PHOTOSYNTHESIS The most important biochemical process on Earth.
What types of organisms can perform the reactions of PHOTOSYNTHESIS? • 1. All Plants (Plant Kingdom) • 2. Algae (Protist groups: red algae, brown algae, green algae, diatoms, dinoflagellates) • 3. Cyanobacteria (Bacteria Kingdom)
Although the reaction looks simple, the process is complex. There are 2 stages:1. Light Dependent Reactions2. Calvin Cycle = Light Independent Reaction
Pigments are held in the thylakoids of a chloroplast:chlorophyll a, chlorophyll b, and accessory pigments (orange, red, blue)
Summary of Light Dependent Reactions: • 1. water is used up and oxygen is produced • 2. Photosystem II captures sunlight and absorbs electrons from water splitting to replace electrons from chlorophyll • 3. Photosythem I also captures sunlight and carries electrons from proteins • 4. Electron is captured by NADP+ along with H+ ions to form higher energy NADPH.
Summary of Light Dependent Reactions (cont): • 5. ATP is produced by H+ ions moving through an enzyme called ATP Synthase • 6. Light Dependent Reactions occur in green parts of a plant = leaves (and not in the roots underground) • Also: algae and cyanobacteria contain pigments to absorb sunlight and conduct photosynthesis
Summary of Calvin Cycle = Light Independent Rx: • 1. The 2 high energy molecules produced in Light Dependent Rx are used up: ATP and NADPH • 2. CO2 is used up • 3. One organic sugar, glucose, is produced for each 6 CO2 used. • 4. RuBP is regenerated at the end of each cycle and ready for the next CO2
Light Dependent Reactions and Calvin Cycle are the 2 stages of PHOTOSYNTHESIS
Why is photosynthesis THE most important biochemical process on Earth? • 1. source of atmospheric oxygen • 2. source of all organic molecules, starting with glucose (a carbohydrate) • 3. mitigates global warming by absorbing CO2