Biology

Photosynthesis in Plants

1,508 Questions

Photosynthesis is the biological process by which plants convert light energy into chemical energy. This page contains practice questions covering essential topics like chlorophyll, light reactions, and the pathways specific to plants. This material is crucial for medical entrance exams and academic assessments.

Chlorophyll and pigmentsLight reactionsCalvin cycleCAM plantsElectron transportPhotosynthesis factors

Photosynthesis in Plants Questions

Multiple choice

The conditions under which RUBP carboxylase starts behaving as RUBP oxygenase are

  1. high temperature and high oxygen concentration

  2. low temperature and high oxygen concentration

  3. high temperature and low oxygen concentration

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

RuBisCO functions as an oxygenase under high temperature and high oxygen concentration conditions, leading to photorespiration. Under normal conditions, it acts primarily as a carboxylase fixing CO2. Low temperature or low oxygen favor carboxylation, while the combination of high temperature and high O2 shifts its activity toward oxygenation.

Multiple choice

The first stable product of Crassulacean acid metabolism is

  1. PGA

  2. Malic acid

  3. Citric acid

  4. Succinic acid
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In Crassulacean Acid Metabolism (CAM) plants, CO2 is fixed at night into oxaloacetate, which is then converted to malic acid and stored in vacuoles. Malic acid is the first stable product of this carbon fixation pathway. PGA is the first stable product in C3 plants, while citric and succinic acids are involved in the Krebs cycle, not CAM photosynthesis.

Multiple choice

C4 plants differ from C3 plants with reference to the

  1. CO2 acceptor

  2. end product

  3. type of pigments involved

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

C4 plants use phosphoenolpyruvate (PEP) as the primary CO2 acceptor in mesophyll cells, whereas C3 plants use ribulose-1,5-bisphosphate (RuBP) directly in the Calvin cycle. The end products of both pathways are ultimately carbohydrates, and both use similar photosynthetic pigments. The key difference is the initial CO2 fixation mechanism and the spatial separation of carbon fixation in C4 plants.

Multiple choice

DCMU is a herbicide, which can prevent

  1. non cyclic photophosphoylation of light reaction

  2. both non cyclic photophosphoylation and oxygen liberation

  3. inhibits dark reaction

  4. promotes photorespiration
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

DCMU (Diuron) inhibits electron transport from Photosystem II to plastoquinone, which blocks both non-cyclic photophosphorylation (linear electron flow) and oxygen evolution from water splitting. This herbicide specifically targets the photosynthetic electron transport chain. It does not directly inhibit dark reactions or promote photorespiration.

Multiple choice

Which of the following statements is/are incorrect?

a. Aquatic plants use the carbon dioxide dissolved in water for photosynthesis. b. Parts of variegated leaves do not have chlorophyll. c. The photosynthesis to make starch in leaves does not take place without sunlight and chlorophyll.

  1. Only a

  2. Only b

  3. Only c

  4. Both a and c

  5. Both a and b
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This statement is incorrect. The photosynthesis to make starch in leaves does not take place without carbon dioxide and water as well as sunlight and chlorophyll.

Multiple choice

Leaves of plants are green in colour because

  1. they can convert chloroplasts into chlorophyll

  2. they contain chloroplyll in chloroplasts

  3. they use the solar energy to prepare food from carbon dioxide and water

  4. they can convert solar energy into chemical energy

  5. they can absorb solar energy by chlorophyll
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is the correct answer. The plants are green because they have green chloroplasts (organelles that carry out photosynthesis). Chlorophyll is a pigment found in the thylakoid membranes of the chloroplasts in the leaves.

Multiple choice

During photosynthesis in plants the gas evolve is

  1. Carbon dioxide

  2. Nitrogen

  3. Oxygen

  4. Hydrogen
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

During photosynthesis, plants release oxygen as a byproduct of the light-dependent reactions. When chlorophyll absorbs light energy, water molecules are split (photolysis) in the thylakoid membranes, releasing oxygen as a waste product. This oxygen comes from water, not from carbon dioxide, which is used in the subsequent Calvin cycle to produce glucose.

Multiple choice

Where is chlorophyll found?

  1. in ozone layer

  2. in sunlight

  3. in snow

  4. in green plants
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Chlorophyll is the green pigment found in chloroplasts of plant cells, essential for photosynthesis. It absorbs light energy to convert carbon dioxide and water into glucose and oxygen. It is not found in the atmosphere, sunlight, or snow.

Multiple choice

Which one of the following conversions takes place in the process of photosynthesis?

  1. Heat energy to kinetic energy.

  2. Thermal energy to chemical energy.

  3. Thermal energy to electromagnetic energy.

  4. Electromagnetic energy to chemical energy.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

During photosynthesis, green plants absorb light energy, which is a form of electromagnetic radiation, and convert it into chemical energy stored in glucose bonds. Solar photons excite electrons, driving the biochemical reactions of the light and dark phases.