Tag: botany

Questions Related to botany

Compensation point refers to the intensity of light at which 

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

  1. Rate of respiration = Rate of photosynthesis

  2. Rate of respiration > Rate of photosynthesis

  3. Rate of respiration < Rate of photosynthesis

  4. None of the above is correct

Show answer
Correct Option: A
Explanation:
Rate of photosynthesis in plants is generally higher than respiration but there comes a point of certain light intensity at which uptake of CO2 for photosynthesis is equal to CO2 released from respiration. This point is known as compensation point at which rate of photosynthesis is equal to rate of respiration.
So, the correct answer is 'Rate of respiration = Rate of photosynthesis'.

During photosynthesis

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

  1. Both ${ CO } _{ 2 }$ and water get oxidised

  2. Both ${ CO } _{ 2 }$ and water get reduced

  3. Water is reduced and ${ CO } _{ 2 }$ is oxidised

  4. Carbon dioxide get reduced and water get oxidised

Show answer
Correct Option: D
Explanation:
Photosynthesis transfers electrons from water to energy-poor CO$ _{2}$ molecules, forming energy-rich sugar molecules. This electron transfer is an example of an oxidation-reduction process:Water is oxidized in photosynthesis, which means it loses electrons, and carbon dioxide is reduced, meaning it gains electrons.
So, the correct option is 'Carbon dioxide get reduced and water get oxidised'.

Oxidative phosphorylation occurs in respiration and _______ occurs in photosynthesis.

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

  1. Oxidative phosphorylation

  2. Reductive phosphorylation

  3. Cyclic phosphorylation

  4. None of the above

Show answer
Correct Option: C
Explanation:

Phosphorylation refers to the process of formation of ATP. During respiration, the oxidation of NADH and FADH$ _{2}$ results in ATP formation, hence called oxidative phosphorylation. In photosynthesis, the photosystem II is involved in cyclic photophosphorylation. 

Hence, the correct answer is 'Cyclic Phosphorylation'

Suppose the interior of the thylakoids (lumen) of isolated chloroplasts were made acidic and then transferred in dark to a $pH = 8$ solution, what would be likely to happen? 

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

  1. The isolated chloroplast will make $ATP$

  2. The Calvin cycle will be activated

  3. Cyclic photophosphorylation will occur

  4. The isolated chloroplast will reduce $NADP^+$ to $NADPH + H^+ $

Show answer
Correct Option: A
Explanation:

The acidic lumen of the thylakoids will have a higher concentration of H$^{+}$ ions. When these are transferred to basic pH of 8, the H$^{+}$ will tend to move outside due to their concentration gradient, which is higher in the lumen and lower in the surrounding. The thylakoids bear ATP synthases that will use the proton motive force H$^{+}$ ions and will make the ATP. So, an isolated chloroplast is capable of synthesizing the ATP when the lumen is made acidic and the outer medium is made alkaline.

Hence, the correct answer is 'The isolated chloroplast will make ATP'

Light reaction or photochemical phase includes
I. light absorption
II. water splitting
III. oxygen release
IV. ATP and NADPH formation
Choose the correct option.

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

  1. I, II and IV

  2. I, II and III

  3. I, III and IV

  4. I, II, III and IV

Show answer
Correct Option: D
Explanation:

Light reaction or photochemical phase is called as photophosphorylation or Hill's reaction. It includes non-cyclic phosphorylation and cyclic phosphorylation. During this reaction, the light is absorbed by the chlorophyll and water splits into H$ _2$ and 1/2O$ _2$. Oxygen is released as the byproduct of the reaction along with formation of carbohydrate. Along with oxygen, ATP and NADPH are also formed.

Thus, the correct answer is 'I, II, III and IV.'

Which of the following events does not occur during the light reaction of photosynthesis?

(1) Photolysis of H$ _2$O
(2) Reduction of NADPH to NADP+
(3) Evolution of molecular oxygen
(4)Synthesis of assimilatory powers
(5)Conversion of CO$ _2$ to carbohydrates

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

  1. 1 and 2 only

  2. 2 and 5 only

  3. 2 ,3 and 5 only

  4. 1, 3 and 4 only

Show answer
Correct Option: B
Explanation:

The events occurring in the light reaction of the photosynthesis are:

  1. Absorption of sunlight by the chlorophyll and release of the electron to the carriers.
  2. Photolysis of water to provide the electron to the chlorophyll.
  3. The release of molecular oxygen due to the photolysis of water.
  4. Assimilatory powers are synthesized in the form of ATP and NADPH
  5. Reduction of NADP$^{+}$ occurs to form NADPH
The oxidation of NADPH and conversion of CO$ _{2}$ occurs during the dark reaction.

Hence, the correct answer is '2 and 5'.

Which of the following is not correct regarding light compensation point?

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

  1. This condition occurs usually in evening and morning

  2. Net production is equal to respiration consumption

  3. Gross production is more than Net production

  4. There is no gaseous exchange with environment by plant

Show answer
Correct Option: A
Explanation:
  • The (light) compensation point is the light intensity on the light curve where the rate of photosynthesis exactly matches the rate of cellular respiration.
  •  When the rate of photosynthesis equals the rate of respiration or photorespiration, the compensation point occurs.
  • The compensation point is reached during early mornings and late evenings.
  • Hence This condition occurs usually in evening and morning is not correct regarding light compensation point.
  • So, the correct answer is 'Option A'.

The site of light reaction is

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

  1. Granum

  2. Stroma

  3. Unit membrane

  4. Stroma lamellae

Show answer
Correct Option: A
Explanation:

The light-dependent reactions take place on the thylakoid membranes. The inside of the thylakoid membrane is called the lumen, and outside the thylakoid membrane is the stroma, where the light-independent reactions take place. Thylakoids are arranged in stacks called grana.
The chloroplast matrix is called the stroma and contains enzymes that catalyze the light-independent reactions of photosynthesis. But stroma is not the site for light reactions. 
Stromal lamellae connect two or more grana to each other. In this way, the lamellae act as a skeleton of the chloroplast, maintaining efficient distances between the grana, thereby maximizing the overall efficiency of the chloroplast. 
Each chloroplast is enclosed by (surrounded) a chloroplast envelope or unit membrane consisting of three layers. Overall the chloroplast envelope is semi-permeable. It is permeable to glucose molecules and certain ions including Fe$^{2+}$and Mg$^{2+}$, and oxygen and carbon dioxide.

So, the correct answer is option A.

In photosynthesis, the energy is transferred in 

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

  1. One energy step

  2. Small energy steps

  3. Large energy steps

  4. All of the above

Show answer
Correct Option: B
Explanation:

In photosynthesis, energy is transferred in small energy steps. Photosynthesis is the primary energy source for most of the biosphere. Even though photosynthetic light harvesting complexes display great variety in their design and function, many of them are membrane proteins that comprise of pigment antenna arrays, which absorb light and transfer the resulting electronic excitation to a reaction center, which in turn converts this excitation energy to a charge gradient across the membrane and help to synthesise ATP. This energy is utilized in dark phase for synthesizing glucose.

So, the correct answer is option B.

Translocation of sugar in angiosperms occur in the form of 

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

  1. Glucose

  2. Starch

  3. Lactose

  4. Sucrose

Show answer
Correct Option: D
Explanation:

Translocation is the process of movement of nutrients from leaves to other parts of plant. During the process of photosynthesis, carbohydrates (sugars) specifically sucrose is synthesized in the cytosol of cell and then translocated to other demanding parts of plant. Sucrose is complex, less reactive and energy efficient sugar so, angiosperms and other plants translocate sugar in the form of sucrose.