Tag: modern concept of photosynthesis

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Questions Related to modern concept of photosynthesis

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

Photolysis is related to 

  1. Calvin cycle

  2. H.S.K. cycle

  3. Cyclic photophosphorylation

  4. Non cyclic flow of electrons
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Photolysis means splitting of water in presence of sunlight. During photosynthesis, light reaction occurs in chloroplasts. In light reaction the water is oxidised and the electrons from water are passed on through a series of electron acceptors and ultimately used to reduce NADP. Since electrons from water molecule are never returned or cycled back, this process is called as non cyclic flow of electrons. It involves PS-II and PS-I both.

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

Photochemical reaction taking place in the chloroplasts is directly involved in the 

  1. Fixation of carbon dioxide.

  2. Synthesis of glucose and starch.

  3. Formation of phosphoglyceric acid.

  4. Photolysis of water and phoshorylation of ADP to ATP.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Chloroplasts contain light trapping chlorophyll molecules. The chlorophyll molecules are an essential requirement for light reaction. The light energy is trapped by chlorophyll molecules for carrying out photolysis of water i.e., light dependent split of water molecules and photophosphorylation i.e., light dependent synthesis of adenosine triphosphate (ATP) by phosphorylation of adenosine diphosphate (ADP).

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

The product of hill reaction are

  1. ATP and $NADPH _{2}$ in chloroplast
  2. ATP and $NADPH _{2}$ in mitochondria

  3. Only oxygen
  4. $NADPH _{2}$, ATP and $O _{2}$ in chloroplast
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Experiments with isolated chloroplasts, in presence of oxidants like ferricyanides and benzoquinone (Hill reagents) were conducted by Hill in 1937 and 1939. By placing the isolated chloroplasts in sunlight, he noticed evolution of oxygen from water. Hill concluded that if there was suitable hydrogen acceptor in the medium it would have been reduced. Arnon 1951 and 1954 repeated the experiment of isolated chloroplast and concluded that, the hydrogen acceptor present in plants is NADP (Nicotinamide adenine dinucleotide phosphate). It is reduced to $NADPH _2$ and an ADP molecule is converted to ATP in light by utilizing inorganic phosphate. This phenomenon is called as photophosphorylation.

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

Hill reaction completes in the

  1. Light.

  2. Dark.

  3. Both A and B.

  4. None of the above.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hill reaction occurs in light or can be called as light reaction. Hill first of all demonstrated that isolated chloroplasts can release oxygen in presence of suitable inorganic electron acceptors. The Hill reaction is the light-driven transfer of electrons from water to Hill reagents (non-physiological oxidants) against a chemical potential gradient. 

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

Which element is essential for photolysis of water?

  1. Nitrogen

  2. Chlorine

  3. Carbon

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

Photolysis of water refers to the light dependent split of water, which occurs during the light phase of photosynthesis in the chloroplast. The minerals essential for the process of photolysis are calcium, chlorine and manganese.

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

Which of the following element is essential for photolysis of water?

  1. Fe

  2. Mg

  3. Mn

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

Photolysis of water occurs during non cyclic electron flow. During non cyclic electron flow, the ultimate source of electrons is water. The water molecule is split in a process, called as photolysis. The electrons are ultimately used in reduction of oxidised NADP to form reduced $NADPH _2$. The oxygen is released as a byproduct of photosynthesis. The mineral ions essential for photolysis are manganese, chlorine and calcium.

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

Oxygen released during photosynthesis comes from

  1. Water

  2. Carbon dioxide

  3. Chloroplast

  4. Chlorophyll
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Photolysis takes place in the light dependent reaction of the photosynthesis. The reaction can be represented as:
H$ _2$O + 2 photons --> 2 e$^-$ + 2H$^+$ + O. 
Here, the electrons released are accepted by the photosystem to fulfill the electron gap. The last electron acceptor is the oxygen and thus, the oxygen is liberated from the water molecule. The experiments conducted by Samuel Ruben and Martin Kamen by using radioactive isotopes helped to prove that the oxygen liberated during photosynthesis came from photolysis the water.
Thus, the correct answer is option A.
Multiple choice botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

In photosynthesis, there is an (a)

  1. Reduction of $H _{2}O$.
  2. Oxidation of $H _{2}O$.
  3. Oxidation of $CO _{2}$.
  4. Oxidation of $NO _{2}$.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The process of photosynthesis occurs in two stages light reaction and dark reaction. The light reaction involves oxidation of water (photolysis i.e., light dependent splitting of water), which releases oxygen as a by product. The photolysis of water also releases electrons, which are used to drive electron flow in the thylakoid membrane ultimately this electron flow results in the synthesis of ATP and $NADPH _2$. These products ATP and $NADPH _2$ are used up subsequently in the process of dark reaction.

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

Manganese, calcium and chloride ions present in PS-II play an important role in.

  1. Absorption of light
  2. $CO _2$ assimilation

  3. Photolysis of water

  4. ATP synthesis
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

As we know that the PS-II or photosystem II constantly supplies electrons during the light reaction.

This is possible because of the splitting of that is associated with PS-II. The water splits into H⁺, (O) and electrons. The ions Manganese, Calcium and chloride that are present plays an important role in this.

2H₂O---------------> 4H⁺ + O₂ + 4e⁻

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