Chapter 2: Basic Chemistry PDF

Chapter 2: Basic Chemistry Introduction to Chemistry – Chemical Elements and Atoms All forms of matter are made up of a limited number of building blocks called chemical elements, substances that cannot be broken down into a simpler form by ordinary chemical means Each element...

Chapter 2: Basic Chemistry Introduction to Chemistry – Chemical Elements and Atoms All forms of matter are made up of a limited number of building blocks called chemical elements, substances that cannot be broken down into a simpler form by ordinary chemical means Each element is designated by a chemical symbol Chemical Elements and Atoms Chemical Elements and Atoms Each element is made up of atoms, the smallest units of matter that retain the properties and characteristics of the element An atom consists of two basic parts A nucleus (protons and neutrons) One or more electrons Chemical Elements and Atoms Atomic Structures of Several Atoms ons, Molecules, and Compounds A molecule consists of two or more atoms sharing electrons A molecular formula indicates the number and type of atoms that make up a molecule A compound is a substance containing atoms of two or more different elements A free radical is an ion or molecule that has an unpaired electron in its outermost shell Molecules Chemical Bonds – Ions and Ionic Bonds  Chemical Bonds – Covalent Bonds The polar covalent bonds that form between hydrogen atoms and other atoms can give rise to a third type of chemical bond, a hydrogen bond Chemical Reactions – Synthesis Chemical Reactions – Decomposition Chemical Reactions – Exchange hemical Reactions – Reversible ntroduction to Chemistry  Matter is made up of chemical elements. The elements oxygen (O), carbon (C), hydrogen (H), and nitrogen (N) make up 96% of the body’s mass.  Each element is made up of units called atoms, which consist of a nucleus that contains protons and neutrons, and electrons that move about the nucleus in electron shells.  The atomic number, the number of protons, distinguishes the atoms of one element from those of another element.  The combined total of protons and neutrons in an atom is its mass number.  An atom that gives up or gains electrons becomes an ion—an atom that has a positive or negative charge. ntroduction to Chemistry  A molecule is a substance that consists of two or more chemically combined atoms.  A compound is a substance that can be broken down into two or more different elements by ordinary chemical means.  A free radical is a destructive ion or molecule that has an unpaired electron in its outermost shell.  Chemical bonds hold the atoms of a molecule together. Electrons in the valence shell (outermost shell) are the parts of an atom that participate in chemical reactions (are involved in forming and breaking bonds). Introduction to Chemistry  Ionic bonds are formed when outer shell electrons are transferred from one atom to another, the transfer forms ions with unlike charges that attract the ions to each other. In a covalent bond, pairs of outer shell electrons are shared between two atoms.  Hydrogen bonds are weak bonds between hydrogen and certain other atoms.  Energy is the capacity to do work.  Potential energy is energy stored by matter due to its position.  Kinetic energy is the energy of matter in motion. Introduction to Chemistry  In a synthesis reaction (anabolic reaction), two or more atoms, ions, or molecules combine to form a new and larger molecule. In a decomposition reaction (catabolic reaction), a molecule is split apart into smaller molecules, ions, or atoms.  When nutrients such as glucose are broken down via decomposition reactions, some of the energy released is temporarily stored in adenosine triphosphate (ATP) and then later used to drive energy requiring synthesis reactions that build body structures, such as muscles and bones.  Exchange reactions are combination synthesis and decomposition reactions. Reversible reactions can proceed in both directions under different conditions. Chemical Compounds and Life Processes Organic compounds – all are carbon-based  Example: C6H12O6 (glucose) Inorganic compounds – Most lack carbon  Tend to be simpler compounds  Examples: H2O (water), NaCl (table salt), CO2 (carbon dioxide) Question – Where does all the carbon in organic compounds originate? Inorganic Compounds – Water Critical properties of water to sustain organisms  Water is an excellent solvent  Water participates in chemical reactions  Water absorbs and releases heat very slowly  Water requires a large amount of heat to change from a liquid to a gas  Water serves as a lubricant norganic Compounds – Acids, Bases nd Salts Acids - release highly reactive hydrogen ions (H+) into solution Bases - release highly reactive hydroxyl ions (OH–) into solution Neutralization reaction - acids and bases react to form water and a salt Salts - easily dissociate into ions in the presence of water, vital to many life processes (e.g. electrolytes conduct electrical currents) norganic Compounds – Acids, Bases nd Salts norganic Compounds – Acids, Bases nd Salts Inorganic Compounds – pH