Explanation:
Non-cyclic photophosphorylation involves both Photosystem I and Photosystem II, leading to the production of ATP, NADPH, and oxygen.
MCQ 59:
What is the role of magnesium in chlorophyll?
A) Energy storage
B) Electron donor
C) Structural component
D) Absorbs light
Answer: C) Structural component
Explanation:
Magnesium is a central atom in the chlorophyll molecule and is essential for maintaining the structure of chlorophyll and its ability to absorb light.
MCQ 60:
Which type of light is least absorbed by chlorophyll during photosynthesis?
A) Red light
B) Blue light
C) Green light
D) Violet light
Answer: C) Green light
Explanation:
Chlorophyll reflects green light, making it the least effective wavelength for photosynthesis.
MCQ 61:
Which of the following is the primary site for the light-dependent reactions in chloroplasts?
A) Stroma
B) Thylakoid membrane
C) Outer membrane
D) Inner membrane
Answer: B) Thylakoid membrane
Explanation:
The thylakoid membrane is where the light-dependent reactions occur, utilizing sunlight to generate ATP and NADPH.
MCQ 62:
What is produced as a waste product during photosynthesis?
A) Glucose
B) Oxygen
C) Carbon dioxide
D) Water
Answer: B) Oxygen
Explanation:
Oxygen is produced as a byproduct of the photolysis of water during the light-dependent reactions of photosynthesis.
MCQ 63:
What is the role of the RuBP in the Calvin cycle?
A) It captures light energy.
B) It fixes carbon dioxide.
C) It is regenerated to continue the cycle.
D) Both B and C.
Answer: D) Both B and C.
Explanation:
RuBP (ribulose bisphosphate) is essential in the Calvin cycle for fixing carbon dioxide and is regenerated to enable the cycle to continue.
MCQ 64:
Which of the following best describes photorespiration?
A) A process that enhances photosynthesis
B) A process that consumes oxygen and releases carbon dioxide
C) A process that occurs in the dark
D) A process that produces glucose
Answer: B) A process that consumes oxygen and releases carbon dioxide
Explanation:
Photorespiration occurs when RuBisCO fixes oxygen instead of carbon dioxide, leading to the consumption of oxygen and release of carbon dioxide, reducing photosynthetic efficiency.
MCQ 65:
In C4 plants, carbon dioxide is first fixed into which compound?
A) Ribulose bisphosphate (RuBP)
B) Phosphoenolpyruvate (PEP)
C) Glucose
D) Acetyl-CoA
Answer: B) Phosphoenolpyruvate (PEP)
Explanation:
In C4 plants, carbon dioxide is initially fixed into phosphoenolpyruvate (PEP) by the enzyme PEP carboxylase, forming a four-carbon compound.
MCQ 66:
Which of the following best describes the structure of chlorophyll?
A) A protein with a heme group
B) A carbohydrate with a lipid tail
C) A porphyrin ring with a magnesium ion
D) A nucleic acid with a sugar-phosphate backbone
Answer: C) A porphyrin ring with a magnesium ion
Explanation:
Chlorophyll consists of a porphyrin ring structure with a central magnesium ion, which is crucial for its light-absorbing properties.
MCQ 67:
What is the role of the stomata in photosynthesis?
A) To absorb sunlight
B) To fix carbon dioxide
C) To exchange gases
D) To transport water
Answer: C) To exchange gases
Explanation:
Stomata are small openings on leaves that allow for gas exchange, enabling carbon dioxide to enter and oxygen to exit during photosynthesis.
MCQ 68:
Which of the following types of plants is least likely to perform photosynthesis?
A) C3 plants
B) C4 plants
C) CAM plants
D) Fungi
Answer: D) Fungi
Explanation:
Fungi do not perform photosynthesis as they lack chlorophyll and are heterotrophic, obtaining nutrients from organic matter.
MCQ 69:
What is the function of the enzyme NADP⁺ reductase in photosynthesis?
