Cycle 4: Primary Metabolism

• Growth rate on growth curve

  = Enzyme Activity
• Temperature increases


  Enzyme gains kinetic energy (bumping into one another, bind substrates)
• Too much thermal energy

  Enzyme denatures
• Extremophiles - tertiary structure dependent on primary structure


  Primary structure different (cold = more rigid = weak, hot = less rigid = strong arrangement)
• Photosynthesis


  Process performed by autotrophs
• Endergonic (+ delta G)


  Needs lights energy
• Redox Reaction


  CO2 is reduced to C3P (used in respiration and other essential process). Water is oxidized to O2 (oxygenetic photosynthesis)
• 2 phases of photosynthesis


  Light -dependent reactions (thylakoid), calvin cycle (stroma)
• Chlorophyll Structure


  Stroma - calvin cycle. Membrane of thylakoid - light reaction. Genome - complete transcriptional and translational apparatus (ex: D1 protein)
• Bacteriorhodopsin


  Similar to channelrhodopsin, captures light energy to move H+ against its concentration - proton gradient
• What is the proton gradient used for?

  To produce ATP using ATP synthase
• Photosynthesis' end goal


  To produce organic molecules such as glucose
• Photosynthetic Electron Transport Steps

  / 1 .Light excites pigment in PSII (P680 to P680*)/ 2. P680* gets oxidized by donating e- to e- carrier (P680* to P680+)/ 3. Movement of e- carrier causing h+ movement across stroma to lumen (proton gradient)/ 4. e- transferred to PSI and excited by another photon (P700 to P700*)/ 5. P700* donates e- to e- carrier/ 6. e- reduces NADP+ into NADPH/ 7. Proton gradient formed creates proton-motive force 8. ATP-synthase uses gradient to synthesize ATP
• Light Dependent Reactions


  Series of redox reactions, electrons are excited by light in the photosystems, the excited state pigment harnesses enough energy to donate electron to the electron carrier
• Each subsequent electron acceptor has


  An increasing redox potential
• Negative redox potential


  = More easily oxidized
• Two photosystems allows to


  Bridge the gap between the redox potential
• Excitation of electrons in photosystems

  Chlorophyll pigment P680 is bound to D1, P680 undergoes redox rxns to pass electrons onto PS1, under high intensity the P680* (very unstable) accumulates, steals e- from D1 (D1 rate of repair > D1 rate of damage, P680* typically gets e- from H2O)
• Facts about the Calvin Cycle

  Happens in the stroma and converts CO2 into sugar
• Calvin Cycle Step 1

  Fixation: CO2 fixation onto RuBP by rubisco which produces PGA
• Calvin Cycle Step 2

  Reduction: ATP and NADPH reduces PGA to produce G3P (6 G3P)
• Calvin Cycle Step 3

  Regeneration: RuBP is regenerated from remaining 5 G3P (RuBP regenerated each time, every 3 turns produces 1 G3P, 2 G3P = 1 molecule of glucose)
• Evolution of oxygenic photosynthesis


  Uses water instead of H2S to donate electrons (very significant), water needs 2 photosystems to be fully oxidized
• Why is using water as a electron donor significant?

  Water is everywhere in the world, so if it is used to photosynthesize, they can grow much larger and longer
• Anoxygenic photosynthesis


  The phototrophic process where light energy is captured and converted to ATP, without the production of oxygen (water is not used as an electron donor)
• Oxygenic photosynthesis


  CO2 + H2O + light energy = carbohydrate + oxygen. In plants, algae and cyanobacteria, photosynthesis releases oxygen
• Catabolism


  Involves the breakdown of large macromolecules into smaller units 
• Anabolism


  Can be thought of as the opposite, requires the input of energy to synthesize large molecules from smaller ones (photosynthesis is anabolic)
• Exergonic pathway (energy coupling)

  Just goes
• Endergonic requires ______ to occur in energy coupling

  ATP
• Can couple endergonic reactions with

  ATP hydrolysis reaction
• Endergonic reactions


  Do not occur in the cell
• Substrate level phosphorylation includes 


  Glycolysis and the citric acid cycle
• Glycolysis is found in the ___ and the ____ is found in the ___ of the ___

  Cytosol, citric acid cycle, matrix, mitochondria
• In the citric acid cycle, energy from


  Acetyl-CoA is used to reduce the electron carriers, NAD+ and FAD, and also form ATP
• Substrate level phosphorylation generates


  Less net ATP than oxidative phosphorylation
• Goal of oxidative phosphorylation is to


  Convert free energy from NADH and FADH2 into ATP
• 2 processes of oxidative phosphorylation


  Oxidative - electron transport, Phosphorylation - chemiosmosis
• Chemiosmosis


  ATP synthase couples the proton gradient to the synthesis of ATP, because the only way to dissipate the proton gradient is to pass through ATP synthase into the matrix. Protons are charged and cannot pass through the membrane. Protons can only pass through ATP synthase to return to matrix
• ATP is not a product of the electron transport chain, instead it is a

  Product of chemiosmosis, which are two distinct process. Water is the product of electron transport, but this is not the purpose of oxidative phosphorylation