Essential Knowledge 2.A.2: Organisms capture and store free energy for use in biological processes

 What happens to pyruvate after glycolysis? ◦ Pyruvate is transported from the cytoplasm to the mitochondrion via a transport protein. ◦ Pyruvate’s carboxyl group (COO - ), which is already fully oxidized, is removed as CO 2 ◦ The remaining 2 carbon fragment is oxidized, forming a 2 C compound called acetate and reducing NAD + to NADH + H + ◦ Acetate joins with Coenzyme-A, which makes it very reactive, forming Acetyl Co-A

CYTOSOLMITOCHONDRION NAD + NADH+H++H Pyruvate Transport protein CO 2 Coenzyme A Acetyl CoA

 Where does the Krebs Cycle take place? ◦ The matrix of the mitochondria  When Acetyl Co-A enters the Krebs Cycle, what does it join with? ◦ It joins with OAA (oxaloacetate). The 2 carbons originally from Pyruvate (and glucose) join with the 4 carbons of OAA to form 6 carbon Citrate.

 What happens in the Krebs cycle? ◦ Through a series of enzyme catalyzed reactions the remaining 2 carbons from pyruvate (originally from glucose) are oxidized and expelled as CO 2. 3 NAD + are reduced to form 3 NADH + 3H + and 1 FAD is reduced to form 1 FADH 2. Indirectly 1 ATP is formed.  How is ATP formed during the Krebs Cycle? ◦ Substrate level phosphorylation

Acetyl CoA CoA—SH Citrate H2OH2O Isocitrate NAD + NADH + H + CO2CO2  -Keto- glutarate CoA—SH CO2CO2 NAD + NADH + H + Succinyl CoA CoA—SH P i GTP GDP ADP ATP Succinate FAD FADH 2 Fumarate Citric acid cycle H2OH2O Malate Oxaloacetate NADH +H + NAD Summary of products from 1 turn of the Krebs Cycle: 2 CO 2 3NADH + H + 1FADH 2 1ATP

Pyruvate NAD + NADH +H++H+ Acetyl CoA CO 2 CoA Citric acid cycle FADH 2 FAD CO NAD H + ADP + P i ATP NADH Summary of products from the end of glycolysis thru the Krebs Cycle per glucose molecule: 6 CO 2 8 NADH + H + 2 FADH 2 2ATP

 Essential Knowledge 4.A.2:The structure and function of subcellular components, and their interactions, provide essential cellular processes. ◦ How do mitochondria specialize in energy capture and transformation?  Mitochondria have a double membrane that allows compartmentalization within the mitochondria and is important to its function  Matrix (within the inner membrane)  Intermembrane Space (between the inner & outer membranes)  The outer membrane is smooth, but the inner membrane is highly convoluted, forming folds called cristae  Cristae contain enzymes important to ATP production; cristae also increase the surface area for ATP production

Free ribosomes in the mitochondrial matrix Intermembrane space Outer membrane Inner membrane Cristae Matrix 0.1 µm

 Where is the electron transport chain of cellular respiration? ◦ The Cristae (inner member of mitochondria) ◦ In prokaryotic organisms it is located in the plasma membrane

 What happens at the electron transport chain? ◦ Electrons delivered by NADH and FADH 2 are passed thru a series of electron acceptors as they move toward the terminal electron acceptor, oxygen.  What happens as electrons move through the electron transport chain? ◦ The energy released by passage of electrons from one electron carrier to the next is used to pump H + from the matrix into the intermembrane space. (In prokaryotes H + is pumped outside the plasma membrane.) ◦ This creates a gradient of H + across the membrane called a proton-motive force.

 How does the proton gradient (H + ) produce ATP? ◦ The energy stored in the proton gradient is released as H + move back across the cristae through H + channels provided by ATP synthases - chemiosmosis INTERMEMBRANE SPACE Rotor H+H+ Stator Internal rod Cata- lytic knob ADP + P ATP i MITOCHONDRIAL MATRIX

Protein complex of electron carriers H+H+ H+H+ H+H+ Cyt c Q    VV FADH 2 FAD NAD + NAD H (carrying electrons from food) Electron transport chain 2 H / 2 O 2 H2OH2O ADP + P i Chemiosmosis Oxidative phosphorylation H+H+ H+H+ ATP synthase ATP 21

 Chemiosmosis couples the electron transport chain to ATP Synthesis… ◦ Electron Transport Chain: Electron transport and pumping protons (H + ), which create an H + gradient across the membrane ◦ Chemiosmosis – ATP synthesis powered by the flow of H + back across the membrane

Maximum per glucose: About 36 or 38 ATP + 2 ATP + about 32 or 34 ATP Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle 2 Acetyl CoA Glycolysis Glucose 2 Pyruvate 2 NADH 6 NADH2 FADH 2 2 NADH CYTOSOL Electron shuttles span membrane or MITOCHONDRION

ProcessNADHFADH2ATP Glycolysis202 Krebs Cycle822 Oxidative Phosphorylation Total x 3 = 10 x 3 = 30 Total X 2 = 2 x 2 = 4 34* Maximum per glucose = 36 to 38 *depends on which shuttle transports electrons from NADH in cytosol – may cost 2 ATP in that case OP = 32 ATP yield per Glucose at each Stage