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Question
(i) Draw a neat and well-labelled diagram of the Chloroplast.
(ii) List the events taking place in the photo-chemical phase of Photosynthesis.
(iii) If you are planning an experiment to show the effect of light on photosynthesis :
(a) Will you select white light or green light? Justify your answer.
(b) Why would you select a destarched plant?
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Solution
(ii) The photochemical phase of photosynthesis is light-dependent. A series of chemical reactions occur is quick succession initiated by light, therefore the phase is called photochemical phase. It takes place in chlorophyll-containing thylakoids of chloroplast.
It occurs in the following steps :
(a) The chlorophyll on exposure to light energy becomes activated by absorbing photons.
(b) This energy is used in splitting the water molecules (photolysis) as below :
H2O → H+ + OH–
(c) OH– ions through a series of steps produce water (H2O) and oxygen (O2). Water may be used inside the plant but O2 released into the atmosphere.
(d) H+ combines with CO2 in dark reaction to produce glucose.
(iii)
(a) I will select white light because photosynthesis is maximum in white light while it is minimum in green light as the green light is reflected by green plants.
(b) I will select the destarched plant so I can demonstrate the synthesis of starch through the iodine test.
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RELATED QUESTIONS
A potted plant with variegated leaves was taken in order to prove a factor necessary for photosynthesis. The potted plant was kept in the dark for 24 hours and then placed in bright sunlight for a few hours. Observe the diagrams and answer the questions:
- What aspect of photosynthesis is being tested in the above diagram?
- Represent the process of photosynthesis in the form of a balanced equation.
- Why was the plant kept in the dark before beginning the experiment?
- What will be the result of the starch test performed on Leaf ‘A’ shown in the diagram? Give an example of a plant with variegated leaves
- Draw a neat labelled diagram of a chloroplast.
Which tissues and cells are mainly concerned with photosynthesis?
Differentiate Between:
Autotrophs and Heterotrophs.
A well-watered healthy potted plant with variegated leaves was kept in darkness for about 24 hours. It was then set up as shown in the diagram and exposed to light for about 12 hours. At the end of this time, leaf X and leaf Y were tested for starch. Study the diagram and answer the questions that follow:
(i) Why was the plant initially kept in darkness for 24 hours?
(ii) What is the function of the sodium hydroxide solution in the flask?
(iii) Select the correct leaf from the five available choices shown in the diagram as A, B, C, D, and E. Rewrite the correct answer for the filling in the appropriate letter from the questions that follow:
1. After the starch test, leaf X would look like.
2. After the starch test, leaf Y would look like.
Mention, if the following statement is True or False. If false rewrite the wrong statement in its correct form:
Photosynthesis occurs only in plants.
Mention, if the following statement is True or False. If false rewrite the wrong statement in its correct form:
CO2 is the life-supporting gas produced due to photosynthesis.
Mention the significance of the following mineral:
Magnesium for green plants.
Write the exact location of chloroplasts in the parts of a plant.
Define the following term:
Chloroplast
Distinguish between the following pairs on the basis of the word indicated in the bracket ( ).
Stoma and Stroma (structure)
