Frank Brothers Solutions for ICSE Class 10 Biology Chapter 6 Photosynthesis

Solution 1:
Answer:
(i) Chemical equation of photosynthesis:
\[ 6CO_2 + 12H_2O \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} C_6H_{12}O_6 + 6O_2 + 6H_2O \]
(ii) Advantages of photosynthesis:
a. To produce food for all the organisms on earth.
b. Release oxygen which is a life supporting gas.

📝 Teacher's Note: Use visual aids to show the photosynthesis equation and emphasize how plants are the foundation of all food chains. Students often confuse reactants and products.

🎯 Exam Tip: Always write the balanced chemical equation with proper arrow notation and mention both products - glucose and oxygen - for full marks.

Solution 2:
Answer:
1. Plant pigments – Plant pigments are a variety of different kinds of molecules present in plants that absorb certain wavelengths of light while reflecting others.
2. Quantum – Quantum are the discrete packets which stores energy and these particles can be changed from one form to another.
3. Organic food – The food that is produced by using methods that do not involve synthetic inputs such as synthetic pesticides and chemical fertilizers is called organic food.
4. Light reaction – The reaction of photosynthesis which takes place in the presence of light is called light reaction.
5. Photolysis in photosynthesis – The process of splitting of water by sunlight during light reaction of photosynthesis is called photolysis in photosynthesis.

📝 Teacher's Note: Use simple analogies like "quantum as energy packets like money in your wallet" and relate organic food to students' daily life experiences.

🎯 Exam Tip: Define each term clearly and mention the key process or location where applicable (e.g., light reaction occurs in thylakoids).

Solution 3:
Answer:
\[ 6CO_2 + 12H_2O \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} C_6H_{12}O_6 + 6O_2 + 6H_2O \]

📝 Teacher's Note: Emphasize the balanced nature of this equation and how it represents the overall process, not the detailed biochemical steps.

🎯 Exam Tip: Write the equation clearly with proper subscripts and arrow notation - this is a common 2-mark question.

Solution 4:
Answer:
(i) Hill Reaction and NADP Reduction in chloroplast:

(ii) Photosynthesis and photophosphorylation:

📝 Teacher's Note: Use diagrams of chloroplasts to show where these reactions occur - Hill reaction in thylakoids and emphasize the energy conversion aspect.

🎯 Exam Tip: Remember that photophosphorylation is just one part of the light reaction, while photosynthesis includes both light and dark reactions.

Solution 5:
Answer:
1. The aim of the experiment is to prove that CO2 is necessary for photosynthesis.
2. Potassium hydroxide absorbs CO2 from the surrounding. It is placed to remove CO2 within the conical flask.
3. The leaf inside the conical flask would be tested for the presence of starch by the application of iodine.
4. The expected result of the above test is – No change in the colour will be observed.
5. Yes, it is necessary to similarly test on the outer leaf also to show that leaves present in CO2 show photosynthesis.

📝 Teacher's Note: Demonstrate this experiment if possible, emphasizing the importance of controls in scientific investigations. Students should understand why we need both experimental and control groups.

🎯 Exam Tip: Always mention the control group when describing experiments and explain the role of potassium hydroxide as a CO2 absorber.

Solution 6:
Answer:
1. 1 – Upper Epidermis; 2 – Palisade layer / chloroplast; 3 – Xylem; 4 – Phloem; 5 – Guard cell
2. The two arrows show the release of oxygen and water vapours during the daytime and carbon dioxide and very less amount of oxygen is released during the night.
3. Yes, one more arrow can be added to show the absorption of carbon dioxide by the leaf.
4. One vein has been shown in this section.

📝 Teacher's Note: Use cross-section models of leaves to help students visualize these structures. Point out how leaf anatomy is perfectly adapted for photosynthesis.

🎯 Exam Tip: When labeling leaf diagrams, be specific about cell types and remember that gas exchange occurs mainly through stomata.

Solution 7:
Answer:
Difference between photosynthesis and respiration:

📝 Teacher's Note: Help students remember that photosynthesis builds up (anabolic) while respiration breaks down (catabolic). Use the analogy of building vs. demolishing a house.

🎯 Exam Tip: Always mention the key differences: location, timing, energy changes, and whether it's anabolic or catabolic.

