Chapter 9: Cellular Respiration 9.1 Chemical Pathways 9.2 The Krebs Cycle and Electron Transport

Alcoholic Fermentation Ch. 9 Map 9 Cellular Respiration Calorie Aerobic 3 Stages Glycolysis Equation Citric Acid Cycle Electron Transport Chain Krebs Cycle Anaerobic Pyruvic Acid Fermentation Alcoholic Fermentation Lactic Acid Fermentation

Getting Energy to Make ATP A Review: The mitochondria in cells breaks down glucose and produces energy-in this case ATP. Cellular Respiration: breaking down glucose to make ATP

Cellular Respiration Three stages of cellular respiration Glycolysis - anaerobic The Citric Acid Cycle (Kreb’s Cycle) - aerobic The electron transport chain – aerobic The aerobic phase produces the most ATP    The process begins with food molecules (glucose) that are broken down into usable energy (ATP).

Overview of Cellular Respiration

Glycolysis Takes place in the cytoplasm of the cell It requires no oxygen (anaerobic). Glucose (a 6 carbon molecule) is broken down into 2 molecules of pyruvate (a 3 carbon compound). It requires 2 ATP It produces 4 ATP A net gain of 2 ATP

Glycolysis

The Citric Acid Cycle Takes place in the mitochondria of the cell. Review: Inner folded membranes. The pyruvate from glycolysis is slightly modified before the citric acid cycle begins. These new molecules (called Acetyl Coenzyme A) are broken down to form ATP and CO2. One ATP per cycle is produced, two cycles occur per glucose molecule. *Generates high energy electrons carried by NADH and FADH2

Citric Acid Cycle/Kreb’s Cycle

The Electron Transport Chain The final stage of respiration Similar to the events of the protein chain in photosynthesis. Electrons are passed from protein to protein, and the energy they give off is used to produce more ATP’s.    The final electron acceptor is an oxygen atom. This is why we cannot live without oxygen! Collects H+ ions and low energy electrons! (waste) pg. 228 Fig. 9.7

Electron Transport Chain

Where do the electrons come from? Electrons for the ETC come from electron carriers: FADH2 and NADH Work like NADPH (from photosynthesis) Formation of FADH2 and NADH occurs during glycolysis and citric acid cycle Glycolysis NAD+ and H+ combine with e- to make NADH Citric Acid Cycle More NADH forms FAD+ and H+ combine with e- to make FADH2

Respiration One glucose molecule is capable of producing a net amount of 34-38 ATP 2 in glycolysis 2 from the Citric Acid Cycle Up to 34 from the electron transport chain

Fermentation When oxygen isn’t available, the aerobic stages of respiration obviously can’t begin. In this situation, fermentation begins after glycolysis as an alternate form of respiration. Why can glycolysis still go on? Fermentation provides small amounts of ATP until the cell can once again obtain enough oxygen to begin the aerobic stages of respiration. **does not last long**

Fermentation Two main types – p. 225, Fig. 9.4 Alcoholic Fermentation Common in yeast cells. CO2 and alcohol is produced. Example: bread Lactic Acid Fermentation Occurs in animal muscle cells. Lactic acid is produced. Example: pain in muscles from exercise

Yeast in Bread Yeast is a fungus It consumes the Sugar in the dough -Dough is left to “rise” -Yeast produces alcohol and CO2 during fermentation -Alcohol evaporates as bread cooks -CO2 makes bubbles – holes in bread

ATP and Exercise Running Sprinting uses energy: Long Term Energy Stored in muslces: runs out quickly; within seconds Made by lactic acid fermentation: (oxygen depleted) made quickly, runs out quickly (about 90 seconds); lactic acid produced = burning sensation in legs Explains why a sprinter breathes very heavily at the end of a race Long Term Energy Made by cellular respiration: needs oxygen which is why runners breathe heavily Makes energy slower than fermentation; runners pace themselves Glycogen stores last for about 15-20 minutes of activity After that, body breaks down fats and other stored molecules for energy Aerobic Exercises = help with weight control

Important Study Tips Table 9.10 on p. 232. Aerobic/Anaerobic Photosynthesis/Respiration/Fermentation Alcoholic/Lactic Acid Fermentation Citric Acid Cycle/Calvin Cycle Light Dependent/Light Independent Rxns. ATP/ADP Stro’hello”ma/Stoma/Stomata Xylem/Phloem What is the definition of a cycle?