Photosynthesis

플레이하며 배우기

이 문제들을 풀어 에너지를 얻은 뒤 낚시하고 탐험하세요. 계정이 필요 없어요.

교육자를 위해: Photosynthesis(Science, Biology)을(를) 위한 바로 쓸 수 있는 수업 슬라이드, 복습 노트 — 수업에 사용하거나, 학습자들이 실시간 게임으로 즐기는 인터랙티브 클래스 활동으로 진행하세요.

수업 노트

The Photosynthetic Reaction

Photosynthesis is the process by which plants make their own food using light, water and carbon dioxide.
Plants are producers because they make their own food, and they are the first organism in most food chains.
Photosynthesis is an endothermic reaction: energy is transferred from the environment to the chloroplasts by light.
The word equation is: carbon dioxide + water → glucose + oxygen (light energy is needed).
The balanced symbol equation is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
The reactants are carbon dioxide and water; the products are glucose and oxygen.
Most photosynthesis happens in the leaves, in mesophyll cells packed with chloroplasts containing chlorophyll to absorb light energy.
The glucose made is used to build all the substances a plant needs and is also used in respiration to release energy.

Factors Affecting the Rate of Photosynthesis

The rate of photosynthesis is affected by light intensity, carbon dioxide concentration, temperature and the amount of chlorophyll.
Although water is needed, it is not considered a limiting factor because the amount required is small compared to the amount lost by transpiration.
A limiting factor is something in short supply that restricts the rate of photosynthesis.
Temperature affects the kinetic energy of particles: lower temperatures mean fewer successful collisions between reactants and enzymes, so the rate is slower.
As temperature increases, particles have more kinetic energy and collisions become more likely, increasing the rate.
At high temperatures, the enzymes controlling photosynthesis can become denatured, so the rate falls.
Light intensity: the more light a plant receives, the faster the rate, until another factor becomes limiting.
Carbon dioxide concentration: more carbon dioxide increases the rate, until another factor becomes limiting.
Chlorophyll: more chloroplasts means more chlorophyll, so the rate is faster; chlorophyll amount can be reduced by diseases (e.g. tobacco mosaic virus), lack of nutrients (e.g. magnesium) or loss of leaves.

Investigating light intensity and rate of photosynthesis

Interactions of Limiting Factors (Higher Tier)

More than one limiting factor can affect the rate of photosynthesis at the same time.
On a graph, if the rate is increasing as the variable on the x-axis increases, that variable is the limiting factor.
If the graph levels off (becomes horizontal), the factor on the x-axis is no longer limiting; something else is now in short supply.
For example, at low light intensities both lines on a graph may show the same rate because light is limiting; at higher light intensities the line for the lower temperature is lower, showing temperature is now limiting.
When three factors interact, the highest rate occurs when temperature and carbon dioxide concentration are both high, and light is not limiting.
In some experiments, carbon dioxide concentration is the limiting factor even when light intensity increases.

Light Intensity and the Inverse Square Law (Higher Tier)

Light intensity decreases as the distance from the light source increases.
Light intensity is inversely proportional to the square of the distance: light intensity ∝ 1/d².
If the distance doubles, the light intensity decreases by a factor of four.
Calculating 1/d² gives a relative light intensity in arbitrary units, not an absolute value in lux.
Example: if the distance is 30 cm, relative light intensity = 1/30² = 1/900 = 0.001 arbitrary units.

Required Practical: Investigating the Rate of Photosynthesis

Aim: investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed (Elodea or Cabomba).
The rate is measured by counting the oxygen bubbles released per minute, or by collecting the gas in a gas syringe to measure volume.
Method: place pondweed in a beaker of water, position a light source a set distance away, record bubbles per minute, repeat at least twice and calculate a mean, then repeat for different distances.
A glass tank of water is placed between the lamp and the plant to absorb heat and prevent the temperature from changing; an LED bulb can also be used as it releases little heat.
To investigate carbon dioxide, use different concentrations of sodium hydrogencarbonate in the water.
To investigate temperature, change the temperature of the water surrounding the pondweed using water baths.
Control variables: keep other factors constant, use the same plant or species, and repeat for reliability.
Results: as distance decreases (light intensity increases), the volume of oxygen produced increases, until another factor becomes limiting.

