Popular in Human Anatomy and Physiology II
Popular in Biological Sciences
This 10 page Class Notes was uploaded by Jess Graff on Monday May 2, 2016. The Class Notes belongs to BMS 508 at University of New Hampshire taught by Mary Katherine Lockwood, PhD in Spring 2016. Since its upload, it has received 5 views. For similar materials see Human Anatomy and Physiology II in Biological Sciences at University of New Hampshire.
Reviews for BMS 508
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 05/02/16
BMS 508.03 4/15/2016 Chapter 25 Digestion & Metabolism (cont) Carbohydrate Metabolism (cont) • Oxidative Phosphorylation and the ETS • Electron Transport System (ETS) • The key reaction in oxidative phosphorylation • In inner mitochondrial membrane • Electrons carry chemical energy • Within a series of integral and peripheral proteins • Oxidation, Reduction, and Energy Transfer • Oxidation (loss of electrons) • Electron donor is oxidized • Reduction (gain of electrons) • Electron recipient is reduced • The 2 reactions are always paired • Energy Transfer • Electrons transfer energy • Energy performs physical or chemical work (ATP formation) • Electrons • Travel through series of oxidation–reduction reactions • Ultimately combine with oxygen to form water • Coenzymes • Play key role in oxidation–reduction reactions • Act as intermediaries • Accept electrons from one molecule • Transfer them to another molecule • In citric acid cycle: • Are NAD and FAD • Remove hydrogen atoms from organic substrates • Each hydrogen atom consists of an electron and a proton • Oxidation–Reduction Reactions • Coenzyme • Accepts hydrogen atoms • Is reduced • Gains energy • Donor molecule • Gives up hydrogen atoms • Is oxidized • Loses energy • Protons and electrons are released • Electrons • Enter electron transport system • Transfer to oxygen • H 2 is formed • Energy is released • Synthesize ATP from ADP • Coenzyme FAD • Accepts two hydrogen atoms from citric acid cycle • Gaining 2 electrons • Coenzyme NAD • Accepts 2 hydrogen atoms • Gains 2 electrons • Releases 1 proton + • Forms NADH + H • The Electron Transport System (ETS) • Also called respiratory chain • A sequence of proteins (cytochromes) • Protein • Embedded in inner membrane of mitochondrion • Surrounds pigment complex • Pigment complex • Contains a metal ion (iron or copper) • General Path of Electrons Captured and Delivered by Coenzymes • 5 Steps • ETS Step 1 • Coenzyme strips two hydrogens from substrate molecule • Glycolysis occurs in cytoplasm • NAD is reduced to NADH • In mitochondria: • NAD and FAD in citric acid cycle • ETS Step 2 • NADH and FADH deliv2r H atoms to coenzymes in inner mitochondrial membrane • Protons are released • Electrons are transferred to ETS • Electron Carriers • NADH sends electrons to FMN (flavin mononucleotide) • FADH pr2ceeds directly to coenzyme Q (CoQ; ubiquinone) • FMN and CoQ bind to inner mitochondrial membrane • ETS Step 3 • CoQ releases protons and passes electrons to cytochrome b • ETS Step 4 • Electrons pass along electron transport system • Losing energy in a series of small steps • ETS Step 5 • At the end of ETS: + • Oxygen accepts electrons and combines with H to form H O 2 • ATP Generation and the ETS • Does not produce ATP directly • Creates steep concentration gradient across inner mitochondrial membrane • Electrons along ETS release energy • As they pass from coenzyme to cytochrome • And from cytochrome to cytochrome • Energy released drives H ion (H ) pumps • That move H from mitochondrial matrix • Into intermembrane space • Ion Pumps + • Create concentration gradient for H across inner membrane • Concentration gradient provides energy to convert ADP to ATP • Ion Channels • In inner membrane permit diffusion of H into matrix • Chemiosmosis • Also called chemiosmotic phosphorylation • Ion channels and coupling factors use kinetic energy of hydrogen ions to generate ATP • Ion Pumps • Hydrogen ions are pumped, as: • FMN reduces coenzyme Q • Cytochrome b reduces cytochrome c • Electrons pass from cytochrome a to cytochrome a 3 • NAD and ATP Generation • Energy of 1 electron pair removed from substrate in citric acid cycle by NAD • Pumps 6 hydrogen ions into intermembrane space • Reentry into matrix generates 3 molecules of ATP • FAD and ATP Generation • Energy of one electron pair removed from substrate in citric acid cycle by FAD • Pumps 4 hydrogen ions into intermembrane space • Reentry into matrix generates 2 molecules of ATP • The Importance of Oxidative Phosphorylation • Oxidative phosphorylation • Is the most important mechanism for generation of ATP • Requires oxygen and electrons • Rate of ATP generation is limited