Transcript Chapter 2
Chapter 2 The Chemistry of Life Section 1 – The Nature of Matter • Atoms are the basic unit of matter. • Subatomic particles that make up atoms are protons, neutrons, and electrons. • Protons – positively charged particles • Neutrons – carry no charge, neutral • Protons and neutrons are found in the nucleus of the atom Electrons • Electron – negatively charged particle • In constant motion in the space surrounding the nucleus. Elements • Element – pure substance that consists entirely of one type of atom. – Represented by a one- or two- letter symbol. – Elements are arranged into the periodic table. Chemical Compounds • A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions. Chemical Bonds • Ionic bonds – formed when one or more electrons are transferred from one atom to another. • Covalent bonds – formed when electrons are shared between atoms. • Van der Waals forces – when molecules are close together, a slight attraction can develop between oppositely charged regions of nearby molecules. These attractions are not as strong as ionic or covalent bonds. Section 2 - Properties of Water • Polarity – a molecule in which the charges are unevenly distributed is a polar molecule. – A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms. Hydrogen Bonds • A single water molecule may be involved in as many as four hydrogen bonds at the same time. – Cohesion: an attraction between molecules of the same substance. – Adhesion: an attraction between molecules of different substances. Mixture • Mixture – a material composed of two or more elements or compounds that are physically mixed together but not chemically combined. Solutions • Solution – all components are evenly distributed throughout. – Solute – the substance that is dissolved – Solvent – the substance in which the solute dissolves Suspensions • Suspension – mixture of water and nondissolved materials. – Materials will separate into pieces but do not settle out Acids, Bases and pH • The pH scale – a measurement system that indicates the concentration of H+ ions in a solution. – Ranges from 1 – 14 – 7 is neutral – Under 7 is acidic – Above 7 is basic Acids • Any compound that forms H+ ions in solutions. – pH value below 7 Bases • Any compound that produces hydroxide (OH-) ions. – pH value above 7 Buffers • Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH. – Help control pH and retain homeostasis in the body. Section 3 – Carbon Compounds • Macromolecule: LARGE carbon molecule • Polymer: Large molecule formed when many smaller molecules bond together Carbohydrates • 2 H atoms for every O & C – 1. Simplest carbs: Called Monosaccharides (one sugar) -Ex: glucose; fructose - 2. Disaccharides – two sugars -Sucrose (glucose + fructose) - 3. Polysaccharides – many sugars -Starch, glycogen, and cellulose Lipids • Lipids: Fats; Organic compounds that have a large proportion of C-H bonds and less O than carbs. • Insoluble in water because lipids are nonpolar • Saturated Fat: Animal fats • Unsaturated Fat: Oils Proteins • A large, complex polymer composed of carbon, hydrogen, oxygen, nitrogen, and usually sulfur; have an “R” group that makes each different • Made from amino acids • 20 common amino acids • Proteins are the building blocks of many structural components Proteins • Amino Acids are linked together when an Hgroup and –OH group are removed to form water • The covalent bond formed between A.A. is a PEPTIDE BOND Nucleic Acids • A complex macromolecule that stores cellular info. in the form of a code • Nucleic acids are made up of smaller subunits called Nucleotides • Nucleotides consist of three basic parts: – 1. Nitrogen-containing base – 2. Pentose sugar – 3. Phosphate group Types of Nucleic Acids • 1. DNA: Deoxyribonucleic acid – Master copy of organism’s genetic info. – Contains instructions used to form organism’s enzymes and proteins 2. RNA: Ribonucleic acid – Forms a copy of DNA for use in making copies and proteins Section 4 - Chemical Reactions • Chemical formulas describe the substances in the reaction and arrows indicate the process of change • Reactants – starting substances on the left side of the arrow • Products – substances formed during the reaction on the right side of arrow • Arrow can be read as “yields” or “react to form” Energy in Reactions • Key to starting a chemical reaction is energy • Energy in the form of heat is need • Most compounds in living things cannot undergo chemical reactions without energy Activation Energy • Minimum amount of energy needed for reactants to form products in a chemical reaction Energy Change in Chemical Reactions • In every chemical reaction, there is a change in energy due to the making and breaking of chemical bonds • Exothermic reactions – energy of the product is lower than the energy of the reactants – Energy is released in the form of heat • Endothermic reactions – energy of the products is higher than the energy of the reactant – Heat energy is absorbed Endothermic Reaction Exothermic Reaction Enzymes • Catalyst – substance that lowers the activation energy needed to start a chemical reaction • Enzymes – special proteins that are the biological catalysts that speed up the rate of chemical reactions in biological processes – – – – Essential to life Not used up by the chemical reaction Can be used again Most enzymes are specific to one reaction Enzymes • Substrates – reactants that bind to the enzyme • Active Site – specific location where a substrate binds on an enzyme – The active site and substrates have complementary shapes – Only the substrate with the same shape as the active site will bind to the enzyme – Example : Lock & Key Enzymes • Once the substrates bind to the active site, the site changes shape and forms the enzymesubstrate complex • The new complex helps chemical bonds in the reactants to be broken and new bonds are formed • The substrates react to form products • The enzyme then releases the products • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html Enzymes • Factors such as pH, temperature, and other substances affect enzyme activity • Enzymes affect many biological processes – Examples: • • • • Photosynthesis Respiration Snake bite Fruit ripening