Solution 8:
Answer:
(i) Dark reaction – It is a reaction in photosynthesis which do not require light and occurs in the stroma of the chloroplast.
(ii) \[ 6CO_2 + 12H_2O \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} C_6H_{12}O_6 + 6O_2 + 6H_2O \]
(iii) Experiment to prove that sunlight is necessary for photosynthesis:
a. A potted plant is kept in the dark for two days to destarch the leaves.
b. A part of a leaf is covered with a black paper by clip.
c. Now the plant is kept in the light for few hours.
d. The leaf is plucked and is boiled in water and is then decolourized with alcohol.
e. The portion of leaf which received light turns blue with iodine because photosynthesis took place in that part of leaf.
f. The part of leaf which was covered with black paper remains colourless because photosynthesis could not take place in the absence of sunlight.
(iv) Photosynthesis and respiration are opposite to each other in the following ways:

📝 Teacher's Note: The dark reaction name is misleading - clarify that it can occur in light but doesn't directly need light. Demonstrate the starch test with actual leaves if possible.

🎯 Exam Tip: For the sunlight experiment, always mention destarching first, then the experimental setup, and finally the iodine test results.

Solution 9:
Answer:
(i) Photosynthesis: It is an anabolic process by which plants manufacture carbohydrates or food material with the help of water and carbon dioxide in the presence of sunlight and chlorophyll.
It is an important process as:
a. It produces food directly or indirectly for all living organisms on earth.
b. It maintains balance between oxygen and carbon dioxide in the atmosphere.
(ii) Experiment to show that starch is not produced in the leaves when carbon dioxide is not available:
a. A potted plant is kept in the dark for two days to destarch the leaves.
b. Take a wide mouth bottle and fill 1/3rd of it with caustic potash solution.
c. Insert half part of the leaf of potted plant in the bottle and do not let the leaf to touch the solution in the bottle.
d. The apparatus is kept in sunlight for few hours.
e. The leaf is plucked and tested for starch.
f. Only the portion of the leaf which is outside the bottle turns blue and the part of the leaf inside the bottle remains colourless because it did not get CO2 for photosynthesis. All the CO2 present in the bottle was absorbed by caustic solution.
(iii) The leaves of the oat plant will turn yellow and the seedling will die because photosynthesis will not take place.

📝 Teacher's Note: Emphasize the importance of photosynthesis as the foundation of all life on Earth. Use real examples of what happens when plants don't get CO2.

🎯 Exam Tip: Always explain the role of caustic potash (KOH) as a CO2 absorber in these experiments and mention both the experimental and control parts of the leaf.

Solution 10:
Answer:
1. The objective of this experiment is to prove that oxygen is released during photosynthesis.
2. Hydrilla
3. Oxygen
4. The rate of photosynthesis will increase and the rate of bubbling also increases when sodium bicarbonate is added.
5. Photosynthesis will not take place.

📝 Teacher's Note: This is a classic experiment that students can easily observe. Explain why we use aquatic plants like Hydrilla - the oxygen bubbles are clearly visible underwater.

🎯 Exam Tip: Remember that sodium bicarbonate provides extra CO2, which increases the rate of photosynthesis and hence more oxygen bubbles are produced.

Solution 11:
Answer:
1. The leaf is then treated with iodine solution.
2. The leaf from first plant will not show starch test while the leaf from second plant will become blue-black showing the presence of starch.
3. It is necessary to grease the glass sheet to prevent the entry of air containing CO2.
4. The hypothesis that CO2 is necessary for photosynthesis is being tested in this experiment.

📝 Teacher's Note: Emphasize the importance of proper sealing in experiments to ensure valid results. Students should understand why we need to prevent CO2 entry.

🎯 Exam Tip: Always mention the color change with iodine - blue-black indicates starch presence, brown/yellow indicates absence.

Solution 12:
Answer:
Light intensity is directly proportional to sunlight. Increase in intensity of light increases the rate of photosynthesis. Photosynthesis is maximum in red light followed by blue light and is least in green light.

📝 Teacher's Note: Use colored filters to demonstrate how different light colors affect photosynthesis rates. Explain why plants appear green (they reflect green light).

