Series of enzymes involved in the given reactions of C 3 cycle (i) A 6 c + B 3 c → C 4 c + D 5 c (ii) C 4 c + E 3 c → F 7 c (iii) D 5 c → G 5 c (iv) G 5 c + ATP → H 5 c

Transketolases, Aldolases, Epimerases, Kinases

Aldolases, Transketolases, Isomerases, Kinases

Aldolases, Transketolases, Phosphatases, Kinases

Transketolases, Aldolases, Kinases, Epimerases

What is the difference between C 3 and C 4 pathway?

Feature C 3 Cycle C 4 Cycle Primary CO 2 acceptor The primary acceptor of CO 2 is a five-carbon compound, RuBP in Calvin Cycle. Three carbon phosphoenol pyruvic acid is the primary CO 2 acceptor in Hatch and Slack Cycle. Nature of chloroplast Chloroplast is monomorphic (one type) in plants that shows Calvin cycle. Chloroplasts are dimorphic in the plants that possess Hatch and Slack pathway in which mesophyll cells contain large chloroplast without grana and in bundle sheath chloroplast contains grana. These plants show kranz anatomy. First stable product The first stable product of C 3 cycle is phosphoglyceric acid, a three-carbon compound. In C 4 cycle, it is a four-carbon compound, oxaloacetic acid.

Two independent experiments related to photosynthesis were conducted, one with O 18 -labelled water (experiment P ) and the other C 14 -labelled CO 2 (experiment Q ). Which one of the following options lists the first labelled products in experiments P and Q , respectively?

P : O 2 Q : 3 - phosphoglycerate

P : 3 -phosphoglycerate Q : NADPH

P : 3 -phosphoglycerate Q : 3 -phosphoglycerate

In an experiment radioactive 14 CO 2 was supplied to green plants. In which of the substance the radioactive 14 CO 2 is supposed to enter and how? Give the various steps sequentially.

An experiment of radioactive 14 CO 2 : This experiment was carried out by Calvin, Benson, and their colleagues in California (USA). Example: They incorporated 14 C in carbon dioxide and fed in Chlorella and Scenedesmus . The radioactive 14 C is traced in the path of CO 2 fixation. This cycle occurs in all photosynthetic plants whether they have C3 or C4 pathways. It is divided into the following three phases: 1. Carbon Fixation or carboxylation: A 14 CO 2 molecule from the atmosphere combines with a five-carbon acceptor molecule called ribulose-1,5-bisphosphate (RuBP). The resulting radioactive six-carbon compound splits into two molecules of the three-carbon compound, radioactive 3-phosphoglyceric acid (3-PGA). This reaction is catalyzed by the enzyme RuBP carboxylase-oxygenase, also known as RuBisCO. 2. Reduction or Glycolytic reversal: In the second stage, the 3-PGA molecules created through the carbon fixation are converted into simple sugar — radioactive glyceraldehyde-3-phosphate (G3P). ATP and NADPH synthesized during light-dependent reactions of photosynthesis are used to fulfill the energy requirement of this stage. The Calvin cycle becomes how plants convert energy from sunlight into long-term storage molecules, such as sugar. The energy of the ATP and NADPH molecules gets stored in the sugar. This step is called reduction because electrons are released from the NADPH and donated to the 3-phosphoglyceric acid molecule to synthesize glyceraldehyde-3-phosphate. 3. Regeneration of RuBP: The remaining glyceraldehyde-3-phosphate molecules are used to make glucose, while others must be recycled to regenerate the five-carbon RuBP compound used to accept new carbon molecules. The regeneration process requires ATP. It is a complex process involving many steps. Since six-carbon molecules are used to synthesize glucose, this cycle must be repeated six times to make a glucose molecule.

What is RuBisCO? Explain its role in C 3 and C 4 photosynthesis.

RuBisCO stands for ribulose 1,5-bisphosphate carboxylase-oxygenase. It is the first enzyme that is involved in the dark reaction to produce glucose molecules. In C3 and C4 plants, the RuBisCO enzyme catalyzes the carboxylation process in the mesophyll cells of C3 plants and bundle sheath cells of C4 plants.

Give comparisons between the C 3 and C 4 pathways.

