Frank ICSE Class 10 Biology Solutions Chapter 6 Photosynthesis

Question 1. Answer the following:
(i) Give the overall chemical equation of photosynthesis in green plants.
(ii) Mention two significant advantages of photosynthesis to the living world as a whole.
Solution 1:
(i) Below is the Chemical equation of Photosynthesis:

(ii) Advantages of photosynthesis:
a.) To produce food for all the organisms on earth.
b.) Release oxygen which is a life supporting gas.

Question 2. Define the following:
(i) Plant pigments
(ii) Quantum
(iii) Organic food
(iv) Light reaction
(v) Photolysis in photosynthesis
Solution 2:
1. Plant pigments:– These are substances that have an ability to absorb light at specific wavelength.
2. Quantum:– Quantum particles are discrete packets that hold energy and can be transformed from one form to another.
3. Organic food:- Organic food is food that is produced without the use of synthetic inputs such as synthetic pesticides and chemical fertilizers.
4. Light reaction:- The membrane system of the chloroplast is responsible for trapping the light energy and also for the synthesis of ATP and ADP h this is known as light reaction
5. Photolysis in photosynthesis:- It is a synthesis of ATP from ADP and inorganic phosphate in the presence of light.

Question 3. Given below is the overall chemical equation of photosynthesis which is incomplete in certain respects.

Solution :

Question 4. Distinguish between the following:
(i) Hill reaction and NADP reduction in chloroplast.
(ii) Photosynthesis and photophosphorylation.
Solution 4:
(i) Hill Reaction and NADP reduction in chloroplast

Hill Reaction	NADP Reduction
Hill reaction is a three-step light reaction that occurs in the presence of light.	NADP reduction is a step in the hill reaction that converts NADP to NADPH.

(ii) Photosynthesis and photophosphorylation

Photosynthesis	Photophosphorylation
Both the light and dark reactions are involved in photosynthesis.	Only during the light response can photophosphorylation occur.
It is the entire process through which food/glucose is created in a plant.	It is a step in photosynthesis when a phosphate molecule is added to ADP to generate ATP.

Question 5. An experiment was set up as shown in the figure given below. The twig in the diagram was intact on the plant and it was left as such in sunlight for a few hours.

(i) What is the aim of the above experiment?
(ii) Why was potassium hydroxide placed inside the conical flask?
(iii) What test would you perform on the leaf inside the flask?
(iv) What is the expected result of the above test?
(v) Is it necessary to similarly test on outer leaf also? Give a reason.
Solution 5:
1. The experiment’s goal is to demonstrate that CO2 is required for photosynthesis.
2. CO2 is absorbed by potassium hydroxide from the environment. It is inserted within the conical flask to remove CO2.
3. Iodine would be used to test the leaf within the conical flask for the presence of starch.
4. The aforementioned test should get the following result: There will be no change in colour.
5. Yes, a similar test on the outer leaf is required to demonstrate that leaves exposed to CO2 are capable of photosynthesis.

Question 6. The figure given below represents the vertical section of a leaf.
(i) Name the part labelled 1 to 5.
(ii) What do the two arrows (dotted and solid) indicated in the daytime and at night?
(iii) Could you add one more arrow in the figure? If yes, what for?
(iv) How many leaf veins have been shown in this section?

Solution :

(ii) The two arrows depict the release of oxygen and water vapours during the day, as well as carbon dioxide and very little oxygen during the night.
(iii) Yes, another arrow can be placed to represent the leaf’s carbon dioxide absorption.
(iv) In this section, only one vein has been presented.

Question 7. Give any four differences between photosynthesis and respiration.
Solution 7:

Photosynthesis	Respiration
(i) Photosynthesis is the process by which green plants create their own food by converting carbon dioxide into glucose and releasing oxygen using light energy from the sun.	(i) Respiration is the process of absorbing oxygen and releasing energy and carbon dioxide.
(ii) In the presence of sunlight, photosynthesis occurs exclusively in chlorophyll-containing cells.	(ii) Respiration is a continuous process that happens in all living cells.
(iii) Anabolic process	(iii) Catabolic process
(iv) It leads to an increase in dry mass.	(iv) It results in a loss in dry mass.

