B2- organisms in the environment

photosynthesis

• photosynthesis is the process of turning light energy into food 
• it can only be carried out by green plants and algae because they contain chloroplasts
• photosynthesis= water+carbon dioxide---(light)--->glucose+oxygen
• 1)carbon dioxide taken in by leaves by gas exchange and water is taken up roots by xylem
• 2)chlorophyll in the chloroplasts traps the light energy needed for photosynthesis
• 3)energy is used to convert co2 and water into glucose 
• 4)oxygen is released as a waste product
• some glucose is converted into insolube starch for storage or structure
• if we test a leaf with iodine solution we can see if photosynthesis has occured because the starch will turn black/blue

limiting factors

• lack of light will slow down photosynthesis as the energy is needed
• plants may be shaded
• if it is cold enzymes do not work as efficiently which slows down the process
• if there is not enough co2 then photosynthesis will slow down for example on a sunny day in a greenhouse
• these are all called limiting factors
• in an experiement for the rate of photosynthesis you must be aware that other factors can limit it
• the independant varible is the one being tested (x axis) and the dependant variable is the one you measure that depends on the independant varible (y axis)

how plants use glucose

• glucose produced in photosynthesis…