C 3 pathways C 4 pathways First stable compound The first product of carbon fixation is a three-carbon atom compound 3-phosphoglyceric acid. The first product of carbon fixation is a four-carbon atom compound oxaloacetic acid. C 3 pathways C 4 pathways ATP and NADPH It requires three ATP and two NADPH to reduce one molecule of carbon dioxide. It requires five ATP and three NADPH to reduce one molecule of carbon dioxide. C 3 pathways C 4 pathways Location of dark reaction It occurs only in the mesophyll cells of the leaves. It occurs in the mesophyll and bundle-sheath cells of the leaves.

Specify how a pentose phosphate is a CO 2 acceptor in the dark reaction of photosynthesis.

A pentose phosphate which is a CO 2 acceptor and takes part in the dark reaction or Calvin cycle is known as ribulose 1,5-bisphosphate (RuBP). RuBP accepts the CO 2 in the first step of the Calvin cycle and the presence of the RuBisCO enzyme. It undergoes carboxylation to produce two molecules of phosphoglyceric acid (PGA).

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The biosynthetic phase of photosynthesis takes place in the of the chloroplast. (grana, stroma, thylakoid)

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Important Questions on Photosynthesis in Higher Plants

HARD

Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

Series of enzymes involved in the given reactions of $C_{3}$ cycle

(i) $A [6 c] + B [3 c] \to C [4 c] + D [5 c]$

(ii) $C [4 c] + E [3 c] \to F [7 c]$

(iii) $D [5 c] \to G [5 c]$

(iv) $G [5 c] + ATP \to H [5 c]$

HARD

Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

What is the difference between C₃ and C₄ pathway?

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

In photosynthesis, the light-independent reactions take place in

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

According to Dr. Arnon, a substance present in chloroplast that acts as H-acceptor is _________.

MEDIUM

Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

Two independent experiments related to photosynthesis were conducted, one with

{}^{18}O

-labelled water (experiment

P

) and the other

{}^{14}C

-labelled

{CO}_{2}

(experiment

Q

). Which one of the following options lists the first labelled products in experiments

P

and

Q,

respectively?

MEDIUM

Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

Consider the following statements regarding photosynthesis and respiration in plants and select the correct option.
I.

RuBisCO

has high affinity to oxygen in low

{CO}_{2}

concentration.
II. The Calvin pathway occurs in the chloroplast of bundle sheath cells of

C_{4}

plants.
III. Yeast position themselves when the concentration of alcohol reaches

7 %

.
IV. Oxygen is a final hydrogen acceptor during aerobic respiration.

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

How many CO2, NADPH and ATP are used in the synthesis of one molecule of glucose in Calvin Cycle?

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

In photosynthetic carbon-fixation, which one of the following reacts with ${CO}_{2}$

MEDIUM

Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

Number of given forms of phosphate ions released during the synthesis of 10 glucose molecules in calvin cycle in series

a)

Inorganic phosphate

b)

H_{2} {PO}_{4}^{-}

c)

ADP

HARD

Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

In an experiment radioactive ¹⁴CO₂was supplied to green plants. In which of the substance the radioactive ¹⁴CO₂is supposed to enter and how? Give the various steps sequentially.

MEDIUM

Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

What is RuBisCO? Explain its role in C₃ and C₄ photosynthesis.

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

RuBisCO is an enzyme that acts both as a carboxylase and oxygenase. Why do you think RuBisCO carries out more carboxylation in C4 plants?

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

The Calvin cycle consists of three phases. What are they? Explain the significance of each of them.

MEDIUM

Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

How many molecules of ATP are required for the synthesis of one molecule of glucose in C₃ and C₄ pathways?

HARD

Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

Compare C₄ and C₃ pathways of CO₂ fixation during photosynthesis. Give well labelled and schematic sketch of C₄ pathways.

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

.............. is a CAM plant.

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

Give comparisons between the C₃ and C₄ pathways.

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

Dark reaction of photosynthesis is called

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

The stomata in CAM plants open during

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Biology>Plant Physiology>Photosynthesis in Higher Plants>Mechanism of Photosynthesis

Specify how a pentose phosphate is a CO₂ acceptor in the dark reaction of photosynthesis.

Fill in the blank with the correct answer from the bracket. The biosynthetic phase of photosynthesis takes place in the of the chloroplast. (grana, stroma, thylakoid)

Important Questions on Photosynthesis in Higher Plants

Learn and Prepare for any exam you want !

Fill in the blank with the correct answer from the bracket.

The biosynthetic phase of photosynthesis takes place in the of the chloroplast. (grana, stroma, thylakoid)