2.12Biology 02. Life Processes

Photosynthesis in chloroplasts and its word equation — Cambridge Checkpoint Science 0893 Revision Notes & Topical Questions

5 min read 10 parts Lesson 13 of 13 1 quiz

📚 Cambridge Checkpoint Science 0893 Hub / Topical Revision

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Lesson summary

2.12 Photosynthesis in chloroplasts and its equation — CHECKPOINT - Lower Secondary Science 0893 notes: Describe photosynthesis in chloroplasts, state its word equation and explain why it is important.Photosynthesis — the process by which plants make food using light energy.Photo…

Raw materials
Symbol equation
Chlorophyll
Starch test
Water plant
Light intensity

Part 1 of 8What photosynthesis is

Photosynthesis

Photosynthesis the process by which plants make food using light energy.
Photo means light and synthesis means making.

Raw materials

Raw materials water from the soil, carbon dioxide from the air and energy from sunlight.

Products

Products glucose and oxygen.

Part 2 of 8Word equation

Word equation

Word equation water + carbon dioxide → glucose + oxygen
The reactants are water and carbon dioxide.
The products are glucose and oxygen.

Symbol equation

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Part 3 of 8Chlorophyll and chloroplasts

Chlorophyll

Chlorophyll the green pigment that captures energy from sunlight.

Chloroplasts

Chloroplasts the structures inside plant cells that contain chlorophyll.
Photosynthesis happens inside chloroplasts.
Not all plant cells have chloroplasts, so not all plant cells photosynthesise.

Leaves

Leaves leaf cells contain the most chloroplasts.

Part 4 of 8Structure of a leaf for photosynthesis

Part	Function
Waxy layer	Stops the leaf cells drying out
Upper epidermis	Protects the cells inside the leaf
Palisade layer	Contains most chloroplasts and does most of the photosynthesis
Spongy layer	Has many air spaces and does a small amount of photosynthesis
Vein	Brings water to the cells in the leaf
Stoma in lower epidermis	Tiny hole that lets carbon dioxide diffuse in and oxygen out

Part 5 of 8Use of the glucose

Storage

Storage plants make more glucose than they need on sunny days and store it as starch in the chloroplasts.

Starch test

Starch test iodine solution turns blue-black when starch is present.

Part 6 of 8Testing a leaf for starch

Drop the leaf in boiling water for about two minutes to break the cell membranes.

Turn off the flame.

Heat the leaf in ethanol in a hot water bath to remove the green colour.

Dip the leaf in warm water to soften it and spread it on a tile.

Add iodine solution and look for a blue-black colour.

Part 7 of 8Evidence of oxygen production

Water plant

Water plant bubbles of gas rise from a water plant in sunlight.
A glowing splint relights in the gas, which shows that it is oxygen.

Light intensity

Light intensity more light gives more bubbles per minute, so the rate of photosynthesis increases.

Part 8 of 8Importance of photosynthesis

Energy for food chains

Energy for food chains it captures sunlight energy as chemical energy in glucose and other carbohydrates.
All the energy in the food of other organisms comes from plants.

Oxygen

Oxygen it provides the oxygen for respiration in the atmosphere, about 20% of the air.

Key terms

Term	Meaning
Photosynthesis	Process in which plants use light energy to make glucose and oxygen from carbon dioxide and water.
Chlorophyll	Green pigment that absorbs energy from sunlight.
Chloroplast	Part of a plant cell that contains chlorophyll.
Stoma	Tiny hole in a leaf that lets gases enter and leave.
Light intensity	The amount of light.

Avoid these mistakes

Plants get food from the soil — plants make glucose from carbon dioxide and water.

Photosynthesis is the opposite of breathing — it is a chemical reaction that happens in chloroplasts.

Oxygen is the food made — glucose is the food and oxygen is a waste product.

Plants photosynthesise only in the daytime and respire only at night — they respire all the time.

Last updated: 12 October 2026