Uses of Glucose from Photosynthesis

Glucose produced in photosynthesis is used for respiration (aerobic and anaerobic) to release energy.
It is converted into insoluble starch for storage in stems, leaves and roots.
It is used to produce fat or oil for storage, especially in seeds.
It is used to produce cellulose, which strengthens the cell wall.
It combines with nitrate ions absorbed from the soil to produce amino acids for protein synthesis.
Glucose is also used to make sucrose for transport in the phloem, and nectar to attract insects for pollination.

Testing a Leaf for Starch

A test for starch shows whether photosynthesis has been taking place.
Method: boil the leaf in water, then place it in ethanol for 10 minutes, wash it in water, place it on a white tile and add iodine solution.
Iodine solution is a qualitative reagent; it starts brown and turns blue-black if starch is present.
Glucose made during photosynthesis is converted to starch, so this test can show the effect of light on photosynthesis.
Plants always respire, but they only photosynthesise during the day if conditions are right.

Testing a leaf for starch

Greenhouses and Limiting Factors (Higher Tier)

Commercial growers use greenhouses to control limiting factors and maximise the rate of photosynthesis.
They control levels of heat, light, water, carbon dioxide and nutrients to increase yield.
The aim is to gain the maximum rate of photosynthesis while still making a profit.
Increasing a factor beyond the point where it has an effect is a waste of money, because another factor is limiting.
For example, adding more carbon dioxide when light is limiting will not increase the rate and wastes money.

슬라이드

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

가입 — 무료 로그인

연습 문제

무료 미리 보기 — 65개 중 8개 문제. 가입하면 전부 볼 수 있어요.

1.Which of the following is the correct word equation for photosynthesis?
Easy
- Acarbon dioxide + water → glucose + oxygen
- Bglucose + oxygen → carbon dioxide + water
- Ccarbon dioxide + oxygen → glucose + water
- Dglucose + water → carbon dioxide + oxygen
2.Which chemical formula represents glucose?
Easy
- AC6H12O6
- BCO2
- CH2O
- DO2
3.Photosynthesis is an endothermic reaction.
Easy
True or false?
4.Which of the following is a limiting factor of photosynthesis?
Medium
- ALight intensity
- BSoil pH
- CWind speed
- DDay length
5.Which of the following are uses of glucose in a plant? (select all that apply)
Medium
- AConverted into starch for storage
- BUsed to produce cellulose for cell walls
- CUsed in respiration to release energy
- DConverted into oxygen for release
- EUsed to produce fat or oil for storage
6.Match each term with its correct definition.
Medium
- Endothermic
- Chlorophyll
- Limiting factor
- A reaction that takes in energy from the environment
- The green pigment that absorbs light energy
- Something in short supply that restricts a process
7.A student investigates the effect of light intensity on the rate of photosynthesis using pondweed. Why is a glass tank placed between the lamp and the plant?
Medium
- ATo absorb heat from the lamp and prevent the temperature of the water changing
- BTo increase the amount of light reaching the plant
- CTo supply carbon dioxide to the plant
- DTo filter out harmful UV radiation
8.Which statement about water as a limiting factor of photosynthesis is correct?
Medium
- AWater is not usually a limiting factor because the amount needed is small compared to the amount transpired.
- BWater is always the main limiting factor in photosynthesis.
- CWater is not needed for photosynthesis.
- DWater limits photosynthesis only at night.