by oxygen or electrons • Cells obtain oxygen by diffusion from extracellular fluid • Energy Yield of Glycolysis and Cellular Respiration • For most cells, reaction pathway: • Begins with glucose • Ends with carbon dioxide and water • Is main method of generating ATP • Glycolysis • 1 glucose molecule is broken down anaerobically to 2 pyruvic acid • Cell gains a net 2 molecules of ATP • Transition Phase • 2 molecules NADH pass electrons to FAD • By an intermediate in intermembrane space • To CoQ and electron transport system • Producing an additional 4 ATP molecules • ETS • Each of 8 NADH molecules • Produces 3 ATP + 1 water molecule • Each of 2 FADH mol2cules • Produces 2 ATP + 1 water molecule • Total yield from citric acid cycle to ETS • 28 ATP • Citric Acid Cycle • Breaks down 2 pyruvic acid molecules • Produces 2 ATP by way of GTP • Transfers H atoms to NADH and FADH 2 • Coenzymes provide electrons to ETS • Summary of ATP Production • For one glucose molecule processed, cell gains 36 molecules of ATP • 2 from glycolysis • 4 from NADH generated in glycolysis • 2 from citric acid cycle (through GTP) • 28 from ETS • Gluconeogenesis • Is the synthesis of glucose from noncarbohydrate precursors • Lactic acid • Glycerol • Amino acids • Stores glucose as glycogen in liver and skeletal muscle • Glycogenesis • Is the formation of glycogen from glucose • Occurs slowly • Requires high-energy compound uridine triphosphate (UTP) • Glycogenolysis • Is the breakdown of glycogen • Occurs quickly • Involves a single enzymatic step Lipid Metabolism • Lipids • Lipid molecules contain carbon, hydrogen, and oxygen • In different proportions than carbohydrates • Triglycerides are the most abundant lipid in the body • Lipid Catabolism (Lipolysis) • Breaks lipids down into pieces that can be: • Converted to pyruvate, or: • Channeled directly into citric acid cycle • Hydrolysis splits triglyceride into component parts • 1 molecule of glycerol • 3 fatty acid molecules • Lipid Catabolism • Enzymes in cytosol convert glycerol to pyruvate • Pyruvate enters citric acid cycle • Different enzymes convert fatty acids to acetyl-CoA (beta-oxidation) • Beta-Oxidation • A series of reactions • Breaks fatty acid molecules into 2-carbon fragments • Occurs inside mitochondria • Each step: • Generates molecules of acetyl-CoA and NADH • Leaves a shorter carbon chain bound to coenzyme A • Lipids and Energy Production • For each 2-carbon fragment removed from fatty acid, cell gains: • 12 ATP from acetyl-CoA in citric acid cycle • 5 ATP from NADH • Cell can gain 144 ATP molecules from breakdown of one 18-carbon fatty acid molecule • Fatty acid breakdown yields about 1.5 times the energy of glucose breakdown • Lipid Storage • Is important as energy reserves • Can provide large amounts of ATP, but slowly • Saves space, but hard for water-soluble enzymes to reach • Lipid Synthesis (Lipogenesis) • Can use almost any organic substrate • Because lipids, amino acids, and carbohydrates can be converted to acetyl-CoA • Glycerol • Is synthesized from dihydroxyacetone phosphate (intermediate product of glycolysis) • Other lipids • Nonessential fatty acids and steroids are examples • Are synthesized from acetyl-CoA • Essential fatty acids • Cannot be produced by the body, must be consumed • Unsaturated 18-carbon fatty acid from plants • Linoleic acid • Linolenic acid • Lipid Transport and Distribution • Cells require lipids • To maintain plasma membranes • Steroid hormones must reach target cells in many different tissues • Solubility • Most lipids are not soluble in water • Special transport mechanisms carry lipids from one region of body to another • Circulating Lipids • Most lipids circulate through bloodstream as lipoproteins • Free fatty acids are a small percentage of total circulating lipids • Free Fatty Acids (FFAs) • Can diffuse easily across plasma membranes • In blood, are generally bound to albumin (most abundant plasma protein) • Sources of FFAs in blood • Fatty acids not used in synthesis of triglycerides diffuse out of intestinal epithelium into blood • Fatty acids diffuse out of lipid stores (in liver and adipose tissue) when triglycerides are broken down • Are an important energy source • During periods of starvation • When glucose supplies are limited • Liver cells, cardiac muscle cells, skeletal muscle fibers, and so forth • Metabolize free fatty acids • Lipoproteins • Are lipid–protein complexes • Contain large insoluble glycerides and cholesterol • 5 classes of lipoproteins • Chylomicrons • Very low-density lipoproteins (VLDLs) • Intermediate-density lipoproteins (IDLs) • Low-density lipoproteins (LDLs) • High-density lipoproteins (HDLs)