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Aerobic Respiration Remember… • Cellular respiration is the breakdown of glucose into energy • So far we have learned about glycolysis • Glycolysis is the first of many steps in cellular respiration • Glycolysis happens in the cytoplasm Remember… • Glycolysis is the formation of 2 ATP, 2 NADH and 2 pyruvate from the energy that is given off by the splitting of glucose • It is a complex process that involves energy investment and energy payoff Before The Next Step • After glycolysis and before our next step some very important things happen • We have to first determine the type of respiration that will follow • If there are mitochondria and oxygen present most cells will perform aerobic respiration Before The Next Step • Before aerobic respiration happens a series of reactions happens to pyruvate • These reactions happen in the mitochondria • This is because the mitochondria is the sight of aerobic respiration Before The Next Step • Pyruvate is acted on by a large multiple enzyme complex that performs three key reactions in a short time 1. Pyruvate loses a carboxyl group (COO-) which is transported out of the cell as CO2 Before The Next Step 2. The remaining 2 carbon compound is oxidized (loses electrons) to create a molecule of NADH from NAD+ 3. A compound called coenzyme A joins in with the two carbon compound to form acetyl CoA Intro Citric Acid Cycle • The next step in the process is the Citric Acid Cycle • This cycle can also be called the “Krebs” cycle in honor of Hans Krebs • Hans Krebs was a German/British researcher that discovered most of the steps to the cycle Intro Citric Acid Cycle • The purpose of the Krebs Cycle is to create ATP, 3 NADH and FADH2 (another electron carrier) • This will create a large amount of electrons that can be carried to the next step in aerobic respiration • A byproduct of this series of reactions is CO2 • This all happens in the mitochondrial Matrix Citric Acid Cycle 1.Acetyl CoA enters the cycle and gets the whole cycle started by leaving. The remaining 2 carbon compound will combine with a 4 carbon compound called oxaloacetate. The product of this reaction is the 6 carbon compound Citrate (does that look familiar?) 2.Citrate is oxidized and NAD+ is reduced. A carboxyl group (COO-) leaves as CO2. The resulting compound is a 5 carbon Alphaketoglutrate. Citric Acid Cycle Citric Acid Cycle 3. The Alpha-ketoglutrate loses a carboxyl group (COO-) and once again NAD+ is reduced to NADH. Through substrate level phosphorylation a molecule of ADP + P is made into ATP. We are left with a 4 carbon compound called Succinate. 4. The succinate is oxidized and the electrons go to a molecule called FAD. This creates FADH2. The resulting compound is a 4 carbon Malate. 5. Finally the Malate is converted to our original 4 carbon compound Oxaloacetate when it loses two electrons and creates another molecule of NADH Citric Acid Cycle Citric Acid Helper! So What Just Happened? • You might have just felt like you were punched in the gut… • That’s ok • Here is something to make you feel better • https://www.youtube.c om/watch?v=Bo8Q88b AXyQ So What Just Happened? • Ok… back to business • The Krebs Cycle produced some very valuable things • 2 ATP • 6 Molecules of NADH (each carrying 2 electrons) • 2 Molecules of FADH2 (carrying 2 electrons) • 4 Molecules of CO2 The Totals These are the totals for all the steps of aerobic respiration so far… Glycolysis Pre Citric Acid 2 Net ATP 2 NADH Citric Acid 2 ATP 2 NADH 6 NADH 2 FADH2 2 CO2 4 CO2 What’s Next? • So far we have produced 4 ATP, 8 NADH and 2 FADH2 • This is not a lot of energy • Considering the process of a cell membrane pump takes one ATP, we would quickly run out of energy for the cell What’s Next? • The next step is going to convert electrons into a huge energy payoff • The process of oxidative phosphorylation is where stored electrons are used to build an H+ concentration and power ATP Synthase Oxidative Phosphorylation • The process of OP starts in the inner membrane • The electron transport chain will be responsible for using electrons to pump H+ ions out of the matrix • This process builds a concentration gradient outside of the mitochondrial maxtix Oxidative Phosphorylation • Moving the electrons from place to place are protein complexes and mobile electron carriers • These complexes pump the H+ ions creating the gradient • This will be used later to create ATP Oxidative Phosphorylation • Once the electrons go through the electron transport chain, they must end up somewhere • They cannot just hang out in the matrix • Oxygen accepts the electrons and two spare H+ ions to create H20 • This means the oxygen you breathe is the final electron acceptor Oxidative Phosphorylation • Once there is a proper concentration gradient, the H+ ions diffuse back into the matrix through ATP Synthase • This enzyme will use the H+ ions to create ATP • This process is called chemiosmosis I Care… Why? • Oxidative phosphorylation creates the bulk of the energy that you and I use • It creates roughly 28 molecules of ATP per glucose • That is over 7 times the amount produced by glycolysis and the citric acid cycle Glycolysis Krebs Cycle Oxidative Phosphorylati on I Care… Why? • This means that cells that are able to perform aerobic cellular respiration have a huge advantage when it comes to total ATP energy • They create more energy per molecule of glucose The Totals These are the totals for all the steps of aerobic respiration so far… Glycolysis Pre Citric Acid 2 Net ATP 2 NADH 2 NADH 2 CO2 Citric Acid Oxidative Phosphorylation Totals 2 ATP 28 ATP 32 ATP 6 NADH USES NADH 2 FADH2 USES FADH2 4 CO2 6 CO2 6 H20 6 H2O