energy transfers

• grana are stacks of thylakoids
• the electron transport chain is in the thylakoid membrane
• thylakoids are flattened fluid filled sacs where the light dependent reaction takes place
• the light independent reaction takes place in the stroma which is the fluid surrounding the grana
• rubisco catalyses the reaction of CO2 and RuBP to form glycerate 3 phosphate (GP)
• the calvin cycle is complete when triose phosphate (TP) is combined with ATP to remake RuBP
• in the LDR GP is reduced into TP by ATP and NADPH
• the photolysis of water produces electrons, protons and oxygen
• why is photolysis needed?

  replaces electrons lost from chlorophyll so the cycle can continue
• adaptations of chlorophyll for photosynthesis

  • Many ATP synthase channels in thylakoid/grana membrane
  • Large surface area of flattened thylakoids for chlorophyll, electron carriers and enzymes
  • Stromal fluid contains enzymes
  • Chloroplasts have their own DNA and ribosomes to manufacture enzymes
  • Photosystems maintain the structure of chlorophyll so it is positioned in a way that allows it to receive maximum sunlight
• not all the energy from the sun is absorbed by chlorophyll because some is reflected, some wavelengths can't be absorbed by chlorophyll, light doesn't hit chlorophyll molecules and because another factor is limiting the reaction
• in photosynthesis protons are actively transported from the stroma into the thylakoid membrane using energy from the ETC
• in respiration protons are actively transported from the matrix into the intermembrane space using energy from the ETC
• when electrons become excited and leave the chlorophyll in photoionisation, the chlorophyll becomes positively charged/ionised
• NPP = GPP-R
• N = I - (F + R). N= net production of new biomass, I = chemical energy store of ingested food, F = energy lost in faeces and urine, R = energy lost in respiration
• coenzymes facilitate the binding of enzyme to substrate. Examples include NAD, FAD and NADP
• in animals: pyruvate + NADH --> lactate + NAD
• in plants and yeast: pyruvate + NADH --> ethanol + CO2 + NAD
• in anaerobic respiration pyruvate is reduced by NADH
• lactate causes cramp, muscle fatigue and lowers pH so may cause enzymes to work less well
• lactate can be oxidised back to pyruvate when oxygen is available
• in aerobic respiration ATP is made in the Krebs cycle, glycolysis and the electron transport chain
• in photosynthesis ATP is made by oxidative phosphorylation
• the electron transport chain is in the inner membrane of the mitochondria