Photosynthesis: Why, where and how…

An overview of photosynthesis

Which organisms can photosynthesise?

Which organisms can photosynthesise?

• Green plants, phytoplankton and cyanobacteria

• Phytoplankton and cyanobacteria supply half of all atmospheric oxygen

• ‘Red tides’ are caused by photosynthetic protists

Where does photosynthesis occur in plants?

Photosynthetic pigmentsan introduction…

Photosynthetic pigments

• A pigment is a substance that absorbs light• Plants have pigments in the thylakoids of their

chloroplasts: chlorophylls, carotenoids and• Chlorophyll a is directly involved in

photosynthesis while chlorophyll b is an accessory pigment, since it assists in capturing light energy

• Caratenoids give leaves their red, orange and brown hues during autumn

• Why are leaves green?

Carotenoids and chlorophyll: welcome to autumn…

The ‘where’ of photosynthesis: The Chloroplast

Carbon dioxide is often a limiting factor on the rate of photosynthesis

Measuring the rate of photosynthesis

• P. 77 in textbook• Oxygen production:

‘direct measurement’• Carbon dioxide

measurement: ‘Direct measurement’

• Biomass measurement: ‘indirect measurement’

Your next IA

• ‘Design an experiment which evaluates the effect of ONE limiting factor (temperature, light intensity,

light colour or carbon dioxide concentration’ on the rate of photosynthesis’

• You may want to compare different types of plants in your experiment…

The reactions of photosynthesis