Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Harvesting Chemical Energy Cellular respiration is the process by which cells break down organic compounds to produce ATP. Both autotrophs and heterotrophs use cellular respiration to make CO 2 and water from organic compounds and O 2. Cellular respiration can be divided into two stages: glycolysis and aerobic respiration. Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Photosynthesis-Cellular Respiration Cycle Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Cellular Respiration Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Glycolysis Cellular respiration begins with glycolysis, which takes place in the cytosol of cells. During glycolysis, one six-carbon glucose molecule is oxidized to form two three-carbon pyruvic acid molecules. A net yield of two ATP molecules is produced for every molecule of glucose that undergoes glycolysis. Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Glycolysis Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Glycolysis Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Fermentation If oxygen is not present, some cells can convert pyruvic acid into other compounds in the cytosol. The combination of glycolysis and this process is fermentation. Fermentation is also called Anaerobic respiration. (without air) Fermentation produces NAD +, which allows for the continued production of ATP through glycolysis. Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Cellular Respiration Versus Fermentation Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Fermentation, continued Lactic Acid Fermentation –In lactic acid fermentation, an enzyme converts pyruvic acid into another three-carbon compound, called lactic acid. –The buildup of lactic acid makes muscles feel tired. –Signal to rest and get more oxygen. Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Fermentation Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Fermentation, continued Alcoholic Fermentation –Some organisms use a process called alcoholic fermentation to convert pyruvic acid into ethyl alcohol and CO 2. Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Two Types of Fermentation Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Comparing Aerobic and Anaerobic Respiration Section 1 Glycolysis and Fermentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Aerobic Respiration Chapter 7 Overview of Aerobic Respiration Aerobic respiration occurs in the mitochondria and only if oxygen is present. The Krebs cycle occurs in the mitochondria.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Aerobic Respiration Chapter 7 The Krebs Cycle Pyruvic acid from glycolysis reacts to form acetyl CoA. Then, acetyl CoA enters the Krebs cycle. Glucose completely broken down in the Krebs cycle. Krebs produces four CO 2, two ATP, six NADH and two FADH 2 molecules (stored energy). The bulk of the energy still has not been transferred to ATP.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 7 Krebs Cycle Section 2 Aerobic Respiration

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Aerobic Respiration Chapter 7 Electron Transport Chain and Chemiosmosis Electrons from NADH and FADH 2 are passed along the electron transport chain in the mitochondrial membrane.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Aerobic Respiration Chapter 7 Electron Transport Chain and Chemiosmosis, continued Protons (hydrogen ions, H + ) are also given up by NADH and FADH 2. As the electrons move through the electron transport chain, they to pump protons into the space between the inner and outer mitochondrial membranes. This results high concentration of protons.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Aerobic Respiration Chapter 7 Electron Transport Chain and Chemiosmosis, continued As protons move through ATP synthase ATP is produced. Oxygen combines with the electrons and protons to form water.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Aerobic Respiration Chapter 7 Electron Transport Chain and Chemiosmosis, continued The Importance of Oxygen –ATP can be synthesized by chemiosmosis only if electrons continue to move along the electron transport chain. –Oxygen allows additional electrons to pass along the chain. –As a result, ATP can continue to be made through chemiosmosis.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Aerobic Respiration Chapter 7 Efficiency of Cellular Respiration Cellular respiration can produce up to 38 ATP molecules from the oxidation of a single molecule of glucose. Cellular respiration is nearly 20 times more efficient than glycolysis alone.