Cellular respiration is the process by which cells break down glucose and other food molecules in the presence of oxygen to release energy. It occurs in three main stages: glycolysis, the Krebs cycle, and the electron transport chain. Glycolysis breaks down glucose and produces a small amount of ATP. The Krebs cycle further breaks down these products and produces more ATP and electron carriers. Finally, the electron transport chain uses these carriers to power ATP synthase and produce the majority of ATP from glucose through chemiosmosis. In total, the complete breakdown of one glucose molecule via cellular respiration can produce up to 36 ATP molecules.

1. Cellular Respiration **Food provides life with the chemical building blocks need to grow and reproduce.**

2. Calorie The amount of energy needed to raise the temperature of 1 gram of water 1oC. On food labels, “Calorie” is a kilocalorie of 1000 calories.

3. Glycolysis It is the beginning process of our food “burning” to release energy. Begins process of respiration and releases a small amount of energy that leads to 2 other processes that release A LOT of energy.

4. What is Cellular Respiration? The process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. There Are 3 Steps: Glycolysis, Kreb’s Cycle, Electron Transport

5. Equation 6 O2 + C6H12O6 6 CO2 + 6 H2O + ATP

6. Glycolysis It is a process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid and a 3 – carbon sugar.

7. ATP & Glycolysis The process releases energy, but needs a boost to get started. It takes 2 ATP’s to start glycolysis. 4 ATP’s are produced at the end. NET ATP after glycolysis = __________

8. NADH Production One of the reactions of glycolysis removes four high energy electrons and passes them to NAD+. NADH then holds those electrons with their energy.

9. Energy Output of Glycolysis The process is so fast, it can produce thousands of ATP in milliseconds. Glycolysis doesn’t require oxygen, so it can supply chemical energy to cells when oxygen is not available. PROBLEM: All the NAD+ becomes filled up with electrons and cells run out.

10. Steps of Glycolysis

11. Step 1 Two phosphates are added to glucose to with an ATP investment of 2 molecules.

12. Step 2 The 2 phosphate sugar molecule is then split to form 2, 3 carbon molecules.

13. Step 3 The two phosphate, 3 carbon molecules are then converted to 2 pyruvate (pyruvic acid). As this occurs electrons are transferred to NAD+ to form NADH. ATP is also formed.

14. Result Two Pyruvates (with a lot of stored energy left) A net of 2 ATP’s

15. Kreb’s Cycle After glycolysis, 90% of of the chemical energy from glucose is still left. For the Kreb’s Cycle, oxygen is necessary. The pyruvic acid will be further broken down into CO2 in a series of energy extracting steps.

16. Step 1 (Citric Acid Production) The pyruvic acid enters the mitochondria and loses a CO2 molecule. The 2 carbons left attach to coenzyme A to from Acetyl CoA. The Acetyl CoA is actually what enters the Krebs Cycle.

17. Step 1 -cont- The 2 C acetyl CoA then joins with a 4 carbon molecule to make Citric Acid.

18. Step 2 The citric acid is broken down, releasing more CO2. One ATP is produced. ⌘ 3 NADH and 1 FADH is converted to FADH2 There is now a 4 carbon molecule left.

19. The Krebs Cycle must occur 2 times in order to break down both of the pyruvicaicds that were created during glycolysis.

20. NADH & FADH2 Both these molecules are electron carriers that trap most of the energy from the Krebs cycle.

21. Electron TransportOccurs in inner Membrane of Mitochondria First Step The electrons from the original glucose molecule are moved to an electron transport chain using NADH. (Electrons move to carriers that they have a stronger attraction for.)

22. Step 1 – cont. – These transfers along the chain release energy. This energy is used to pump H+ ions into the inner membrane of the mitochondria. The electrons in the chain are “pulled” toward oxygen and once there the oxygen, electrons and hydrogen combine to form water.

23. Step 2 Those H+ ions then rush back out of the membrane through ATP synthases. This energy is used to then to convert ADP to ATP. Up to 36 ATP’s can be made from one glucose molecule.

24. Total ATP’s Produced 36 ATP Molecules For 1 Glucose Molecule 