photosynthesis

• interrelationship between respiration and photosynthesis

  photosynthesis makes glucose for respiration. Resporation makes ATP and C02 for photosynthesis.

  In respiration oxygen is combined with hydrogen, in photosynthesis photolysis occurs to break down them down
• structure of a chloroplast

  Outer membrane, inner membrane, stroma (cytoplasm) Granum are the stacks made of lamella. Lamella membrane is made from thylakoid membrane
• Light dependant stage summary

  1. light energy is used to excite electrons causing for photolysis (H+ ions and Oxygen left)

  2. The H plus ions pass on the inside of the membrane to ATP synthase, forming ATP

  3. The excited electrons escape from the chlorophyll into PS 11 then move down the electron transport chain. (ETC)

  4. As they pass through ETC they lose energy. This energy is used to drive the synthesis of ATP from ADP and Pi.

  5. The electrons are accepted by PS1 and then energised again to pass along a different ETC.

  6. At the end of this chain, the electrons react with H+ ions and NADP to form NADPH.

  7. The ATP and NADPH produced or used in the light independent stages.
• What is photolysis?

  The splitting of a molecule using light energy
• Photolysis equation

  2H2O -> 4H+ + 4e- + O2
• What is phosophorylation: cyclic?

  synthesis of ATP from ADP and Inorganic Phosphate
• What is phosophorylation: non cyclic?

  formation of NADPH from NADP
• Light independent stage summary

  1. carbon dioxide reacts with RuBP in the stroma and the reaction is catalysed by RuBisCO. this forms two molecules of a three carbon compound GP.

  2. Each molecule of GP is converted to TP via a reduction reaction using hydrogen ions from NADPH and energy from ATP.

  3. Some of the TP formed is used to regenerate RuBP, some forms glucose and other useful organic compounds

  4. 6 turns of the cycle results in an output of one molecule of glucose

  5. During the reaction, NADPH is oxidised to NADP, and ATP is hydrolysed to ADP, and Phosphate. Both are reused in the light dependent reactions.
• factors affecting photosynthesis

  temperature, light intensity, CO2 conc, number of chlorophyll molecules (the availability of water.)
• How does the lack of water affect photosynthesis?

  stomata close to prevent water loss. CO2 cannot enter the leaf, so there is less CO2 for light independent stage.
• where in the chloroplast does light dependant stage occur

  thylakoid membrane
• where in the chloroplast does the light independent stage occur?

  stroma
• Rate of photosynthesis: describe and explain with TEMPERATURE

  As temperature increases, the rate of reaction increases. Until above the optimum temperature where the rate of reaction decreases as temperature increases. This is because of collision theory. As temperature increases, the substrates move with more kinetic energy, so more frequently collide with enzymes to form enzyme substrate complexes. Above optimum temperature, the enzymes denature so the shape of the active sites change. The substrate's now no longer fit into the active sites so the rate of reaction decreases rapidly.

  Examples of enzymes effected are Rubisco catalysing G.P, or ATP synthase.
• Rate of photosynthesis: describe and explain with CO2 AND TEMP

  As CO2 increases, the rate of photosynthesis increases. This is because CO2 is required for photosynthesis. At a certain point, any further increase in CO2 concentration does not affect the rate of photosynthesis, and the rate plateaus. This is because CO2 no longer limits the reaction - another factor is limiting. This graph indicates that this factor is temperature.

  At higher temperature, the rate of photosynthesis increases more rapidly. This is because of collision theory.

  At a certain point, any further increase in CO2 does not affect the rate of photosynthesis and the rate plateaus, although at a higher rate compared to when there was less heat. This is because another factor is limiting.
• ways to measure photosynthesis

  - counting bubbles - but assumes bubbles are same size, all oxygen and no counting error

  - measuring the uptake of CO2 using radioactive carbon-14.

  - production of carbohydrates - measuring change in mass of discs of plants or whole plants after drying - have to kill plant tho
• chromatography experiment method for photosynthetic pigments

  1. Draw a straight dotted pencil 2cm above bottom of chromatography paper. Not pen (will split and effect results)

  2. Take leaf and add delergent and then grind in pestle and mortar to physically and chemically break down celt walls and mem.

  3. Add sample to center of dotted pencil line

  4. Add solvent 1cm above bottom of chromatography paper.

  5. wait until solvent has moved to top of paper

  6. Remove paper, mark where pigments (seperated) have moved up to. (middle) distance trasselled by pigment

  7. Calculak RF value for each: distance travelled by pigment/ distance travelled by solvent.

  8. compare with researched Rf values to identify pigments
• How to calculate the Rf value

  distance moved by substance/distance moved by solvent
• accessory pigments examples

  carotenoids and chlorophyll b
• difference between cyclic and non cyclic phosphorylation

  Cyclic photophosphorylation happens only in the photosystem I but non-cyclic photophosphorylation occurs in both the photosystems I and II

  
  

  In cyclic photophosphorylation only ATP is produced, whereas, in non-cyclic photophosphorylation both NADPH and ATP are produced.