Tag: modern concept of photosynthesis

Questions Related to modern concept of photosynthesis

Photolysis of water takes place in 

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. Calvin cycle

  2. Glycolysis

  3. Light phase

  4. Dark phase

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Correct Option: C
Explanation:

Photolysis as the name suggests is the process, which happens in the presence of light. Photolysis is the process of splitting of water molecule to liberate oxygen in the presence of light. It takes place in the light phase of photosyntehsis and closely in proximation of PS-II.

PS II performs

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. Reduction of $CO _2$

  2. Photolysis of water

  3. Liberation of energy

  4. Formation of water

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Correct Option: B
Explanation:

Photolysis means to break down of the water molecule in the presence of light into H$^+$ nascent oxygen and an electron this process constitute in the PS II and the electron release is utilized by it as the compensation of electrons given by it to PS I during the Z scheme.

So, the correct option is 'Photolysis of water'

In photosynthesis, oxygen is liberated during

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. Hydrolysis of carbohydrates

  2. Breakdown of proteins

  3. Reduction of $CO _2$

  4. Hydrolysis of water

Show answer
Correct Option: D
Explanation:

During this process, the electrons in water are removed and passed to the reaction center chlorophyll. The associated hydrogen ions are released from the water molecule, and after two water molecules are thus split, the oxygen atoms join to form molecular oxygen (O 2 ), a waste product of photosynthesis.


So, the correct option is 'Hydrolysis of water'.

Hill reaction shows

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. Electron excitation

  2. Removal of water

  3. Fixation of $CO _{2}$

  4. $O _{2}$ is obtained from water

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Correct Option: D
Explanation:

Robin Hill demonstrated Hill reaction in 1939. Hill's reaction proves that oxygen is evolved during the light requiring steps of photosynthesis. It is isolated in chloroplasts.

Evidence for the liberation of O$ _2$ from water during photosynthesis comes from

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. Release of $^{18}$O if water contains the same

  2. Isolated chloroplast supplied with reducing agent like potassium ferrocyanide evolves O$ _2$ even in absence of CO$ _2$

  3. Photosynthetic bacteria do not Iiberate O$ _2$ and they use H$ _2$S for obtaining reducing power

  4. All of the above

Show answer
Correct Option: D
Explanation:

A. Ruben and Kamen used the radioactive isotope of oxygen ($^1$$^8$O) in water and found that O$ _2$ liberated in the process was isotopically labelled. On the contrary, when $^1$$^8$O in CO$ _2$ was used, the evolved O$ _2$ did not show radioactivity.

B. Hill and Bendall isolated chloroplast from leaves of Stellaria media and experimented in the absence of CO$ _2$.
$ 2A + 2H _2O\rightarrow 2AH _2+O _2$
In the presence of Artificial Hill reagent Potassium ferricyanide and sunlight, this experiment is performed.
C.  Van Niel observed that during bacterial photosynthesis hydrogen sulphide was broken down to hydrogen and sulphur. The hydrogen reduces carbon dioxide to synthesize carbohydrate and sulphur is accumulated as a waste product.
Hence, the correct answer is 'All the above'.

A specific function of light in the process of photosynthesis is

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. Reduction of $CO _2$

  2. Activate other molecules

  3. Split water molecules

  4. None of the above.

Show answer
Correct Option: C
Explanation:

Photolysis of water means splitting of water in the presence of light to get $H^+$ nascent oxygen and electron that compensate the loss of an electron from PS II during Z scheme and oxygen is released a the by-product with $H^+$ that acts as a proton and collects in the stroma.

So the correct option is 'Split water molecules'.

In photosynthesis, photolysis of water is used in

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. Reduction of NADP$^+$

  2. Oxidation of NADP

  3. Oxidation of FAD

  4. None of the above

Show answer
Correct Option: D
Explanation:

Photolysis of water is mainly carried out to compensate the electrons that are transferred to photosystem I by photosystem II during the non-cyclic photophosphorylation that reduce NADP$^+$ into NADPH.

So the correct option is 'None of the above'.

Photolysis of water requires

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. Light

  2. Chlorophyll

  3. Both A and B

  4. Electron transport

Show answer
Correct Option: C
Explanation:

A) As the name suggests, photolysis of water requires light.

B) Photolysis is the breakdown of water into hydrogen and oxygen using the light during the photosynthesis process. Light energy is absorbed by chlorophyll and is used to regenerate adenosine tri-phosphate or ATP and split water. Photolysis of water results in the release of oxygen, as a by-product, and the release of hydrogen.
C) Both light and chlorophyll are required in the photolysis of water.
D) Electron transport is not required in the photolysis of water.
So the correct answer is 'Both A and B'.

Which of the following provides electrons for reduction reactions in photosynthesis?

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. NADPH

  2. Chlorophyll

  3. Cytochrome

  4. Water

Show answer
Correct Option: D
Explanation:

Photolysis of water: Occurs at grana i.e., lumen side of grana thylakoid membrane with the help of water splitting complex or OEC (oxygen evolving complex). This step is associated with PS- II of Z- scheme.

$2H _2O\rightarrow4{H}^++ O _2+4{e}^-$

It is believed that oxygen evolves as oxygen gas, electrons are accepted by PS II reaction centre through unknown substance and hydrogen ions temporarily stay in the thylakoid space.

Hence, the correct answer is 'Water'.

Four electrons produced during photolysis of water will enter

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. PS I

  2. PQ

  3. PS II

  4. PC

Show answer
Correct Option: C
Explanation:
    • The photolysis of water (H$ _2$O) in the light reactions of photosynthesis occurs in the water-splitting complex of photosystem II.
    • photosystem II  in thylakoid membranes of chloroplasts where light is used to split water molecules as represented by the following equation: 2H$ _2$O → 4H+ + 4e- + O$ _2$.
    • Oxygen (O$ _2$) is liberated to the atmosphere as a waste product in this process and the electrons (e-) are gained to replace those lost through photoexcitation from chlorophyll a in the reaction center of photosystem II which begins noncyclic photophosphorylation. Hence four electrons produced during photolysis of water will enter PS  II.
    • So, the correct answer is 'PS  II'.