더 많은 문제

9.Which of the following are products of photosynthesis? (select all that apply)
Medium
- Aoxygen
- Bglucose
- Ccarbon dioxide
- Dwater
- Echlorophyll
10.Which of the following factors can limit the rate of photosynthesis? (select all that apply)
Hard
- Atemperature
- Blight intensity
- Ccarbon dioxide concentration
- Doxygen concentration
- Eamount of chlorophyll
11.A student investigates the effect of light intensity on the rate of photosynthesis using pondweed. Which of the following variables should be controlled? (select all that apply)
Hard
- Atemperature
- Bcarbon dioxide concentration
- Clight intensity
- Dvolume of water in the beaker
- Edistance from the lamp
12.Which of the following statements about the inverse square law and light intensity are correct? (select all that apply)
Hard
- ALight intensity is inversely proportional to the square of the distance from the light source.
- BIf the distance from the light source doubles, the light intensity decreases by a factor of four.
- CLight intensity is directly proportional to the distance from the light source.
- DAs the distance from the light source increases, light intensity decreases.
- EIf the distance from the light source halves, the light intensity decreases by a factor of two.
13.Water is usually not considered a limiting factor of photosynthesis because the amount needed is relatively small compared to the amount lost by transpiration.
Easy
True or false?
14.At high temperatures, the enzymes controlling photosynthesis can be denatured, reducing the rate of photosynthesis.
Medium
True or false?
15.If the distance between a plant and a light source is doubled, the light intensity increases by a factor of four.
Medium
True or false?
16.Match each limiting factor of photosynthesis with its effect on the rate.
Medium
- Temperature
- Light intensity
- Carbon dioxide concentration
- Chlorophyll amount
- Affects kinetic energy and enzyme activity
- Provides energy for the reaction
- Raw material for making glucose
- Pigment that absorbs light energy
17.Match each use of glucose in a plant with its correct description.
Hard
- Respiration
- Starch
- Cellulose
- Amino acids
- Releases energy for cell processes
- Insoluble storage molecule in stems, leaves and roots
- Strengthens the cell wall
- Made by combining glucose with nitrate ions
18.Place the steps of the starch test in the correct order.
Medium
- Boil the leaf in water
- Place the leaf in ethanol
- Wash the leaf in water
- Add iodine solution to the leaf
19.Arrange the steps of the pondweed practical in the correct order.
Medium
- Place pondweed in a beaker of water
- Set the light a fixed distance from the plant
- Record the number of bubbles produced in one minute
- Repeat at different distances
20.A student sets up pondweed 10 cm from a lamp and records 24 bubbles per minute. They then move the lamp so the pondweed is 20 cm away. Assuming light intensity is the only limiting factor, what is the expected number of bubbles per minute?
Medium
- A12
- B6
- C48
- D24
21.A plant is placed 25 cm from a lamp. Using the inverse square law, what is the relative light intensity in arbitrary units?
Easy
- A0.04
- B0.0016
- C0.0025
- D0.16
22.A student investigates the effect of light intensity on pondweed. They place a glass tank of water between the lamp and the plant. Why is this done?
Medium
- ATo absorb heat from the lamp so the temperature of the pondweed does not change.
- BTo increase the amount of carbon dioxide available to the plant.
- CTo filter out harmful ultraviolet light.
- DTo magnify the light so the plant receives more light.
23.Which of the following are valid ways to measure the rate of photosynthesis in an aquatic plant? (Select all that apply.)
Medium
- ACounting the number of bubbles produced per minute.
- BMeasuring the volume of gas collected in a gas syringe over a set time.
- CMeasuring the change in temperature of the water.
- DMeasuring the change in mass of the plant over one hour.
- ECounting the number of leaves on the plant.
24.If the distance between a plant and a light source is halved, the light intensity increases by a factor of four.
Easy
True or false?
25.A farmer grows tomatoes in a greenhouse. Adding extra carbon dioxide increases the yield up to a concentration of 700 ppm, but above this the yield does not increase further. Which statement best explains this?
Medium
- AAnother factor, such as light intensity or temperature, has become limiting.
- BThe plants have become resistant to carbon dioxide.
- CThe extra carbon dioxide is toxic to the plants.
- DThe plants have stopped respiring.
26.A plant is kept in the dark for 48 hours. A leaf is then tested with iodine solution. What is the expected result and why?
Easy
- AThe leaf turns blue-black because starch is still present.
- BThe leaf stays brown because no starch has been made in the dark.
- CThe leaf turns blue-black because glucose is stored as starch.
- DThe leaf stays brown because the plant has been respiring.
27.A plant is placed 20 cm from a lamp. The relative light intensity is 0.0025 arbitrary units. If the plant is moved to 40 cm from the lamp, what is the new relative light intensity?
