Photosynthesis
Essential Standard
Bio.4.2.1 Analyze photosynthesis and cellular respiration in terms of
how energy is stored, released, and transferred within the and between
these systems.
Photosynthesis
• Photosynthesis – process by which plants
capture energy in light and store it in
organic compounds
• 2 steps:
1. Light (dependent) reactions
• produce chemical energy
2. Dark (Light independent) reactions
• synthesize sugar
1. Light (Dependent)Reactions
• Pigments absorb and reflect different colors of light
• Visible Light Spectrum – array of colors from splitting a
beam of white light
• Chlorophyll reflects green light
• Plants appear green
• Carotenoids are accessory pigments that reflect orange,
red, and yellow lights
• Autumn Colors!
1. Light (Dependent) Reactions
• Light reactions – initial phase of photosynthesis
where light energy is transferred into chemical
energy.
• Chlorophyll
Process:
Sun  Series of Pigments  ATP Synthesis
2. Dark Reactions (Calvin Cycle)
• Dark reactions are known as light
independent reactions
• Calvin Cycle – series of biochemical
reactions that produces organic molecules
using energy stored in ATP and NADPH
Carbon Fixation  Reduction 
Regeneration (sugar)
Photosynthesis Equation
• Equation for both light dependent and light independent
cycles
CO2 + H2O + light energy  Sugar (C6H12O6) + O2
Factors that Affect Photosynthesis
• Sunlight
• Carbon dioxide
• Water
• Temperature
• pH