Photosynthesis
Trapping Energy from
Sunlight
• Photosynthesis – is the process
plants use to trap the sun’s
energy and build
carbohydrates, called glucose,
that store energy
• Ultimate source of energy that
powers cells
Overview
• Two Phases
– Light dependent
– Light independent
• Overall equation
– 6CO2 + 6H2O -> C6H12O6 + 6O2
enzymes, light , chlorophyll
Chloroplasts and Pigments
• Chloroplast – cell organelle
where photosynthesis occurs
• Chlorophyll – absorbs most
wavelengths of light except
green
Light Dependent Reactions
• Requires light
• Takes place in the thylakoid
• Light strikes chlorophyll
• Excites the electrons
• Goes through the first electron
transport chain = ATP
Second Electron Transport Chain
• Goes through second electron
transport chain
• NADP+ + H -> NADPH
• Storage of energy
Restoring Electrons
• Water is split = photolysis
• Water molecule is split to
produce two hydrogen ions,
oxygen, and two electrons
• 2H2O -> 4H+ + O2 + 4e• This is how we get our oxygen
• Pg. 234 fig. 9.7
Light Independent Reactions
• Does not require light
• Calvin Cycle or Dark reaction
• Takes place in the stroma
• Energy from the lightdependent fuels Calvin Cycle
• Cycle – one of last molecules
needed for first
Process
• One CO2
enters
the cycle
• Has to go
through
the cycle
six times
Questions?
6CO2 + 6H2O -> C6H12O6 + 6O2
enzymes, light , chlorophyll