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 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?) Citrate is oxidized and NAD+ is reduced. A carboxyl group (COO-) leaves as CO2. The resulting compound is a 5 carbon Alpha-ketoglutrate.

Citric Acid Cycle 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?) Citrate is oxidized and NAD+ is reduced. A carboxyl group (COO-) leaves as CO2. The resulting compound is a 5 carbon Alpha-ketoglutrate. The Alpha-ketoglutrate loses a carboxyl group (COO-) and once again NAD+ is reduced to NADH. Through substrate level phosporilation a molecule of ADP + P is made into ATP. We are left with a 4 carbon compound call succinate. The succinate is oxidized and the electrons go to a molecule called FAD. This creates FADH2. The resulting compound is a 4 carbon Malate. 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 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 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?) Citrate is oxidized and NAD+ is reduced. A carboxyl group (COO-) leaves as CO2. The resulting compound is a 5 carbon Alpha-ketoglutrate. The Alpha-ketoglutrate loses a carboxyl group (COO-) and once again NAD+ is reduced to NADH. Through substrate level phosporilation a molecule of ADP + P is made into ATP. We are left with a 4 carbon compound call succinate. The succinate is oxidized and the electrons go to a molecule called FAD. This creates FADH2. The resulting compound is a 4 carbon Malate. 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 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?) Citrate is oxidized and NAD+ is reduced. A carboxyl group (COO-) leaves as CO2. The resulting compound is a 5 carbon Alpha-ketoglutrate. The Alpha-ketoglutrate loses a carboxyl group (COO-) and once again NAD+ is reduced to NADH. Through substrate level phosporilation a molecule of ADP + P is made into ATP. We are left with a 4 carbon compound call succinate. The succinate is oxidized and the electrons go to a molecule called FAD. This creates FADH2. The resulting compound is a 4 carbon Malate. 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 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.com/watch?v=Bo8Q88bAXyQ

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

These are the totals for all the steps of aerobic respiration so far… Glycolysis Pre Citric Acid Citric Acid 2 Net ATP 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

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

Oxidative Phosphorylation The Totals These are the totals for all the steps of aerobic respiration so far… Glycolysis Pre Citric Acid Citric Acid Oxidative Phosphorylation Totals 2 Net ATP 2 ATP 28 ATP 32 ATP 2 NADH 6 NADH USES NADH 2 FADH2 USES FADH2 2 CO2 4 CO2 6 CO2 6 H20 6 H2O