Question 8. (i) Define dark reaction.
(ii) Give an overall balanced equation of this process.
(iii) Describe an experiment to prove that sunlight is necessary for photosynthesis.
(iv) Mention any two points in which photosynthesis and respiration in plants are opposite to each other.
Solution 8:
(i) Dark reaction- This is a photosynthetic process that happens in the stroma of the chloroplast and does not require light

(iii) a.) To destarch the leaves, a potted plant is kept in the dark for two days.
b.) A clip is used to cover a portion of a leaf with black paper.
b.) The plant is now exposed to light for a few hours.
d.) The leaf is plucked and cooked in water, after which it is decolored with alcohol.
(.) Because photosynthesis took occurred in that area of the leaf, the portion that received light becomes blue with iodine.
f.) Because photosynthesis cannot occur in the absence of sunshine, the section of the leaf that was covered with black paper stays colourless.

(iv)

Photosynthesis	Respiration
It’s an anabolic procedure.	It’s a catabolic reaction.
It leads to an increase in dry mass.	Dry mass is lost as a result.

Question 9. (i) What is meant by photosynthesis? Why is it so important in nature?
(ii) Describe fully one experiment with potted green plant to show that starch is not produced in the leaves when carbon dioxide is not available (diagrams essential)
(iii) A healthy oat seeding in a pot is transferred from light to any airy but completely dark room. How would it differ from its original condition in appearance after about a week? Explain the difference.
Solution 9:
(i) Photosynthesis:- It’s an anabolic process in which plants use water and carbon dioxide to make carbohydrates or food in the presence of sunshine and chlorophyll. It is significant because:
a.) It provides nourishment to all living things on the planet, either directly or indirectly.
b.) It keeps the atmosphere’s oxygen and carbon dioxide levels in check.
(ii) Perform an experiment to demonstrate that when carbon dioxide is unavailable, starch is not formed in the leaves:
a.) To destarch the leaves, a potted plant is kept in the dark for two days.
b.) Fill a wide mouth container with a third of a cup of caustic potash solution.
c.) Place half of a potted plant leaf in the bottle, making sure the leaf does not come into contact with the solution.
d.) For a few hours, the equipment is exposed to sunlight.
e.) The leaf is plucked and the starch content is determined.
f.) Because it did not get CO2 for photosynthesis, just the section of the leaf outside the bottle becomes blue, while the portion of the leaf within the bottle remains colourless. The caustic solution absorbed all of the CO2 in the bottle.

Question 10. An experiment was set up as shown in the figure alongside. Look at the figure and answer the following questions:
(i) What is the objective of this experiment?
(ii) Which plant is used in this experiment?
(iii) Which gas is evolved in this process?
(iv) What will happen to the rate of evolution of this gas if a pinch of sodium bicarbonate is added?
(v) What will happen if the apparatus is kept in dark?

Solution 10:
1. The main aim of the experiment is to prove that oxygen is released during the photosynthesis.
2. Hydrilla is used in this experiment.
3. Oxygen is evolved in this process.
4. On adding a pinch of sodium bicarbonate increase the rate of photosynthesis that will increase the rate of bubbling also.
5. Photosynthesis will not occur.

Question 11. Two healthy green plants were placed in the dark for 24 hours. They were then set up, as shown in the figure, for 4 hours. Then a leaf was taken from each plant and the chlorophyll was removed from the leaves:
(i) What is the next and final step in this experiment?
(ii) What would be the result of the final step?
(iii) Why was it necessary to grease the glass sheet?
(iv) What hypothesis is being tested in this experiment?

Solution 11:
1. Iodine Solution is then applied to the leaf.
2. The first plant’s leaf will not pass the starch test, however the second plant’s leaf will turn blue-black, indicating the presence of starch.
3. To prevent CO2 from entering the glass, it is required to lubricate the heet.
4. In this experiment, the idea that CO2 is required for photosynthesis is investigated.

Question 12. What is the effect of light intensity on the rate of photosynthesis in leaves?
Solution 12:
Sunlight has a direct relationship with light intensity. The rate of photosynthesis increases as the intensity of light increases. Photosynthesis is most efficient in red light, then blue light, and finally green light.

