Photosynthesis

1

• Photosynthesis The light dependent reaction
• The light dependent reaction takes place in the
  grana of the chloroplasts
• The useful products of the light dependent
  reaction are reduced NADP and ATP
• Light provides the energy to split water and
  transfer electrons
• Light energy is captured by chlorophyll
• Leaves are adapted to carry out the reaction
  because they have large surface areas, many
  chloroplasts and stacked grana
• The light dependent reaction produces oxygen as a
  waste product.
• The light dependent reaction takes place on
  membranes because they position the chlorophyll
  and electron transfer proteins

2
Photosynthesis - The light independent
reaction These reactions take place in the
chloroplast stroma. Together they form the
Calvin cycle. First ribulose biphosphate reacts
with carbon dioxide to form glycerate phosphate
(GP). ATP and reduced NADP from the light
dependent reaction convert GP to glyceraldehyde
phosphate (GAP). This enters pathways that
produce a variety of organic molecules e.g.
glucose. However, some regenerates ribulose
biphosphate. Some plants follow a different
pathway to increase the efficiency of carbon
fixation.
3

• Glycolysis and the link reaction
• Glycolysis is the way that carbohydrates are fed
  into aerobic respiration.
• It happens in the cytoplasm.
• First ATP is used to activate the glucose.
• It splits into two 3C sugars.
• They are oxidised to produce 3C acids producing
  reduced NAD.
• The end product is pyruvic acid and some ATP.
• The pyruvate enters the mitochondrion.
• The pyruvic acid is then converted to acetyl CoA.
• Carbon dioxide is lost and more NAD is reduced.

4

• The Krebs cycle and oxidative phosphorylation
• The Krebs cycle takes place in the matrix.
• The acetyl CoA feeds a 2C compound into the cycle
  forming a 6C compound from a 4C intermediate.
• Carbon dioxides are progressively lost
  regenerating the 4C compound.
• Reduced NAD and FAD are produced with some ATP.
• The reduced NAD and FAD pass their electrons to
  carrier proteins in the cristae.
• The electrons pass along producing ATP.
• Oxygen collects the electrons and it is reduced
  to water.