Photosynthesis

• Where does the light dependent reaction take place?

  The Thylakoid membranes
• In the light dependent stage of photosynthesis there are four stages:

  Photoionisation of chlorophyll

  Production of ATP and NADPH

  Chemiosmosis

  Photolysis
• What is the equation of the photolysis of water

  H₂O --> +1/2 O₂ + 2e⁻ +2H⁺
• After photolysis, H⁺ reduces NADP to form NADPH to be used in the LIR. e⁻ are passed alonga chain of electron carrier proteins. Oxygen is used for respiration or diffuses out through the stomata.
• Chlorophyll absorbs light energy, exciting electrons and causing them to raise up an energy level to leave the chlorophyll. Thus the chlorophyll is ionised.
• ATP synthase uses the proton gradient created by chemiosmosis to make ATP.
• Electrons released by the chlorophyll travel along electron carrier proteins releasing energy as they did. This energy is used to pump H⁺ ions across the thylakoid membrane.

  These H⁺ ions travel down the chemiosmotic gradient through ATP synthase to produce ATP.

  Once it has passed through ATP synthase, it binds with NADP and the electrons released to form NADPH
• Where does the light independent reaction (the calvin cycle) occur?

  The stroma
• The Calvin cycle uses carbon dioxide, reduced NADP and ATP to form a hexose sugar.
• Lable the Calvin Cycle

  A) CO2

  B) 2 x GP

  C) 2 X TP

  D) RuBP

  
• Rubisco is an important enzyme in the calvin cylce and catalyses the formation of 2 x GP from RuBP and CO₂
• In the Calvin Cycle, GP stands for Glycerate-3-phosphate
• GP is converted to TP using energy provided by ATP hydrolysis and by accepting a H⁺ from NADPH
• 2 TP molecules release a single carbon sugar to build up a hexose sugar. Using ATP the remaing 5 carbon sugar becomes RuBP
• Chloroplasts contain several different photosynthetic pigments within the thylakoids each absorbing different wave lengths of light.

  There are two groups of photosynthetic pigment, these being Chlorophylls and Carotenoids.
• Chlorophyll comes in two types, chlorophyll a and chlorophyll b
• Carotenoids come in two types these being Beta-Carotene and Xanthophyll
• Label the structure of a light havesting complex

  A) Carotenoids

  B) Chlorophyll b

  C) chlorophyll a

  D) Reaction centre

  
• Which pigments absorb which wavelengths

  A) chlorophyll a

  B) Chlorophyll b

  C) Carotenoids

  D) Chlorohpylls and carotenoids

  E) Chlorophylls only

  
• The formula for Rf value is:

  Rf = Distance travelled by the spot / Distance travelled by the solvent