Question 13. (i) Mention two ways in which photosynthesis is useful to life.
(ii) Explain why respiration is said to be a reversal of photosynthesis?
(iii) What is the role of chlorophyll in green plant?
Solution 13:
1. Advantages of photosynthesis:
(a) It is the world’s principal source of food.
(b) It is also responsible for the green plant’s release of oxygen into the atmosphere, which is required by almost all life forms.
2. While respiration is a catabolic process in which oxygen is taken in and carbon dioxide is released, photosynthesis is an anabolic process in which carbon dioxide is taken in and oxygen is produced.
3. Chlorophyll is a substance found in green plants that gives them their colour. It absorbs light energy, which is utilised to create ATP and reduce NADP during photosynthesis.

Question 14. Difference between an autotroph and a heterotroph. Give one example of each organism.
Solution 14:

Autotroph	Heterotroph
(i) They are capable of preparing their own meals.	(i) They are unable to make their own meals.
(ii) They have chlorophyll in them.	(ii) They are devoid of chlorophyll.
(iii) Green Plants	(iii) Animals

Question 15. What is the difference between chloroplast and the chlorophyll?
Solution 15:

Chloroplast	Chlorophyll
(i) It is a cellular organelle.	(i) Chloroplasts contain a green pigment.
(ii) It is living.	(ii) It is non-living.

Question 16. Name only two plants you are familiar with, which have no chlorophyll.
Solution 16:
Plants which have no chlorophyll are Coelus and mushroom.

Question 17. Why is the upper surface of broad leaves greener than their lower surface?
Solution 17:
Upper surface of broader leaves greener than their lower surface because directly in contact with the sunlight which leads to maximize the rate of photosynthesis compared to the lower which has less exposed of sunlight.

Question 18. (i) Fill in the blanks in the following equations of two chemical reactions:

(ii) Name the two processes represented by the above two reactions.
(iii) State any two differences in these processes other than those already indicated in the reactions.
(iv) Which one of these two reactions is the supporter of all life on earth?
Solution 18:

(ii) The two processes represented by the two reactions are Photosynthesis and Respiration
(iii) Below are the difference between photosynthesis and respiration:-
Photosynthesis Respiration
It’s an anabolic procedure. It’s a catabolic reaction.
It leads to an increase in dry mass. Dry mass is lost as a result.

(iv) Photosynthesis is the supporter of all life on earth.

Question 19. Complete the following statement by choosing the correct alternative from the ones given within the brackets:
All animals would die on the earth if there was no __. (chlorophyll, haemoglobin, penicillin)
Solution 19:
All animals would die on the earth if there was no Chlorophyll.

Question 20. Photosynthesis stops to occur at a temperature above 35˚C. (True/False)
Solution 20:
The above statement is true.

Question 21. Photosynthesis occurs in all the cells of the plant. (True/False)
Solution 21:
The above statement is False

Question 22. Explain briefly how during the day transpiration and photosynthesis are interlinked.
Solution 22:
During the day, the stomata open to allow inward diffusion of carbon dioxide for photosynthesis, but this also results in the loss of water vapours to the outside during transpiration.

Question 23. A potted destarched plant was taken in order to prove that light is necessary for photosynthesis.
(i) What is meant by ‘destarched plant’? How can it be destarched?
(ii) Using the destarched plant describe step by step how you would proceed to prove that in the absence of light the leaf cannot manufacture starch.
Solution 23:
During the day, transpiration and photosynthesis are related because the stomata open to allow inward diffusion of carbon dioxide for photosynthesis, but this also allows water vapours to escape to the exterior during transpiration.
(i) A destarched plant is one that has no starch. Destarching can be accomplished by keeping the plant in the dark for 2-3 days or clipping a section of a leaf with black paper.
(ii) a) The leaf is plucked and boiled in water before being de-coloured with alcohol.
(b) Because photosynthesis took place in that area of the leaf, the portion that received light turns blue with iodine.
(c) Because photosynthesis could not take place in the area of the leaf that was covered with black paper, it remains colourless

