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 botany ecosystem energy flow in food chain food chain and energy flow energy flow in ecosystem

Which fractions of the visible spectrum of solar radiations are primarily absorbed by carotenoids of higher plants?

  1. Blue and green

  2. Green and red

  3. Red and violet

  4. Violet and blue
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Carotenoids are organic pigments that are found in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms, including some bacteria and some fungi. Carotenoids absorb light in the blue-green and violet region and reflect the longer yellow, red, and orange wavelengths. These pigments also dispose excess energy out of the cell. Thus, option A is correct and other options are incorrect.

Multiple choice botany ecosystem energy flow in food chain food chain and energy flow energy flow in ecosystem

The most effective wavelength of visible light in photosynthesis is in the region

  1. Violet

  2. Blue

  3. Yellow

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

Plants and other oxygenic photosynthetic organisms harvest light energy from the sun to fix carbon dioxide into the food and fiber required to sustain the biosphere. Since plants cannot move, they must cope with regular day-night cycles, seasonal cycles and neighbouring vegetation, all of which influence the intensity, direction and spectral quality of light impinging on their leaves. 

To optimize light harvesting under low light conditions and to minimize photo damage when light is too bright, plants must continuously adjust the sensitivity of light harvesting by regulating the components of the photosynthetic apparatus or by altering the architecture of their leaves and stems. The ability to sense the ambient light level is conferred by protein light sensors that perceive different colors of visible light that are most effective in photosynthesis. For plants, red light is the most effective wavelength to drive photosynthesis therefore the most important of these photo sensors, the phytochromes, are most sensitive to this region of the light spectrum. Thus, option D is correct.

Multiple choice botany ecosystem energy flow in food chain food chain and energy flow energy flow in ecosystem

The percentage of sunlight utilized for photosynthesis by higher plants is 

  1. 100 %

  2. 110 %

  3. 50 %

  4. 1 - 2 %
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Higher plants utilize 1 to 2 % of sunlight for photosynthesis. Most crop plants store nearly 0.25% to 0.5% of the sunlight in the product. Examples are corn kernels, potato starch, etc. Photosynthesis increases linearly with light intensity at low intensity, but at higher intensity this is no longer the case.

Multiple choice botany ecosystem energy flow in food chain food chain and energy flow energy flow in ecosystem

 The wavelength of light most absorbed during photosynthesis is

  1. 400 nm

  2. 55 mm

  3. 660 nm

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

Photosynthesis occurs in small portion of spectrum, called as 'photosynthetically active radiation' or PAR (400-700 nm). Maximum absorption of light occurs in blue region (around 400 nm) followed by red light (around 700 nm). Maximum photosynthesis, however, occurs in red light. Least photosynthesis occurs in green light.

Multiple choice botany ecosystem energy flow in food chain food chain and energy flow energy flow in ecosystem

Which of the following wavelength of light is abosrbed maximum for photosynthesis?

  1. Red light

  2. Blue light

  3. Green light

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

Blue light of the spectrum is absorbed more for the process of photosynthesis. Plants have two types of chlorophylls - a and b. Chloropphyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light. A yellow-green chlorophyll pigment which occurs only in plants and green algae. It functions as a light harvesting pigment that pass on the light excitation to chlorophyll a. It absorbs well at wavelength of 450-500 nm and 600-650 nm.

Multiple choice botany ecosystem energy flow in food chain food chain and energy flow energy flow in ecosystem

The most effective wavelength of visible light in photosynthesis is in the region of 

  1. Violet

  2. Green

  3. Yellow

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

Chlorophyll absorbs red and violet-blue light, while transmitting and reflecting green light. Chlorophyll 'a' absorbs blue light with wavelengths of 430 nm and red light of 662 nm. 453 nm and 642 nm wavelengths are absorbed by chlorophyll 'b'.

