Chapter 9 Cellular Respiration Lesson Overview Chapter 9 Cellular Respiration

Overview of Cellular Respiration If oxygen is available, organisms can obtain energy from food by a process called cellular respiration. The summary of cellular respiration is presented below. In symbols: 6 O2 + C6H12O6  6 CO2 + 6 H2O + Energy In words: Oxygen + Glucose  Carbon dioxide + Water + Energy The cell has to release the chemical energy in food molecules (like glucose) gradually, otherwise most of the energy would be lost in the form of heat and light.

2. Burning glucose requires energy to begin the process. CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cellular Respiration – the release of chemical energy 1. Release of chemical energy in the cell often occurs through the oxidation or breakdown of glucose. 2. Burning glucose requires energy to begin the process.

CopyrightThe McGraw-Hill Companies, Inc CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3. The end-products of these reactions are heat as well as stored energy. 4. This stored energy is called ATP which has a chain of three phosphates.

2. ATP molecules contain three phosphates in a chain. CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. ATP Molecules 1. Up to 38 molecules of ATP are produced for each molecule of glucose oxidized. 2. ATP molecules contain three phosphates in a chain.

CopyrightThe McGraw-Hill Companies, Inc CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3. Energy is stored in the last phosphate bond. 4. Energy is stored while converting ADP to ATP; when energy is released, ATP becomes ADP, ready to be regenerated into ATP.

Stages of Cellular Respiration The three main stages of cellular respiration are glycolysis, the Krebs cycle, and the electron transport chain.

2.The result is two 3-C molecules of pyruvate. CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anaerobic Respiration 1.The first part of cellular respiration is the splitting of 6-C glucose that occurs through a series of enzyme- catalyzed steps called glycolysis. 2.The result is two 3-C molecules of pyruvate.

CopyrightThe McGraw-Hill Companies, Inc CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3. Glycolysis occurs in the cytoplasm and does not require oxygen (is anaerobic). 4. Energy from ATP is used to start the process but there is a net gain of energy as a result.

CopyrightThe McGraw-Hill Companies, Inc CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aerobic Respiration 1.Oxygen is needed for aerobic respiration, which occurs within the mitochondria. 2.There is a much greater gain of ATP molecules from aerobic respiration. 3.The final products of glucose oxidation are carbon dioxide, water, and energy.

Stages of Cellular Respiration During the Krebs cycle, a little more energy is generated from pyruvic acid.

Stages of Cellular Respiration The electron transport chain produces the bulk of the energy in cellular respiration by using oxygen, a powerful electron acceptor.

Energy Totals In the presence of oxygen, the complete breakdown of glucose through cellular respiration results in the production of 36 ATP molecules. Glycolysis; 2 ATP Krebs: 2 ATP ETC: 32-34 ATP This represents about 36 percent of the total energy of glucose. The remaining 64 percent is released as heat. The cell can generate ATP from just about any source, even though we’ve modeled it using only glucose. Complex carbohydrates are broken down into simple sugars like glucose. Lipids and proteins can be broken down into molecules that enter the Krebs cycle or glycolysis at one of several places

CopyrightThe McGraw-Hill Companies, Inc CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fermentation Fermentation is a process by which energy can be released from food molecules in the absence of oxygen. Fermentation occurs in the cytoplasm of cells. Under anaerobic conditions, fermentation follows glycolysis. During fermentation, cells convert NADH produced by glycolysis back into the electron carrier NAD+, which allows glycolysis to continue producing ATP. Alcoholic Fermentation(autotrophs) Yeast and a few other microorganisms use alcoholic fermentation that produces ethyl alcohol and carbon dioxide. This process is used to produce alcoholic beverages and causes bread dough to rise. Lactic Acid Fermentation(heterotrophs) Most organisms(heterotrophs), including humans, carry out fermentation using a chemical reaction that converts pyruvic acid to lactic acid