Question 24. Name the following:
(i) The principle site in a green leaf for photosynthesis.
(ii) The products that are formed as a result of photosynthesis.
(iii) Three organisms that cannot prepare their own food by photosynthesis.
(iv) The main reaction by which the molecule of water is broken down by means of light.
(v) The main mineral constituent of chlorophyll.
(vi) The cell organelle responsible for photosynthesis.
Solution 24:
1. The principle site in a green leaf for photosynthesis is chloroplast.
2. The products that are formed as a result of photosynthesis is glucose and oxygen.
3. Three organisms that cannot prepare their own food by photosynthesis are
a) Fungi
b) Insects
c) Animals
4. The main reaction by which the molecule of water is broken down by means of light is photolysis.
5. The main mineral constituent of chlorophyll is magnesium
6. The cell organelle responsible for photosynthesis is chloroplast

Question 25. The following statements are about photosynthesis in a green plant. Write whether each is True or False.

(i) The raw materials for photosynthesis include water and carbon dioxide.

(ii) Land plants obtain their carbon dioxide from the atmosphere.

(iii) Photosynthesis occurs in underground organs as well as in aerial ones.

(iv) Photosynthesis results in a gain in dry weight.

(v) A variegated leaf (one that has white as well as green patches) will only photosynthesize in the green areas.

(vi) The source of energy is light.

(vii) Green light is more effective than any other colour.

(viii) The growing tips of stems and roots will be photosynthesizing actively compared with the rest of the plant.

(ix) Photosynthesis produces oxygen.

Question 26. Fill in the blanks:

(i) ______ is the process which replenishes the atmospheric oxygen which the animal life consumes in respiration.

(ii) Land plants obtain their carbon dioxide from the ______.

(iii) Photosynthesis produces oxygen and ______.

(iv) Xanthophyll is ______ coloured pigment.

(v) Quanta some is the basic unit of ______.

(vi) The end products of photosynthesis are ______ and ______.

(vii) CO² enters the leaf through ______.

Question 27. Match the terms of column I with those is column

Column I	Column II
(i) Stomata closed	(a) decomposers
(ii) Autotrophs	(b) light reaction
(iii) By-products of photosynthesis	(c) animals
(iv) Photolysis	(d) during night
(v) Bacteria and fungi	(e) green plants
	(f) oxygen

Solution 27:

Column I	Column II
(i) Stomata closed	(d) During night
(ii) Autotrophs	(e) Green plants
(iii) By-products of photosynthesis	(f) Oxygen
(iv) Photolysis	(b) Light reaction
(v) Bacteria and fungi	(a) Decomposers

Question 28. Fill in the blank with the function: Chloroplasts ______.
Solution 28
Chloroplasts are chlorophyll-containing cell organelles that serve as the primary location of photosynthesis in green plants.

Question 29. Mention any three adaptations found in plants to favour the process of photosynthesis.
Solution 29:
1. The leaves have a large surface area.
2. More stomata are present.
3. The leaf’s thinness

Question 30. Write a short note on carbon cycle.
Solution 30:
Carboncycleisaseriesofchemicalreactionsinwhichatmosphericcarbondioxideisused by the organisms and returned to the atmosphere. Photosynthetic plants use carbon as carbon dioxide from the air synthesizing organic compounds. By respiration, burning, decay, etc. the carbon is returned to the atmosphere.

Question 31. How does the carbon cycle maintain the balance of nature?
Solution 31:
Carbon dioxide enters living creatures and then exits through multiple paths to return to the atmosphere, producing the actual carbon cycle. As a result, it contributes to the preservation of natural balance

Question 32. “Human activities are harmful to the balance of nature.” Comment.
Solution: 32:
Carbon dioxide levels in the atmosphere are rising as a result of increased human activity such as fossil fuel use, deforestation, and other factors that contribute to rising global temperatures. Melting of polar ice caps, coastal flooding, disruption of the hydrogenic cycle, and other effects of global warming As a result, “human activities are damaging to the natural balance.”

