Chapter 27 Bioenergetics; How the Body Converts Food to Energy 1
Metabolism Metabolism: The sum of all chemical reactions involved in maintaining the dynamic state of a cell or organism. Pathway: A series of biochemical reactions. Catabolism: The process of breaking down large nutrient molecules into smaller molecules with the concurrent production of energy. Anabolism: The process of synthesizing larger molecules from smaller ones. 2
Metabolism Metabolism is the sum of catabolism and anabolism. 3
Metabolism Figure 27-1 Simplified schematic diagram of the common metabolic pathway, an imaginary funnel representing what happens in the cell. 4
Cells and Mitochondria Animal cells have many components, each with specific functions; some components along with one or more of their functions are: Nucleus: Where replication of DNA takes place. Lysosomes: Remove damaged cellular components and some unwanted foreign materials. Golgi bodies: Package and process proteins for secretion and delivery to other cellular components. Mitochondria: Organelles in which the common catabolic pathway takes place in higher organisms; the purpose of this catabolic pathway is to convert the energy stored in food molecules into energy stored in molecules of ATP. 5
A Rat Liver Cell Figure 27-2 Diagram of a rat liver cell, a typical higher animal cell. 6
A Mitochondrion Figure 27-3 Schematic of a mitochondrion cut to reveal the internal organization. 7
The Common Metabolic Pathway The two parts to the common catabolic pathway: The citric acid cycle, also called the tricarboxylic acid cycle (TCA) or Krebs cycle. Electron transport chain and phosphorylation, together called oxidative phosphorylation. Four principal compounds participating in the common catabolic pathway are: AMP, ADP, and ATP: agents for the storage and transfer of phosphate groups. NAD + /NADH: agents for the transfer of electrons in biological oxidation-reduction reactions. FAD/FADH 2 : agents for the transfer of electrons in biological oxidation-reduction reactions. Coenzyme A; abbreviated CoA or CoA-SH: An agent for the transfer of acetyl groups. 8
Adenosine Triphosphate (ATP) ATP is the most important compound involved in the transfer of phosphate groups. ATP contains two phosphoric anhydride bonds and one phosphoric ester bond. 9
Adenosine Triphosphate (ATP) Hydrolysis of the terminal phosphate (anhydride) of ATP gives ADP, dihydrogen phosphate ion, and energy. Hydrolysis of a phosphoric anhydride liberates more energy than the hydrolysis of a phosphoric ester. We say that ATP and ADP each contain high-energy phosphoric anhydride bonds. ATP is a universal carrier of phosphate groups. ATP is also a common currency for the storage and transfer of energy. 10
NAD + /NADH Nicotinamide adenine dinucleotide (NAD + ) is a biological oxidizing agent. 11
NAD + /NADH NAD + is a two-electron oxidizing agent, and is reduced to NADH. NADH is a two-electron reducing agent, and is oxidized to NAD +. The structures shown here are the nicotinamide portions of NAD + and NADH. NADH is an electron and hydrogen ion transporting molecule. 12
FAD/FADH 2 Flavin adenine dinucleotide (FAD) is also a biological oxidizing agent. 13
FAD/FADH 2 FAD is a two-electron oxidizing agent, and is reduced to FADH 2. FADH 2 is a two-electron reducing agent, and is oxidized to FAD. Only the flavin moiety is shown in the structures below. 14
Coenzyme A Coenzyme A (CoA) is an acetyl group carrier. Like NAD + and FAD, coenzyme A contains a unit of ADP. CoA is often written CoA-SH to emphasize the fact that it contains a sulfhydryl group. The vitamin part of coenzyme A is pantothenic acid. The acetyl group of acetyl CoA is bound as a highenergy thioester. 15
Coenzyme A Figure 27-7 The structure of coenzyme A The business end is the -SH (sulfhydryl) group at the left end. 16
End quiz III, end Exam III Material after Exam III starts after this slide 17