3. Photosynthesis

• The photosynthesis equation.

  
• Light energy from the sun is captured by the chlorophyll found in the chloroplasts.
• Photosynthesis is a two stage process:

  • Light reactions
  • Carbon fixation
• Light reactions -

  Light from the sun is captured in the chlorophyll and converted into chemical energy to make ATP.

  Water is split to make Hydrogen and Oxygen.
• Carbon Fixation:

  Enzyme-controlled reactions.

  Hydrogen and ATP from the light reactions combine with Carbon Dioxide to make sugar.
• Light Reactions: In this stage, light energy from the sun is captured in the chlorophyll in the chloroplasts, converted into chemical energy and used to generate ATP.
• Light reactions - Water is split to produce Hydrogen and Oxygen through a process known as photolysis. The oxygen diffuses out of the cell.
• Carbon fixation - Carbon fixation is a series of enzyme-controlled reactions that use Hydrogen and ATP produced by the light reactions, combined with Carbon dioxide to produce sugar (glucose)
• The sugar produced in photosynthesis can be used in 3 ways:

  • Energy source - Sugar can be used in Respiration to make ATP for cellular activities
  • Energy storage - Sugar molecules can be joined together into Starch to be used later
  • Building material - Sugar can be joined into long strands of Cellulose to make cell wall
• Anything that holds back the rate of a reaction is known as a limiting factor.
• In photosynthesis, there are 3 limiting factors:

  • Carbon dioxide concentration
  • Light intensity
  • Temperature
• As carbon dioxide concentration increases, so too the rate of photosynthesis also increases.
• As light intensity increases, so too does the rate of photosynthesis increase.
• As temperature increases, the rate of photosynthesis also increases until the enzyme reaches its optimum.
• Past the optimum the enzyme denatures and the rate slows down.