[5 Mark Question Answer]

Question 15 Marks

What is the importance of photosynthesis in the life of the following:

Animals

Answer

Animals eat green plants or eat animals that feed on green plants.
Respiration - The process of biochemical decomposition of organic compounds like simple carbohydrates, glucose, in living cells with the release of energy.

→ Energy is released in the form of ATP (Adenosine triphosphate).
→ One mole of glucose on complete oxidation yields 38 molecules of ATP.
→ It is a high energy molecule which serves as an immediate source of energy.
→ It is a form of chemical energy which can be used for all processes in the cell.
→ Therefore ATP is called the currency of the cell.
Metabolism Is the set of life-sustaining chemical reactions within the cells of living organisms
Two Types of metabolic processes take place in living things

Catabolic process - it is a destructive (breaking down) process in which energy is released.e.g. Respiration

Anabolic process - It is a construction (uses energy to construct) process in which energy is used for biosynthetic processes.e.g. Photosynthesis

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Question 25 Marks

List the events taking place in the photo-chemical phase of Photosynthesis.

Answer

The photochemical phase of photosynthesis is light-dependent. A series of chemical reactions occur in quick succession initiated by light, therefore the phase is called photochemical phase. It takes place in chlorophyllcontaining thylakoids of chloroplast.
It occurs in the following steps:
1. The chlorophyll on exposure to light energy becomes activated by absorbing photons.
2. This energy is used in splitting the water molecules (photolysis) as below:- $H _2 O -> H ^{+}+ OH ^{-}$
3. $OH ^{-}$ions through a series of steps produce water $\left( H _2 O \right)$ and oxygen $\left( O _2\right)$. Water may be used inside the plant but $O _2$ released into the atmosphere.
4. $H ^{+}$combines with $CO _2$ in dark reaction to produce glucose.

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Question 35 Marks

Using the destarched plant describe step by step how would you proceed to prove that in the absence of light the leaf cannot manufacture starch?

Answer

In a dark room, a leaf on the destarched plant is covered on either side with strips of black paper which are kept in place by paper clips or cellophane tape.
Now the potted plant is kept in the light.
After a few hours, the leaf is detached from the plant and the black strips are removed.
Then the leaf is boiled in water for 2-3 minutes and then boiled in alcohol to remove the green chlorophyll.
The leaf is then washed in water and tested with iodine.
The region of the leaf that was under the black strip turns yellowish-brown showing that no starch was made, while the rest of the leaf turns bluish-black showing the starch was made in the presence of light.

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Question 45 Marks

Column ‘II’ is a list of items related to ideas in Column ‘I’. Match the term in Column ‘II’ with the suitable idea given in Column ‘I’.

	Column I		Column II
(i)	Grana	(a)	Decomposers
(ii)	Autotrophs	(b)	Light reaction
(iii)	By-products of photosynthesis	(c)	Animals
(iv)	Photolysis	(d)	Oxygen
(v)	Bacteria and fungi	(e)	Stimulated by light
(vi)	Chloroplast	(f)	Power
(vii)	Oxygen and water	(g)	Raw material
(viii)	Sunlight	(h)	Machinery
(ix)	$CO_2$ and water	(i)	End products
(x)	Glucose (sugar)	(j)	Workrooms
(xi)	Cells in the leaf	(k)	By-products.

Answer

	Column I		Column II
(i)	Grana	(f)	Power
(ii)	Autotrophs	(d)	Oxygen
(iii)	By-products of photosynthesis	(e)	Stimulated by light
(iv)	Photolysis	(b)	Light reaction
(v)	Bacteria and fungi	(a)	Decomposers
(vi)	Chloroplast	(c)	Animals
(vii)	Oxygen and water	(f)	Power
(viii)	Sunlight	(a)	Decomposers
(ix)	$CO_2$ and water	(b)	Light reaction
(x)	Glucose (sugar)	(d)	Oxygen
(xi)	Cells in the leaf	(e)	Stimulated by light

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Biology [5 Mark Question Answer]

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