Medium
- A0.000625 arbitrary units
- B0.00125 arbitrary units
- C0.005 arbitrary units
- D0.01 arbitrary units
28.A student investigates the effect of light intensity on pondweed. They place a glass tank of water between the lamp and the plant. What is the purpose of the glass tank?
Medium
- ATo absorb heat from the lamp so the temperature of the water around the pondweed does not change.
- BTo increase the light intensity reaching the pondweed.
- CTo provide carbon dioxide for the pondweed.
- DTo magnify the light so the pondweed photosynthesises faster.
29.A graph shows the rate of photosynthesis of pondweed against light intensity at two different carbon dioxide concentrations. At low light intensities, both curves are identical. At higher light intensities, the curve for the higher carbon dioxide concentration is higher. What does this show?
Hard
- AAt low light intensities, light is the limiting factor; at higher light intensities, carbon dioxide becomes limiting.
- BAt low light intensities, carbon dioxide is the limiting factor; at higher light intensities, light becomes limiting.
- CLight intensity never limits photosynthesis.
- DCarbon dioxide concentration has no effect on the rate of photosynthesis.
30.A farmer adds extra carbon dioxide to a greenhouse. The yield increases until the carbon dioxide concentration reaches 700 ppm, but above this the yield does not increase further. Which statement best explains why the farmer should not add more carbon dioxide above 700 ppm?
Medium
- AAt 700 ppm, another factor such as light intensity or temperature is limiting the rate, so adding more carbon dioxide would be a waste of money.
- BAt 700 ppm, carbon dioxide becomes toxic to the plants and stops photosynthesis.
- CAt 700 ppm, the plants stop respiring, so they cannot grow.
- DAt 700 ppm, the stomata close and prevent any gas exchange.
31.Which of the following is the correct balanced symbol equation for photosynthesis?
Medium
- A6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
- BC₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
- C6CO₂ + 6H₂O → C₆H₁₂O₆ + O₂
- DCO₂ + H₂O → C₆H₁₂O₆ + O₂
32.Which of the following statements about the inverse square law and light intensity is correct?
Medium
- AIf the distance between a plant and a light source is doubled, the light intensity decreases by a factor of four.
- BIf the distance between a plant and a light source is doubled, the light intensity increases by a factor of four.
- CIf the distance between a plant and a light source is halved, the light intensity decreases by a factor of two.
- DLight intensity is directly proportional to the distance from the light source.
33.Which of the following statements about limiting factors of photosynthesis are correct? (Select all that apply.)
Medium
- AAt low light intensities, light is usually the limiting factor.
- BWater is usually not a limiting factor because the amount needed is small compared to the amount lost by transpiration.
- CAt high temperatures, enzymes can denature and reduce the rate of photosynthesis.
- DIf carbon dioxide concentration is increased indefinitely, the rate of photosynthesis will continue to increase indefinitely.
- EChlorophyll deficiency can limit the rate of photosynthesis.
34.Photosynthesis is an endothermic reaction because it takes in energy from the environment.
Easy
True or false?
35.If the distance between a plant and a light source is tripled, the light intensity decreases by a factor of three.
Easy
True or false?
36.Plants respire only at night and photosynthesise only during the day.
Easy
True or false?
37.Match each limiting factor of photosynthesis with its effect on the rate of photosynthesis.
Medium
- Low temperature
- High temperature
- Low light intensity
- Low carbon dioxide concentration
- Fewer successful collisions between reactants and enzymes, reducing the rate
- Enzymes denature and the rate decreases
- Less energy is available for photosynthesis, reducing the rate
- Fewer carbon dioxide molecules are available to react, reducing the rate
38.A student sets up pondweed in a beaker and shines a lamp on it. They count the number of bubbles produced in one minute at each distance. Why do they repeat the experiment at least twice at each distance and calculate a mean?
Medium
- ATo increase the reliability of the results
- BTo increase the rate of photosynthesis
- CTo make the bubbles easier to count
- DTo control the temperature of the water
39.In an investigation into the effect of light intensity on pondweed, the student uses a 1% sodium hydrogencarbonate solution instead of plain water. What is the purpose of this solution?
Medium
- ATo provide a controlled supply of carbon dioxide
- BTo provide a controlled supply of oxygen
- CTo prevent the pondweed from overheating
- DTo ensure the pondweed sinks to the bottom of the beaker
40.A student investigates the effect of light intensity on pondweed. They place the lamp at 10 cm, 20 cm, 30 cm and 40 cm from the plant. Which variable is the independent variable?
Hard
- AThe distance of the lamp from the pondweed
- BThe number of bubbles produced per minute
