photosynthesis

🌞 What Is Photosynthesis?

Photosynthesis is a chemical process that takes place in green plants, mainly in their leaves. Using light energy from the Sun, plants turn carbon dioxide (from the air) and water (from the soil) into a kind of sugar called glucose.

As a bonus, this process releases oxygen, which humans and animals need to breathe!

🧪 The Photosynthesis Equation

Here’s a simple word equation for photosynthesis:

Carbon dioxide + Water → Glucose + Oxygen

This reaction only happens when light energy is available – so mostly during the day.
The energy needed comes from sunlight.

🌱 Where Does Photosynthesis Happen?

Photosynthesis takes place in a special part of plant cells called chloroplasts.

🍀Chloroplasts contain a green pigment called chlorophyll.

🍀 Chlorophyll is what gives leaves their green colour and helps absorb sunlight.

🍀 Remember: Only green parts of the plant, especially the leaves, do photosynthesis well.

What Happens to the Glucose?

Some glucose is used straight away for energy.
Some is stored as starch in the leaves or other parts of the plant.
Plants store starch so they can use it later when there's no light (like at night).

✅ To test if a leaf has done photosynthesis, scientists use iodine solution. If starch is present, the leaf turns blue-black. If not, it stays yellow-brown.

Gas Exchange in Leaves

Stomata are tiny holes on the underside of leaves.
They let carbon dioxide in and oxygen out.
Water vapour can also escape through stomata in a process called transpiration.

🌍 Why Is Photosynthesis So Important?

It provides oxygen for animals and humans to breathe.
It removes carbon dioxide from the atmosphere, helping reduce climate change.
It creates glucose, which is food not just for the plant, but also for animals (including us!) who eat plants.

⛔ What Stops Photosynthesis?

Photosynthesis needs:

Light – No light means no photosynthesis.
Carbon dioxide – Without it, plants can't make glucose.
Water – It's a key reactant in the process.

Things that slow down photosynthesis:

Low light intensity
Low carbon dioxide levels
Low temperature (enzymes inside plants work slower)

Structure	Function
Chloroplast	Organelles where photosynthesis happens
Chlorophyll	Pigment that absorbs light energy
Stomata	Tiny pores that allow gases to enter and exit
Palisade cells	Leaf cells packed with chloroplasts for photosynthesis
Xylem	Tubes that carry water from roots to leaves
Phloem	Tubes that carry glucose to other parts of the plant

Top Tips

🍃 Chloroplast = place, Chlorophyll = pigment

🍃 Photosynthesis needs sunlight, carbon dioxide, and water.

🍃 Oxygen is a waste product, but a very useful one for us!

🍃 Glucose is either used for energy or stored as starch.

🍃 Starch test = iodine solution, blue-black = starch is present.

🍃 Most photosynthesis happens in green leaves – because they’re packed with chloroplasts!

🍃 Plants help the planet by reducing carbon dioxide and making oxygen.