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 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

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'.

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

In overall photosynthetic pathway, for one molecule of $O _2$ liberated eight light quanta are required two molecules of NADPH$2$ are formed. Beside this, certain amount of energy is also released along with electron transport. This energy is liberated as.

  1. $2$ ATP molecules
  2. $8$ ATP molecules
  3. $3$ ATP molecules
  4. $4$ ATP molecules
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the light-dependent reactions of photosynthesis, the electron transport chain generates a proton gradient that drives the synthesis of ATP. For the production of 2 NADPH, 2 ATP are typically produced via non-cyclic photophosphorylation.

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

$CO _{2} : NADPH _{2} : ATP$ ratio for $C _{4}$ plants is

  1. $1 : 2 : 3$
  2. $2 : 3 : 4$
  3. $1 : 2 : 5$
  4. $1 : 5 : 10$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In C$ _4$ pathway for production of one molecule of glucose we require 12 NADPH$ _2$, 30 ATP and 6CO$ _2$ are required.

CO$ _2$ : NADPH$ _2$ : ATP =  6 : 12 : 30

CO$ _2$ : NADPH$ _2$ : ATP =  1 : 2 : 5

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

Internal source of CO2 in CAM plants is

  1. Oxaloacetic acid

  2. Malic acid

  3. RUBP

  4. PEPA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In  CAM plant, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect CO$ _{2}$. This CO$ _{2}$ is fixed into oxaloacetate by PEP carboxylase, which is then converted to malate. The CO$ _{2}$ is stored as malate in vacuoles at night, and then in the daytime, it is transported to chloroplasts where it is converted back to CO$ _{2}$, which is then used during photosynthesis.  

So, the correct option is 'Oxalo acetic acid'.

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

In CAM plants, $ C{ O } _{ 2 } $ acceptor is

  1. RuBP

  2. PEP

  3. OAA

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

Crassulacean Acid Metabolism (CAM) is a specialised photosynthetic process which is characterized by the following criteria given by  Osmond (1978) and Cluge and Tuge (1978). These are:

  1. CO$ _2$ uptake takes place mainly at night
  2. stomata are open during the night and closed during the day when CO$ _2$ uptake is mostly negligible.
  3. Malate accumulates at night by carboxylation of PEP.
  4. Decarboxylation of malate during the day yields CO$ _2$ which is fixed up by RuBP carboxylase. 
During the night time when the stomata are open, the CO$ _2$ is absorbed and fixed by phosphoenol pyruvic acid (PEP, 3C) in presence of enzyme PEP carboxylase. As a result of this PEP gets converted into oxaloacetic acid (OAA, 4C).
So the correct option is 'PEP'

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

In CAM plants the site of  light reaction and glucose synthesis are 

  1. Mesophyll, Bundle seath

  2. Bundle sheath, Mesophyll

  3. Mesophyll, Mesophyll

  4. Bundle seath, Bundle seath
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Unlike C4 plants which segregate light reactions and carbon fixation between mesophyll and bundle sheath cells, CAM plants perform both processes within the mesophyll cells. The temporal separation (night vs day) allows both the light-dependent reactions and glucose synthesis (Calvin cycle) to occur inside the mesophyll cells.

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

Which of the following metabolic cycle is an adaptation against Glycolate metabolism?

  1. Crassulacean acid metabolism

  2. Co-operative photosynthesis

  3. Reductive pentose phosphate pathway

  4. Photochemical reaction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photorespiration involves the production of glycolate. C4 and CAM pathways are adaptations that concentrate CO2 around Rubisco to minimize photorespiration.

Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

In CAM plants, the acceptor of ${CO _2}$ is

  1. Pyruvic acid.

  2. Oxaloacetate.

  3. Phosphoenol pyruvate.

  4. Nucleic acid.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions.
  •  At low temperatures (frequently at night), plants using CAM open their stomata, CO2 molecules diffuse into the spongy mesophyll's intracellular spaces and then into the cytoplasm. Here, they can meet phosphoenolpyruvate (PEP), the CO2 acceptor.
  • Hence, In CAM plants, the acceptor of CO2 is Phosphoenolpyruvate. 
  •  So, the correct answer is 'Phosphoenol pyruvate'.
Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

The internal source of $C{ O } _{ 2 }$ in CAM plants is

  1. Oxalo-acetic acid

  2. Malic acid

  3. RUBP

  4. PEPA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. In a plant using full CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide (CO$ _2$). So the correct option is 'Oxalo-acetic acid'.
Multiple choice botany photosynthesis cam cycle cam plants photosynthetic cycle

In which of the following respects the photosynthetic adaptations of $C _4$ plants and CAM plants are similar?

  1. In both cases, stomata normally close during the day

  2. Both types of plants make their sugar without the Calvin cycle

  3. In both cases, an enzyme other than rubisco carries out the first step in carbon fixation
  4. Neither $C _4$ plants nor CAM plants have grana in their chloroplasts
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$C _4$ and CAM  plants are plants that use certain special compounds to gather carbon dioxide (CO 2 ) during photosynthesis. Exploitation of dry and arid habitats required adaptations in the form of $C _4$ and CAM photosynthesis, which independently evolved many times during periods of low atmospheric $CO _2$ levels carried out by carried out by a non-rubisco enzyme, PEP carboxylase, that has no tendency to bind $O _2$.

So, the correct option is, 'In both cases, an enzyme other than rubisco carries out the first step in carbon fixation'.

Multiple choice dyes dyes and pigments chemistry in daily life applied chemistry chemistry

An auxochrome is a group of atoms which will impart a particular color when
attached to a_________.

  1. chromophore

  2. chlorophyll

  3. autochrome

  4. none of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Auxochrome is a Greek word arising from; Auxo meaning to increase and chrome meaning color. An auxochrome is a group of atoms which will impart a particular color when attached to a chromophore but when present alone, will fail to produce that color.
Chromophore is that part of the molecule which when exposed to visible
light will absorb and reflect a certain color.
Hence option A is correct.

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

In which of the following phosphorylation in absent?

  1. Glycolysis

  2. Kreb cycle
  3. $C _4$ cycle

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

$C _4$ cycle or the Hatch-Slack pathway is a photosynthetic process in some plants. It is the first step in extracting carbon from carbon dioxide to be able to use it in sugar and other biomolecules. $C _4$ plants do not undergo phosphorylation due to their special mechanism to increase the $CO _2$ level for enzyme binding.

So, the correct answer is '$C _4$ cycle'.

Multiple choice bio-chemistry biological oxidation oxidative phosphorylation living organisms and energy production glycolysis

Enzymes required for phosphorylation are located in .......... of chloroplast.

  1. Peristromium

  2. Plastidome

  3. Stroma

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

In chloroplast, the space enclosed by the inner membrane is called the stroma. It is colorless and homogeneous fluid. Phosphorylation is the process of addition of a phosphate group to ADP. The process of non-cyclic photophosphorylation takes place in the stroma lamellae with the help of enzymes present in it. Thus, the correct answer is option C.