Biology

Photosynthesis in Plants

1,492 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

During photosynthesis plants take in and release what?

  1. Carbon Dioxide and oxygen

  2. Carbon monoxide and oxygen

  3. Hydrogen and argon

  4. Chlorine and ammonia
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

During photosynthesis, plants take in carbon dioxide and water, and release oxygen as a byproduct. This is the reverse of cellular respiration in many ways.

Multiple choice

The primary site of photosynthesis

  1. Paint

  2. Flower

  3. Potassium Nitrate

  4. Leaves
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Leaves are the primary site of photosynthesis in most plants because they contain chlorophyll, the pigment that captures light energy.

Multiple choice biology movement in and out of the cell diffusion across cells diffusion and osmosis inter cellular movement

To initiate cell photosynthesis, salt solution should be 

  1. Isotonic

  2. Hypotonic

  3. Hypertonic

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

(A) An isotonic solution is a solution where there is no net movement of molecules due to equal concentration on both sides of the cell.
(B) Hypotonic solution is a solution where the movement of molecules is from outside to the inside of the cell.
(C) A hypertonic solution is a solution where the movement of molecules is from inside to outside of the cell.
A hypertonic solution is a solution which contains a high concentration of salt.
When the salt solution is the hypertonic solution then water will enter from outer soil inside the cell so that water will be available for photosynthesis.
So, the correct answer is 'Hypertonic'.
Multiple choice bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

In a plant cell, O.P. is equal to 

  1. T.P. - D.P.D.

  2. D.P.D - T.P.

  3. T.P. - D.P.

  4. D.P.D + T.P.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Here O.P. stands for osmotic pressure, D.P.D. stands for diffusion pressure deficit and T.P. stands for turgor pressure. 

Diffusion pressure deficit( DPD) is the reduction in the diffusion pressure of water in a solution over its pure state due to the presence of solutes and consequent development of turgor pressure. It is equal to the osmotic pressure of the system minus wall pressure:
$D.P.D=O.P.-W.P.(=T.P.)$

Thus the osmotic pressure is the sum of DPD and TP.
So the correct answer is 'D.P.D +T.P'.

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

In CAM plants, $CO _2$ required for photosynthesis enters the plant body during

  1. Daytime when the stomata are open.

  2. Night when the hydathodes are open.

  3. Daytime through the lenticels.

  4. Nights through the stomata which are kept open.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

CAM plants are those plants whose stomata open at night so that they can fix carbon-dioxide in the form of organic acids because these plants are adapted to grow in arid conditions. They accumulate carbon dioxide at night in vacuoles whereas in day time malic acid in transported to chloroplasts where it is again converted into carbon dioxide for photosynthesis. 

Thus, the correct answer is option D. 

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

The carbon dioxide acceptor in CAM plants is

  1. Malic acid

  2. Oxalo-acetic acid

  3. Pyruvic acid

  4. Phosphoenol pyruvic acid
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Certain plants which have Crassulacean Acid metabolism (CAM) are known as CAM plants. They have scotoactive stomata. These plants fix carbon dioxide during the night but form sugars only during the day when RuBisCO is active. sedum, kalanchoe, pineapple, opuntia are the examples of CAM plants. These plants also perform double carbon dioxide fixation. The carbon dioxide acceptor in CAM plants is Phosphoenol pyruvic acid (PEP) during the night and Ribulose bisphosphate is carbon dioxide acceptor during day time. The first stable product in case of CAM plants is Oxalo acetic acid (OAA).

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

In CAM plants, $CO _2$ required for photosynthesis enters the plant during

  1. Daytime when stomata are open

  2. Night when stomata are open

  3. Night when hydathodes are open

  4. Daytime through lenticels
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Certain plants which have Crassulacean Acid Metabolism (CAM) are known as CAM plants. They have scotoactive stomata. $CO _{2}$ required for photosynthesis enters the plant during the night when stomata are open. Then, this carbon dioxide is fixed during the night but form sugars only during the day when RuBisCO is active. Sedum, Kalanchoe, Pineapple, Opuntia are the examples of CAM plants. These plants also perform double carbon dioxide fixation. The carbon dioxide acceptor in CAM plants is Phosphoenol pyruvic acid (PEP) during the night and Ribulose bisphosphate is carbon dioxide acceptor during the daytime. The first stable product in case of CAM plants is Oxalo acetic acid (OAA).

