photosynthesis

• Chloroplasts


  Organelles in plant cells where photosynthesis takes place

  
• Chloroplast outer membrane


  • Semi-permeable - allows for entry and exit of reactants and products of photosynthesis
  • Clear membranes allow light to pass into chloroplast
  • Semi permeable membrane allows CO2 to easily pass through to the stroma for dark phase
• Chloroplast inner membrane


  • Separates the stroma from the intermembrane space allowing for compartmentalisation
  • The clear membranes / stroma allow light to pass through to the thylakoids / grana where the light reaction occurs

  
• Grana (Granum)


  • Green structures that absorb light energy and use it in a light-dependent reaction which starts photosynthesis
  • Chlorophyll found in grana / thylakoid is the pigment that allows light reaction to proceed

  
• Thylakoid


  • A stack of grana
  • Maximises the surface area available for the reaction
  • Large surface area of grana / thylakoid will maximise light capture for light dependent reaction
• Stroma


  • A clear, jelly-like liquid inside the chloroplast
  • It's clear, so it allows light to pass through to the thylakoid
  • The stroma is the site of the light-independent reaction
  • Stroma contains enzymes which catalyse reactions
  • Carbon dioxide from light independent reaction is used to produce the glucose

  
• Photosynthesis


  1. Energy from sunlight is used to convert carbon dioxide and water into glucose and oxygen

  2. The plant then uses the glucose for respiration

  3. Oxygen is also produced as a waste product

  
• Photosynthesis chemical equation


  Carbon dioxide + water→ glucose +oxygen

  
• Light Dependent Reaction


  1. Chlorophyll absorbs light energy from the sun, exciting electrons in the thylakoid membrane

  2. Highly excited electrons are used to make ATP from ADP

  3. Water is split up into Hydrogen and Oxygen gas

  4. The oxygen is released as a waste product

  5. Hydrogen is picked up by a carrier molecule called NADP, and NADPH transfers the hydrogen to the stroma of the chloroplast
• Light Independent Reaction


  1. CO2 and H (from the NADPH) enter a complex series of reactions called the Calvin Cycle

  2. Glucose is produced as a result

  3. ATP made in the Light Dependent reaction is used to run this part of the cycle

  
• Factors affecting Photosynthesis


  • Temperature
  • pH
  • Inhibitors
  • Concentration of substrates (CO2, water)
  • Light intensity
  • Minerals/Ions (Mg, Fe)

  
• Temperature effect on photosynthesis

  • Low temperature - low rate of photosynthesis
  • Optimum temperature - photosynthesis ideal
  • High temperature - enzymes denature, rate of photosynthesis stops

  
• pH effect on photosynthesis


  Can denature enzymes that control photosynthesis

  
• Inhibitors effect on photosynthesis


  Substances that prevent enzymes from catalysing a reaction affect photosynthesis

  
• Light intensity effect on photosynthesis

  • Increasing light intensity/energy will increase photosynthesis up to a maximum point
  • Red & blue wavelengths of light are fully utilised by chlorophyll while green wavelengths are reflected
• Minerals/Ions effect on photosynthesis

  Important ions in the making of the chlorophyll molecule