🎯 Exam Tip: Remember the order: red light (maximum photosynthesis) > blue light > green light (minimum photosynthesis).

Solution 13:
Answer:
1. Advantages of photosynthesis:
• To produce food for all the organisms on earth.
• Release oxygen which is a life supporting gas.
2. Respiration is a catabolic process while photosynthesis is an anabolic process. During respiration oxygen is taken and carbon dioxide is given out while during photosynthesis carbon dioxide is taken and oxygen is given out.
3. Chlorophyll is a green coloured pigment found in green plants. it absorbs light energy which is utilized for the formation of ATP and reduction of NADP during photosynthesis.

📝 Teacher's Note: Help students understand that photosynthesis and respiration are complementary processes that maintain atmospheric balance. Use simple analogies for anabolic vs catabolic processes.

🎯 Exam Tip: Always mention that chlorophyll converts light energy into chemical energy (ATP and NADPH) during the light reactions.

Solution 14:
Answer:
Difference between autotroph and heterotroph:

📝 Teacher's Note: Use examples from students' environment - plants in the school garden (autotrophs) vs pets and humans (heterotrophs).

🎯 Exam Tip: Remember the key difference: auto = self, hetero = other. Autotrophs make their own food, heterotrophs depend on others.

Solution 15:
Answer:
Difference between chloroplast and chlorophyll:

📝 Teacher's Note: Use the analogy of a factory (chloroplast) and the machines inside it (chlorophyll). The organelle contains the pigment.

🎯 Exam Tip: Remember: chloroplast is the structure, chlorophyll is the substance inside that captures light.

Solution 16:
Answer:
Coelus and mushroom.

📝 Teacher's Note: These are examples of plants that lack chlorophyll and cannot perform photosynthesis. Discuss how they obtain nutrition differently.

🎯 Exam Tip: Remember that not all plants can photosynthesize - some are parasitic or saprophytic like mushrooms and Coleus variants.

Solution 17:
Answer:
It is because the upper surfaces of broad leaves are directly exposed to sunlight which leads to maximize the rate of photosynthesis.

📝 Teacher's Note: Connect this to leaf adaptations for photosynthesis - large surface area, thin structure, and proper orientation toward sunlight.

🎯 Exam Tip: Mention that broad leaves have more surface area for light absorption and chloroplast concentration is higher on the upper side.

Solution 18:
Answer:
(i) (a) \[ 6CO_2 + 12H_2O \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} C_6H_{12}O_6 + 6O_2 + 6H_2O \]
(b) \[ C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy} \]
(ii) Photosynthesis and respiration.
(iii) Difference between photosynthesis and respiration:

(iv) Photosynthesis.

📝 Teacher's Note: Show students how these two equations are essentially reverse of each other, maintaining the balance in nature.

🎯 Exam Tip: Write both equations clearly and remember that photosynthesis stores energy while respiration releases it.

Solution 19:
Answer:
Chlorophyll.

📝 Teacher's Note: This is the key pigment that makes photosynthesis possible. Without it, plants cannot capture light energy.

🎯 Exam Tip: Remember that chlorophyll is essential for capturing light energy and converting it to chemical energy.

Solution 20:
Answer:
True

📝 Teacher's Note: This statement emphasizes the global importance of photosynthesis for all life forms.

🎯 Exam Tip: Remember that even carnivores ultimately depend on photosynthesis through food chains.

Solution 21:
Answer:
False

📝 Teacher's Note: Clarify the misconception here - identify what makes this statement false.

🎯 Exam Tip: Always read true/false questions carefully and think about exceptions or specific conditions.

Solution 22:
Answer:
During the day transpiration and photosynthesis are interlinked as the stomata opens to facilitate the inward diffusion of carbon dioxide for photosynthesis which also leads to loss of water vapours to the outside during transpiration.

📝 Teacher's Note: Help students understand that stomata serve dual purposes - gas exchange for photosynthesis and water loss through transpiration.

🎯 Exam Tip: Mention that stomata opening for CO2 uptake inevitably leads to water loss - this is the link between the two processes.

