1 Cellular Respiration and Fermentation Chapter 9

2 Sunlight Powers Life

3 Making Chemical Energy Available for Cellular Work Cells break complex organic molecules into smaller molecules with less chemical energy This process is called cellular respiration Glucose + Oxygen → Carbon Dioxide + Water + Energy 40% Chemical 60% Thermal

4 Measuring Energy Energy is measured in units called calories A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 ◦ C 1000 calories = 1 kcal or Calorie (a nutritional calorie) However, food is not used directly by cells to do work, it must be converted into another usable form called ATP.

5 What is ATP? ATP is called the "currency" of the cell – ATP is a small packet of Energy that can be used a little at a time, like coins – ATP is constantly reused and recycled – You can’t buy things without $$, cells can’t Work without Energy from ATP

6 Copyright Pearson Prentice Hall Chemical Energy and ATP – Storing Energy  ADP has two phosphate groups instead of three.  A cell can store small amounts of energy by adding a phosphate group to ADP. ADP ATP Energy Partially charged battery Fully charged battery + Adenosine Diphosphate (ADP) + Phosphate Adenosine Triphosphate (ATP)

7 Copyright Pearson Prentice Hall Chemical Energy and ATP P ADP 2 Phosphate groups – Releasing Energy Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates.

8 The ATP Cycle ATP → ADP + phosphate + energy for Work ADP + Energy (from food) + phosphate → ATP

9 A Metabolic Pathway called Cellular Respiration Cells harvest energy by breaking bonds and shifting electrons from one molecule to another. – aerobic respiration - final electron acceptor is oxygen – anaerobic respiration - final electron acceptor is a molecule other than oxygen

10 Aerobic Respiration C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + Energy Occurs in 3 Stages: 1.Glycolysis 2.The Kreb’s Cycle 3.Electron Transport Chain and ATP Synthase

11 Adding up the ATP from Cellular Respiration Mitochondrion Glycolysis Glucose 2 Pyruvic acid 2 Acetyl- CoA Krebs Cycle Electron Transport Maximum ATP per glucose: ATP Synthase CO 2 H2OH2O O2O2

12 Harvesting Energy WITHOUT Oxygen If oxygen is not available to capture the 2 low energy electrons at the end of the ETC, the Kreb’s cycle and the ETC will stop producing ATP Glycolysis will continue to generate 2 ATP molcules, 2 NADH, and 2 Pyruvic Acid molecules NADH reacts with the pyruvic acid, making NAD+ available to carry electrons so glycolysis can continue making ATP

13 Two Types of Fermentation ALCOHOLIC Pyruvic Acid → CO 2 + ethyl alcohol Occurs in yeast CO 2 makes dough rise and bubbles in beer & champagne Ethyl alcohol makes alcoholic beverages LACTIC ACID Pyruvic Acid → Lactic Acid Occurs in muscles during vigorous exercise (can feel “burn”) Occurs in prokaryotes used to make cheese, yogurt, sour cream, and sauerkraut