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

In CAM plants, photophosphorylation occurs in

  1. Bundle sheath cell, during night

  2. Mesophyll cell, during day time

  3. Mesophyll cell, during night

  4. Bundle sheath cell, during day time
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In CAM plants, photophosphorylation occurs in bundle sheath cell during night. Hence, stomata is open during night in order to fix the carbon dioxide. During night, a four carbon acid is produced when stomata are open. RuBisCo enzyme fixes carbon during the day time during the light reactions. Examples of plants that show CAM photosynthesis are cactus and pineapple.

Thus, the correct answer is 'Bundle sheath cell, during night.'

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

C A M photosynthesis occurs in plants with 

  1. Thin green leaves with reticulate venation

  2. Thin green leaves with parallel venation

  3. Fleshy green leaves

  4. Thin coloured leaves
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

CAM (Crassulacean Acid Metabolism) photosynthesis is found in most desert plants, particularly the succulents (plants that store water in thick, fleshy leaves). CAM plants keep their stomata closed during the day to conserve water. At night, the stomata open to allow CO$ _{2}$ to enter. CO$ _{2}$ is incorporated into organic acids which are then stored within the mesophyll cells. During the day, CO$ _{2}$ is released from the organic acids to supply the Calvin Cycle. Thus, CAM photosynthesis occurs in fleshy green leaves and not in thin green leaves with reticulated venation or Thin green leaves with parallel or thin colored leaves. Thus, option C is correct and other options are incorrect.

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

In the mesophyll cells of CAM plants, $CO _{2}$ fixation during the day occurs through 

  1. RuBP oxygenase

  2. PEP carboxylase

  3. RuBP carboxylase

  4. Both RuBP carboxylase and PEP carboxylase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

CAM photosynthesis is a carbon fixation pathway present in some plants, such as desert plants. These plants fix carbon dioxide during night, storing it as the four carbon acid malate. The malate is then reduced to a three carbon compound oxaloacetate and the carbon dioxide. This carbon dioxide is released during the day, where it is concentrated around the enzyme RuBP carboxylase and increases the efficiency of photosynthesis. The carboxylating enzyme used during day is RuBP carboxylase and during the night its PEP carboxylase.

Answer is option C.

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

The source of $CO _{2}$ for photosynthesis in the CAM plants is

  1. 3-PGA.

  2. Malic acid.

  3. Oxaloacetic acid.

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

In CAM plants there is temporal separation between initial carbon dioxide fixation and Calvin cycle. In these plants, during night time the stomata are open and atmospheric carbon dioxide is fixed into organic acids like malic acid. The organic acids are stored in cell vacuoles during night time. During day time the stomata are closed and organic acids are decarboxylated to release carbon dioxide. The released carbon dioxide is fixed by the RuBisCO and usual reactions of the Calvin cycle.

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

Select the incorrect statement from the following.

  1. C4 pathway for CO$ _2$ fixation were discovered by Hatch and Slack.
  2. CO$ _2$ is essential for photosynthesis.

  3. Addition of sodium carbonate in water retards photosynthetic rate in Vallisneria.

  4. Phloem is the principal pathway for translocation of solutes.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Sodium bicarbonate acts as a source of carbon-dioxide to the plant which helps in the production of carbohydrates during photosynthesis acting as the carbon source for the same. Its addition in the water increases the photosynthetic rate in Vallisneria. Thus, CO2 is essential for photosynthesis. 
The C4 pathway is also known as the Hatch and Slack pathway in the name of their discoverers Hatch and Slack.
Phloem in plants acts the pathway for transport of plant solutes and metabolites whereas xylem acts as the pathway for transport of water.
The correct answer is 'addition of sodium carbonate in water retards photosynthesis rate in Vallisneria'.
Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

In CAM plants, organic acid content

  1. Decreases during night

  2. Increases during day

  3. Increases during night

  4. Both A and B
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In CAM plants, organic acid content increases during the night because the stomata remain open at the night and close during the daytime to conserve water. When stomata are open during the night, carbon dioxide is fixed by the action of phosphoenolpyruvate carboxylase to malic acid, this is called as acidification. During daytime, when the stomata are closed, malic acid is converted to pyruvic acid and carbon dioxide, this is called as deacidification. Hence acid concentration increases at night and decreases at daytime. So, the correct answer is 'Increases during night'.