Tag: botany

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Questions Related to botany

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

Photolysis of water involves

  1. Excitement of water

  2. Evolution of oxygen

  3. Breakdown of water by light
  4. Splitting of water into its ions, $H^+$ and $OH$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Photolysis, as the name suggests, is the breakdown of water in the presence of sunlight to form H⁺ and  O₂ and electron. This takes place during the light phase of photosynthesis in the PS-II. This creates the oxygen which is the net product of photolysis.

So, the correct option is 'Breakdown of water by light'

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

Source of protons within the chloroplasts is

  1. Water

  2. Excited chlorophyll

  3. Carbon dioxide

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

Chemiosmotic hypothesis explains how ATP is synthesized in the chloroplast. ATP synthesis is linked to the development of a proton gradient across the membrane of the thylakoid of chloroplast and proton accumulation is towards the inside of the membrane i.e., in the lumen. Source of protons within the chloroplasts is water. The splitting of water molecule takes place on the inner side of the membrane and so the protons (hydrogen ions) are produced, they accumulate within the lumen of the thylakoids. Thus, the correct answer is option A.

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

Which of the following helped in confirming that oxygen evolved in photosynthesis comes from water?

  1. $H _2 \,\,\, ^{18}O$
  2. $^{14}CO _2$
  3. $^{15}NO _3$
  4. $^{3}H _2O$.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the process of photosynthesis, water acts as a stable oxygen donor. To prove the theory radioisotopic technique was used. 

Instead of the normal oxygen, the radioisotope was taken. It was seen that after the oxidation of water, the oxygen formed was ¹⁸O₂.
So, the correct option is '¹⁸O'

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

The evidence that during photosynthesis oxygen comes from water

  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.
Reveal answer Fill a bubble to check yourself
D Correct answer
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.'

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

Photolysis of water takes place in 

  1. Calvin cycle

  2. Glycolysis

  3. Light phase

  4. Dark phase
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

PS II performs

  1. Reduction of $CO _2$

  2. Photolysis of water

  3. Liberation of energy

  4. Formation of water
Reveal answer Fill a bubble to check yourself
B Correct answer
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'

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

In photosynthesis, oxygen is liberated during

  1. Hydrolysis of carbohydrates

  2. Breakdown of proteins
  3. Reduction of $CO _2$

  4. Hydrolysis of water
Reveal answer Fill a bubble to check yourself
D Correct answer
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'.

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

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

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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'.