CHAPTER 7 CELLULAR RESPIRATION Section 1 Glycolysis And Fermentation Harvesting Chemical Energy Cellular Respiration a series of redox reactions in which cells make ATP by breaking down organic compounds. Glycolysis a biochemical pathway that begins cellular respiration and yields a small amount of ATP. The other products of glycolysis can follow one of two pathways:1. Anaerobic Pathway yields additional ATP from oxygen lacking products. If oxygen is present, products enter aerobic respiration . Aerobic respiration produces a much larger amount of ATP than glycolysis alone Glycolysis Glycolysis is a pathway in which one six-carbon molecule of glucose is oxidized to produce two three-carbon molecules of pyruvic acid Reactions of glycolysis take place in the cytosol and are catalyzed by enzymes. Step 1 (Energy Investment): Two phosphate groups are attached to glucose, forming a new six-carbon compound. The phosphate groups are supplied by two molecules of ATP,which are converted into molecules of ADP in the process. Step 2 (Cleavage of Sugar): The six-carbon compound formed in Step 1 is split into two three-carbon molecules of PGAL. Step 3: The two PGAL molecules are oxidized, and each receives a free-floating phosphate group. This produces two molecules of a new three-carbon compound. Two molecules of NAD + are reduced to NADH after accepting the electrons from the oxidation reaction. Step 4 (Energy Generation): The phosphate groups added in Steps 1 and 3 are removed from the three-carbon compounds.This produces two molecules of pyruvic acid. Each of the four phosphate groups combine with ADP to make four molecule sof ATP. Because 2 ATP molecules are required to transport NADH intothe mitochondria, the net product of glycolysis is 2 ATP.3. Fermentation the combination of glycolysis with additional pathways to convert pyruvic acid into other compounds in the lack of oxygen.

These additional pathways do not produce ATP. Instead, they regenerate NAD + w which can be used to power glycolysis. Lactic Acid Fermentation the process by which an enzyme converts pyruvic acid into another three-carbon compound,called lactic acid. NADH is oxidized b back to NAD + . It occurs in muscle cells When oxygen is once again available, the liver can convert lactic acid b back into pyruvate. Alcoholic Fermentation the process by which cells convert pyruvic acid into ethyl alcohol. Yeast uses this pathway; and hence they form the basis for the wine a and beer industry Organisms can only use alcoholic fermentation at concentration of alcohol a at or below 14%. Otherwise,the organism could die. E Energy Yield Kilocalorie (kcal) a value used to obtain the efficiency of anaerobic pathways. The complete oxidation of a standard amount of glucose released 686 kcal. S Section 2 Aerobic Respiration O Overview Of Aerobic Respiration Mitochondrial Matrix a space inside the inner membrane of a mitochondrion. The pyruvic acid that is produced in glycolysis diffuses across the m mitochondrions double membrane into the matrix. Acetyl CoA (acetyl coenzyme A) the product of a reaction involving pyruvic a acid and coenzyme A. One carbon atom is lost during the reaction,which combine swith two oxygen molecules to form CO 2 . The reaction also reduces a molecule of NAD + to N NADH. The Krebs Cycle a biochemical pathway that breaks down acetyl CoA, producing h hydrogen atoms and ATP. The reactions that comprise the cycle were discovered in 1937 by Hans Adolf K Krebs. Step 1: A two-carbon molecule of acetyl CoA combines with a four-carbon compound, oxaloacetic acid, to produce a six carbon compound, citric acid. This reaction regenerates coenzyme A, which moves back out to carry and change more pyruvic acid.

Step 2: Citric acid releases a CO 2 molecule and a hydrogen atom to form a fivecarbon compound. By losing a hydrogen atom with its electron, citric acid is o oxidized. The hydrogen is transferred to NAD + , reducing it to NADH. Step 3: The five-carbon compound formed in Step 2 also releases a CO 2 molecule and a hydrogen atom, forming a four-carbon compound. Again, NAD + i is reduces to NADH.A molecule of ATP is also synthesized from ADP. Step 4: The four-carbon compound formed in Step 3 releases a hydrogen atom to form another four-carbon compound. This time, the hydrogen atom is used to r reduce FAD to FADH L Like NAD +, FAD accepts electrons during redox reactions. Step 5: The four-carbon compound formed in Step 4 releases a hydrogen atom to regenerate oxaloacetic acid, which keeps the Krebs cycle operating. They hydrogen atom r reduces NAD + to NADH. E Electron Transport Chain constitutes the second stage of aerobic respiration. The electrons in the hydrogen atoms from NADH and FADH are in a high energy level. These electrons pass through a series of molecules, and lose a portion of t their energy in the process. Energy shed off of electrons is used to pump protons from the mitochondrial matrix to the other side of the inner membrane.The concentration of protons b becomes greater on the outside the matrix. The concentration gradient drives chemiosmosis via the ATP synthase, located in the inner membrane. Energy harnessed from protons moving back into the matrix s synthesizes ATP from ADP. The last molecule in the chain transfers electrons to oxygen atoms, which combine with four protons supplied by NADH and FADH 2 to form two molecule o of water. E Energy Yield In total, the sum of all chemical reactions in aerobic respiration generate the f following amounts of NADH, FADH 2, and ATP: 10 NADH each molecule that supplies to the electron transport chain can m make up to 3 ATP 2 FADH 2 each FADH 2 molecule can generate 2 ATP T The Krebs cycle and Glycolysis generate a product 4 ATP 38 ATP molecules are produced . However, the actual number of ATP

molecules made can vary from cell to cell The equation above is the general opposite of photosynthesis.However, aerobic respiration is not the exact reverse of photosynthesis. Cellular respiration provides the ATP that all cells need to support the activities of life.