Photosynthesis

• The cells in algae and plant leaves are full of small green parts called chloroplasts, which contain a green substance called chlorophyll
• during photosynthesis, energy is transferred from the environment to the chloroplasts by light
• The energy is then transferred to convert carbon dioxide from the air, plus water from the soil into a simple sugar called glucose
• The chemical reaction also produces oxygen gas as a by-product. the oxygen is released into the air, which you can then use when you breathe it in
• photosynthesis is an endothermic reaction - it needs an input of energy from the environment
• the energy is transferred from the environment when the bonds holding carbon dioxide and water are broken is more than that transferred back to the environment with the formation of the new bonds in glucose and oxygen
• the extra energy is required for the reaction to take place is transferred from the environment by light
• most leaves are broad, giving them a big surface area for light to fall on
• most leaves are thin so diffusion distances for the gases are short
• they contain chlorophyll in the chloroplasts to absorb light
• leaves have veins which bring water in the xylem to the cells of the leaves and remove the products oh photosynthesis in the phloem
• leaves have air spaces that allow carbon dioxide to get to the cells and oxygen to leave by diffusion
• leaves have guard cells the stomata to regulate gas exchange and prevent water loss
• Algae are aquatic so they are adapted to photosynthesising in water
• Algae have large surface area and absorb carbon dioxide dissolved in water around them. the oxygen they produce also dissolvesi n the water around them as it is released