Photosynthesis The process of capturing, converting and storing energy from the sun by green plants.

In simple terms: sunlight sunlight 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 This is the OPPOSITE reaction to cell respiration. This is the OPPOSITE reaction to cell respiration. Plants do BOTH photosynthesis and cell respiration. Plants do BOTH photosynthesis and cell respiration.

3 Steps in Photosynthesis 1. Absorption of sunlight 2. Conversion of sunlight energy (TO ENERGY CARRIERS) 3. Storage of energy in sugar (carbon “fixing”) *Steps MUST take place in the light *Steps MUST take place in the light ( LIGHT DEPENDENT REACTIONS) *Step 3 Can happen in the light or in the dark (LIGHT INDEPENDENT REACTIONS)

Light Dependent Reactions Absorption by Pigments Requires pigments to absorb light Requires pigments to absorb light Chlorophyll A (absorbs red, orange and violet) Chlorophyll A (absorbs red, orange and violet) Chlorophyll B (extends range of absorption to include more blue light) Chlorophyll B (extends range of absorption to include more blue light) Carotenoids (absorbs blue and green light) Carotenoids (absorbs blue and green light)

Light Dependent Reactions Conversion to Energy Carriers Electrons in the pigments are excited and passed (“transferred”) to other molecules (NADPH) Electrons in the pigments are excited and passed (“transferred”) to other molecules (NADPH) Water is split into Hydrogen and Oxygen Water is split into Hydrogen and Oxygen The oxygen from water is released The oxygen from water is released Electrons (from Hydrogen) are used to power the creation of ATP and NADPH Electrons (from Hydrogen) are used to power the creation of ATP and NADPH Like ATP, NADPH can be used to make reactions happen Like ATP, NADPH can be used to make reactions happen

The ATP and NADPH is used to make molecules of glucose (C 6 H 12 O 6 ) from carbon dioxide (CO 2 ) The ATP and NADPH is used to make molecules of glucose (C 6 H 12 O 6 ) from carbon dioxide (CO 2 ) This process is called carbon fixing or the CALVIN CYCLE. This process is called carbon fixing or the CALVIN CYCLE. Light Independent Reactions Carbon Fixing

Summary of Photosynthesis InputOutput Stage 1 (light dependent) Stage 2 (light dependent) Stage 3 (LIGHT INDEPENDENT) Sunlight & water Electrons NADPH, CO2 NADPH, CO2 Oxygen & electrons ATP & NADPH Glucose (C6 H12 O6)