Tag: botany

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Questions Related to botany

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 not included in photochemical phase?

  1. Light absorption

  2. Photosphorylation
  3. ${ H } _{ 2 }O$ splitting
  4. ${ CO } _{ 2 }$ reduction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • The photochemical step is dependent upon light, therefore it is also called as Light or Hill reaction. It involves the following reactions:
  • Photolysis of water: It is the phenomenon of breaking up of water into hydrogen and oxygen in the illuminated chloroplasts 
  • Production of assimilatory power: While passing over cytochrome complex, the electron loses sufficient energy for the creation of proton gradient and synthesis of ATP from ADP and inorganic phosphate. The process is called photophosphorylation
  • So, the correct option is 'CO2 reduction'.
Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Chlorophylls absorb visible light of wavelengths

  1. 400-500 nm only

  2. 300-400 nm only

  3. 600-800 nm only

  4. 400-500 nm and 600-700 nm.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Chlorophyll present in the plants can absorb the the wavelength of both blue and red regions of VIBGYOR which ranges from 400-500 nm and 600-700 nm respectively. It reflects the green light range of 500-600 nm hence the leaves appear green. 

Therefore the correct option is D

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

Hill used a dye for his famous hill reaction is

  1. Sulphur green

  2. Eosine

  3. Methylene blue

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

In the year 1937 and 1939, Robert hill studied the light dependent reaction and revealed that oxygen evolved during photosynthesis came from water. In his experiment, he used Dichlorophenolindophenol (DCPIP) as a redox dye to measure the rate of photosynthesis. The dye is blue in oxidized state with a maximal absorption at 600 nm whereas in reduced, DCPIP is colourless.

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.