- CThe temperature of the water
- DThe concentration of carbon dioxide
41.Complete the word equation for photosynthesis.
Medium
carbon dioxide + ____ → glucose + ____
42.Name the green pigment in chloroplasts that absorbs light energy for photosynthesis.
Easy
43.A plant is placed 30 cm from a lamp. Using the inverse square law, calculate the relative light intensity in arbitrary units. Give your answer to 3 decimal places.
Medium
44.A lamp is placed 50 cm from a plant. Using the inverse square law, calculate the relative light intensity in arbitrary units. Give your answer to 4 decimal places.
Medium
45.Complete the sentence about the effect of temperature on photosynthesis.
Medium
At low temperatures, particles have less ____ energy, so fewer successful ____ occur.
46.Complete the sentence about the inverse square law.
Medium
If the distance from a light source is tripled, the light intensity becomes ____ times smaller.
47.A lamp is placed 40 cm from a plant. Using the inverse square law, calculate the relative light intensity in arbitrary units. Give your answer to 5 decimal places.
Medium
48.A lamp is placed 15 cm from a plant. Using the inverse square law, calculate the relative light intensity in arbitrary units. Give your answer to 4 decimal places.
Medium
49.A lamp is placed 5 cm from a plant. Using the inverse square law, calculate the relative light intensity in arbitrary units.
Medium
50.A plant is placed 60 cm from a lamp. Using the inverse square law, calculate the relative light intensity in arbitrary units. Give your answer to 5 decimal places.
Hard
51.A student counts 40 bubbles per minute when pondweed is 10 cm from a lamp. They move the lamp so the pondweed is 40 cm away. Assuming light intensity is the limiting factor, how many bubbles per minute would be expected?
Hard
52.A pondweed plant releases 18 bubbles of gas in one minute. Calculate the rate of bubble production per second. Give your answer to 2 decimal places.
Medium
53.Explain why the rate of photosynthesis levels off at high light intensities.
Hard
54.A farmer grows tomato plants in a greenhouse. Suggest three things the farmer could do to increase the yield of the tomato plants.
Hard
55.A student sets up pondweed in a beaker of water and shines a lamp on it from 10 cm away. They count 30 bubbles in one minute. They then place the lamp 20 cm away and count 8 bubbles in one minute. The student expects the count to be 7.5. Explain why the student's expectation is reasonable, and suggest why the actual count might be slightly higher.
Hard
56.A student sets up pondweed in a beaker of water and shines a lamp on it from 10 cm away. They count 30 bubbles in one minute. They then place the lamp 20 cm away. Explain how the number of bubbles would change and why.
Hard
57.A gardener is advised to cover all the greenhouse windows with black card to stop the plants getting too hot. Explain why this advice is not good for growing vegetables.
Medium
58.A plant is placed 30 cm from a lamp. Using the inverse square law, calculate the relative light intensity in arbitrary units. Give your answer to 3 decimal places.
Medium
- A1.001 arbitrary units
- B-0.999 arbitrary units
- C0.001 arbitrary units
- D2.001 arbitrary units
59.A lamp is placed 50 cm from a plant. Using the inverse square law, calculate the relative light intensity in arbitrary units. Give your answer to 4 decimal places.
Medium
- A-0.9996 arbitrary units
- B0.0004 arbitrary units
- C2.0004 arbitrary units
- D1.0004 arbitrary units
60.A lamp is placed 40 cm from a plant. Using the inverse square law, calculate the relative light intensity in arbitrary units. Give your answer to 5 decimal places.
Medium
- A-0.9994 arbitrary units
- B1.0006 arbitrary units
- C2.0006 arbitrary units
- D0.00063 arbitrary units
61.A lamp is placed 15 cm from a plant. Using the inverse square law, calculate the relative light intensity in arbitrary units. Give your answer to 4 decimal places.
Medium
- A1.0044 arbitrary units
- B2.0044 arbitrary units
- C-0.9956 arbitrary units
- D0.0044 arbitrary units
62.A lamp is placed 5 cm from a plant. Using the inverse square law, calculate the relative light intensity in arbitrary units.
Medium
- A1.04 arbitrary units
- B0.04 arbitrary units
- C-0.96 arbitrary units
- D2.04 arbitrary units
63.A plant is placed 60 cm from a lamp. Using the inverse square law, calculate the relative light intensity in arbitrary units. Give your answer to 5 decimal places.
Hard
- A2.0003 arbitrary units
- B1.0003 arbitrary units
- C0.00028 arbitrary units
- D-0.9997 arbitrary units
64.A student counts 40 bubbles per minute when pondweed is 10 cm from a lamp. They move the lamp so the pondweed is 40 cm away. Assuming light intensity is the limiting factor, how many bubbles per minute would be expected?
Hard
- A1.5 bubbles per minute
- B2.5 bubbles per minute
- C3.5 bubbles per minute
- D4.5 bubbles per minute
65.A pondweed plant releases 18 bubbles of gas in one minute. Calculate the rate of bubble production per second. Give your answer to 2 decimal places.
Medium
- A1.3 bubbles per second
- B0.3 bubbles per second
- C2.3 bubbles per second
- D-0.7 bubbles per second