Solution 23:
Answer:
1. Destarched plant is the plant which lacks starch. Destarching is done by keeping the plant in dark for 2-3 days or covering a part of a leaf with a black paper by clip.
2. (a) The leaf is plucked and is boiled in water and decolourized with alcohol.
(b) The portion of leaf which received light turns blue with iodine because photosynthesis took place in that part of leaf.
(c) The part of leaf which was covered with black paper remains colourless because photosynthesis could not take place in the absence of sunlight.
This shows that starch is not manufactured in the absence of light.

📝 Teacher's Note: Explain why destarching is necessary - to ensure that any starch detected is newly formed during the experiment, not from previous photosynthesis.

🎯 Exam Tip: Always mention the three steps: destarching, experimental setup, and iodine testing with expected results.

Solution 24:
Answer:
1. Chloroplast.
2. Glucose and oxygen.
3. Fungi, insects and animals.
4. Photolysis.
5. Magnesium.
6. Chloroplast.

📝 Teacher's Note: These are key terms students must know. Create memory aids or mnemonics to help them remember.

🎯 Exam Tip: Practice these fill-in-the-blank type questions as they test precise knowledge of terminology.

Solution 25:
Answer:
1. True
2. True
3. False
4. True
5. True
6. True
7. False
8. False
9. True

📝 Teacher's Note: Go through each statement and explain why it's true or false. This reinforces key concepts.

🎯 Exam Tip: Read each statement carefully and think about the scientific accuracy before marking true or false.

Solution 26:
Answer:
1. Photosynthesis
2. Atmosphere
3. Glucose
4. Yellow
5. Chloroplast
6. Glucose and oxygen
7. Stomata

📝 Teacher's Note: These terms are fundamental to understanding photosynthesis. Ensure students can spell them correctly.

🎯 Exam Tip: Pay attention to spelling in fill-in-the-blank questions as marks may be deducted for incorrect spelling.

Solution 27:
Answer:
1. (d) During night
2. (e) Green plants
3. (f) Oxygen
4. (b) Light reaction
5. (a) Decomposers

📝 Teacher's Note: These matching questions test understanding of when, where, and what happens in photosynthesis.

🎯 Exam Tip: Read all options before matching and ensure each answer makes logical sense in the context.

Solution 28:
Answer:
Chloroplasts are the cell organelles in green plants which have chlorophyll and thus serve as the main site of photosynthesis.

📝 Teacher's Note: Emphasize that chloroplasts are like tiny factories where photosynthesis occurs. Show diagrams of chloroplast structure.

🎯 Exam Tip: Mention that chloroplasts contain chlorophyll and are the specific location where photosynthesis takes place.

Solution 29:
Answer:
1. Large surface area of leaves.
2. Presence of more stomata.
3. The thinness of leaves.

📝 Teacher's Note: Relate each adaptation to its function - large surface for light capture, stomata for gas exchange, thinness for efficient diffusion.

🎯 Exam Tip: Always explain HOW each structural feature helps in photosynthesis for complete answers.

Solution 30:
Answer:
Carbon cycle is a series of chemical reactions in which atmospheric carbon dioxide is used 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.

📝 Teacher's Note: Draw a simple carbon cycle diagram showing how carbon moves between atmosphere, plants, animals, and soil.

🎯 Exam Tip: Mention both the removal of CO2 (by photosynthesis) and return of CO2 (by respiration, combustion, decay) to show the complete cycle.

Solution 31:
Answer:
Carbon in the form of carbon dioxide enters living organisms and then goes back to the atmosphere through several pathways forming the true carbon cycle. Thus, it helps in maintaining the balance of nature.

📝 Teacher's Note: Emphasize how this cycle maintains atmospheric balance and supports all life on Earth.

🎯 Exam Tip: Always mention that the carbon cycle maintains balance between CO2 production and consumption in nature.

Solution 32:
Answer:
The amount of carbon dioxide in the atmosphere is increasing due to increased human activities like burning of fossil fuels, deforestation, etc. which cause the rise in global temperatures. This global warming result in melting of polar ice caps, floods in coastal areas, disturbance in hydrogenic cycle etc. Thus "Human activities are harmful to the balance of nature".

📝 Teacher's Note: Connect this to current environmental issues and help students understand their role in environmental conservation.

🎯 Exam Tip: Mention specific human activities and their consequences to show understanding of environmental impact.