A) Splits water molecules
B) Converts NADP⁺ to NADPH
C) Fixes carbon dioxide
D) Synthesizes ATP
Answer: B) Converts NADP⁺ to NADPH
Explanation:
NADP⁺ reductase catalyzes the reduction of NADP⁺ to NADPH during the light-dependent reactions, providing the reducing power needed for the Calvin cycle.
MCQ 70:
Which of the following wavelengths of light is most effective for driving photosynthesis?
A) Green light
B) Red light
C) Yellow light
D) Infrared light
Answer: B) Red light
Explanation:
Red light is most effectively absorbed by chlorophyll and is crucial for driving the photosynthetic process.
MCQ 71:
What is the main function of the photosystem II complex in photosynthesis?
A) To synthesize glucose
B) To capture light energy and split water
C) To regenerate RuBP
D) To produce ATP
Answer: B) To capture light energy and split water
Explanation:
Photosystem II captures light energy and facilitates the photolysis of water, producing oxygen and electrons for the electron transport chain.
MCQ 72:
Which of the following statements is true about the energy conversions in photosynthesis?
A) Light energy is converted to heat energy.
B) Chemical energy is converted to kinetic energy.
C) Light energy is converted to chemical energy.
D) Electrical energy is converted to light energy.
Answer: C) Light energy is converted to chemical energy.
Explanation:
Photosynthesis involves converting light energy from the sun into chemical energy stored in glucose.
MCQ 73:
What is the function of the thylakoid lumen?
A) Site of glucose synthesis
B) Storage of chlorophyll
C) Site for proton accumulation during light-dependent reactions
D) Site for carbon fixation
Answer: C) Site for proton accumulation during light-dependent reactions
Explanation:
The thylakoid lumen accumulates protons during the light-dependent reactions, creating a proton gradient used to generate ATP.
MCQ 74:
Which of the following processes contributes to the regulation of water loss in plants during photosynthesis?
A) Photolysis
B) Stomatal closure
C) Carbon fixation
D) ATP synthesis
Answer: B) Stomatal closure
Explanation:
Stomatal closure helps regulate water loss during hot or dry conditions, impacting the rate of photosynthesis.
MCQ 75:
What is the primary advantage of using ATP and NADPH in the Calvin cycle?
A) They provide structural support.
B) They serve as energy carriers.
C) They fix carbon dioxide.
D) They release oxygen.
Answer: B) They serve as energy carriers.
Explanation:
ATP and NADPH provide the energy and reducing power needed for the reactions in the Calvin cycle to synthesize glucose from carbon dioxide.
MCQ 76:
Which of the following statements about chloroplasts is correct?
A) They are found only in root cells.
B) They contain chlorophyll and perform photosynthesis.
C) They are responsible for cellular respiration.
D) They store starch exclusively.
Answer: B) They contain chlorophyll and perform photosynthesis.
Explanation:
Chloroplasts contain chlorophyll and are the sites of photosynthesis in plant cells.
MCQ 77:
What is the main function of the granum in chloroplasts?
A) Gas exchange
B) Light absorption
C) Storage of glucose
D) Photosynthetic reaction site
Answer: D) Photosynthetic reaction site
Explanation:
Grana are stacks of thylakoids in chloroplasts where the light-dependent reactions of photosynthesis occur.
MCQ 78:
Which of the following types of plants primarily utilize the Calvin cycle during the day?
A) CAM plants
B) C4 plants
C) C3 plants
D) All of the above
Answer: C) C3 plants
Explanation:
C3 plants primarily utilize the Calvin cycle during the day, fixing carbon dioxide directly when light is available.
MCQ 79:
What role does the enzyme RuBisCO play in photosynthesis?
A) It synthesizes ATP.
B) It fixes carbon dioxide.
C) It splits water molecules.
D) It reduces NADP⁺.
Answer: B) It fixes carbon dioxide.