플래시카드

What is the word equation for photosynthesis?

Carbon dioxide + water → glucose + oxygen (light energy is also required).

What is the balanced symbol equation for photosynthesis?

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Which chemical formula represents carbon dioxide?

CO₂

Which chemical formula represents water?

H₂O

Which chemical formula represents oxygen?

O₂

Which chemical formula represents glucose?

C₆H₁₂O₆

What are the reactants (raw materials) of photosynthesis?

Carbon dioxide and water. Light energy is needed too, but it is not a substance so it is not a raw material.

What are the products of photosynthesis?

Glucose and oxygen.

Why is photosynthesis described as an endothermic reaction?

It takes in energy, transferring energy from the environment to the chloroplasts by light.

Where in a plant cell does photosynthesis take place?

In the chloroplasts, which contain the pigment chlorophyll that absorbs light energy.

Where in a leaf does most photosynthesis occur?

In the mesophyll cells, which are packed with chloroplasts.

Why are plants called producers in food chains?

They can make their own food (glucose) by photosynthesis, so they are the first organism in most food chains.

Define a limiting factor in photosynthesis.

Something present in the environment in such short supply that it restricts the rate of photosynthesis.

Name the three main limiting factors of photosynthesis.

Temperature, light intensity and carbon dioxide concentration.

Why is water not usually considered a limiting factor of photosynthesis?

The amount needed for photosynthesis is relatively small compared with the amount transpired, so there is hardly ever too little water for photosynthesis.

How does low temperature reduce the rate of photosynthesis?

