Paper 2

• where do the light dependent and light independent reactions take place ?

  LDR= thylakoid membrane/granum

  LIR= Stroma
• basics of LDR:

  • water + light energy= ATP, NADH (useful in LIR)
• steps of LDR:

  1. photolysis
  2. photoionisation of chlorophyll
  3. chemiosmosis
  4. production of ATP + reduced NAD
• Photolysis:

  light energy is absorbed by the chlorophyll causing the split of water H20= 1/2 o2 + 2e- +2h+

  • H+ picked up by NAD= NADH
  • e- passed along electron carrier proteins
  • o2 used for respiration or diffuses out through stomata
• Photoionisation:

  Light energy absorbed by chlorophyll - excites electrons= ^ energy level, e- leaves chlorophyll + chlorphyll ionised

  • some energy left from released e- can be used to synthesis ATP + NADH in chemiosmosis
• Chemiosmosis:

  1. electrons gained energy, left chlorophyll- move along proteins embedded in thylakoid membrane
  2. as they move along the electron transport chain they release energy that promotes protons being pumped across chloroplast membrane from stroma into thylakoid lumen
  3. electrochemical gradient created
  4. protons move by facilitated diffusion down concentration gradient to stroma - they can only attach to ATP synthase, enabling enzyme to phosphorylate ATP
  5. protons back in stroma, combine with NAD= NADH
• Where does the Calvin cycle take place?

  Stroma
• LIR: Calvin Cycle

  • enzyme Rubisco catalyses reaction
  • temperature sensitive - involvement of enzymes
  • uses co2 +NADH +ATP= hexose sugar
  • ATP hydrolysed to provide energy
  • NADH donates h+ to reduce GP into TP
• Calvin Cycle:

  1. co2 reacts with ribulose biphosphate to form 2 Glycerate 3 phosphate molecules (3c)
  2. GP reduced by energy from ATP and H+ into triose phosphate= NAD reformed
  3. 1 Triose phosphate loses a carbon molecule that will be used to synthesise a hexose sugar
  4. Tp is regenerated into ribulose biphosphate (5c) using ATP
• What is significant about the Calvin Cycle?

  It has to occur 6 times to result in the synthesis of a hexose sugar- that can become a di/polysaccharide or glycerol which can bind to fatty acids to form lipids for plants
• limiting factors of the Calvin Cycle:

  • temperature - less successful collision + less kinetic energy
  • light energy - necessary in LDR
  • co2 concentration - reactant in Calvin Cycle
• processes in Aerobic respiration?

  1. Glycolysis
  2. link reaction
  3. krebs cycle
  4. oxidative phosphrylation
• where does Glycolysis take place?


  cyptoplasm
• where do the Link reaction and the Krebs cycle take place?

  Mitochondrial matrix
• where does oxidative phosphorylation take place?

  mitochondrial inner membrane cristae
• overview of Glycolysis:

  • occurs in cyptoplasm
  • produces few ATP
  • 1st stage of Aerobic & Anaerobic respiration#
• process of Glycolysis:

  1. Phosphorylation of glucose into glucose phosphate
  2. production of Triose Phosphate - due to unstable 6c compound
  3. oxidation of Triose Phosphate to produce Pyruvate (3c)- ADP phosphorylated into ATP + NAD oxidised into NADH
• what are the products of Glycolysis?

  2 x Pyruvate molecules

  net gain of 2 x ATP ( 2 used in process)

  2 x NADH
• What happens to the pyruvate and NADH after Glycolysis?

  pyruvate is transported into the mitochondrial matrix to be further broken down in krebs cycle
• Link Reaction:

  1. pyruvate is oxidised into acetate- loses proton
  2. NAD picks up h+ - becomes NADH (is reduced)
  3. Acetate combines with co-enzyme A =acetyl CoA
• What is significant in the Link reaction?

  the link reaction occurs twice for every glucose molecule- therefore there are products per cycle and per glucose
• products of Link reaction?

  2 x acetyl CoA

  2 Co2 released

  2 NADH
• what happens to Acetyl CoA before it can enter the Krebs Cycle?

  Acetyl CoA reacts with a 6 carbon molecule - releasing co-enzyme A, producing 6c compound to enter Krebs cycle
• Krebs Cycle:

  series of redox reactions = reduced coenzymes + ATP through substrate-level phosphorylation - co2 lost
• what are the products of the Krebs Cycle?

  per cycle: per glucose :

  3 x NADH 6 x NADH

  1 x FADH 2 x FADH

  1 x ATP 2 x ATP

  2 x Co2 4 x Co2
• Oxidative Phosphorylation is where most of the ATP is produced (34)
• Oxidative Phosphorylation:

  • in mitochondrial matrix coenzymes produced release protons and electrons
  • the electrons move across ETC - releasing energy to actively transport protons into inner membrane space = electrochemical gradient
  • protons move by facilitated diffusion down ATP sythase phosphorylating ADP into ATP
  • at the end of ETC o2 is final electron acceptor
  • reformation of water
• Anaerobic Respiration:

  • occurs only in cyptoplasm
  • has only glycolysis in common with Aerobic respiration
• what happens to Pyruvate produced in Glycolysis in Anaerobic respiration?

  pyruvate is reduced to

  ethanol + co2 in plants & microbes

  lactate in animals
• what happens to NAD in anaerobic respiration and why?

  NADH is oxidised so glycolysis can occur - reactant in Glycolysis
• Lactate formed by gain of h+ from oxidised NADH - pyruvate reduced - NAD can be reused
• what is the issue with both Lactate and Ethanol?

  they are both acidic - can denature enzymes - therefore organisms cannot respire anaerobically for long
• How can energy be lost between trophic levels?

  • through respiration
  • excretion
• remaining energy of organism, not lost is the biomass
• what can the amount of biomass in organisms be described as ?

  drymass per given area
• What does the productivity of an ecosystem depend on ?

  abiotic & biotic factors
• give an example of factors affecting productivity of an ecosystem:

  plenty of warmth, light, water & green plants can maximise photosynthesis = more carbohydrates produced

  • quantified by NPP & GPP
• what does GPP stand for and mean?

  Gross Primary poduction : chemical energy stored in plant biomass in given area/volume - total energy resulting from Photosynthesis
• what does NPP stand for and mean?

  Net Primary Productivity: chemical energy stored in plant biomass - taking into account respiratory loss
• what is the equation for NPP?

  NPP = GPP - R