Tag: phases of photosynthesis

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Questions Related to phases of photosynthesis

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

In the light-dependent reactions

  1. carbon dioxide is fixed
  2. $CO _2$ accepts electrons

  3. ATP and NADPH are formed

  4. sugar phosphates are formed
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The ATP and NADPH from the light-dependent reactions are used to make sugars in the next stage of photosynthesis. The net result of this reaction is the production of 2 ATP and 9 NADPH and the photolysis of water. Light is absorbed and the energy is used to drive electrons from water to generate NADPH and to drive protons across a membrane. These protons return through ATP synthase to make ATP.

So, the correct option is ' ATP and NADPH are formed'.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

When a photosystem absorbs light

  1. sugar phosphates are produced

  2. electrons are transferred to ATP

  3. RuBP accepts electrons

  4. light-dependent reactions begin
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When photosystem II absorbs light, electrons in the reaction-centre chlorophyll are excited to a higher energy level and are trapped by the primary electron acceptors. Photoexcited electrons travel through the cytochrome b6f complex to photosystem I via an electron transport chain set in the thylakoid membrane. The light-dependent reactions use light energy to make two molecules needed for the next stage of photosynthesis: the energy storage molecule ATP and the reduced electron carrier NADPH. In plants, the light reactions take place in the thylakoid membranes of organelles called chloroplasts.

So, the correct option is, 'light-dependent reactions begin'.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Assume a thylakoid which is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will have the most direct effect on which of the following processes?

  1. Splitting of water

  2. Absorption of light energy by chlorophyll

  3. Flow of electrons from photosystem II to photosystem I

  4. Synthesis of ATP
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The thylakoid membranes have pigment system, electron transport proteins as well as the ATP synthases. When the transfer of electron down the transport proteins occurs, many H$^{+}$ are transported into the thylakoid lumen from the stroma. This high concentration of H$^{+}$ is then used by the ATP synthases to make ATP by transferring these H$^{+}$ out of the thylakoid lumen in the stroma. The punctured thylakoid will not have an intact thylakoid lumen, so the concentration of the H$^{+}$ ins will not be developed. As a result, ATP synthase will not function and so ATP will not be synthesized. 

Hence, the correct answer is 'Synthesis of ATP' 

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

The function of light in photosynthesis is

  1. photolysis of water

  2. assimilation of carbon dioxide

  3. production of organic food

  4. activation of enzymes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The process of photosynthesis occurs when green plants use the energy of light to convert carbon dioxide (CO2) and water (H2O) into carbohydrates. Light energy is absorbed by chlorophyll, a photosynthetic pigment of the plant. This process is to change the energy in sunlight into the energy in sugar, the end product of photosynthesis. Photosynthesis of water resulting H+ion for the reduction of NADPH2.
So, the correct option is, 'photolysis of water'.
Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Synthesis of an assimilatory power takes place in _____________ phase of photosynthesis.

  1. Light phase

  2. Dark phase

  3. Glycolysis

  4. All the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Photochemical phase is also called as the light phase or hill reaction and it occurs inside the thylakoids. This photochemical phase is mainly dependent on light and it functions to produce assimilatory power, which consists of reduced coenzyme NADPH and energy rich ATP molecules.
So the correct option is 'Light phase'
Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Which statement are not true for photosynthesis?

  1. $CO _2$ reduction occur in dark reaction
  2. $H _2O$ oxidation occur in light reaction

  3. Light reaction is an enzymatic phase of photosynthesis

  4. Dark reaction may occur in dark if light reaction products are available there
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The overall function of light-dependent reactions is to capture the energy from the light for the generation of ATP and NADPH molecules. The dark reactions of the C$ _{3}$ cycle utilize the energy from short-lived electronically excited carriers to convert CO$ _{2}$ & H$ _{2}$O into glucose catalyzed by the enzyme RuBisCo, and this constitutes carbon fixation and makes it the enzymatic phase.

So the correct  option is 'Light reaction is an enzymatic phase of photosynthesis'.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Which one is not included in photochemical phase?

  1. Light absorption

  2. Photosphorylation
  3. ${ H } _{ 2 }O$ splitting
  4. ${ CO } _{ 2 }$ reduction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • The photochemical step is dependent upon light, therefore it is also called as Light or Hill reaction. It involves the following reactions:
  • Photolysis of water: It is the phenomenon of breaking up of water into hydrogen and oxygen in the illuminated chloroplasts 
  • Production of assimilatory power: While passing over cytochrome complex, the electron loses sufficient energy for the creation of proton gradient and synthesis of ATP from ADP and inorganic phosphate. The process is called photophosphorylation
  • So, the correct option is 'CO2 reduction'.
Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Chlorophylls absorb visible light of wavelengths

  1. 400-500 nm only

  2. 300-400 nm only

  3. 600-800 nm only

  4. 400-500 nm and 600-700 nm.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Chlorophyll present in the plants can absorb the the wavelength of both blue and red regions of VIBGYOR which ranges from 400-500 nm and 600-700 nm respectively. It reflects the green light range of 500-600 nm hence the leaves appear green. 

Therefore the correct option is D

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Which one directly transfers electrons to $NADP^+$ during light reaction?

  1. PS I

  2. PS II

  3. Cytochromes

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

The light-dependent reactions start in photosystem II (PSII). When the pigment in the reaction centre of PS II i.e, P$ _{680}$ absorbs a photon, an electron in this molecule gets excited and transferred to a primary electron acceptor, Pheophytin and then go through molecules in a series of redox. The electron flow goes from PSII to cytochrome b6f complex than to PSI. In PSI, the electron is finally accepted by NADP. Thus photosystem I in light-dependent reaction directly transfers electrons to NADP.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

Light energy is converted into chemical energy through the formation of

  1. $NADPH _2$
  2. $ATP$
  3. $ATP$ and $NADPH _2$

  4. None of the above.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
In light-dependent reactions, the energy from sunlight is absorbed by chlorophyll and converted into chemical energy in the form of electron carrier molecules like ATP and NADPH.
Light energy is harnessed in Photosystems I and II, both of which are present in the thylakoid membranes of chloroplasts.
Just as the name implies, light-dependent reactions require sunlight. In the light-dependent reactions, energy from sunlight is absorbed by chlorophyll and converted into stored chemical energy, in the form of the electron carrier molecule NADPH (nicotinamide adenine dinucleotide phosphate) and the energy currency molecule ATP (adenosine triphosphate). The light-dependent reactions take place in the thylakoid membranes in the granum (stack of thylakoids), within the chloroplast.