Where does most photosynthesis happen in a leaf?

palisade mesophyll. Palisade cells have the most chloroplasts.

What is the job of the waxy cuticle?

to reduce water loss. It is a waterproof layer.

Through which structures does carbon dioxide enter a leaf?

the stomata. They are tiny pores, mostly on the lower surface.

What do the air spaces in the spongy mesophyll do?

let gases diffuse through the leaf. Carbon dioxide can reach all the photosynthesising cells.

Which cells open and close the stomata?

guard cells. A pair of guard cells surrounds each stoma.

Leaf structure · Cambridge IGCSE Biology (9

In plain words

A leaf is a solar panel that also has to breathe. It is thin and flat to catch light, has pores to let carbon dioxide in, air spaces for gases to move about, and tiny pipes to bring water and take sugar away.

Three things to know

From the top: waxy cuticle (stops water loss), upper epidermis (transparent), palisade mesophyll (packed with chloroplasts, where most photosynthesis happens), spongy mesophyll (air spaces for gas exchange), lower epidermis with stomata.
Stomata are pores, mostly on the underside. Each is opened and closed by a pair of guard cells. Carbon dioxide diffuses in; oxygen and water vapour diffuse out.
The veins (vascular bundles) contain xylem, which brings water, and phloem, which takes sucrose away.

Tips and tricks

Each feature needs its reason: "thin, so gases have a short distance to diffuse"; "large surface area, to absorb more light".
Palisade cells are near the top because that's where the light is strongest.

5 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Leaf structure: 5 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

Where does most photosynthesis happen in a leaf?
- upper epidermis
- palisade mesophyll (the answer)
- spongy mesophyll
- cuticle
Palisade cells have the most chloroplasts.
What is the job of the waxy cuticle?
- to absorb light
- to reduce water loss (the answer)
- to let gases in
- to carry water
It is a waterproof layer.
Through which structures does carbon dioxide enter a leaf?
- the cuticle
- the veins
- the stomata (the answer)
- the xylem
They are tiny pores, mostly on the lower surface.
What do the air spaces in the spongy mesophyll do?
- store water
- let gases diffuse through the leaf (the answer)
- absorb light
- carry sugar
Carbon dioxide can reach all the photosynthesising cells.
Which cells open and close the stomata?
- palisade cells
- guard cells (the answer)
- root hair cells
- xylem cells
A pair of guard cells surrounds each stoma.

5 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

3 questions, 7 marks. Write your answers on paper, then check them.

Leaf structure

Cambridge IGCSE Biology (9–1) 0970 · 7 marks · papermunch.org

Name ______________________________ Date ______________

Explain three ways in which a leaf is adapted for photosynthesis.[3]
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Any three, each with its reason: large surface area to absorb light; thin, so gases diffuse quickly; palisade cells near the top with many chloroplasts; stomata to let carbon dioxide in; air spaces for diffusion; veins to supply water.
I got this one
State the function of the guard cells.[2]
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They open and close the stomata, controlling gas exchange and water loss.
I got this one
Explain why the upper epidermis is transparent.[2]
Show answerHide answer
So that light can pass through it to the palisade cells underneath.
I got this one

Answers: Leaf structure

1. Any three, each with its reason: large surface area to absorb light; thin, so gases diffuse quickly; palisade cells near the top with many chloroplasts; stomata to let carbon dioxide in; air spaces for diffusion; veins to supply water.
2. They open and close the stomata, controlling gas exchange and water loss.
3. So that light can pass through it to the palisade cells underneath.