Solution 33:
Answer:
Carbon dioxide is removed from the atmosphere by:
1. Producers – Producers or green plants use carbon dioxide through photosynthesis. A small amount of carbon dioxide is used by chemosynthetic bacteria also.
2. 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.

📝 Teacher's Note: Highlight the importance of forests and oceans as carbon sinks. Discuss why deforestation and ocean pollution are major concerns.

🎯 Exam Tip: Mention both terrestrial (land plants) and aquatic (marine organisms) methods of CO2 removal.

Solution 34:
Answer:
1. Carbon dioxide is returned back to the atmosphere mainly through the following ways:
• Respiration – Animals and plants respire and release carbon dioxide in the atmosphere.
• Decay – Plants and animals decay organic matter with the help of bacteria and fungi and release carbon dioxide.
• Combustion – Plants and animals which got buried under the soil changed into coal and oil and releases carbon dioxide when these are burnt.
• Ocean water – Carbon dioxide occurs in the form of lime stone in molluscan shells and as by product of photosynthesis in marine water.
2. (i) To show that sunlight is needed for photosynthesis.
(ii) Yes, the uncovered portion of the experimental leaf is the control.
(iii) To destarch the leaf.
(iv) 1. Boil the leaf in alcohol.
2. Wash the leaf in water to make it soft.
3. Add iodine solution on the leaf. The portion uncovered shows blue-black colour and the portion covered shows brown colour. This indicates that sunlight is needed for photosynthesis.

📝 Teacher's Note: Explain how human activities like burning fossil fuels add extra CO2 beyond natural cycles, causing imbalance.

🎯 Exam Tip: List all four ways CO2 returns to atmosphere and always mention the control in experimental descriptions.

Solution 35:
Answer:
1. (e) 5
2. (a) 1
3. (b) 2
4. (e) 5

📝 Teacher's Note: These matching questions require understanding of experimental procedures and their purposes.

🎯 Exam Tip: Read the question carefully and match based on logical sequence or functional relationships.

Solution 36:
Answer:
1. leaves
2. water
3. hydrogen ion
4. photolysis
5. hydrogen
6. NADPH2
7. ATP
8. photophosphorylation
9. glucose
10. polymerization

📝 Teacher's Note: These terms describe the biochemical pathway of photosynthesis. Help students understand the sequence of events.

🎯 Exam Tip: Understand the order of these processes in photosynthesis - from light absorption to glucose formation.

Solution 37:
Answer:
1. (d) 3.5
2. (b) Oxygen
3. (c) Water
4. (c) Decrease because the temperature drops.
5. (b) Increases because more photosynthesis occurs.

📝 Teacher's Note: These questions test understanding of factors affecting photosynthesis rate and the relationship between temperature, light, and photosynthesis.

🎯 Exam Tip: Remember that photosynthesis rate is affected by light intensity, temperature, and CO2 concentration.

Solution 38:
Answer:
(i) Sunlight
(ii) To destarch the leaf.
(iii) (1) The leaf was kept in boiling water to kill the cells/releases the starch grains.
(2) It is kept in methylated spirit to remove chlorophyll.
(iv) Iodine
(v) At the end of the starch test it is observed that the covered part of the leaf remains brown and the exposed part of the leaf remains blue-black.
(vi) \[ 6CO_2 + 12H_2O \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} C_6H_{12}O_6 + 6O_2 + 6H_2O \]

📝 Teacher's Note: Walk through each step of the starch test experiment, explaining the scientific reason for each procedure.

🎯 Exam Tip: Remember the complete procedure: destarch, cover part of leaf, expose to light, test with iodine, observe results.

Solution 39:
Answer:
1. (d) To stop synthesis process in the leaves.
2. (c) Chloroplasts
3. (d) split water
4. (c) Palisade mesophyll
5. (b) ADP
6. (b) liberate O2
7. (a) Grana
8. (b) Red light
9. (d) Carbon dioxide
10. (d) water, carbon dioxide, chlorophyll and sunlight

📝 Teacher's Note: These multiple choice questions cover various aspects of photosynthesis structure and function. Review each concept thoroughly.

🎯 Exam Tip: Remember that photosynthesis requires four main things: water, CO2, chlorophyll, and sunlight. Red light is most effective for photosynthesis.