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

Which pigment, present in Phaeophyta, is responsible for its brown colour?

  1. Laminarin

  2. Phycocyanin

  3. Fucoxanthin

  4. Phycoerythrin

  5. Paramylon
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The colour of Phaeophyta reflects the presence of the brown pigment fucoxanthin. It is a type of carotenoid found naturally in edible brown seaweed, which are used widely in Asian cuisine and also available as a nutritional supplement in capsule form. It is explored for weight loss, and to decrease insulin and blood glucose levels, etc. It may have anti-tumour effects also.

Multiple choice

Which species of Pyrrhophyta can produce light and are responsible for the phosphorescence seen in ocean waters at night?

  1. Chlamydomonas

  2. Chlorella

  3. Gonyaulax

  4. Gambierdiscus

  5. Cryptomonas
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Gonyaulax, a species of Pyrrhophyta or dinoflagellates, can produce light and are responsible for much of the luminescence or phosphorescence seen in ocean waters at night when the water is disturbed. In the phosphorescent bays, high densities of a single species occur. Red tides are blooms, essentially monocultures of a given dinoflagellate species, which may or may not be luminous.

Multiple choice

Which of the following statements is NOT true?

  1. The immediate product of photosynthesis is glucose.

  2. Photosynthesis is maximum at 35°C.

  3. Dark reaction of photosynthesis utilises oxygen.

  4. Photolysis is carried out in thylakoids.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Dark reaction of photosynthesis utilises CO2. Dark reactions make use of organic energy molecules (ATP and NADPH). This reaction cycle is also called Calvin Benison Cycle, and it occurs in the stroma. ATP provides the energy, while NADPH provides the electrons required to fix the CO2 (carbon dioxide) into carbohydrates.

Multiple choice

During light reaction of photosynthesis, which of the following happens?

  1. Polysaccharides are generated in pyrenoid.

  2. Carbohydrates are synthesised from CO2 and water.

  3. Photons from sunlight are trapped to produce ATP and O2.

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

Photons from sunlight are trapped to produce ATP and O2. The light reaction of photosynthesis is also called Hill reaction. This is the first step of photosynthesis where light energy from the sun is absorbed by chlorophyll and hydrolyses H2O to produce O2 and H+ ions. This H+ further reduces NADP to NADPH which finally produces ATP from ADP and Pi. This total step is called photophosphorylation.

Multiple choice

Which of the following is an abnormal and hazardous process for biological systems?

  1. Chemosynthesis

  2. Photorespiration

  3. Photo-oxidation

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

Photo-oxidation is the degradation of a polymer surface in the presence of oxygen or ozone. The effect is facilitated by radiant energy, such as UV or artificial light. This process is the most significant factor in weathering of polymers. Proteins, carbohydrates, fats and nucleic acids are all polymers.

Multiple choice

Amongst chlorophyll-a (C55H72O5N4Mg) and chlorophyll-b (C55H70O6N4Mg), which one has –CHO group and which has –CH3 group at C-3 position, respectively?

  1. CHO in Chl-a and CH3 in Chl-b

  2. Chl-a has both CHO and CH3 groups

  3. CH3 in Chl-a and CHO in Chl-b

  4. No CHO in Chl-b and CH3 in Chl-a
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Both the chlorophylls have similar structures but they do differ in their compositions, which cause the adaptability in different scenarios. From the given formula, it can be estimated that Chl-a has two more H and an O less than Chl-b. Therefore, CHO is present in Chl-b.

Multiple choice

How does photosynthesis reduce global warming?

  1. Photosynthesis gives out O2.

  2. Photosynthetic plants absorb toxins from air.

  3. It decreases the concentration of CO2.

  4. Photosynthetic plants bring rain.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Photosynthesis decreases the concentration of CO2 which is being added to the atmosphere by the respiration of organisms and burning of organic fuels. The reduction in the concentration of CO2 reduces global warming.