ch 6,8

Question: What is the word equation for photosynthesis?
Answer: Carbon dioxide + water → glucose + oxygen (in the presence of light and chlorophyll).

2. Question: Why is light energy not considered a raw material for photosynthesis?
Answer: Light energy is not a substance; it is a form of energy required for the reaction.

3. Question: What is the role of nitrogen in plants?
Answer: Nitrogen is needed to make amino acids, which are used to synthesize proteins.

4. Question: Which mineral is essential for chlorophyll synthesis?
Answer: Magnesium.

5. Question: What happens to leaves without chlorophyll during a starch test?
Answer: They remain orange-brown because photosynthesis does not occur, and no starch is produced.

6. Question: Why are plants destarched before photosynthesis experiments?
Answer: To ensure any existing starch is used up, so results reflect starch produced during the experiment only.

7. Question: How does light intensity affect the rate of photosynthesis?
Answer: As light intensity increases, the rate of photosynthesis increases, until another factor becomes limiting.

8. Question: What are the three main limiting factors of photosynthesis?
Answer: Light intensity, carbon dioxide concentration, and temperature.

9. Question: Why is water not considered a limiting factor in photosynthesis?
Answer: Plants need only a small amount for photosynthesis compared to the water lost through transpiration.

10. Question: What is the primary function of guard cells?
Answer: To regulate the opening and closing of stomata for gas exchange.

11. Question: What is the role of phloem in plants?
Answer: To transport food materials (sucrose and amino acids) from photosynthetic regions to other parts of the plant.

12. Question: How do root hair cells absorb water?
Answer: By osmosis, as the water potential in the soil is higher than that in the root hair cells.

13. Question: What is lignin, and what is its role in the xylem?
Answer: Lignin is a substance that thickens and strengthens xylem walls, helping them withstand water pressure.

14. Question: What is the transpiration stream?
Answer: The continuous movement of water through the xylem from roots to leaves.

15. Question: What is the primary cause of wilting in plants?
Answer: More water evaporates from leaves than is available for absorption by roots.

16. Question: What is the function of stomata during the day?
Answer: To allow the exchange of gases (intake of CO₂ and release of O₂) for photosynthesis.

17. Question: What does sodium hydroxide do in photosynthesis experiments?
Answer: It absorbs carbon dioxide to test its necessity for photosynthesis.

18. Question: How do increasing temperatures affect the rate of photosynthesis?
Answer: The rate increases until enzymes denature at high temperatures, reducing the rate.

19. Question: What is the purpose of a control experiment?
Answer: To compare results and confirm that the observed effect is due to the tested variable.

20. Question: What is the primary gas exchanged during photosynthesis?
Answer: Carbon dioxide is taken in, and oxygen is released.

21. Question: What adaptations help the leaf maximize photosynthesis?
Answer: Large surface area, thin structure, and presence of chloroplasts in palisade mesophyll cells.

22. Question: What is the significance of air spaces in spongy mesophyll?
Answer: They allow the diffusion of gases (CO₂ and O₂) within the leaf.

23. Question: How is sucrose transported in plants?
Answer: Through the phloem via translocation.

24. Question: How can wind speed influence transpiration?
Answer: Increased wind speed removes water vapor near the leaf, increasing the rate of transpiration.

25. Question: Why is the upper epidermis transparent?
Answer: To allow sunlight to pass through to the photosynthetic tissues below.

26. Question: What does the presence of bubbles in a pondweed experiment indicate?
Answer: Oxygen gas being released during photosynthesis.

27. Question: Why is the xylem important for photosynthesis?
Answer: It transports water, a raw material for photosynthesis, to the leaves.

28. Question: What color does iodine turn in the presence of starch?
Answer: Blue-black.

29. Question: What happens when light is a limiting factor in photosynthesis?
Answer: The rate of photosynthesis increases only as light intensity increases.

30. Question: How does high humidity affect transpiration?
Answer: It decreases transpiration because the air is already saturated with water vapor.

