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Cecie Starr Christine Evers Lisa Starr www.cengage.com/biology/starr Chapter 3 Molecules of Life (Sections 3.1 - 3.3) Albia Dugger • Miami Dade College 3.1 Fear of Frying • Trans fats in hydrogenated vegetable oils raise blood cholesterol more than any other fat, and directly alter the function of arteries and veins • Eating as little as 2 grams a day of hydrogenated vegetable oils increases risk of atherosclerosis (hardening of the arteries), heart attack, and diabetes Trans fats, an unhealthy food • The arrangement of hydrogen atoms around a double bond makes a fat trans or cis 3.2 Molecules of Life— From Structure to Function • Only living things make the molecules of life—complex carbohydrates and lipids, proteins, and nucleic acids • All of these molecules are organic • organic • Type of compound that consists primarily of carbon and hydrogen atoms Carbon and Hydrocarbons • Carbon chains or rings form the backbone of molecules of life • An organic molecule that consists only of hydrogen and carbon atoms is a hydrocarbon • hydrocarbon • Compound or region of one that consists only of carbon and hydrogen atoms Modeling an Organic Molecule A glucose B glucose C glucose D glucose E glucose carbon hydrogen oxygen nitrogen phosphorus Fig. 3.2, p. 38 Functional Groups • Most molecules of life have at least one functional group • functional group • A group of atoms bonded to a carbon of an organic compound • Imparts a specific chemical property such as polarity or acidity Common Functional Groups Common Functional Groups Stepped Art Fig. 3.3, p. 38 What Cells Do • Metabolic activities (mediated by enzymes) help cells stay alive, grow, and reproduce • metabolism • All enzyme-mediated chemical reactions by which cells acquire and use energy as they build and break down organic molecules • enzyme • Compound (usually a protein) that speeds a reaction without being changed by it Building and Breaking Down • Condensation reactions build polymers from monomers of simple sugars, fatty acids, amino acids, and nucleotides • Hydrolysis reactions release monomers by breaking apart polymers • monomers • Molecules that are subunits of polymers • polymer • Molecule that consists of multiple monomers Condensation • Builds a large molecule from smaller ones • Enzyme removes –OH group from one molecule and -H atom from another • Covalent bond forms between two molecules – water also forms Hydrolysis • Splits a large molecule into smaller ones by a water-requiring reaction • Enzyme attaches –OH group and -H atom from water at cleavage site Hydrolysis A Condensation. Cells build a large molecule from smaller ones by this reaction. An enzyme removes a hydroxyl group from one molecule and a hydrogen atom from another. A covalent bond forms between the two molecules, and water also forms. B Hydrolysis. Cells split a large molecule into smaller ones by this water-requiring reaction. An enzyme attaches a hydroxyl group and a hydrogen atom (both from water) at the cleavage site. Stepped Art Fig. 3.4, p. 39 Animation: Condensation and hydrolysis To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE Common Metabolic Reactions Key Concepts • Structure Dictates Function • We define cells partly by their capacity to build complex carbohydrates and lipids, proteins, and nucleic acids • All of these organic compounds have functional groups attached to a backbone of carbon atoms Animation: Functional groups To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE 3.3 Carbohydrates • Enzymes assemble complex carbohydrates such as cellulose, glycogen, and starch from simple carbohydrate (sugar) subunits • Cells use carbohydrates for energy, and as structural materials • carbohydrate • Molecule that consists primarily of carbon, hydrogen, and oxygen atoms in a 1:2:1 ratio Simple Sugars • Monosaccharides (one sugar unit) are the simplest type of carbohydrate • Components of the nucleic acids DNA and RNA have five carbon atoms • Glucose has six Short-Chain Carbohydrates • An oligosaccharide is a short chain of covalently bonded monosaccharides • Disaccharides consist of two sugar monomers • Lactose (glucose + galactose) • Sucrose (glucose + fructose) • Oligosaccharides with three or more sugar units are often attached to lipids or proteins that have important functions in immunity Synthesis of a Sucrose Molecule • Sucrose (common table sugar) is synthesized from monomers of glucose and fructose in a condensation reaction Synthesis of a Sucrose Molecule glucose + fructose sucrose + water Stepped Art Fig. 3.5b, p. 40 Complex Carbohydrates • Polysaccharides, are straight or branched chains of many sugar monomers—often hundreds or thousands • Common polysaccharides: cellulose, glycogen, and starch • All consist of glucose monomers • Each has different chemical properties due to different patterns of covalent bonds that link glucose monomers Cellulose • Tough structural component of plants • Chains of glucose units stretch side by side and hydrogen bond at many -OH groups • Hydrogen bonds stabilize chains in tight bundles of long fibers Starch (Amylose) • Main energy reserve in plants, which store it in roots, stems, leaves, fruits, and seeds • In amylose, a series of glucose units form a coiled chain Glycogen • In humans and other animals, glycogen stored in muscles and liver functions as an energy reservoir Chitin • Monomers are glucose with nitrogen-containing carbonyl group • Long, unbranching chains linked by hydrogen bonds. • Strengthens hard parts of many small animals, such as crabs Key Concepts • Carbohydrates • Carbohydrates are the most abundant biological molecules • They function as energy reservoirs and structural materials • Different types of carbohydrates are built from the same sugars, bonded in different patterns