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 metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Which one directly transfers electrons to $NADP^+$ during light reaction?

  1. PS I

  2. PS II

  3. Cytochromes

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

The light-dependent reactions start in photosystem II (PSII). When the pigment in the reaction centre of PS II i.e, P$ _{680}$ absorbs a photon, an electron in this molecule gets excited and transferred to a primary electron acceptor, Pheophytin and then go through molecules in a series of redox. The electron flow goes from PSII to cytochrome b6f complex than to PSI. In PSI, the electron is finally accepted by NADP. Thus photosystem I in light-dependent reaction directly transfers electrons to NADP.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Light energy is converted into chemical energy through the formation of

  1. $NADPH _2$
  2. $ATP$
  3. $ATP$ and $NADPH _2$

  4. None of the above.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
In light-dependent reactions, the energy from sunlight is absorbed by chlorophyll and converted into chemical energy in the form of electron carrier molecules like ATP and NADPH.
Light energy is harnessed in Photosystems I and II, both of which are present in the thylakoid membranes of chloroplasts.
Just as the name implies, light-dependent reactions require sunlight. In the light-dependent reactions, energy from sunlight is absorbed by chlorophyll and converted into stored chemical energy, in the form of the electron carrier molecule NADPH (nicotinamide adenine dinucleotide phosphate) and the energy currency molecule ATP (adenosine triphosphate). The light-dependent reactions take place in the thylakoid membranes in the granum (stack of thylakoids), within the chloroplast.
Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

In the light reactions of photosynthesis,

  1. PS I produces strong oxidant while PS II a strong reductant.
  2. PS I produces strong reductant $NADPH$ while PS II a strong oxidant.

  3. PS I emits electrons for PS II.

  4. PS I produces ATP which is not formed by PS II.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

PS I: This system produces a strong reductant which reduces ${NADP}^+$ to $NADPH$.

This system does not directly involve with the photooxidation of water and evolution of molecular oxygen.
PS II: This system is directly involved with the photooxidation of water and evolution of molecular oxygen.
It donates electrons to PS I when ${NADP}^+$ is reduced.
Hence, the correct answer is 'PS I produces strong reductant $NADPH$ while PS II a strong oxidant'.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Photosynthesis is considered as an oxidation reaction, because

  1. $CO _2$ is oxidised
  2. $H _2O$ is oxidised
  3. $O _2$ is released
  4. $(CH _2O)$ is oxidised.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A) Carbon dioxide is reduced, not oxidised. 
B) Water is oxidised to form protons and release oxygen. ${ H } _{ 2 }O\longrightarrow { O } _{ 2 }+{ 2H }^{ + }$

C) Oxygen is released after water undergoes oxidation.
D) ${ CH } _{ 2 }O$ does not undergo oxidation.
So the correct answer is '${ H } _{ 2 }O$ is oxidised'.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction
The absorption spectrum of chlorophyll

  1. approximates the action spectrum of photosynthesis

  2. shows that some colours of light are absorbed more than others

  3. explains why chlorophyll is a green pigment

  4. all of the above are correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Green plants are green because they contain a pigment called chlorophyll as in the absorption spectra, chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum. The green light is not absorbed but reflected, making the plant appear green. An absorption spectrum shows all the light typically absorbed by a leaf. An action spectrum, meanwhile, shows all the light that is actually used for photosynthesis. The similarity of the action spectrum of photosynthesis and the absorption spectrum of chlorophyll tells us that chlorophyll is the most important pigments in the process. The spectra are not identical, though, because carotenoid, which absorbs strongly in the blue, play a role as well.

So, the correct option is, 'all of the above are correct'.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Choose the correct answer from the alternatives given.
NADPH and ATP from the light-dependent reactions are used to

  1. cause rubisco to fix $CO _2$

  2. cause electrons to move along their pathways

  3. reform the photosystems

  4. convert PGA to PGAL
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Light-dependent reactions provide NADPH (electrons) and ATP (energy) to reduce PGA to PGAL. PGAL, the product of the Calvin Cycle can be converted into all sorts of other molecules. 2. Glucose phosphate is one result of PGAL metabolism; it is a common energy molecule
So, the correct answer is 'convert PGA to PGAL'

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Which one is directly involved in light reaction of photosynthesis

  1. Chlorophyll a

  2. Chlorophyll b

  3. Carotenoids

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

Photosynthesis takes place in the green leaves of plants and other green part of plants like stem etc. The most active photosynthetic tissue in higher plants is the mesophyll of leaves. Mesophyll cells have many chloroplasts, which contain the specialised light absorbing green pigments, the chlorophylls. When chlorophyll absorbs light, it gets excited and emits electrons. Chlorophyll a is the primary photosynthetic pigment. It shows bright or blue green colour in chromatogram. Chlorophyll a is directly involved in light reaction of photosynthesis. It is present in the reaction centres of Photosystem I and Photosystem II which absorbs light energy of longer wavelength. These centres can release electron upon absorption of energy.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

When chlorophyll absorbs light, it gets excited and emits (releases)

  1. Oxygen

  2. Water

  3. Electrons

  4. Energy rich compounds.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Photosynthesis takes place in the green leaves of plants and other green parts of plants like stem etc. When chlorophyll absorbs light, it gets excited and emits electrons. These chlorophylls are found in photosynthetic units called Photosystem I and Photosystem II. Each unit has a specific reaction center which contains pigment molecules. These molecules absorb light of different wavelengths and emit electrons. These electrons are picked up by an electron acceptor which passes them to an electron transport system of cytochromes.

Multiple choice

A reactant of photosynthesis is:

  1. Oxygen

  2. Your Agriculture Teacher

  3. Fish

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

Carbon dioxide is a primary reactant in photosynthesis, along with water and light energy. Oxygen is a byproduct.

Multiple choice

A product of photosynthesis is:

  1. Your Agriculture Teacher

  2. Carbon Dioxide

  3. Glucose

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

Glucose is the primary sugar produced during photosynthesis. Carbon dioxide is a reactant, and table salt is not involved.

Multiple choice

The process that plants use to make food is called

  1. digestion

  2. photosynthesis

  3. respiration

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

Plants perform photosynthesis to convert light energy into chemical energy, which serves as their food. Digestion is the breakdown of food in animals, while respiration is the process of releasing energy from food.

Multiple choice carbohydrates - definition and classification introduction to carbohydrates biomolecules chemistry

The light coming from the sun is stored as energy in plants by the process of photosynthesis. This happens by converting carbon dioxide and water into:

  1. green leaves

  2. carbohydrates

  3. fats

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

Photosynthesis is the process by which plants utilize the energy from the sunlight in order to convert carbon dioxide and water into carbohydrates.