ELECTRON TRANSPORT CHAIN Stage 4:

How far have we come? We began with our simple glucose molecule Through the processes of... – GLYCOLYSIS – PYRUVATE OXIDATION – KREBS CYCLE...we have used the energy stored in the C-C bonds of glucose to help ATP Directly (substrate-level phosphorylation) Indirectly (oxidative phosphorylation)

Energy Totals GLYCOLYSIS PYRUVATE OXIDATION KREBS CYCLE ATP USEDATP produced NADH produced FADH 2 produced ATP USEDATP produced NADH produced FADH 2 produced 2440 ATP USED ATP produced NADH produced FADH 2 produced 2420

So what’s the deal with ATP?? C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + 36 ATP We need to produce 36 ATP in Cell. Resp. After 3 stages, we have only produced 6 ATP through substrate-level oxidation Thus, there are 30 ATP left to create – We produce the remaining 30 ATP through oxidative phosphorylation in the ETC

ELECTRON-TRANSPORT-CHAIN In this step, we will utilize the energy provided by the electron carriers NADH and FADH2 Extremely EXERGONIC ∆G = kJ/Mol

How it works NADH + FADH2 eventually transfer the electrons they carry to a series of proteins that are located in the inner membrane The components of the ETC are arranged in order of increasing electronegativity Thus, allowing the electrons to flow, or BE TRANSPORTED, between the compounds Every step involves oxidation and reduction rxns.

How it works Every time an electron moves from one molecule to the next, free energy is released The free energy is used to pump H+ ions, or PROTONS, from the mitochondrial matrix into the INTERMEMBRANE SPACE The ETC needs a highly electronegative compound to oxidize the last protein – OXYGEN is used here, as it is one of the most electronegative compounds on earth

How it works An oxygen atom removes two é from the final protein complex Oxygen then combines with 2 protons (H + ) in the mitochondrial matrix to form an H2O molecule Diagram The red path shows the path that é travel through the ETC KNOW NAMES OF THESE MOLECULES

How it works NADH DEHYDROGENASE CYTOCHROME b-c1 COMPLEX CYTOCHROME OXIDASE COMPLEX UBIQUINONE (Q)cytochrome C

NADH + FADH2... Not so similar NADH passes its electrons to the first protein complex – NADH DEHYDROGENASE FADH2 passes its electrons to Q (or ubiquinone) This distinction means that: – NADH = 3 H+ pumped out – FADH2 = 2 H+ pumped out SO... – NADH produces 3 ATP – FADH2 produces 2 ATP

NADH + FADH2... Not so similar The NADH you produced in glycolysis works differently than the NADH produced in pyruvate oxidation and Krebs cycle – Why? Glycolysis occurs in the cytoplasm, thus NADH has to travel through the double membrane of mitochondria – it can’t pass the inner membrane NADH passes its é through a protein transport to FAD thus forming FADH2

ATP PRODUCTION Electrochemical Gradient: A concentration gradient created by pumping ions into a space surrounded by a membrane that is impermeable to the ions – This is exactly what we are doing when we pump H+ ions into the intermembrane space using the ETC – Thus, the inner membrane becomes a H+ reservoir – An potential difference, or VOLTAGE, is created across the membrane +ve charge in the intermembrane space –ve charge in the mitochondria matrix

ATP PRODUCTION H+ ions can not diffuse back through the innermembrane They need to be pumped back by the transport protein ATP SYNTHASE As H+ ions are passed through ATP SYNTHASE, the free energy of the gradient is reduced, thus releasing enough energy to produce ATP ADP + Pi  ATP

ATP PRODUCTION This process was coined: CHEMIOSMOSIS ATP synthesized was caused by the ‘osmosis of H+ ions’ Chemiosmosis is said to be COUPLED to the ETC

Final Energy Tally

Theoretical Yield vs. Actual Yield It is possible that we will not always obtain 36 ATP for every glucose molecule that we used 2 reasons: 1.Some H+ ions may make it through the inner mitochondrial membrane reducing the number of H+ ions that pass through ATP synthase. 2.Some of the protons in the H+ reservoir might get used up in other cellular reactions