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Cellular Respiration Cellular Respiration is how we derive energy from the food we eat (specifically glucose) Overview Sugar combines with oxygen to produce carbon dioxide plus water and energy (in the form of ATP) FIRST, we need to know why we want ATPs ATP is needed to use energy. Here’s how it works: Adenosine triphosphate is made up of a nitrogenous base called adenine with a sugar called ribose and three phosphate groups attached to it (do not like to be in a row like that) ATP shoots off one of the phosphate groups off the end. Now it’s ADP (adenosine diphosphate) and when this happens energy is released. Through cellular respiration, one molecule of glucose can yield a bit of heat and 38 molecules of ATP. 3 stages of Cellular Respiration 1. Glycolysis 2. Kreb’s Cycle 3. Electron Transport Chain Stage 1: Glycolysis Glycolysis Overview Breaks up of glucose’s 6 carbon ring into two 3-carbon molecules called pyruvic acids or pyruvate molecules FUN FACT: GLYCOLYSIS DOES NOT NEED OXYGEN. This is called an anaerobic process. If there is not oxygen for the next step, it goes to fermentation. Fun facts: Fermenation Fermentation uses more NAD+ and creates interesting byproducts: Yeast – ethyl alcohol Our muscles don’t make alcohol, they make lactic acid which is what makes you feel sore after a workout (the muscles ran out of oxygen and kick into anaerobic respiration) Stage 2: Kreb’s Cycle Steps of Kreb’s Cycle 1. One of the pyruvates is oxidized (means it’s combined with oxygen). One of the carbons off the three-carbon chain bonds with an oxygen and leaves the cell as CO2 What’s left? Two carbon compound called acetyl coenzyme A 2. Then 2 NAD+ comes along and each pick up a hydrogen and becomes 2 NADHs (to use later) (remember: glycolysis made 2 NADHs and now there are 2 more, which means we now have 4) 3. Enzymes bring together a phosphate with ADP to create another ATP molecule for each pyruvate. (remember, we had 2 ATPs from glycolysis and now we have 2 more, we now have 4) 4. Enzymes also help join the acetyl CoA and a 4 carbon molecule (called oxaloacetic acid) to form a 6-carbon molecule called citric acid 5. The citric acid is oxidized (oxygen comes in and bonds with a bunch of carbons. The carbons left over in the form of CO2 which are pushed out of the cell and out of our mouths, etc (that’s why we breathe out CO2!) This gets us back to oxaloacetic acid (that is why it’s called a 6. Each pyruvate makes 3 NADHs and 1 FADH2. Since there are two pyruvates, that means 6 NADHs and 2 FADH2s Let’s see what we have so far: From the beginning of cellular respiration, we now have: 1. 2. 3. 4. 5. 10 NADHs (4 from glycolysis and 6 from Kreb’s Cycle) 2 FADH2s (From the Kreb’s Cycle) 4 ATPs (2 from Glycolysis and 2 from Kreb’s Cycle) Carbon Dioxide byproducts Water byproducts Stage 3: Electron Transport Chain All of the electrons in the NADHs and FADH2s are going to provide the energy that will work as a pump along a chain of channel proteins across the inner membrane of the mitochondria. 1.These proteins swap the electrons to send hydrogen protons from inside the center of the mitochondria. So they go from the inner membrane to the outer compartment of the mitochondria. 2. Once they are out, the protons want to get back in because there are too many protons in the outer compartment and nature always wants to seek a balance 3. So they are allowed back in through a protein called ATP synthase. The energy of this proton drives a spinning mechanism that puts together some ADP and phosphates together to form ATPs. That makes a lot of ATPs! spins Final count: 38 ATPs! Now those ATPs can be used to make energy