B4: Photosynthesis

Question 1

Why is the top surface of a leaf waxy?

Answer 1

To stop water escaping from the leaf.

Question 2

Which gas diffuses into a leaf?

Answer 2

Carbon dioxide

Question 3

Why are there fewer chloroplasts in the cells of the bottom side of a leaf?

Answer 3

Because sunlight mainly hits the top of leaves so chloroplasts aren’t needed on the bottom as much.

Question 4

Stomata (holes) in leaves are opened and close by special cells called…

Answer 4

……..guard cells

Question 5

How does being thin help a leaf to carry out photosynthesis?

Answer 5

Gases can move in and out of the leaf easily.

Question 6

Why is a leaf normally dark green on top but lighter on the bottom?

Answer 6

There are fewer chloroplasts on the bottom so there is less chlorophyll.

Question 7

How do gases and water get in and out of a leaf?

Answer 7

Through holes called stomata

Question 8

What is the name of the tube that carries glucose around the plant?

Answer 8

Phloem tubes

Question 9

How is the structure of a leaf suited to carry out photosynthesis?

Answer 9

• Contain chlorophyll to capture sunlight.
• They are thin
• They have a large surface area
• They have veins

Question 10

How do veins help a leaf to carry out photosynthesis?

Answer 10

They are made from xylem tubes which can transport water for photosynthesis to take place.

Question 11

How does a large surface area help a leaf to carry out photosynthesis?

Answer 11

A large surface area can absorb as much light as possible.

Question 12

Which gases are made during photosynthesis and diffuse out of a leaf?

Answer 12

Oxygen

(Water vapour)

Question 13

By which process do plants produce their own food?

Answer 13

Photosynthesis

Question 14

What is the equation for photosynthesis?

Answer 14

Carbon dioxide + water (+ sunlight) –> glucose + oxygen

Question 15

Name the reactants of photosynthesis.

Answer 15

carbon dioxide + water

Question 16

Name the products of photosynthesis.

Answer 16

glucose + oxygen

Question 17

Where does photosynthesis take place inside plant or algal cells?

Answer 17

Within the chloroplasts

Question 18

What is the name of the green pigment found inside chloroplasts?

Answer 18

Chlorophyll

Question 19

What does chlorophyll do?

Answer 19

Absorbs light energy from the Sun

Question 20

Describe the journey of water through a plant.

Answer 20

1. Water enters through the root hair cells of the roots.
2. Water travels through tubes called xylem tubes
3. Water evapourates out of the leaves.

Question 21

Why do roots not contain chloroplasts?

Answer 21

Because they are underground and so cannot capture sunlight.

Question 22

Plants store the glucose produced in photosynthesis as…

Answer 22

……..starch

Question 23

Describe (step-by-step) can we test a leaf to see if it has been photosynthesising?

Answer 23

1. Remove the waxy cuticle with boiling water
2. Remove the chlorophyll with hot ethanol
3. Drop iodine on to leaf
4. If the iodine turns blue/black - starch is present
5. This means the leaf has been photosynthesising

Question 24

What colour does iodine change to if starch is present?

Answer 24

From orange to blue/black

Question 25

If a plant is lacking in magnesium it might be pale in appearance. Can you explain this?

Answer 25

Magnesium is a mineral needed by plants to make chlorophyll. The plant would be lacking in chlorophyll and appear pale.