Explanation:
RuBisCO catalyzes the fixation of carbon dioxide onto RuBP in the Calvin cycle, initiating the process of carbon fixation.
MCQ 80:
Which of the following is a feature of the light-independent reactions?
A) They require light directly.
B) They occur in the stroma.
C) They produce oxygen.
D) They take place in thylakoids.
Answer: B) They occur in the stroma.
Explanation:
Light-independent reactions, or the Calvin cycle, take place in the stroma of chloroplasts and do not require light directly.
MCQ 81:
Which process is responsible for the synthesis of ATP during the light-dependent reactions of photosynthesis?
A) Photolysis
B) Chemiosmosis
C) Carbon fixation
D) Glycolysis
Answer: B) Chemiosmosis
Explanation:
Chemiosmosis is the process by which ATP is synthesized in the thylakoid membrane using the proton gradient created during the light-dependent reactions.
MCQ 82:
What is the first stable product of carbon fixation in the Calvin cycle for C3 plants?
A) G3P
B) RuBP
C) 3-PGA
D) Glucose
Answer: C) 3-PGA
Explanation:
In C3 plants, the first stable product of carbon fixation in the Calvin cycle is 3-phosphoglycerate (3-PGA), which is formed when RuBP combines with carbon dioxide.
MCQ 83:
Which of the following processes occurs in the thylakoid membranes?
A) The Calvin cycle
B) Water splitting
C) Carbon dioxide fixation
D) Oxygen uptake
Answer: B) Water splitting
Explanation:
Water splitting occurs in the thylakoid membranes during the light-dependent reactions, providing electrons and releasing oxygen.
MCQ 84:
What is the role of the enzyme ATP synthase in chloroplasts?
A) To fix carbon dioxide
B) To transport electrons
C) To synthesize ATP
D) To split water molecules
Answer: C) To synthesize ATP
Explanation:
ATP synthase synthesizes ATP from ADP and inorganic phosphate using the energy from the proton gradient established during the light-dependent reactions.
MCQ 85:
Which of the following molecules serves as the primary electron donor in the light-dependent reactions?
A) Water
B) NADPH
C) ATP
D) Glucose
Answer: A) Water
Explanation:
Water is the primary electron donor in the light-dependent reactions, where it is split to provide electrons and release oxygen.
MCQ 86:
In the context of photosynthesis, what does the term “photophosphorylation” refer to?
A) The conversion of light energy into chemical energy
B) The addition of a phosphate group to ADP to form ATP
C) The splitting of water molecules
D) The synthesis of glucose
Answer: B) The addition of a phosphate group to ADP to form ATP
Explanation:
Photophosphorylation specifically refers to the process of adding a phosphate group to ADP to form ATP using light energy during the light-dependent reactions.
MCQ 87:
What is the main advantage of photosynthesis for plants?
A) Producing oxygen
B) Storing energy
C) Absorbing carbon dioxide
D) All of the above
Answer: D) All of the above
Explanation:
Photosynthesis provides several advantages, including the production of oxygen, storage of energy in the form of glucose, and the absorption of carbon dioxide.
MCQ 88:
In CAM plants, during which part of the day do they fix carbon dioxide?
A) During the day
B) At night
C) During both day and night
D) During dawn only
Answer: B) At night
Explanation:
CAM plants fix carbon dioxide at night when they open their stomata, allowing them to conserve water.
MCQ 89:
What is the primary purpose of the light-harvesting complex in photosynthesis?
A) To transport sugars
B) To capture light energy
C) To fix carbon dioxide
D) To synthesize glucose
Answer: B) To capture light energy
Explanation:
The light-harvesting complex captures light energy and transfers it to the reaction center in the thylakoid membrane for photosynthesis.
MCQ 90:
Which of the following statements about chlorophyll b is true?
A) It absorbs primarily red light.
B) It is essential for the light-dependent reactions.
C) It absorbs light in the blue and orange wavelengths.
