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Wong_Katrina_Block5_MM6 (fermentation (fermentation vs cellular…

- - - - pyruvate--> ethanol
        
        CO2 released from pyruvate--> 2-C acetaldehyde
        
        aldehyde is reduced by NADH--> ethanol...regenerates NAD+ supply needed to continue glycolysis
    - - pyruvate is reduced directly by NADH to form lactate, no CO2
        
        Human muscle cells make ATP by lactic acid fermentation when oxygen is scarce (during strenuous excercise, when sugar catabolism for ATP production exceeds muscle's oxygen supply from blood). Accumalation of lactate=muscle fatigue and pain, but is graddually carried away by blood to the liver, and is converted back to pyruvate by liver cells
- - - - reducing agent: electron donor
      - oxidizing agent: electron acceptor
    - - organic molecules w a lot of H are good fuels because bonds's energy may be released when e- fall down an energy gradient when transferred to oxygen
        
        food = reservoirs of e- assoc w hydrogen
      - status of e- changes as H is transferred to oxygen, freeing energy (dG<0)
    - - glucose and other organic fuels are broken down in a series of steps by enzymes to improve efficiency
        
        e- are stripped, travelling w a protein, passed to a coenzyme: NAD+ (oxidizing agent during respiration
        
        enzyme dehydrogenase remove a pair of hydrogen atoms from substrate, oxidizing it. then it delivers the 2 e- w 1 H+ to its coenzyme, NAD+, NAD+ has its charge neutralized when reduced to NADH. NAD+ (most versatile)
- - - - glucose enters cell, is phosphorylateed by enzyme, which transfers a phosphate group from ATP--> sugar. the phosphate group charge traps sugar in cell (plasma membrane is impermeable to ions). phosphorylation makes it more reactive
        
        ATP--> ADP (loses phosphate group)
      - glucose-6-phosphate --> fructose-6-phosphate (isomer)
      - enzyme transfers phosphate group from ATP--> sugar. sugar now has 2 phosphate groups on opposite ends, can now split in half
        
        ATP--> ADP
      - enzyme splits sugar into 2 3-carbon sugars: dihydroxyacetone phosphate + glyceraldehyde-3-phophate (isomers)
      - enzyme catalyzes the reversible conversion between the 2 3-C sugars (never reaches equilibrium because the next enzyme uses glyceraldehyde-3-phosphate as its substrate
    - - enzyme catalyzes 2 reactions while holding glyceraldehyde-3-phosphate in its active site. First, sugar is oxidized: H+-->NAD+==> NADH (exergonic redox), uses released energy to attach a phosphate group to the oxidized substrate--> high EA product
      - glycolysis produces some ATP by substrate-level phosphorylation. the phosphate group previously added is transferred to ADP in an exergonic reaction. produces 2 ATP/glucose
      - enzyme relocates remaining phosphate group, prepping the substrate for next reaction
      - enzyme causes a double bond to form in substrate by extracting a H2O, yields phosphoenolpyruvate (PEP). electrons of the substrate are very unstable, prepping the substrate for next reaction
      - phosphate group is transferred: PEP--> ADP==> ATP (substrate level phosphorylation). occurs 2x bc 2 glucose...2ATP produced. final product: 2 pyruvate...if oxygen is present, chemical energy in pyruvate can be extracted by the citric acid cycle
- - - - electron carriers alternate between reduced/oxidized states as they accept/donate electrons. accept from uphill = reduced, v.v.
      - e- removed from food by NAD+ during glycolysis + citric acid cycle are transferred from NADH--> first molecule of ETC (flavoprotein)
      - falavoprotein returns to oxidized form as it passes e- --> FE.S in complex I
      - iron sulfur protein FE.S then passes e- to ubiquinone (Q), a small hydrophobic molecule (not a protein). It's mobile within the membrane
      - remaining e- carriers between Q and O2 = proteins called cytochromes, their prosthetic group: heme group, has an iron atom that accepts/donates e-. each cytochrome has a slightly different e- carrying heme group.
      - last cytochrome: cyt a3, passes its electrons to oxygen. each oxygen atom also pics up a pair of hydrogen ions from the aqueous solution, forming H20
      - when electron source is FADH2, FADH2 adds e- to ETC @ complex II, (lower energy level than NADH...ETC provides 1/3 for ATP synthesis
  - - - 4 main parts: (each has multiple polypeptides)
        
