Cellular Respiration Stage 2 Oxidation of Pyruvate Stage

Cellular Respiration Stage 2: Oxidation of Pyruvate Stage 3: Krebs Cycle Stage 4: ETC AP Biology 2006 -2007

Cellular respiration AP Biology

Mitochondria Structure § Double membrane u u highly folded inner membrane called cristae Importance: increases surface area § Fluid filled interior called “matrix” u u DNA, ribosomes, enzymes Site of the Krebs Cycle outer intermembrane inner space membrane cristae matrix AP Biology mitochondrial DNA

Mitochondria – Form fits Function Divide like bacteria Supports endosymbiosis Internal folds Advantage = more surface area AP Biology Membrane-bound proteins passive & active transport

Stage 2: Oxidation of pyruvate § Pyruvate enters mitochondria [ 2 x pyruvate acetyl Co. A + CO 2 3 C 2 C 1 C NAD ] § Pyruvate OXIDIZED and forms acetyl Co. A 1. 2. AP Biology releases 1 CO 2 reduces 2 NAD+ 2 NADH

Stage 3: Krebs Cycle Aka citric acid cycle § What? oxidation/reduction process that forms CO 2 and H 2 O [wastes] § Where? Matrix of mitochondria § Significance evolved later than glycolysis, but fundamental to aerobic respiration AP Biology

OXIDATION – in the presence of O 2 - aerobic Produces: § CO 2 and H 2 O § energy carriers [8 NADH and 2 FADH 2] § 2 net ATP AP Biology

Electron Carriers = Hydrogen Carriers H+ H+ NADH u FADH 2 u go to Electron Transport Chain H+ H+ H+ u AP Biology ADP + Pi ATP H+

Energy accounting of Krebs cycle 4 NAD + 1 FAD 4 NADH + 1 FADH 2 2 x pyruvate CO 2 3 x 1 C 3 C 1 ADP 1 ATP Net gain = 2 ATP = 8 NADH + 2 FADH 2 AP Biology

H+ Electron carriers are important because they … H+ H+ § Set up a H+ gradient u allow H+ to flow through ATP synthase ADP + Pi ATP AP Biology ADP + P ATP H+

Stage 4: Electron Transport Chain AP Biology

ETC § transport proteins and enzymes are built into inner mitochondrial membrane [cristae] u transport electrons down ETC using protons donated by energy carriers (NADH, FADH) § yields ~34 ATP from 1 glucose § only in presence of O 2 (aerobic respiration) AP Biology O 2

Glycolysis glucose Krebs cycle PGAL 8 NADH 2 FADH 2 Time to break open the bank! AP Biology

Electron Transport Chain Building proton gradient! NADH NAD+ + H e p intermembrane space H+ H+ H e- + H+ C e– NADH H FADH 2 NAD+ NADH dehydrogenase inner mitochondrial membrane e– Q AP Biology H+ e– H FAD 2 H+ + cytochrome bc complex 1 2 O 2 H 2 O cytochrome c oxidase complex mitochondrial matrix

Stripping H from Electron Carriers § NADH and FADH pass electrons to ETC u u u electrons stripped from H atoms H+ (protons) electrons passed from one electron carrier to next in mitochondrial membrane (ETC) transport proteins in membrane pump H+ (protons) across inner membrane to intermembrane space H+ H+ H+ H H+ C e– NADH AP Biology Q e– FADH 2 FAD NAD+ NADH dehydrogenase e– 2 H+ cytochrome bc complex + 1 2 O 2 H 2 O cytochrome c oxidase complex ADP + Pi ATP H+

But what “pulls” the electrons down the ETC? O 2 AP Biology oxidative phosphorylation

§ Oxidative phosphorylation is the process in which ATP is formed as a result of the transfer of electrons from NADH or FADH 2 to O 2 by a series of electron carriers. This process, which takes place in mitochondria, is the major source of ATP in aerobic organisms AP Biology

Electrons flow downhill § Electrons move from carrier to carrier downhill to O 2 each carrier more electronegative u controlled oxidation u controlled release of energy u AP Biology

H+ gradient § Allows protons H+ H+ to flow through ATP synthase H+ H+ H+ § Synthesizes ATP ADP + Pi ATP AP Biology H+

Chemiosmosis § The diffusion of ions across a membrane u build up of proton gradient just so H+ could flow through ATP synthase enzyme to build ATP Chemiosmosis links the Electron Transport Chain to ATP synthesis AP Biology

Pyruvate from cytoplasm Inner + mitochondrial H membrane H+ Intermembrane space Electron transport C system Q NADH Acetyl-Co. A 2. Electrons provide energy 1. Electrons are harvested to pump protons and carried to the transport across the system. membrane. - NADH Krebs cycle e- e FADH 2 e- ATP Mitochondrial matrix AP Biology e- H 2 O 3. Oxygen joins with protons to form water. 1 O 2 +2 2 H+ O 2 H+ CO 2 2 H+ 32 ATP 4. Protons diffuse back in down their concentration gradient, driving the synthesis of ATP. H+ ATP synthase

Cellular respiration 2 ATP AP Biology + 2 ATP + ~34 ATP