Photosynthesis: How Plants Make Food
Photosynthesis: How Plants Make Food
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Photosynthesis: How Plants Make Food
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Learning goal
I can explain the basics of photosynthesis in simple terms, including what plants need for it, where it happens, and why it is important.
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What words come to mind when you hear photosynthesis?
Use this as a prior-knowledge activation. Expect words such as plants, light, leaves, oxygen, food, green, Sun, and water.
What is photosynthesis?
Photosynthesis is the process plants use to make their own food.
Using light energy, plants change carbon dioxide and water into glucose and oxygen.
Emphasise that 'photo' means light and 'synthesis' means putting together. Keep the idea simple: plants are making food, not eating food.
Why do plants need photosynthesis?
Plants need food for energy and growth
The food they make is glucose
Glucose helps build new cells and tissues
Without photosynthesis, plants could not make enough food to stay alive
Students may think soil is a plant's food. Clarify that soil provides minerals, but the plant's food is made during photosynthesis.
Plants make their own food
Plants are called producers because they make food themselves.
Unlike animals, plants do not need to eat other living things to get glucose. They use light energy to make it.
This slide sets up the later link to the food chain. Keep the contrast with animals simple and clear.
Why are plants called producers?
They make food
They absorb oxygen
They eat animals
They move seeds
Checks understanding from slides 2–4. A common misconception is that plants get food from soil or by taking in substances rather than making glucose.
Complete the summary
Photosynthesis is the process plants use to make their own food. Using light energy, plants change carbon dioxide and water into glucose. Plants are called producers because they make food themselves.
Echoes the wording from the first teaching block and reinforces the contrast between food, water, and producer.
Where does it happen?
Photosynthesis happens mainly in the leaves
Leaf cells contain many chloroplasts
Chloroplasts are the parts of the cell where photosynthesis takes place
If useful, mention that green stems can also photosynthesise, but leaves are the main place and should stay the focus at KS3 level.
Chlorophyll and chloroplasts
Chloroplasts are tiny structures inside plant cells
They contain chlorophyll
Chlorophyll is the green substance that absorbs light energy
Students often mix up chlorophyll and chloroplasts. Stress that chlorophyll is inside chloroplasts, and chlorophyll absorbs the light.
What absorbs light energy in photosynthesis?
Leaf veins
Chlorophyll
Glucose
Oxygen
Targets the chlorophyll/chloroplast confusion from slides 5–6. Chlorophyll absorbs light; chloroplasts are the cell structures that contain it.
Where does photosynthesis happen in a plant?
Expected answer elements: photosynthesis happens mainly in the leaves, in leaf cells, inside chloroplasts. Students may mention chlorophyll if they explain further.
What goes into photosynthesis?
Plants need three main inputs:
Carbon dioxide from the air
Water from the soil
Light energy from the Sun
Keep 'inputs' as the exact term and reuse it later with 'outputs'.
Inputs and outputs
Outputs
Inputs
Carbon dioxide
Water
Light energy
Glucose
Oxygen
Point out that glucose stays in the plant as food, while oxygen is released into the air.
How the process works
Carbon dioxide + water + light energy → glucose + oxygen
Use the arrow as 'makes' or 'changes into'. This is not the full chemical symbol equation; it is the simple word summary appropriate for this lesson.
The word equation
carbon dioxide + water → glucose + oxygen
This happens using light energy absorbed by chlorophyll.
The user asked for a simple word equation, so keep it readable. Mention orally that light is needed even though it is often written above the arrow rather than in the line.
Which list shows only inputs of photosynthesis?
Glucose, oxygen, water
Water, glucose, light
Carbon dioxide, water, light
Oxygen, carbon dioxide, glucose
Checks that students can separate inputs from outputs after slides 7–10.
Complete the word equation idea
In photosynthesis, carbon dioxide and water are changed into glucose and oxygen. This happens using light energy absorbed by chlorophyll.
Matches the simple word equation on slides 9–10 and keeps light energy linked to chlorophyll.
How photosynthesis helps plants grow
Glucose gives plants energy
Glucose can be stored or used straight away
It helps plants make roots, stems, leaves, flowers, and fruits
Avoid going into respiration in detail. The key idea is that glucose supports growth and living processes.
Why oxygen matters
Oxygen is a product of photosynthesis
Much of it is released into the air
Animals and many other living things need oxygen for life
Keep this link simple and biological. Do not over-expand into atmospheric science.
Photosynthesis and the food chain
Plants make glucose by photosynthesis
Animals cannot make their own food this way
Food chains begin with plants because they provide food for other organisms
Connect back to 'producers' from slide 4. This resolves why photosynthesis matters beyond the plant itself.
Why do food chains begin with plants?
They make glucose
They breathe oxygen
They grow in soil
They eat insects
Builds on slides 11–13 by linking glucose production to the food chain.
Complete the final summary
Glucose helps plants grow and make new roots, stems, and leaves. Photosynthesis also makes oxygen for the air. Food chains begin with plants because they make food for other organisms.
Consolidates the importance of photosynthesis for growth, oxygen release, and the food chain.
What is one thing you learned about photosynthesis?
Reflection prompt with no single correct answer. Students may mention inputs and outputs, chlorophyll, chloroplasts, leaves, glucose, oxygen, or food chains.
Which part of this lesson helped you most?
Reflection prompt with no correct answer. Encourage students to name a specific part, such as the word equation, inputs and outputs, or where photosynthesis happens.
Glossary
photosynthesis - the process plants use to make food using light energy
glucose - a sugar made by plants as food
carbon dioxide - a gas in the air used in photosynthesis
oxygen - a gas produced during photosynthesis
chloroplast - the part of a plant cell where photosynthesis happens
chlorophyll - the green substance that absorbs light energy
producer - a living thing that makes its own food
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Glossary
input - something needed for a process to happen
output - something made by a process
light energy - energy from the Sun used in photosynthesis
leaf cell - a cell in the leaf that contains chloroplasts
word equation - a sentence-like equation written with words instead of symbols
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