Photosynthesis

• Photosynthesis

  The process by which green plants, algae, and some bacteria convert light energy, usually from the sun, into chemical energy stored in glucose
• Chloroplasts


  • Organelles in plant cells where photosynthesis occurs
• Chlorophyll


  • Green pigment in chloroplasts that absorbs light energy
• Carbon dioxide (CO2)


  • Taken in by plants from the atmosphere
• Water (H2O)


  • Taken in by plants from the soil through roots
• Light-dependent Reactions


  1. Occur in the thylakoid membranes of chloroplasts

  2. Require light energy captured by chlorophyll

  3. Water molecules are split (photolysis) into oxygen, protons (H+), and electrons

  4. ATP and NADPH are produced as energy carriers
• Light-independent Reactions (Calvin Cycle)

  1. Occur in the stroma of chloroplasts

  2. Utilize ATP and NADPH produced in the light-dependent reactions

  3. Carbon dioxide is fixed into glucose through a series of enzyme-catalyzed reactions
• Light Intensity


  Higher light intensity increases the rate of photosynthesis, up to a certain point
• Carbon Dioxide Concentration


  Higher CO2 levels generally increase photosynthesis until it reaches a saturation point
• Temperature


  Optimal temperatures (around 25-30°C) promote photosynthesis, but extremes can inhibit the process
• Water Availability


  Lack of water can slow down or stop photosynthesis
• Light-dependent stage


  1. Can only proceed in the presence of light

  2. Transforms sunlight energy captured by chlorophyll into chemical energy of loaded coenzymes
• Light-independent stage (Calvin cycle)

  1. Can only proceed in the presence of high-energy coenzymes

  2. Assembles simple inorganic carbon dioxide molecules into more complex organic glucose molecules