Neutral pH = 7 Inorganic Compounds – pH norganic Compounds – Buffers Chemical compounds that act quickly to temporarily bind H, removing the highly reactive, excess H from solution but not from the body Prevent rapid, drastic changes in the pH of a body fluid Less Reactive rganic Compounds – Carbohydrate Sugars and starches Categorized by size  Monosaccharides—simple sugars  Disaccharides—two simple sugars linked together  Polysaccharides—long-branching chains of linked monosaccharides arbohydrates – Monosaccharides a saccharides arbohydrates – Polysaccharides Organic Compounds – Lipids There are 3 principle lipids in the human body  Neutral fats (triglycerides) – stored fat deposits  Phospholipids – form cellular membranes  Steroids – lipid-based hormones, cholesterol, bile salts, & vitamin D Triglycerides Phospholipids Steroids Organic Compounds – Proteins Consist of chains of amino acids Make up over half of a body’s organic matter Function as enzymes, hormones, and antibodies If a protein encounters a hostile environment in which temperature, pH, or ion concentration is significantly altered, it may unravel and lose its characteristic shape  This process is called denaturation  Denatured proteins are no longer functional Organic Compounds – Proteins Organic Compounds – Proteins Actions of an Enzyme The substrates attach to the active site of the enzyme molecule, the specific part of the enzyme that catalyzes the reaction, forming a temporary compound called the enzyme– substrate complex. In this reaction, the substrates are the disaccharide sucrose and a molecule of water. The substrate molecules are transformed by the rearrangement of existing atoms, the breakdown of the substrate molecule, or the combination of several substrate molecules into products of the reaction. Here the products are two monosaccharides: glucose and fructose. After the reaction is completed and the reaction products move away from the enzyme, the unchanged enzyme is free to attach to another substrate molecule. rganic Compounds – Nucleic Acids DNA – provides the blueprint of life  Nucleotide bases: A=Adenine G=Guanine C=Cytosine T=Thymine RNA – intermediary between DNA and protein  Nucleotide bases: A=Adenine G=Guanine C=Cytosine U=Uracil Adenosine triphosphate (ATP)  Chemical energy used by all cells  Energy released when high energy phosphate bond is broken DNA rganic Compounds – Nucleic Acids Structure of ATP and ADP Chemical Compounds and Life Processes  Inorganic compounds usually are structurally simple and lack carbon. Organic compounds always contain carbon, usually contain hydrogen, and always have covalent bonds.  Water is the most abundant substance in the body. It is an excellent solvent, participates in chemical reactions, absorbs and releases heat slowly, requires a large amount of heat to change from a liquid to a gas, and serves as a lubricant.  Inorganic acids, bases, and salts dissociate into ions in water. An acid ionizes into hydrogen ions (H); a base usually ionizes into hydroxide ions (OH2). A salt ionizes into neither H nor OH ions. Chemical Compounds and Life Processes  The pH of body fluids must remain fairly constant for the body to maintain homeostasis. On the pH scale, 7 represents neutrality. Values below 7 indicate acidic solutions, and values above 7 indicate basic (alkaline) solutions.  Buffer systems help maintain pH by converting strong acids or bases into weak acids or bases.  Carbohydrates include sugars, glycogen, and starches. They may be monosaccharides, disaccharides, or polysaccharides. Carbohydrates provide most of the chemical energy needed to generate ATP. Chemical Compounds and Life Processes  Carbohydrates, and other large, organic molecules, are synthesized via dehydration synthesis reactions, in which a molecule of water is lost. In the reverse process, called hydrolysis, large molecules are broken down into smaller ones upon the addition of water.  Lipids are a diverse group of compounds that include triglycerides (fats and oils), phospholipids, and steroids. Triglycerides protect, insulate, provide energy, and are stored in adipose tissue. Phospholipids are important membrane components. Steroids are synthesized from cholesterol.  Proteins are constructed from amino acids. They give structure to the body, regulate processes, provide protection, help muscles to contract, transport substances, and serve as enzymes. Chemical Compounds and Life Processes Enzymes are molecules, usually proteins, that speed up chemical reactions and are subject to a variety of cellular controls.  DNA is a double helix and is the primary chemical in genes. RNA differs in structure and chemical composition from DNA; its main function is to carry out the instructions encoded in DNA for protein synthesis.  Adenosine triphosphate (ATP) is the principal energy-transferring molecule in living systems. When it transfers energy, ATP is decomposed by hydrolysis to adenosine diphosphate (ADP) and P. ATP is synthesized from ADP and P using primarily the energy supplied by the breakdown of glucose. Holes’s Essentials of Biology: McGraw-Hill 2 - 45