Year 9 Biology Topic Plants and Photosynthesis

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KS3 Biology

9C Plants and Photosynthesis



Contents

Leaves and glucose

Summary activities

Roots and water

What is photosynthesis?


How do plants grow?

Many years ago people thought that plants ate soil and that made them grow.

Think about it, if that really happened then there wouldn’t be any soil left!

Plants actually grow by making their own food, not by eating soil!

So where does the stuff that plants are made of come from?


How do plants make their own food?

One of the raw materials that plants need to make food does come from the soil, the other comes from the air.

What are these two raw materials called?

Plants use carbon dioxide and water to make their own food in a chemical reaction. What is the name of this reaction?

carbon dioxide (from the air)

water (from the soil)


How do plants make their own food?

Plants make their food from carbon dioxide and water in a chemical reaction called...

photosynthesis.

The food made by photosynthesis is the sugar glucose.

Oxygen gas is also made as a by-product of photosynthesis.

oxygen

glucosecarbon dioxide

(from the air)



How do plants grow?

Plants need energy for photosynthesis to take place. Where does this energy come from?

The energy for photosynthesis comes from the Sun.

Where in a plant does photosynthesis take place?

oxygen


(from the air)


light energy


How do plants grow?

Plant cells in the upper surface of leaves have chloroplasts which contain the green pigment called chlorophyll.

oxygen


(from the air)


light energy

It is chlorophyll that absorbs light energy from the Sun to make photosynthesis happen.

chlorophyll


Photosynthesis summary

Plants make their own food by the process of photosynthesis.

In this chemical reaction, chlorophyll in plant cells absorbs light energy to change carbon dioxide and water into glucose and the by-product oxygen.

What is the word equation for photosynthesis?

glucose

light energy

chlorophyll

carbondioxide water oxygen

This equation can be read as:“carbon dioxide and water, in the presence of light energy and chlorophyll, produces glucose and oxygen”.


What is needed for photosynthesis?


Photosynthesis: word equation activity



Contents

Leaves and glucose

Summary activities

Roots and water



How are leaves adapted?

Leaves are small ‘factories’ that produce food for plants by photosynthesis.

Leaves are adapted so that photosynthesis can take place.

Plants need carbon dioxide, water, sunlight and chlorophyll to carry out this important process.

What features of leaves make them suitable for photosynthesis?


How are leaves adapted?

The features of leaf that make it suitable for photosynthesis are:

A leaf is broad and flat to capture lots of sunlight.

carry water to the leaf and take food from the leaf to the rest of the plant. Veins also help to support the leaf.

Certain plant cells contain chloroplasts with chlorophyll.

Small holes called stomata in the underside of a leaf allow gases in and out.

Veins


Inside a leaf


What do plants use glucose for?

glucose

Some glucose is used straight away in respiration. Plants also carry out respiration to release the energy they need for life processes.

Some glucose is converted into starch and othersubstances for storage. These stores of energycan be used later when the plant needs them.

Some glucose is used to make new chemicals such as proteins, sugars and fats that the plant also needs to function properly.

What do plants with the glucose made by photosynthesis?


Testing leaves for starch



Contents

Leaves and glucose

Summary activities

Roots and water



How does water enter a plant?

Water is one of the raw materials needed for plants to carry out photosynthesis.

How does water enter a plant?

Water from the soil enters a plant through the roots.

You can’t normally see them but roots are a very important part of a plant.

Why are roots branched and spread out through the soil?


How are roots adapted?

Roots are branched and spread out for two reasons:

to absorb water (and mineral salts) from a large amount of soil.

to anchor the plant in the soil.

Taking a closer look, roots are covered in root hair cells.

Root hair cells have thin walls and a large surface area to help them absorb lots of water.

How are roots adapted to their job?

water


Why do plants need water?

Water is needed by plants for photosynthesis but this important liquid is also used in many other ways:

to provide dissolved minerals that keep the plants healthy;

to transport substances around the plant;

to keep the plant rigid and upright;

to keep the plant cool;

to allow other chemical reactions to occur in plant cells.

What happens to a plant if it does not get enough water?



Contents

Leaves and glucose

Summary activities

Roots and water



Glossary

chlorophyll – The green pigment inside chloroplaststhat plants need for photosynthesis to take place.

chloroplast – The part of a plant cell where photosynthesis occurs.

glucose – The sugar plants make during photosynthesis.palisade cell – A type leaf cell with lots of chloroplasts.photosynthesis – The process by which plants use

carbon dioxide and water to produce glucose and oxygen in the presence of light and chlorophyll.

starch – Extra glucose from photosynthesis is stored as this substance which can be tested for with iodine.

stomata – Small holes in the lower surface of a leaf that allow gases in and out.

xylem – Tubes in veins that carry water around a plant.


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Multiple-choice quiz

Year 9 Biology Topic Plants and Photosynthesis

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