1. 9C Plants and photosynthesis
Green and growing
Leaves and photosynthesis
Photosynthesis and the environment

2. 9C Plants and photosynthesis
Green and growing

3. What’s the role of the Sun in helping the tomatoes grow?
9C Photosynthesis matters
Brian started with bare soil and a packet of seeds. Now he has tomatoes for his family all summer.
The tomatoes contain lots of chemicals that were not there at the start. Where have they come from?
What’s the role of the Sun in helping the tomatoes grow?

4. Photosynthesis is a chemical reaction that happens in the leaf.
9C The process of photosynthesis
Photosynthesis is a chemical reaction that happens in the leaf.
carbon dioxide
sunlight
oxygen
water
glucose
photosynthesis
TO AIR OR USED FOR RESPIRATION
What are the reactants?
PRODUCT
Where do they come from?
REACTANT
FROM AIR
What are the products of the reaction?
PRODUCT
USED BY PLANT
What happens to the products?
REACTANT
FROM SOIL

5. Plants make glucose by photosynthesis. This is how they grow.
9C Where does the sugar go?
Plants make glucose by photosynthesis. This is how they grow.
carbon dioxide from the air
water from soil
photosynthesis
oxygen
glucose
out of leaf through stomata
carbon dioxide from the air
water from soil
photosynthesis
oxygen
glucose
out of leaf through stomata
some oxygen and glucose used in respiration
cellulose for cell walls
proteins for growth and enzymes
starch for storage
fats and oils for storage
Glucose is a sugar. But a plant is not just sugar! It makes lots of other chemicals so it can grow.
Starch is one chemical that a plant makes. A potato stores starch. How does the starch get there, when glucose is made in the leaf?

6. 9C All mixed up
Match the reactants with their products to complete the word equations.
Respiration
oxygen +
sugar
carbon dioxide +
water
Photosynthesis
light energy taken in
carbon dioxide +
water
oxygen +
sugar
carbon dioxide
sugar
water
oxygen

7. We can use this apparatus to measure the rate of photosynthesis. How?
9C Faster photosynthesis
How fast does a plant photosynthesise? This question is very important to farmers and growers.
light source
oxygen collects
test tube
water
pondweed (Elodea)
beaker
funnel
We can use this apparatus to measure the rate of photosynthesis. How?
We might count the oxygen bubbles per minute, or collect the gas given off in one minute and measure its volume.
What would happen if we increased the light level?

8. bubbles of oxygen per minute
9C Faster photosynthesis
Here are some results from the pondweed experiment.
light level
bubbles of oxygen per minute
very high 24
high 22
medium 15
low 7
very low
What effect does light have on the rate of photosynthesis?
What would happen if we put a layer of oil on the water?
This stops carbon dioxide from the air dissolving in the water.

9. 9C Photosynthesis myths?
True or false?
5. Roots carry out half the photosynthesis that takes place in a healthy oak tree.
4. Plants look green because they contain the chemical chlorophyll.
6. Plants give out carbon dioxide when they are photosynthesising.
3. Photosynthesis and respiration work in opposite directions.
1. Photosynthesis only happens in the light.
2. Plants make food from oxygen and sunlight.
They are vital to the plant but roots cannot carry out photosynthesis – they’re underground in the dark.
FALSE!
Plants need carbon dioxide from the air and water from the soil to build sugars. Oxygen is produced in photosynthesis. 
FALSE!
Chlorophyll absorbs all the colours in light except green – we see the green light because it is reflected from the plant.
TRUE!
They take in carbon dioxide. Oxygen is produced by photosynthesis.
FALSE!
Without light energy, the reactions of photosynthesis cannot work.
TRUE!
Photosynthesis produces glucose and oxygen, while respiration breaks them down to make carbon dioxide and water.
TRUE!

10. Leaves and photosynthesis
9C Plants and photosynthesis
Leaves and photosynthesis

11. 9C Food factories
Plants are food factories! They are adapted to carry out photosynthesis quickly. How does this help them?
Most photosynthesis happens in the leaves. Can you give three ways in which these leaves are adapted to be food factories?

12. 9C Design a food factory
Photosynthesis needs light. You are going to design a light-catching machine.

13. 9C Design a food factory
Chloroplasts use light to make sugar. Where would you put these to make the most of the light?

14. 9C Design a food factory
Photosynthesis needs carbon dioxide. How does this gas get into the leaf?

15. Photosynthesis needs water. How can you get it into the leaf?
9C Design a food factory
Photosynthesis needs water. How can you get it into the leaf?

16. stomata to let carbon dioxide into the leaf
9C Design a food factory
If you’re a dynamite designer, you should have a food-making factory that looks something like this:
tightly packed palisade cells full of chloroplasts
spongy mesophyll with air spaces so gases can move around
veins to bring water up from the roots, and also take sugar back down to the roots for storage
stomata to let carbon dioxide into the leaf

17. 1. Leaves are adapted for… a) pollination b) photosynthesis
9C Quiz
1. Leaves are adapted for…
a) pollination
b) photosynthesis
c) photography.
2. Stomata are...
a) holes in a leaf that can open and close to let gases in and out
b) the cells that carry out photosynthesis
c) small stones found in your stomach.

18. 3. Leaves are covered with a thin waterproof layer called the…
9C Quiz
3. Leaves are covered with a thin waterproof layer called the…
a) popsicle
b) cuticle
c) waxicle.
4. Leaves have a large surface area to...
a) increase the rate of reactions
b) catch the maximum amount of sunlight
c) look pretty in parks and gardens.

19. 5. Palisade mesophyll is in the upper part of the leaf because…
9C Quiz
5. Palisade mesophyll is in the upper part of the leaf because…
a) it needs to capture as much sunlight as possible
b) the lower areas were already full
c) it stops the upper surface from collapsing.
6. Spongy mesophyll has large air spaces between the cells to...
a) allow veins into the leaf
b) cut down the amount of cellulose needed to build new cell walls
c) give room for gases to move more easily.

20. Photosynthesis and the environment
9C Plants and photosynthesis
Photosynthesis and the environment

21. Respiration and photosynthesis are like a pair of energy twins.
9C Meet the energy twins
Respiration and photosynthesis are like a pair of energy twins.
oxygen + glucose
sunlight energy
photosynthesis
respiration
carbon dioxide + water
energy released
How do these energy twins work together to keep our atmosphere in balance?
Where would we be without sunlight and green plants?

22. All of our food comes originally from plants.
9C Food, medicines, and ...
All of our food comes originally from plants.
That’s true even if you only eat steak!
Why?
Many powerful drugs come from plants. Aspirin first came from the bark of willow trees. Powerful new anti-cancer drugs are made from yew trees.
Wood, hay and bamboo are used all over the world for building.
Linen and cotton are both fabrics made from plants.
What else can we get from plants?

23. What does deforestation do to the atmosphere?
9C The rainforest question
Rainforests are very complex ecosystems. Scientists estimate that thousands of unknown species live there.
But the people living in rainforests need to live now. They cut down the trees for building and furniture. They grow crops on the land, but this destroys the soil.
What does deforestation do to the atmosphere?
What other problems does it cause?

24. Local people need money. They need to harvest the forests now.
9C Rainforest answers?
Most of the money is earned by a few rich companies. The people who live in the forests get nothing – and they lose their homes.
Local people need money. They need to harvest the forests now.
People in the rich world cut down all of their forests centuries ago – they can’t tell people in the developing world not to do the same!
How many future life-saving drugs have we already lost from the rainforests? How many unknown species have we made extinct?
What do you think?