Cellular respiration (Parts 2 and 3)

 In general: Pyruvate (3-C molecule) enters the mitochondrion, and enzymes oxidize it.  Transition between Glycolysis and CAC: Pyruvate is converted to acetyl CoA.  (CO2 is removed)  Like a furnace because of all the oxidizing!  Output per molecule of pyruvate (Remember: 2 per glucose) –  3CO 2, 1 ATP, 1 FADH 2, 4 NADH … carry high- energy electrons to ETC

 1) acetyl group on acetyl CoA combines with oxaloacetate to form citrate  2) water is removed then added to make isocitrate (isomer of citrate)  3) CO 2 is removed and the compound is oxidized (NADH is formed)  4) CO 2 is removed and the compound is oxidized and attached to CoA (NADH is formed)

 5) CoA is displaced by a phosphate that is eventually transferred to ADP to make ATP  6) H’s are transferred to FAD to form FADH 2  7) water is added to break and form bonds  8) NAD+ is reduced to NADH by oxidizing the substrate to reform oxaloacetate

CO 2 ATP

 Now we see how most ATP is made from energy in food!  The “taxis” that escort the electrons from Glycolysis & CAC to the Electron Transport Chain are NADH and FADH 2.  Electron Transport Chain:  Made of molecules (mostly proteins) embedded in the inner membrane of the mitochondrion  Many folds (“cristae”) provide more surface area  Proteins become reduced when they receive electrons, then oxidized when they pass on the electrons to their more electronegative neighbor  Free energy decreases with each step

 1. NADH (carrying electrons from food) releases its electrons to a flavoprotein.  2. The flavoprotein then passes the electrons to an Iron-Sulfur protein.  3. From there, the electrons are transferred to ubiquinone (a mobile, non- protein electron carrier).

 4. Other protein carriers known as cytochromes then pass the electrons on to oxygen.  5. Oxygen is VERY electronegative, so it readily grabs the electrons as well as hydrogen ions to form water.  *Note: FADH 2 adds its electrons at a lower energy level, so it provides less energy for ATP synthesis.  Permits H+ to move down its concentration gradient.

 ATP Synthase is a protein complex in the mitochondrial inner membrane that uses an ion gradient to make ATP.  This gradient (or proton motive force) drives H+ back across the membrane through ATP synthase  Chemiosmosis – the process in which energy stored as a H+ gradient across a membrane drives cellular work (i.e. – generates ATP)  Electron transfers cause protons (H+) to be pumped across the mitochondrial membrane by some members of the ETC.

 ATP synthase is composed of a rotor, a knob, a rod, a stator  ATP synthase’s rotor spins as H+ pass through it, then the knob’s enzymes are activated by conformational changes  Total = ATP produced from 1 glucose