Cellular respiration is the process by which cells convert the chemical energy in food, primarily glucose, into ATP, the energy currency of the cell. The key stages include glycolysis, the Krebs cycle, and the electron transport system, which together produce 36-38 ATP per glucose molecule. Energy is released and captured through various phosphorylation processes, including substrate-level and oxidative phosphorylation.

1. Cellular Respiration: Energy for Life

2. What is Energy? Types of Energy: Light Heat Potential Chemical

3. Where Does Cellular Energy Come From? Sunlight Autotrophs Food ATP

4. Cellular Respiration Converts the Chemical Energy in Food into ATP

5. ATP is used as cellular energy currency Energy is released when ATP is converted to ADP

6. ATP Synthesis Substrate Level Phosphorylation (view) Phosphate group is taken off a high energy substrate Added directly to ADP Glycolysis and Krebs Cycle Chemiosmotic Phosphorylation (view) Involves electron transport system embedded in membranes Oxidation/Reduction releases energy for active transport of H + across membrane to build gradient H + diffuse through ATP Synthestase to power ATP synthesis Photophosphorylation in photosynthesis Oxidative phosphorylation in cellular respiration

8. The Reactions of Cellular Respiration All living things require energy from food The primary energy molecule is glucose The Process of Cellular Respiration converts the energy in glucose into ATP for use by the cell

9. The Reactions of Cellular Respiration Cellular Respiration Breaks Glucose Down Gradually All at once = energy wasted as heat Occurs in several steps

10. Complete Breakdown of Glucose is Aerobic Produces 36-38 ATP per Glucose

11. Glycolysis The “Glucose Splitting” reaction

12. Glycolysis Occurs in the cytoplasm (many enzymes involved) End Product is Pyruvate Glucose is oxidized to pyruvate ATP and NADH are generated. 2 Major Phases Energy investment: 2 ATP Energy payoff: 4 ATP and 2NADH See animated glycolysis

13. The Krebs Cycle Intermediate Reactions

14. Intermediate Reactions Pyruvate converted to Acetyl CoA (enters Krebs Cycle) CO 2 is released NAD + is reduced to NADH

15. The Krebs Cycle Occurs in the matrix of the mitochondrion Acetyl CoA combines with Oxaloacetate to produce Citrate. The Krebs Cycle is also called the Citric Acid Cycle. A series of oxidation and reduction reactions generate 1 ATP, 3 NADH, and 1 FADH 2 per pyruvate CO 2 is released as a by-product Oxaloacetate is regenerated to begin the cycle again See animated Krebs Cycle

16. The Electron Transport System

17. The Electron Transport System Series of electron carriers embedded in cristae NADH and FADH 2 are oxidized and pass electrons to carriers. As electrons move down ETS, energy is released to pump H + from matrix to intermembrane space. A concentration gradient is established. The electrons combine with O 2 to produce water. H + diffuse through ATP synthetase, producing ATP. Process is called oxidative phosphorylation Produces 32-34 ATP See animated ETS

18. Total ATP Production

19. Total ATP Production Process ETS ATP Glycolysis 2 2 NADH x2 4 Intermediate RXN 2NADH x3 6 Krebs Cycle 2 6NADH x3 18 2FADH 2 x2 4 _____ 36