2. Overview of Cellular Respiration Section 4.4 Cellular respiration makes ATP by breaking down sugars. If a step requires oxygen, it is called aerobic. If a step occurs in the absence of oxygen, it is called anaerobic. It takes place in three steps: Glycolysis Krebs cycle Electron transport chain

3. Cellular respiration The equation for cellular respiration is: C 6 H 12 O 6 + 6 O 2  6 H 2 O + 6 CO 2 + energy The equation for photosynthesis is: 6 H 2 O + 6 CO 2 + light energy  C 6 H 12 O 6 + 6 O 2

4. Comparing photosynthesis with respiration

5. Glycolysis Is anaerobic Occurs in the cytoplasm One 6 carbon glucose molecule is broken down into two three carbon pyruvate molecules. Produces 2 ATP molecules

6. Krebs Cycle Is aerobic Occurs in mitochondria Pyruvate is broken down One 2 carbon molecule 1 CO 2 molecule High energy electrons CoEnzyme A bonds to the 2 carbon molecule

7. Krebs Cycle Acetyl CoA enters the Krebs cycle (2C) Combines with a 4 carbon molecule to form citric acid (6C) Loses a CO 2 (5C) Loses another CO 2 (4C) Combines with acetyl CoA. Produces 2 ATP

8. Electron Transport Chain Is aerobic Occurs in mitochondria NADH and FADH 2 donate electrons and transport hydrogen ions. Produces 34 ATP molecules Hydrogen ions and electrons combine with oxygen to produce water.

9. Electron Transport Chain

10. Aerobic respiration Aerobic respiration can produce up to 38 ATP molecules from 1 molecule of glucose. Most ATP is produced in the electron transport chain.

11. Anaerobic Respiration Also called fermentation In the absence of oxygen If there is no oxygen to accept electrons or hydrogen ions NADH and FADH 2 cannot be converted to NAD + and FAD2 + Citric acid is not broken down in the Krebs cycle Acetyl CoA cannot enter the Krebs cycle

12. Anaerobic respiration Pyruvate has to be broken down another way. In yeasts: Pyruvate  ethanol and CO 2 Produces 2 ATP molecules In animals: Pyruvate  lactic acid Produces 2 ATP molecules

14. Uses of fermentation Cheese Alcohol Breads