Photosynthesis

• 2 main stages of photosynthesis

  1. Light dependant reaction
  2. Light independent reaction
• Chloroplasts act as transducers as they convert light to chemical energy.
• Stages of photosynthesis in a chloroplast: Light reactions Calvin cycle Electron transport chain.

  
• Which stage uses water and produces oxygen?

  Light dependant reaction
• Which stage reduces carbon dioxide to produce glucose?

  Light independent reaction
• What key products are produced in the light dependant reaction?

  ATP, NADPH and Oxygen
• What key products are produced in the light independent reaction?

  ADP, NADP and glucose
• Where does the light dependant reaction take place?

  Thylakoids
• Where does the light independent reaction take place?

  Stroma
• Structure of a chloroplast

  
• A photosynthetic pigment is a coloured biological compound that is present in chloroplasts and photosynthetic bacteria that absorb light for photosynthesis.
• What are 2 groups of pigments?

  1. Chlorophylls
  2. Carotenoids
• Chlorophylls and accessory pigments are grouped in clusters of several hundred molecules. Each is known as a photosystem or antenna complex.

  
• Photosystems are found in the thylakoid membrane of chloroplasts.
• A photosystem captures light energy and uses it to generate ATP and NADPH.
• What are the main primary pigments?

  1. Chlorophyll A
  2. Chlorophyll B
• What are the main accessory pigments?

  1. Carotenes
  2. Xanthophylls
• Photosystem 1: absorption peak of 700nm - P700
• Photosystem 2: absorption peak of 680 nm - p680
• Absorption spectra is a graph to show the wavelength of light best absorbed by different pigments.

  
• Action spectra shows the rate of photosynthesis at different wavelengths of light.

  
• what is the importance of the accessory pigment?

  Assisting chlorophyll A with the absorption of light
• Redox reactions are when molecules are reduced or oxidised. This happens a lot during certain stages of photosynthesis.
• When a molecule is reduced it may have:

  • Gained electrons
  • Gained Hydrogen
  • Lost oxygen
• When a molecule is oxidised it may have:

  • Lost electrons
  • Lost Hydrogen
  • Gained oxygen
• Coenzymes are molecules that aid an enzyme. In photosynthesis NADP is the coenzyme.
• 2 products of the light dependant stage

  1. ATP - light energy is transformed into chemical energy. Electrons are used to make ATP in phosphorylation and then used for other biochemical reactions in the light dependant stage.
  2. Reduced NADP - protons are used to reduce NADP (which acts as a hydrogen carrier) which is then used in the light independent reactions.
• Z-scheme: the flow of electrons in the light independent reaction is important in the production of ATP.

  
• 2 ways that ATP can be synthesized

  1. Non cyclic phosphorylation - involves PS1 and PS2
  2. Cyclic phosphorylation - involves only PS1
• Which process splits water into hydrogen ions, oxygen and electrons?

  Photolysis
• Phosphorylation produces ATP and NADPH
• Chemiosmosis: The diffusion of ions through a semipermeable membrane into a region of lower ion concentration for the synthesis of ATP.
• The light independent reaction is the second stage of photosynthesis and occurs in the stroma of chloroplasts.
• It uses NADP and ATP from the LDR to supply protons (reducing power) and energy to make organic molecules needed by the plant.
• Calvin cycle: Co2 binds with RuBP to form GP, catalysed by the enzyme Rubisco
• Calvin cycle: GP is converted into TP using ATP and NADPH from the light dependant reaction.
• Calvin Cycle: 5/6 carbons and ATP are used from TP to make RUBP again.
• Calvin Cycle: 1/6 of the carbons from TP are used for hexose sugars, lipids and amino acids.
• What does chlorosis mean?

  Loss of chlorophyll
• What is the role of magnesium?

  Forms part of a chlorophyll molecule.