NCERT Class 11-Biology: Chapter –13 Photosynthesis in Higher Plants Part 5

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Question 11:

Find out how Melvin Calvin worked out the complete biosynthetic pathway for synthesis of sugar.


By experimenting at the University of California, Melvin Calvin and his staff found the complete way for sugar synthesis. The following measures were used: carbon dioxide, a radioactive isotope of carbon, was labelled and was supplied to the plants for this experiment.

The path was then monitored and analysed, e.g. in dark and in light, under different conditions.

Once the experiment with the live plant was over, the plant was killed and the labelled compound was extracted from the dead plant for further analysis.

Based on the analysis in live and dead plants, Calvin and his co-workers finally discovered the pathway during light independent reactions.

Question 12:

Six turns of Calvin cycle are required to generate one mole of glucose. Explain.


In the course of the Calvin cycle, the reduction of one molecule requires two ATP molecules and two NADPH molecules. We know glucose is a 6-carbon compound, so six carbon dioxide molecules are required to produce a single glucose molecule. Hence, six turns of Calvin Cycle are required to generate one mole of glucose.

Question 13:

Complete the flow chart for cyclic photophosphorylation of the photosystem-I

Chapter 13 - Question 13 - Image of the Flow Chart for Cycli …

Flow Chart for Cyclic

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Photophosphorylation is the synthesis of ATP from ADP and inorganic phosphate in the presence of light.

When only PS I is functional, the electron is circulated within the photosystem and the phosphorylation occurs due to cyclic flow of electrons.

While the membrane or lamellae of the grana have both PS I and PS II the stroma lamellae membranes lack PS II as well as NADP reductase enzyme. The excited electron does not pass on to but is cycled back to the PS I complex through the electron transport chain. The cyclic flow hence, results only in the synthesis of ATP, but not of . Cyclic photophosphorylation also occurs when only light of wavelengths beyond are available for excitation.

Question 14:

In what kind of plants do you come across ‘Kranz’ anatomy? To which conditions are those plants better adapted? How are these plants better adapted than the plants, which lack this anatomy?


, such as maize, sugar cane etc. are found in Kranz anatomy. These plants can withstand high temperatures and high light intensity. These plants are also suitable for a limited nitrogen and carbon dioxide supply. Unlike plants, these plants do not contain photo-suspiration. This helps to create optimal glucose levels. Consequently, in contrast to plants produce more biomass.

Question 15:

A process is occurring throughout the day, in ‘X’ organism. Cells are participating in this process. During this process ATP, and water are evolved. It is not a light dependent process.

a. Name the process.

b. Is it a catabolic or an anabolic process?

c. What could be the raw material of this process?


(a) Respiration

(b) This is a catabolic process.

(c) Carbohydrate

Question 16:

Tomatoes, carrots and chillies are red in colour due to the presence of one pigment. Name the pigment. Is it a photosynthetic pigment?


Chloroplast and mitochondria contain additional genomic DNA. This improves organelles ‘reproduction. Thus, semi-autonomous organelles are called Chloroplast and mitochondria, which contain additional genomic DNA. Because of this, they can replicate themselves. These organelles are therefore called semi-autonomous.

Question 17:

Why do we believe chloroplast and mitochondria to be semi-autonomous organelle?


Extra genomic DNA is present in the chloroplast and mitochondria. This enhances the replication of these organelles. These organelles are therefore called semi-autonomous.