Tag: botany

Questions Related to botany

In plants, light-dependent reactions proceed at the

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

  1. cytoplasm

  2. stroma

  3. plasma membrane

  4. thylakoid membrane

Show answer
Correct Option: D
Explanation:

In plants, the light reactions take place in the thylakoid membranes of organelles called chloroplasts. 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. 

So, the correct option is, 'thylakoid membrane'.

Choose the correct answer from the alternatives given.
The first step in photosynthesis is

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

  1. formation bf $NADPH _2$

  2. photolysis of water

  3. formation of ATP

  4. excitation of an electron of chlorophyll by a photon of light

Show answer
Correct Option: D
Explanation:

During the first stage of photosynthesis, called the light-dependent reaction, sunlight excites the electrons in the chlorophyll pigment. The organism uses this energy to create the energy carrier molecules ATP and NADPH, which are crucial for carbon fixing during the second stage. 

Thus, the correct answer is 'Excitation of an electron of chlorophyll by a photon of light.'

Photophosphorylation in chloroplast requires movement of:

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

  1. electrons across the membrane

  2. ions across the membrane

  3. protons across the membrane

  4. electrons and protons across the membrane

Show answer
Correct Option: D
Explanation:

Phosphorylation in the electron-transport chain in the mitochondrion.

Hence the correct answer is A.

Choose the correct answer from the alternatives given.
In a plant cell, which of the following pigments participates directly in the light reaction of photosynthesis

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

  1. chlorophyll a

  2. chlorophyll b

  3. carotenes

  4. xanthophylls

Show answer
Correct Option: A
Explanation:

Green pigments are located within the chloroplasts of plant. Chlorophyll a can participate directly in light reaction which convert solar energy to chemical energy.

Thus, the correct answer is 'Chlorophyll a.'

In the light-dependent reactions

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

  1. carbon dioxide is fixed

  2. $CO _2$ accepts electrons

  3. ATP and NADPH are formed

  4. sugar phosphates are formed

Show answer
Correct Option: C
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'.

When a photosystem absorbs light

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

  1. sugar phosphates are produced

  2. electrons are transferred to ATP

  3. RuBP accepts electrons

  4. light-dependent reactions begin

Show answer
Correct Option: D
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'.

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?

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

  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

Show answer
Correct Option: D
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' 

The function of light in photosynthesis is

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

  1. photolysis of water

  2. assimilation of carbon dioxide

  3. production of organic food

  4. activation of enzymes

Show answer
Correct Option: A
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'.

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

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

  1. Light phase

  2. Dark phase

  3. Glycolysis

  4. All the above

Show answer
Correct Option: A
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'

Which statement are not true for photosynthesis?

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

  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

Show answer
Correct Option: C
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'.