Question 33. How is carbon dioxide removed from the atmosphere? Explain.
Solution 33:
Carbon dioxide is removed from the atmosphere by:
Producers:– Producers or green plants use carbon dioxide through photosynthesis. A small amount of carbon dioxide is used by chemosynthetic bacteria also.
Marine Organisms:– Some amount of carbon dioxide is directly fixed by a few marine organisms and sea water absorbs carbon dioxide in the form of dissolved carbon dioxide, carbonic acid, carbonate and bicarbonates.

Question 34. How does carbon dioxide return to the atmosphere? Explain. A student in order to study the importance of certain factors of photosynthesis took a potted plant and kept it in the dark for over 24 hours. Then in the early hours of the morning the student covered one of the leaves with black paper in the centre only. Student placed the potted plant in the sunlight for a few hours, and then tested the leaf which was covered with black paper for starch.
(i) What aspect of photosynthesis was being investigated?
(ii) Is there any control in this experiment? If so, state the name.
(iii) Why was the plant kept in the dark before the experiment?
(iv) Describe step by step how the candidate proceeded to test the leaf for the presence of starch.
Solution 34:.
(a) Carbon dioxide is primarily returned to the atmosphere in the following ways:
Respiration – Animals and plants breathe and emit carbon dioxide into the atmosphere through respiration.
(ii) Decay – Plants and animals need bacteria and fungus to break down organic materials and release carbon dioxide.
(iii) Combustion – When plants and animals are buried under the soil, they are transformed into coal and oil, which emit carbon dioxide when burned.
(iv) Ocean water – Carbon dioxide is found in molluscan shells as lime stone and as a byproduct of photosynthesis in marine water.
(b) (i) To demonstrate that photosynthesis requires sunshine.
(ii) The control is the uncovered portion of the experimental leaf.
(iii) To detach the leaf from the stem.
(iv) 1. Bring the leaf to a boil in the alcohol.
2. Soak the leaf in water to soften it.
3. Spray the leaf with an iodine Sol.. The uncovered portion is blue-black in colour, while the covered portion is brown in colour. This demonstrates that photosynthesis requires sunshine.

Question 35. The diagram is set up to demonstrate an experiment. Pond weed was placed in five water-filled tubers. The experiment was set up as shown in the diagram. The tubes were then left for 24 hours. Write the correct answer out of the five available choices.

(i) In which tube would you except to find the plant with the least amount of starch?
(a) 1
(b) 2
(c) 3
(d) 4
(e) 5

(ii) The tube in which most oxygen would be found is
(a) 1
(b) 2
(c) 3
(d) 4
(e) 5

(iii) The tube in which least carbon dioxide would be found is
(a) 1
(b) 2
(c) 3
(d) 4
(e) 5

(iv) The tube in which the plant would survive for the shortest length of time is
(a) 1
(b) 2
(c) 3
(d) 4
(e) 5

Question 36. Complete the following by filling in the blanks numbered 1 to 10 with the appropriate word/term: Photosynthesis involves light reaction and dark reaction. During light reaction, the chlorophyll present in the (1) ______ gets activated by absorbing light energy. This energy splits (2) ______ molecules to (3) ______ and oxygen and releases two electrons. This process is called (4) ______. The (5) ______ ions are picked up by NADP to form (6) ______. The ADP is converted to (7) ______. This process is called (8) ______. During the dark phase, the compound produced at the end of the light reaction reacts with carbon dioxide to form (9) ______. This product is converted to starch. The process is called (10) ______
Solution 36:
Photosynthesis involves light reaction and dark reaction. During light reaction, the chlorophyll present in the leaves gets activated by absorbing light energy. This energy splits water molecules to hydrogenion and oxygen and releases two electrons. This process is called photolysis. The hydrogen ions are picked up by NADP to form NADPH2. The ADP is converted to ATP. This process is called photophosphorylation During the dark phase, the compound produced at the end of the light reaction reacts with carbon dioxide to form glucose. This product is converted to starch. The process is called polymerization.