1. Photosynthesis can be defined as the process by which plants manufacture __________ from raw materials using energy from __________.
(Answer: carbohydrates, light)

2. The __________ is a green pigment found in chloroplasts that reflects __________ light and absorbs light energy for photosynthesis.
(Answer: chlorophyll, green)

3. Glucose is converted to __________ for transport in the phloem and __________ for energy storage.
(Answer: sucrose, starch)

4. The movement of water through the xylem from roots to leaves is called the __________.
(Answer: transpiration stream)

5. The process of __________ involves the transport of soluble products of photosynthesis, like sucrose and amino acids, in the __________.
(Answer: translocation, phloem)

6. When investigating the rate of photosynthesis, the effect of changing light intensity can be measured by adjusting the __________ from the beaker containing pondweed.
(Answer: distance of the lamp)

1. Question: What are the raw materials required for photosynthesis?
Answer: Carbon dioxide and water.

2. Question: What is the function of chlorophyll in photosynthesis?
Answer: Chlorophyll absorbs light energy and transfers it into chemical energy for synthesizing carbohydrates like glucose.

3. Question: Name three ways plants use carbohydrates produced during photosynthesis.
Answer:

1. Converted to starch for energy storage.

2. Used in respiration to provide energy.

3. Converted into cellulose for building cell walls.

4. Question: What is translocation in plants?
Answer: The transport of sugars (mainly sucrose) and amino acids in the phloem from source to sink.

5. Question: Which vessel transports water and minerals in plants?
Answer: Xylem vessels.

6. Question: What is the primary cause of transpiration in plants?
Answer: The loss of water vapor through the stomata due to evaporation at the mesophyll cell surfaces.

1. Question: Why is ethanol used during a starch test on leaves?
Answer: Ethanol removes chlorophyll, making it easier to see the color change with iodine.

2. Question: What precautions must be taken when using ethanol in a starch test?
Answer: Ethanol is flammable, so a water bath should be used instead of an open flame.

3. Question: How do you test for the need for carbon dioxide in photosynthesis?
Answer: Use two destarched plants, placing one near sodium hydroxide (absorbs CO₂) and the other near water. The plant near sodium hydroxide will not turn blue-black during a starch test.

4. Question: What does covering part of a leaf with aluminum foil during a light investigation show?
Answer: It demonstrates that light is essential for photosynthesis, as the covered area remains orange-brown during a starch test.

5. Question: How is the effect of light intensity on photosynthesis measured?
Answer: By counting the number of oxygen bubbles produced by pondweed at different distances from a light source.

1. Question: What symptoms does a plant show when it has a magnesium deficiency?
Answer: Yellowing of leaves (chlorosis) due to lack of chlorophyll.

2. Question: How does a nitrogen deficiency affect plant growth?
Answer: Plants have stunted growth and pale leaves due to insufficient protein and chlorophyll synthesis.

3. Question: Why is potassium important for plants?
Answer: It is required for enzyme activation and photosynthesis. A deficiency can cause poor flower and fruit development.

4. Question: What happens to a plant with a phosphorus deficiency?
Answer: Poor root growth and purple coloration on leaves.

5. Question: How do plants absorb mineral ions from the soil?
Answer: Mineral ions are actively transported into root hair cells from the soil.

Question: What are the steps to test a leaf for starch in a photosynthesis investigation?

Answer (Step-by-Step):

1. Boil the leaf in water – This kills the cells and breaks down the cell membranes.

2. Soak the leaf in hot ethanol – Removes chlorophyll, making it easier to see the iodine color change.

3. Rinse the leaf in warm water – Softens the leaf after ethanol treatment.

4. Place the leaf on a white tile – Ensures a clear background for observing the test.

5. Add iodine solution – Tests for starch. Areas with starch turn blue-black; areas without starch remain orange-brown.

Question: What are the steps to investigate the effect of light on photosynthesis?

Answer (Step-by-Step):

1. Destarch the plant – Place it in the dark for 24 hours to remove existing starch.

2. Cover part of a leaf with aluminum foil – Blocks light from reaching that area.

3. Expose the plant to sunlight – Place it in sunlight for a few hours.

4. Remove and test the leaf for starch – Follow the starch test procedure.

   • Observation: The covered area remains orange-brown, while the exposed area turns blue-black.

Question: How do you investigate the need for carbon dioxide in photosynthesis?

Answer (Step-by-Step):

1. Destarch two plants – Place them in the dark for 24 hours.

2. Place one plant near sodium hydroxide – This absorbs carbon dioxide.

3. Place the other plant near water – This acts as a control, as water does not absorb CO₂.

4. Expose both plants to sunlight – Allow photosynthesis to occur in the control plant.

5. Test a leaf from each plant for starch –

   • The plant near sodium hydroxide will remain orange-brown (no CO₂, no photosynthesis).

   • The plant near water will turn blue-black (photosynthesis occurred).