B2- Photosynthesis

Light energy

Photosynthesis: Photosynthesis literally means using light to put together or make. Plants photosynthesise to create glucose, enabling them to grow. The chlorophyll inside chloroplasts in the palisade cells in a plants’ leafs enable it to use energy from the sun to convert carbon dioxide, from the air, and water, from the soil, into sugar (glucose), and oxygen is a waste-product. Carbon dioxide enters the leave on the underside through diffusion and the water travels from the roots up the stem into the leaves. Root hair cells are specialised to collect water from the soil and the carbon dioxide enters the plant’s leaves by diffusion through pores called stomata. Glucose is a form of chemical energy which means the light energy has been converted into chemical energy that the plant can now use.

Chlorophyll

carbon dioxide + water                        glucose + oxygen

     6CO₂        +    6H₂O      C₆H₁₂0₆  + 6O₂

Limiting Factors: The rate of photosynthesis may be limited by the concentration of carbon dioxide, the light intensity and the temperature. A factor is only a limiting factor if when you change the amount it increases or decreases the rate of photosynthesis. When the line on a limiting factors graph has levelled off it means that the factor is no longer a limiting factor and something else has become the limiting factor. Only one factor can be the limiting factor at any one time.

Glucose: Plants produce a sugar called glucose during photosynthesis. There are five things which plants do with this glucose it is: used in respiration to release energy; converted to starch to be stored; converted to fats for storage in seeds; used to make protein for growth; and converted into cellulose to make cell walls. To make proteins, nitrates from the soil combine with the glucose.

Testing for starch: Plants convert glucose into starch to store it. It is made of long chains of glucose molecules and is a carbohydrate…