Tag: photosynthesis

Questions Related to photosynthesis

The evidence that during photosynthesis oxygen comes from water

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. Photosynthetic bacteria employ $H _2S$ and $CO _2$ to form carbohydrates, water and sulphur.

  2. Isolated illuminated chloroplasts release oxygen if provided with potassium ferrocyanide.

  3. Isotopic $^{18}O$ provided as $H _2\,\, ^{18}O$ appears as $^{18}O _2$ liberated in photosynthesis.

  4. All the above.

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Correct Option: D
Explanation:

A)In 1930, C.B.Van Niel proved that the sulphur bacteria use H$ _2$S and CO$ _2$ to synthesize carbohydrates.

B)When an isolated chloroplast is placed in potassium ferrocyanide it reacts with copper to make a complex and water is split to release oxygen.
C)In 1942 Ruben and Kamen using Chlorella algae prove that oxygen in photosynthesis come out during slitting of water by using an isotope of oxygen in water i.e.,$H _2^ {18}O$.
So, the correct option is 'All the above.'

The oxygen in photosynthesis is released from

botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

  1. $CO _2$

  2. $H _2O$

  3. Carbohydrate

  4. Chlorophyll

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Correct Option: B
Explanation:

The oxygen in photosynthesis is released from photolysis of water in which water get split into hydrogen ions oxygen in the presence of sunlight.

So, the correct option is 'H$ _2$O.'

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

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  1. Hydrolysis of carbohydrates

  2. Breakdown of proteins

  3. Reduction of $CO _2$

  4. Hydrolysis of water

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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

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  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

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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.

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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

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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

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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'.