Tag: modern concept of photosynthesis

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

In photosynthesis, splitting of water occurs during

  1. Cyclic photophosphorylation

  2. Non-cyclic photophosphorylation

  3. Oxidative photophosphorylation

  4. Calvin cycle
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The other pathway, non-cyclic photophosphorylation, is a two-stage process involving two different chlorophyll photosystems. Being a light reaction, non-cyclic photophosphorylation occurs in the thylakoid membrane. First, a water molecule is broken down into 2H+ + 1/2 O2 + 2e− by a process called photolysis (or light-splitting). The two electrons from the water molecule are kept in photosystem II, while the 2H+and 1/2O2 are left out for further use. Then a photon is absorbed by chlorophyll pigments surrounding the reaction core centre of the photosystem. The light excites the electrons of each pigment, causing a chain reaction that eventually transfers energy to the core of photosystem II, exciting the two electrons that are transferred to the primary electron acceptor, phaeophytin. 

So, the correct option is 'Option B'.
Multiple choice botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

Photolysis of a water molecule yields

  1. 2 electrons and 4 protons

  2. 4 electrons and 4 protons

  3. 4 electrons and 2 protons

  4. 2 electrons and 2 protons
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Photolysis is part of the light-dependent reactions of photosynthesis. The general reaction of photosynthetic photolysis can be given as 

H2AH2A + 2 photons (light) → 2 e−e− + 2 H+H+ + A

So, the correct option is 'Option D'.

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

Minerals involved in photolysis are

  1. Mg and CI

  2. K and Mn

  3. Mo and Mn

  4. Mn and Cl
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A) Mg is responsible for the activation of many enzymes, but is not involved in photolysis. Cl ions help in the photolysis of water.

B) K is involved in maintaining the anion-cation balance and activates several enzymes connected with phosphorylation and synthesis of chlorophyll. Mn helps in splitting water to liberate oxygen .
C) Mo is a component of several enzymes like nitrogenase and nitrate reductase.
D) Mn and Cl are involved in photolysis.
So the correct answer is 'Mn and Cl'.

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

Extrusion of electron from reaction centre of PS II leaves a hole which is filled by electron released from

  1. $H _2O$
  2. $CO _2$

  3. Chlorophyll

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

Non-cyclic phosphorylation involves both Photosystem I and Photosystem II. These two photosystems work in series, first PS II and then PS I. The two photosystems are connected through an electron transport chain. $NADPH$ is synthesized by this kind of electron flow. Electrons are transferred from the PS II and then passed on to the pigments of PS I. Then, electrons get excited and transferred to another acceptor. These electrons are then moved downhill again to a molecule of $NADP^{+}$. The addition of these electrons results in the formation of $NADPH$. Extrusion of the electron from reaction centre of PS II leaves a hole which is filled by electron released from $H _{2}O$. This is achieved by electrons available due to the splitting of water. The water splitting complex is associated with PS II, which itself is physically located on the inner side of the membrane of the thylakoid. Water is split into $H^{+}$, $O$ and electrons. The protons and oxygen formed by splitting of water is released within the lumen of the thylakoids. The oxygen produced is released as one of the net products of photosynthesis.

$2H _{2}O$ $\longrightarrow$ $4H^{+}$ + $O _{2}$ + $4e^{-}$

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

Isotope of oxygen used in studying photolysis is

  1. $^{16}O$
  2. $^{15}O$
  3. $^{17}O$
  4. $^{18}O$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A) $ _{ \quad  }^{ 16 }{ O }$ is not used to study photolysis.
B) $ _{ \quad  }^{ 15 }{ O }$ is not used to study photolysis.

C) $ _{ \quad  }^{ 17 }{ O }$ is not used to study photolysis.
D) $ _{ \quad  }^{ 18 }{ O }$ is the isotope that is abundantly present and is used in the study of photolysis.
So the correct answer is '$ _{ \quad  }^{ 18 }{ O }$'.

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

Mineral involved in photolysis of water are
(a) Mn
(b) Ca
(c) Mg
(d) Cl

  1. a, b

  2. a, b, d

  3. c, d

  4. a, b, c
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A) Mn and Ca are involved in the photolysis of water.
B) Mn, Cl and Ca are involved in the photolysis of water.

C) Mg is not involved in the photolysis of water while Cl is involved.
D) Mn and Ca are involved in the photolysis of water. but Mg is not involved.
So the correct answer is 'a, b, d'.

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

Mn, Ca and Cl 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

A) Absorption of light is carried out by photosynthetic pigments.

B) Carbon dioxide assimilation is done by enzymes in the mesophyll cells.
C)| Mn, Ca and Cl are present in the light-harvesting complex (LHC) of PS II and help in the splitting of water
D) PS I and PS II are involved in ATP synthesis
So, the correct answer is 'Photolysis of water'

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

The essential element required for water splitting in photosynthesis leading  to release of oxygen is

  1. Mo

  2. Mn

  3. Mg

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

During ATP synthesis in the chloroplast, the proton gradient is formed. There are several processes that take place during activation of electrons and their transport which lead to the development of a proton gradient. Photolysis of water is the first process of this activation. The splitting of the water molecule takes place on the inner side of the thylakoid membrane and so the hydrogen ions (protons) that are produced, they accumulate within the lumen of the thylakoids. Oxygen-evolving complex called Z-enzyme is attached to the inner surface of the thylakoid membrane. The enzyme has four Mn ions. Light energized  Mn and removes electrons from $OH^{-}$ component of water forming oxygen. So, the essential element required for water splitting in photosynthesis leading to release of oxygen is Mn.

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

State whether the following statements are true or false
The ultimate electron donor in photosynthesis is water

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In oxygenic photosynthesis, the first electron donor is water, creating oxygen as a waste product. In anoxygenic photosynthesis, various electron donors are used. Cytochrome b6f and ATP synthase work together to create ATP. This process is called photophosphorylation.

Thus, the correct answer is 'True.'

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

Which statements is correct for given reaction for photosynthesis:-
${ 2H } _{ 2 }A+C{ O } _{ 2 }\underrightarrow { light } 2A+{ C }H _{ 2 }O+{ H } _{ 2 }O$

  1. H donor from ${ H } _{ 2 }O$ if reducible compound is ${ H } _{ 2 }O$
  2. ${ O } _{ 2 }$ evolve from ${ H } _{ 2 }O$ if a reducible compound is${ H } _{ 2 }O$
  3. Glucose gain its oxygen from ${ H } _{ 2 }O$
  4. $(1)$ & $(3)$ both
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The oxygen evolution is part of the light-dependent reactions of photosynthesis in cyanobacteria and the chloroplasts of green algae and plants. It utilizes the energy of light to split a water molecule into its protons and electrons for photosynthesis. Free oxygen, generated as a by-product of this reaction, is released into the atmosphere.

So, the correct option is 'O$ _{2}$ evolve from H$ _{2}$O if a reducible compound is H$ _{2}$O'