Mitochondrial Membrane Transport   &   the Electron Transfer Chain 

                                                Mitochondrial spaces*
  outer membrane contains - porin* - a channel protein
                             that allows diffusion molecules ≈ < 5,000 daltons

  inner membranes - IMPERMEABLE to most molecules,  esp.  to  H+  
   mitochondria  &  ecb 14.8 pg461* &  mitochondrial tomographyviewed earlier
   inner membranes - some 70% protein & 30% lipid...  & its components* include:
       a.  redox proteins* of Electron Transfer Chain












       b.  ATP synthase*                                    -->
       c.  many carrier proteins*    phosphate translocases,
               ADP/ATP translocases,   pyruvate/H+ symporter,
              α-glycerol-P,                  malate shuttles,  and    
              fatty acid metabolism (β-oxidation) enzymes  
     2  
    

 

 

 

 

 

 

 

 
the  ORIGINs of MITOCHONDRIAL were likely by endosymbiosis*
    
   mitochondrial DNA... 
       Human mitochondrial DNA* has  16,569+ np's...       (mito DNA) 
       Only 13 out of some ≈ 1,100 mito proteins are gene coded in the mito...
                    the rest are coded for by nucleus & made in cytoplasm.
       Mitochondrial DNA also codes for some tRNA & rRNA. 
       in 2008 V. Mootha generated a complete inventory of ≈ 1,098 mito-proteins.
                  figure of some proteins encoded by nuclear & mitochondrial DNA*  
              gene transfer between plant nucleus & plastids is common

       The 1,000+ mito per cell are maternally inherited; mtDNA does not change
       as rapidly as nuclear DNA and it is not mixed with paternal DNA, thus it has
       a clearer record of maternal ancestry sequence homology.
       Analysis of mtDNA and its short tandem repeat sequences [2 to 16 base
       pairs long]  -->   can indicate phylogeny relatedness.  
               mtDNA & Human Evolution             mitochondrial "Eve"
               genetic variation among peoples     mitochondrial diseases     forensic uses of Mito-DNA        
      

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


How Electron Transport Works
Mitochondrial aerobic cell respiration is driven by e-transport* 
         REDOX POTENTIAL                     Text description - REDOX REACTION*a text description
                - is a measure of tendency of molecular couple (acceptor/donor) to GAIN-LOSE e's
               - strong reducing agent (electron donor - NADH) has negative    - E'o  (redox potential)
               - strong oxidizing agent (electron acceptor - O2) has positive     + E'o  (redox potential)   
               - by chemical convention e- flow from more negative to more positive potentials
               - electrical potential difference (voltage) is difference in work to move charge from point to point    
                           How ΔE'o are measured & expresed – Reference half-cell*  &  table )
           How to calculate Free Energy Changes due to Electron Transfers:   
           Free Energy  &  Redox Potential:   ΔG'o  = -n (0.096) ΔE'o  in kJ/mol   
               NADH <---> NAD+ +  H+ + 1e-      - 0.320V     (-320 millivolts) 
                   QH2  <--->  + H+ + 1e-                        + 0.030V     (-30 millivolts)      [ΔE'o = 350mv]
                                 ΔGo'  =   - (1)  (0.096 kJ/volt)  (0.35v)    =    -33.6 kJ   or   -8.03 Kcal/mol
              H2O   <--->  ½ O2 + H+ + 1e-       + 0.82V       (+820 millivolts)    [ΔE'o = 1140mv]
                      ΔE'o (NADH - H2O) = 1,140mv  thus 
                     ΔGo'  =   - (1)  (0.096 kJ/volt)  (1.14v)  =  -109.4 kJ    or    -26.14 Kcal/mol

            theoretical P to O ratio for  1 NADH = 3 ATP = -7.3Kcal x 3  =  -21.9 Kcal/mol
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What are the molecular component that pass electrons from NADH to O2
    Electron Transfer Chain and the order of its e- carrier molecules...    
   ETC

        ETC is a series of electron CARRIER MOLECULES that that transfer e-'s
       from a more negative redox potential to a more positive redox potential,
        while "driving" protons out of the mitoplasm into perimitochondrial space. 

--> carriers are aligned linearly...    via increasing Redox Potential... table*
         from more electronegative [ - ]  toward more electropositive to [ + ]
              and therefore by their energy differentials:  
                sequence of major components*      

-->  membranes themselves have no electrical charge, but instead they separate
                         electrical charges making the membrane an insulator...
                         an insulator that separates electric charges until used like a battery: (ecb 14.11 pg 463)

  next  

 

 

 

 

 

 

 

 

   
Properties of ETC Molecular Carrier Components
  Pyridine nucleotides NAD+                               ecb-14.10*  &  ecb 3.34b
        enzyme bound hydrogen carriers                                            
        accept  2e's and/or protons                                   
        show spectral shifts @ 340nm NADH vs. NAD
  Flavoproteins FMN & FAD                  ecb 13.13b*                                
        protein bound hydrogen carriers                                   
        spectral shift @ 340, 370, & 450 nm
  Iron sulfur proteins FeS                               mcb12.14b p495*  - karp-5.12
        non-heme iron electron carriers within complexes I, II,  & III
        (ferrous+2 <--> ferric+3)     
  Ubiquinone CoQ - quinone & hydroquinone  ecb 14.23*     
        mobile, membrane bound, non-protein hydrogen carriers

Cytochromes (a, a3, b562, b566, c1, c)        ecb 14.25-heme*       
      "colored proteins" with bound Fe atoms [ ferric+3 ox vs. ferrous+2 red]
       via iron porphyrin (heme) bound protein carriers
                                                                  ecb 14.26 - cytochrome-C-oxidase
       the molecular structures of the carrier molecules - Karp figure 5.11