        rotar in the inner mitochondrial membrane
        
        internal rod extending from rotar into the knob
        
        statored, anchored next to the rotar, holds knob in place
        
        knob that protrudes into mitochondrial matrix
      - H+ flow between stator + rotor--> rotates--> conformational changes in stationary knob--> activates 3 catalytic sites in subunits that make up the knob, so ADP + Pi ==> ATP
    - - how does inner mitochondrial membrane generate/maintain H+ gradient?
        ETC makes H+ gradient. chain=energy convertor that uses exergonic flow of e- to pump H+ across membrane.
        
        ATP synthases are the only sites permeable to H+, ions pass through a channel in synthase using exergonic flow of H+ to drive ADP phosphorylation... energy stored in gradient couples redox reactions of ETC to ATP synthesis
      - how does ETC pump H+?
        certain member of ETC accept/release H+ as well as e-. e- transfers cause H+ to be taken up/released into surrounding solution.
        
        e- carriers are arranged in the membrane so H+ is accepted from the matrix and put in the intermembrane space. H+ gradient that results = proton-motive force
  - - - ATP yield varies of type of transportation of e- from cytosol into mitochondrion
      - proton motive force generated by redox reaction is used for other work
        if all of proton motive force generated by ETC was used for ATP synthesis, there'd be 34 ATP produced, + 4 ATP from substrate level phosphorylation
- - - - pyruvate's carboxyl group is removed, given off as 1 CO2
        
        first step in which CO2 is released during respiration
      - remaining 2 C is oxidized--> acetate. enzyme transfers extracted electrons to NAD+, storing energy as NADH
      - coenzyme A is attached to acetate by an unstable bond, =very reactive. acetyl CoA is ready to feed its acetyl group into citric acid cycle for further oxidation
    - - generates 1ATP/turn by substrate-level phosphorylation, but most chemical energy--> NADH and the related coenzyme FAD during redox reaction. reduced coenzymes: NADH + FADH2 shuttle electrons to ETC
        
        acetyl Coa: 2-Cacetyl group + oxaloacetate--> citrate
        
        citrate--> isomer isocitrate by removal of 1H20, and +1H20
        
        citrate loses 1 CO2, resulting compound is oxidized, NAD+-->NADH
        
        another CO2 is lost, resulting compound is oxidized, NAD+--> NADH. remaining molecule is attached to coenzyme A by an unstable bond
        
        CoA is displaced by a phosphate group--> GDP, forming GTP--> ADP, forming ATP (substrate level phosphorylation)
        
        2 hydrogens--> FAD==> FADH2 and oxidizing succinate
        
        addition of H2O rearranges bonds in substrate
        
        substrate is oxidized, NAD+--> NADH. regenerating oxaloacetate, continuing cycle
- - - - digestive tract: starch hydrolyzed--> glucose--> glycolysis--> citric acid cycle // glycogen in liver/muscles--> hydrolyzed
      - proteins -- > amino acids (amino groups must be removed...waste products)
      - fats--> glycerol+fatty acids--> glyceraldehyde-3-phosphate. beta oxidatioon breaks fatty acids into 2-C fragmens, which enter citric acid cycle as acetyl CoA
  - - - for compounds not found in food, compounds formed as intermediates can be diverted into anabolic pathways to synthesize the molecules it requires
  - - - eg: phosphofructokinase = allosteric enzyme w receptor sites for specific inhibitors (ATP)/activators (AMP)