Multiple choice botany ecosystem energy flow in food chain food chain and energy flow energy flow in ecosystem

Engelmann's experiment with Spirogyra demonstrated that 

  1. The full spectrum of sunlight is needed for photosynthesis

  2. Only red wavelengths are effective in causing photosynthesis

  3. Only Blue wavelengths are effective

  4. Both blue and red wavelengths are effective
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Theodor Wilhelm Engelmann was a German botanist, phsiologist, microbiologist, university professor and musician, whose 1882 experiment measured the effects of different colours of light on photosynthetic activity and showed that the conversion of light energy to chemical energy took place in the chloroplast. Both blue and red wavelength are effective because the amount of oxygen released was found to be maximum in blue and red absorption bands of the chlorophyll.

Multiple choice botany ecosystem energy flow in food chain food chain and energy flow energy flow in ecosystem

The percentage of light energy utilized for photosynthesis by higher plants is 

  1. 100%

  2. 50%

  3. 10%

  4. 1 to 2%
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

During photosynthesis 1 to 4% light is utilized. Photosynthesis is more in intense light and is also counted as a limiting factor. Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of water and carbon dioxide. Increasing the light intensity will boost the speed of photosynthesis.

Multiple choice botany ecosystem energy flow in food chain food chain and energy flow energy flow in ecosystem

The wavelength of light most absorbed during photosynthesis is 

  1. 440 nm

  2. 550 nm

  3. 660 nm

  4. 700 nm
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Wavelength of light absorbed during photosynthesis is 440 nm (violet to blue light). It is the main function of chlorophyll molecule, which is called as the photosynthetic pigment. the violet, blue light have shorter wave length and higher energy content. 

Multiple choice botany ecosystem energy flow in food chain food chain and energy flow energy flow in ecosystem

Leaves appear green because they

  1. Reflect green light

  2. Absorb green light

  3. Both reflect and absorb green light

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Chlorophyll which is the abundant plant pigment absorbs red and blue light making it photosynthetically efficient. The green wavelengths are reflected giving leaves the green colour. Thus, green is the photosynthetically least efficient wavelength. 
Multiple choice botany ecosystem : structure and function energy flow in food chain food chain and energy flow energy flow in ecosystem

The principles which bind all living systems together are _______________.

  1. Laws of thermodynamics

  2. Laws of heredity

  3. Mechanisms of photosynthesis

  4. Modes of germination
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The laws of thermodynamics govern the flow and transformation of energy in all systems, including living ones. Living systems must obey these laws to maintain order and perform life processes.

Multiple choice botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

Oxygen released in photosynthesis is due to 

  1. Photophosphorylation.

  2. Photolysis of water.

  3. Photorespiration.

  4. Photons.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Photosynthesis is a process which occurs in two stages. The first is the light dependent reaction where the captured energy of light is used to make the ATP and NADPH. The second stage is where the reactions independent of light use these products to capture and reduce carbon dioxide. Photolysis is part of the light dependent reaction of the photosynthesis process.  
Photosynthesis photolysis can be represented as H$ _2$A + 2 photons --> 2 e$^-$ + 2H$^+$ + A, where the chemical nature of the 'A' depends on the organism. The experiments conducted by Samuel Ruben and Martin Kamen by using radioactive isotopes helped to prove that the oxygen liberated during photosynthesis came from photolysis the water.
Thus, the correct answer is option B.
Multiple choice botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

During photosynthesis, oxygen is evolved from

  1. $H _{2}S$.
  2. $H _{2}O$.
  3. $CO _{2}$.
  4. $HCO _{3}$.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Photosynthesis is a redox reaction in which carbon dioxide is reduced to sugars and water is oxidised to release oxygen.

Photolysis refers to light dependent split of water molecule, which occurs during photosynthesis. The process of photolysis provides electrons for non cyclic electron flow during non cyclic photophosphorylation. Mineral ions required for the process of photolysis are manganese, calcium and chlorine.

Multiple choice botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

In the process of photosynthesis, the water molecule is broken down in

  1. Red drop.

  2. Photolysis.

  3. Phoshorylation.

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

Photosynthesis is chemically a redox reaction in which carbon dioxide is reduced and water is oxidised. During light reaction phase of photosynthesis, the electron that has been donated to the electron transport chain is replaced through photolysis (light dependent splitting) of water, a process that not only yields electrons but also is the source of almost all the oxygen in Earths atmosphere.