D) It is the main pigment used for photosynthesis.
Answer: C) It absorbs light in the blue and orange wavelengths.
Explanation:
Chlorophyll b absorbs light in the blue and orange wavelengths, complementing chlorophyll a in capturing light for photosynthesis.
MCQ 91:
What type of energy is stored in glucose produced during photosynthesis?
A) Thermal energy
B) Kinetic energy
C) Chemical energy
D) Electrical energy
Answer: C) Chemical energy
Explanation:
The energy stored in glucose produced during photosynthesis is chemical energy, which can be used by the plant for growth and metabolism.
MCQ 92:
Which structure in chloroplasts is responsible for the formation of a proton gradient?
A) Thylakoid lumen
B) Stroma
C) Granum
D) Outer membrane
Answer: A) Thylakoid lumen
Explanation:
The thylakoid lumen is where protons accumulate during the light-dependent reactions, creating a proton gradient used to generate ATP.
MCQ 93:
What is the main purpose of the light-dependent reactions of photosynthesis?
A) To produce glucose
B) To convert light energy into chemical energy
C) To absorb carbon dioxide
D) To release oxygen
Answer: B) To convert light energy into chemical energy
Explanation:
The main purpose of the light-dependent reactions is to convert light energy into chemical energy in the form of ATP and NADPH.
MCQ 94:
In which part of the chloroplast do the light-independent reactions take place?
A) Thylakoid membrane
B) Granum
C) Stroma
D) Outer membrane
Answer: C) Stroma
Explanation:
The light-independent reactions, also known as the Calvin cycle, occur in the stroma of chloroplasts.
MCQ 95:
What is the primary role of the enzyme PEP carboxylase in photosynthesis?
A) To fix oxygen
B) To transport glucose
C) To fix carbon dioxide in C4 plants
D) To synthesize ATP
Answer: C) To fix carbon dioxide in C4 plants
Explanation:
PEP carboxylase is crucial for fixing carbon dioxide in C4 plants, allowing them to efficiently utilize CO2 even in low concentrations.
MCQ 96:
What is the effect of increased temperature on photosynthesis in most plants?
A) It always increases the rate of photosynthesis.
B) It has no effect.
C) It can lead to denaturation of enzymes and decrease photosynthesis.
D) It increases the rate of respiration only.
Answer: C) It can lead to denaturation of enzymes and decrease photosynthesis.
Explanation:
Increased temperatures can enhance photosynthesis to a point, but excessive heat can denature enzymes, reducing the rate of photosynthesis.
MCQ 97:
Which of the following is NOT a product of the light-dependent reactions?
A) ATP
B) NADPH
C) Oxygen
D) Glucose
Answer: D) Glucose
Explanation:
Glucose is produced during the light-independent reactions (Calvin cycle), not during the light-dependent reactions.
MCQ 98:
What molecule serves as the primary electron carrier in the light-dependent reactions?
A) NADH
B) ATP
C) NADPH
D) FADH₂
Answer: C) NADPH
Explanation:
NADPH serves as the primary electron carrier, transporting electrons to the Calvin cycle for the synthesis of glucose.
MCQ 99:
Which pigment is responsible for the yellow and orange colors in plants?
A) Chlorophyll
B) Carotenoids
C) Anthocyanins
D) Xanthophylls
Answer: B) Carotenoids
Explanation:
Carotenoids are responsible for the yellow and orange colors in plants and also assist in photosynthesis by capturing light energy.
MCQ 100:
What is the role of light energy in photosynthesis?
A) To break down glucose
B) To convert chemical energy into kinetic energy
C) To excite electrons and initiate the light-dependent reactions
D) To synthesize starch
Answer: C) To excite electrons and initiate the light-dependent reactions
Explanation:
Light energy excites electrons in chlorophyll, initiating the light-dependent reactions of photosynthesis and leading to the synthesis of ATP and NADPH
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