 

 

 

 

 

 

 

 

 

 

 

 
 
  How Electron Transport Chain Works*
  
  The 4 Mitochondrial Respiratory Assemblies       
 
      I. NADH dehydrogenase
           II. Succinate dehydrogenase
      III. Cytochrome-C-Reductase  
      IV. Cytochrome Oxidase          text description - Components of ELECTRON TRANSFER CHAIN*		               Click on image below
  
  ETC*  =   the ETC carrier Complexes
  
  PMF* -  Proton Motive Force* 
                  pH difference    ΔpH = 0.7 to 1.0 pH units     
                  membrane potential difference
                               Δcharge =   140mV  in(-) vs. out(+)
            Electron Transport: The Movie*view@home  

      the PMF drives transports ecb-14.18*

cytochrome oxidase
cytochrome-C-oxidase

        

               



 

 

 


 

 

 

 

 

 

 

  
Chemiosmosis...     [linking the PMF to Oxidative Phosphorylation]...
   Proton Motive Force gradient  leads to Synthesis of ATP
        movement of protons down electrochemical gradient
     through an ATP synthase drives ATP synthesis.

Peter Mitchell 1978 - Chemiosmotic Coupling*read-history 
     hypothesized a fundamental cell energy mechanism that
     arose early in evolution & was retained by cells to make ATP. 
   
  Evidence:    fractionation*   &  reconstitution*
                         pH gradients*  &  bacteriorhodopsin*

  Chemiosmosis in bacteria, mitochondria, & chloroplasts*

*
 ATP Synthase   condenses ADP  +  Pi  --->   ATP   
                                  has a hydrophilic channel (F0) for H+ flow
                                  & makes 100 ATP per 300 H+ per sec 
           F1 – 'matrix' soluble piece:              9 proteins
           F0 – membrane bound piece stalk:   15 proteins              
  
                    (its origin may be hydrolytic)              

* 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Structure of the cellular macromolecular machine - ATP SYNTHASE
      Humbeto Fernandez (60's) sees lollipops on inner mito membranes*
      Efraim Racker (1966) isolates 'lollipop' - Coupling Factor 1 - F1     
       
    'mushroom' shaped complex* composed of 2 membrane subunits
           F1 (extrinsic-mitoplasmic)   &   F0 (intrinsic-inner membrane)
 		                         EM's

   
       Click on pic for larger image*
 ATP synthase in liver mitochondria number about 15,000  and is
         made of 24 polypeptides with membrane & mitoplasmic pieces.

   F1  (mitoplasmic side) - has 5 polypeptides (nuclear DNA coded): 
                      3α ,  3β ,  1γ ,  1δ,  &   1ε
                      arranged like sections of grapefruit.     
         3 catalytic sites for ATP synthesis - 1 on each β  subunit
   F0   (cytoplasmic side) - 3 polypeptides in ratio of  1a, 2b, and 12c's
                      C-ring binds H+ and conformationally rotates.
 
   


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  
 
Binding Charge Mechanism of ATP Synthesis - A Rotary Motor   Paul Boyer 1979 Nobel
          1.  H+ movement changes binding affinity of the synthase's F1's β's active site,
                    thus when ADP & P bind to β'-active site, they readily condense into ATP
                   (removed from aqueous solution Keq =  1  &  ΔG close to zero, thus ATP readily forms)
          2.  the β-subunits   change conformation*  through 3 successive shapes (O-L-T)
                        O - open - site has low affinity to bind ATP - thus releases it  [see E]
                        L - loose - ADP & P loosely bound to site  [1 & 2] 
                        T - tight - ADP & P tightly bound favoring condensation without water  [3]
         3.  conformational changes result in rotation of subunits relative to central stalk (γ)
                        α & β subunits of F1 form hexagonal ring that rotates around central axis.
                        γ stalk extends from F0  & interacts with 3 β's differently as it rotates thru 360o


makes 100 ATP per 300 H+ per sec

 a machine anim*        &           water wheels*     

   

 

 



 






 
 


 

 

 

 

 

  How ATP Synthase converts Mechanical Energy into Chemical Bond Energy...
       via a Proton Pathway is thru Fo-ring of C proteins.

text description - ATP SYNTHASE  a description
       12 C-proteins reside in lipid bilayer (C-ring)
            C-ring is attached to γ stalk of F1 subunit
                 H+ diffuse through Fo half-channel
                      rotating the 12C's of the Fo ring 

      



rotation
 *click

  each C protein has a channel space with a neg charged aspartate
  C's-ASP bind H+ & via shape changes each C-rotates 300 CCW
  the next C-ASP in the ring picks up H+ - thus 12 C's rotates thru 3600
       release of H+ is into matrix happens at end of cycle     Karp 5.29
              4 H+ moves ring 120o (γ stalk) shifts 120o --> change in F1-β's
             4 rotation of C-ring drives γ stalk through 360o
             4 H+s result in one ATP being made
         3 rotary conformations of F1 (L-T-O) make an ATP 
            


                   a summary figure of Aerobic Cell Respiration* 

                          
    next lecture is photosynthesis               Energy Rap         
        

 

 

     

 

 

 

 



























 

 

 

 

 

skip this for now...
         photosynthesis analogy* & animation*@home & bacteria, mito, chlp comparisons

SKIP this =    ex: how Q-cycle moves protons mcb-12.17*
                 animation  

     
                      An unusual ATP synthase

    
   homoplasmic vs. heteroplasmic mtDNA?