Question 37. The diagram alongside refers to an experiment in which the apparatus was set up with the light source 10 cm away from the plant. After 15 minutes the number of bubbles evolved per minute from the cut stem was recorded. The light source was moved to 20 cm away from the plant, left for 15 minutes and the number of bubbles evolved per minute was again recorded. The experiment was repeated with the light source at distances of 40, 60, 80 and 100 cm away from the plant. Plot a graph for the results obtained and answer the following questions.

(i) From the graph it seems likely that the rate of bubbling per minute at 50 cm would have been:
(a) 2.0
(b) 2.5
(c) 3.0
(d) 3.5

(ii) The gas produced by the plant during the experiment was
(a) air
(b) oxygen
(c) carbon dioxide
(d) nitrogen
(e) hydrogen

(iii) The gas collected comes due to the breakdown of:
(a) glucose
(b) starch
(c) water
(d) air
(e) ATP

(iv) If ice cubes were added to the water, the rate of bubble formation would:
(a) Stay the same.
(b) Increase because more water is added.
(c) Decrease because the temperature drops.
(d) Decrease because water freezes.
(e) Cannot tell from the information given.

(v) If some sodium bicarbonate is added to the water the rate of bubble formation:
(a) Increases because more respiration occurs.
(b) Increases because more photosynthesis occurs.
(c) Increases because the gas becomes less soluble.
(d) Decreases because carbon dioxide acts as a limiting factor.
(e) Decreases because respiration decreases.

Question 38. The diagram alongside represents an experiment conducted to prove the importance of a factor in photosynthesis.

Study the same and then answer the questions that follow:
(i) Name the factor being studies in his experiment.
(ii) Why was the plant kept in a dark room before conducting the experiment?
(iii) Why was the experimental leaf then kept in
1. boiling water
2. methylated spirit
(iv) Name the solution used to test for the presence of starch in the leaf.
(v) What will we observe in the experimental leaf at the end of the starch test?
(vi) Give a balance chemical equation to represent the process of photosynthesis.
Solution 38:
(i) The factor being studies in this experiment is Sunlight.
(ii) The plant kept in a dark room before conducting the experiment because to destarched the leaf.
(iii) 1. The experimental leaf kept in boiling water to kill the cells releases the starch grains.
The experimental leaf kept in methylated spirit to remove chlorophyll.
(iv) The solution used to test for the presence of starch in the leaf is iodine.
(v) We observe in the experimental leaf at the end of the starch test that the covered part of the leaf remains brown and the exposed part of the leaf remains blue-black.

Question 39. Choose the correct answer:

(i) Which one of the following is the best reason for leaving a plant in a dark place before carrying out
experiments on photosynthesis?
(a) To remove chlorophyll from the leaves.
(b) To increase the release of CO2 by the leaves.
(c) To remove starch from the leaves.
(d) To stop synthesis process in the leaves.

(ii) Which one of the following features of plant leaves plays an important part in photosynthesis?
(a) Thick cuticle
(b) Spongy mesophyll
(c) Chloroplasts
(d) Stomata

(iii) The specific function of light energy in the process of photosynthesis is to
(a) Reduce carbon dioxide
(b) synthesize glucose
(c) Activate chlorophyll
(d) split water

(iv) In a typical leaf, photosynthesis occurs mainly in
(a) Cuticle
(b) epidermis
(c) Palisade mesophyll
(d) spongy Mesophyll

(v) Energy is transformed from the light reaction to the dark reaction by
(a) Chlorophyll
(b) ADP
(c) ATP
(d) RuDP

(vi) A cell that lacks chloroplast does not
(a) Evolve CO2
(b) liberate O2
(c) Require water
(d) utilize carbohydrates

(vii) Light reaction takes place in
(a) Grana
(b) stroma
(c) Chloroplast membrane
(d) endoplasmic reticulum

(viii) Photosynthesis is more active in
(a) green light
(b) red light
(c) Yellow light
(d) violet light

(ix) Which of the following gas is used in photosynthesis?
(a) Oxygen
(b) Hydrogen
(c) Nitrogen
(d) Carbon dioxide

(x) The process of photosynthesis occurs by
(a) carbon dioxide and water
(b) carbon dioxide, chlorophyll and water
(c) water, chlorophyll, sunlight
(d) water, carbon dioxide, chlorophyll and sunlight