Photosynthesis Quiz with Answers and Explanations

Photosynthesis Quiz

Test your photosynthesis understanding

20 Questions with answers and explanations

Ready?

What is the primary function of photosynthesis?

  1. To produce oxygen
  2. To convert light energy into chemical energy
  3. To absorb carbon dioxide
  4. To release water

Answer: b) To convert light energy into chemical energy

Explanation: While photosynthesis does produce oxygen and absorb carbon dioxide, its primary function is to convert light energy from the sun into chemical energy stored in glucose.

Which organelle in plant cells is responsible for photosynthesis?

  1. Mitochondria
  2. Nucleus
  3. Chloroplast
  4. Ribosome

Answer: c) Chloroplast

Explanation: Chloroplasts are specialized organelles in plant cells that contain chlorophyll and are the site of photosynthesis.

What pigment gives plants their green color and is essential for photosynthesis?

  1. Carotene
  2. Chlorophyll
  3. Anthocyanin
  4. Phycobilin

Answer: b) Chlorophyll

Explanation: Chlorophyll is the primary pigment responsible for absorbing light energy and giving plants their green color.

Which of the following is NOT a reactant in photosynthesis?

  1. Water
  2. Carbon dioxide
  3. Oxygen
  4. Light

Answer: c) Oxygen

Explanation: Oxygen is a product of photosynthesis, not a reactant. The reactants are water, carbon dioxide, and light energy.

What is the chemical formula for glucose, the main product of photosynthesis?

  1. C₆H₁₂O₆
  2. C₁₂H₂₂O₁₁
  3. CH₄
  4. CO₂

Answer: a) C₆H₁₂O₆

Explanation: Glucose, a simple sugar produced during photosynthesis, has the chemical formula C₆H₁₂O₆.

Which stage of photosynthesis requires light energy?

  1. Calvin cycle
  2. Light-dependent reactions
  3. Krebs cycle
  4. Glycolysis

Answer: b) Light-dependent reactions

Explanation: The light-dependent reactions, also known as the light reactions, directly require light energy to produce ATP and NADPH.

Where does the oxygen released during photosynthesis come from?

  1. Carbon dioxide
  2. Glucose
  3. Water
  4. Air

Answer: c) Water

Explanation: The oxygen released during photosynthesis comes from the splitting of water molecules during the light-dependent reactions.

What is the name of the process by which plants take in carbon dioxide?

  1. Transpiration
  2. Respiration
  3. Stomatal opening
  4. Carbon fixation

Answer: c) Stomatal opening

Explanation: Plants take in carbon dioxide through small pores called stomata. The process of these pores opening to allow gas exchange is called stomatal opening.

Which of the following is NOT directly involved in the Calvin cycle?

  1. RuBisCO
  2. CO₂
  3. ATP
  4. Chlorophyll

Answer: d) Chlorophyll

Explanation: Chlorophyll is involved in the light-dependent reactions but not directly in the Calvin cycle. RuBisCO, CO₂, and ATP are all involved in the Calvin cycle.

What is the primary purpose of the Calvin cycle in photosynthesis?

  1. To produce oxygen
  2. To absorb light energy
  3. To fix carbon into organic compounds
  4. To split water molecules

Answer: c) To fix carbon into organic compounds

Explanation: The Calvin cycle, also known as the light-independent reactions or dark reactions, is responsible for fixing carbon from CO₂ into organic compounds like glucose.

Which of the following is a product of the light-dependent reactions?

  1. Glucose
  2. NADPH
  3. Carbon dioxide
  4. RuBP

Answer: b) NADPH

Explanation: NADPH (along with ATP) is produced during the light-dependent reactions and is used in the Calvin cycle.

What is the role of RuBisCO in photosynthesis?

  1. To absorb light energy
  2. To catalyze the first step of carbon fixation
  3. To split water molecules
  4. To transport electrons

Answer: b) To catalyze the first step of carbon fixation

Explanation: RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) is the enzyme that catalyzes the first major step of carbon fixation in the Calvin cycle.

Which wavelengths of light are most effective for photosynthesis?

  1. Green
  2. Red and blue
  3. Ultraviolet
  4. Infrared

Answer: b) Red and blue

Explanation: Chlorophyll absorbs red and blue light most effectively, while reflecting green light (which is why plants appear green).

What is the term for the process where plants convert glucose into starch for storage?

  1. Glycolysis
  2. Fermentation
  3. Gluconeogenesis
  4. Polymerization

Answer: d) Polymerization

Explanation: Plants convert glucose into starch through a process of polymerization, linking glucose molecules together to form long chains.

Which of the following factors does NOT directly affect the rate of photosynthesis?

  1. Light intensity
  2. Carbon dioxide concentration
  3. Temperature
  4. Soil pH

Answer: d) Soil pH

Explanation: While soil pH can affect plant health, it doesn’t directly impact the rate of photosynthesis. Light intensity, CO₂ concentration, and temperature directly influence photosynthetic rate.

What is the first stable product of carbon fixation in C3 plants?

  1. Glucose
  2. Pyruvate
  3. 3-Phosphoglycerate (3-PGA)
  4. Phosphoenolpyruvate (PEP)

Answer: c) 3-Phosphoglycerate (3-PGA)

Explanation: In C3 plants, which include the majority of plant species, 3-Phosphoglycerate (3-PGA) is the first stable product formed when CO₂ is fixed by RuBisCO.

Which of the following is a difference between C3 and C4 photosynthesis?

  1. C4 plants don’t use the Calvin cycle
  2. C3 plants don’t produce glucose
  3. C4 plants have an additional carbon fixation step
  4. C3 plants don’t use RuBisCO

Answer: c) C4 plants have an additional carbon fixation step

Explanation: C4 plants have an additional carbon fixation step that concentrates CO2 before it enters the Calvin cycle, making them more efficient in certain conditions.

What is the function of ATP in photosynthesis?

  1. To absorb light energy
  2. To provide energy for carbon fixation
  3. To split water molecules
  4. To produce oxygen

Answer: b) To provide energy for carbon fixation

Explanation: ATP (Adenosine Triphosphate) provides the energy needed for various steps in the Calvin cycle, including carbon fixation.

Which of the following is a potential limiting factor for photosynthesis?

  1. Excess oxygen
  2. Too much chlorophyll
  3. Low carbon dioxide concentration
  4. Abundance of water

Answer: c) Low carbon dioxide concentration

Explanation: Low CO₂ concentration can limit the rate of photosynthesis as it’s a key reactant. Excess oxygen, abundant chlorophyll, or water typically don’t limit photosynthesis.

What is photorespiration?

  1. The process of plants releasing oxygen at night
  2. An alternative pathway that reduces photosynthetic efficiency
  3. The main way plants produce glucose
  4. The breakdown of chlorophyll in low light

Answer: b) An alternative pathway that reduces photosynthetic efficiency

Explanation: Photorespiration is a process that occurs when RuBisCO fixes oxygen instead of carbon dioxide, leading to a pathway that reduces the efficiency of photosynthesis.

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