Particles have less kinetic energy, so there are fewer successful collisions between reactants and enzymes.

Why does the rate of photosynthesis fall at very high temperatures?

The enzymes controlling photosynthesis become denatured, so their active sites are no longer complementary to their substrates.

How does increasing light intensity affect the rate of photosynthesis?

The rate increases, until some other factor becomes limiting and the rate levels off.

How does increasing carbon dioxide concentration affect the rate of photosynthesis?

The rate increases, until some other factor becomes limiting and the rate levels off.

What happens to the rate of photosynthesis when light intensity increases beyond the point where the graph levels off?

It stays constant, because another factor (such as carbon dioxide or temperature) is now limiting.

How does the amount of chlorophyll affect the rate of photosynthesis?

More chloroplasts means more chlorophyll, so more light energy is absorbed and the rate is faster.

Give three factors that can reduce the amount of chlorophyll in a plant.

Disease (e.g. tobacco mosaic virus), lack of nutrients (e.g. magnesium) and loss of leaves.

State the inverse square law for light intensity and distance.

Light intensity ∝ 1/d², so if the distance doubles the light intensity falls by a factor of four.

Calculate the relative light intensity when a plant is 30 cm from a lamp.

1/30² = 1/900 = 0.001 arbitrary units.

Why is relative light intensity measured in arbitrary units rather than lux?

Calculating 1/d² gives a mathematical measure of relative intensity, not an absolute value.

In the pondweed practical, what is measured to indicate the rate of photosynthesis?

The volume of oxygen gas produced (or the number of bubbles released) in a set time.

Why is a glass tank placed between the lamp and the pondweed?

To absorb heat from the lamp so the temperature of the water around the plant does not change.

Why is sodium hydrogencarbonate solution added to the water in the pondweed practical?

It dissolves to provide a controlled supply of carbon dioxide for the plant.

How can you investigate the effect of carbon dioxide concentration on photosynthesis using pondweed?

Add different concentrations of sodium hydrogencarbonate to the water surrounding the plant.

How can you investigate the effect of temperature on photosynthesis using pondweed?

Place the tube containing the pondweed in water baths at different temperatures.

Why is a gas syringe better than counting bubbles in the pondweed practical?

It measures the volume of gas produced, so it is not affected by bubbles being different sizes or too small to see.

Give three uses of the glucose produced in photosynthesis.

Respiration to release energy; converted to insoluble starch for storage; used to make cellulose for cell walls.

How is glucose used to make amino acids in a plant?

Glucose is combined with nitrate ions absorbed from the soil to produce amino acids for protein synthesis.

Why do plants store glucose as starch?

Starch is insoluble, so it is a suitable store of energy in the stems, leaves and roots.

What is the test for starch in a leaf?

Add iodine solution to the leaf; a blue-black colour shows starch is present.

Why is a leaf boiled in ethanol before testing for starch?

To remove the chlorophyll so the colour change of the iodine can be seen clearly.

What does a positive iodine test on a leaf show?

That the leaf contains starch, so photosynthesis has been taking place.

Why do plants respire both day and night?

Respiration releases energy for cell processes all the time, whereas photosynthesis only happens when there is enough light.

How can a farmer increase the yield of tomato plants in a greenhouse?

Control limiting factors, e.g. add artificial light, heat the greenhouse and increase carbon dioxide concentration.

Why should a farmer not raise carbon dioxide levels above the point where another factor limits photosynthesis?

It would cost money without increasing the rate of photosynthesis, so it would reduce profit.

Why can growing crops in a greenhouse be profitable despite the costs?

The increased yield and more frequent harvesting mean the farmer makes more money than the extra costs.

Unlock all 65 questions, flashcards & more

무료 계정을 만들어 이 주제의 모든 문제, 슬라이드, 플래시카드, 복습 노트를 확인하세요.

가입 — 무료 로그인

기출 문제

이 주제의 기출 문제 연습이 곧 나와요.

곧 출시