Photosynthesis

Photosynthesis is the CHEMICAL CHANGE that happens in plants to produce energy

CARBON DIOXIDE + WATER ---> GLUCOSE + OXYGEN

During photosynthesis:

• LIGHT ENERGY is absorbed by CHLOROPHYLL which is found in the CHLOROPLASTS of some plants and algae
• Absorbed light energy is used to convert WATER and CARBON DIOXIDE into a sugar called GLUCOSE
• OXYGEN is also released

Some glucose produced is used for RESPIRATION whilst others is used as STORED STARCH.

Storage - Cells need to use glucose for respiration but this can't occur at night because there is no light energy and so the cells store the glucose as insoluble products like FATS, OILS and STARCH

Use - Some glucose is used for respiration to release energy. Some cells use it to produce CELLULOSE (which strengthens the cell wall) and PROTEINS (like enzymes and chlorphyll).

Plants also need NITRATES to make proteins. These are absorbed from the soil and NITRATE IONS.

Factors affecting photosynthesis are:

• TEMPERATURE - If it gets too hot or too cold the cells can't photosynthesise and so the rate of photosynthesis DECREASES.
• LIGHT INTENSITY - Without enough light the plant cant photosyntheise properly even if it has enough CO2 and water. Increasing the light intensity will mean the the rate of photosynthesis INCREASES.
• CONCENTRATION OF CARBON DIOXIDE - Plants can't perform photosynthesis if there isnt enough CO2 in the air and so the rate DECREASES.