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Anatomy and Physiology, Sixth Edition Rod R. Seeley Idaho State University Trent D. Stephens Idaho State University Philip Tate Phoenix College Chapter 02 Lecture Outline* *See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. 2-1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 2 The Chemical Basis of Life 2-2 Basic Chemistry • Matter, Mass, and Weight – Matter: Anything that occupies space and has mass – Mass: The amount of matter in an object – Weight: The gravitational force acting on an object of a given mass • Elements and Atoms – Elements: The simplest type of matter with unique chemical properties – Atoms: Smallest particle of an element that has chemical characteristics of that element 2-3 Atomic Structure • Atoms: composed of subatomic particles – Neutrons: no electrical charge – Protons: positive charge – Electrons: negative charge • Nucleus – Formed by protons and neutrons – Most of volume of atom occupied by electrons 2-4 Atomic Number and Mass Number • Atomic Number: Equal to number of protons in each atom which equals the number of electrons • Mass Number: Number of protons plus number of neutrons 2-5 Isotopes and Atomic Mass • Isotopes: Two or more forms of same element with same number of protons and electrons but different neutron number – 3 types of hydrogen – Denoted by using symbol of element preceded by mass number as 1H, 2H, 3H • Atomic Mass: Average mass of naturally occurring isotopes 2-6 Electrons and Chemical Bonding • Ion: When an atom loses or gains electrons and become charged – Cation: Positively charged ion – Anion: Negatively charged ion • Ionic Bonding – Cations and anions are attracted to each other 2-7 Covalent Bonding • Atoms share one or more pairs of electrons – Single covalent: Electron pair between 2 atoms – Double covalent: Two atoms share 4 electrons • Nonpolar covalent: Electrons shared equally • Polar covalent: Electrons not shared equally 2-8 Molecules and Compounds • Molecules: Two or more atoms chemically combine to form and independent unit – Example: Water • Compounds: A substance composed of two or more different types if atoms chemically combined – Example: Hydrogen Molecule • Molecular Mass: Determined by adding up atomic masses of its atoms or ions – Example: NaCl (22.99 + 35.45) 2-9 Intermolecular Forces • Result from weak electrostatic attractions between oppositely charged parts or molecules, or between ions and molecules • Weaker than forces producing chemical bonding 2-10 Intermolecular Forces • Hydrogen Bonds – Water: Positively charged hydrogen atoms bond with negatively charged oxygen atoms of other water molecules – Important role in determining shape of complex molecules 2-11 Intermolecular Forces • Solubility: Ability of one substance to dissolve in another – Example: Sugar dissolves in water • Dissociation or Separation – Ionic compounds – Cations are attracted to negative end and anions attracted to positive end of water molecules 2-12 Intermolecular Forces • Electrolytes: Cations (+) and anions (-) that dissociate in water – Capacity to conduct an electric current – Currents can be detected by electrodes • Nonelectrolytes: Molecules that do not dissociate form solutions that do not conduct electricity 2-13 Chemical Reactions • Chemical Reactions: Atoms, ions, molecules or compounds interact to form or break chemical bonds – Metabolism: All anabolic and catabolic reactions in the body • Catabolism: Decomposition reactions – Hydrolysis: Reactions that use water • Anabolism: Growth, maintenance, and repair of the body in synthesis reactions – Produce molecules characteristic of life: ATP, proteins, carbohydrates, lipids, and nucleic acids 2-14 Synthesis and Decomposition Reactions • Synthesis Reactions – Two or more reactants chemically combine to form a larger product – Anabolism: All body’s synthesis reactions • Decomposition Reactions – Reverse of synthesis reactions – Catabolism: Reactions of decomposition in body 2-15 Oxidation-Reduction Reactions • Oxidation – Loss of an electron by an atom • Reduction – Gain of an electron by an atom • Oxidation-Reduction Reactions – The complete or partial loss of an electron by one atom is accompanied by the gain of that electron by another atom 2-16 Energy • Energy: The capacity to do work – Potential Energy: Stored energy – Kinetic Energy: Does work and moves matter – Mechanical Energy: Energy resulting from the position or movement of objects – Chemical Energy: Form of potential energy in the chemical bonds of a substance – Heat Energy: Energy that flows between objects of different temperatures 2-17 Energy and Chemical Reactions 2-18 Speed of Chemical Reactions • Activation Energy: Minimum energy reactants must have to start a chemical reaction – Catalysts: Substances that increase the rate of chemical reactions without being permanently changed or depleted – Enzymes: Increase the rate of chemical reactions by lowering the activation energy necessary for reaction to begin 2-19 Activation Energy and Enzymes 2-20 Chemistry • Inorganic Chemistry: Generally substances that do not contain carbon – Water – Oxygen • Organic Chemistry: Study of carboncontaining substances 2-21 Water • • • • Inorganic Stabilizes body temperature Protection Necessary for many chemical reactions of life • Mixing Medium – Mixture: Substance physically but not chemically combined • Solution: Liquid, gas, or solid uniformly distributed – Solvent: What dissolves the solute – Solute: What is to be dissolved 2-22 Acids and Bases; Salts and Buffers • Acid: A proton donor or any substance that releases hydrogen ions • Bases: A proton acceptor or any substance that binds to or accepts hydrogen ions • Salts: A cation consisting of other than a hydrogen ion and other than an anion or hydroxide ion • Buffers: A solution of a conjugate acid-base pair in which acid and base component occur in similar concentrations 2-23 The pH Scale • Refers to the Hydrogen ion concentration in a solution – Neutral: pH of 7 or equal hydrogen and hydroxide ions – Acidic: a greater concentration of hydrogen ions – Alkaline or basic: a greater concentration of hydroxide ions 2-24 Organic Chemistry • Carbohydrates – Composed of carbon, hydrogen, oxygen • Lipids – Composed mostly of carbon, hydrogen, oxygen • Proteins – Composed of carbon, hydrogen, oxygen,nitrogen • Nucleic Acids: DNA and RNA – Composed of carbon, hydrogen, oxygen, nitrogen, phosphorus • Adenosine Triphosphate (ATP) – Composed of adenosine and three phosphate groups 2-25 Carbohydrates • Monosaccharides – Simple sugars: glucose, fructose, galactose • Disaccharides – Two simple sugars bound together by dehydration: sucrose, lactose, maltose • Polysaccharides – Long chains of many monosaccharides: glycogen in animals; starch and cellulose in plants 2-26 Monosaccharides 2-27 Disaccharide and Polysaccharide 2-28 Lipids • Lipids: Can be dissolved in nonpolar organic solvents as alcohol or acetone but relatively insoluble in water – Fats: Ingested and broken down by hydrolysis – Triglycerides: composed of glycerol and fatty acids – Phospholipids: Important structural component of cell membranes – Eicosanoids: Derived from fatty acids – Steroids: Cholesterol, bile salts, estrogen, testosterone – Fat-soluble Vitamins 2-29 Phospholipids 2-30 Steroids 2-31 Proteins • Amino acids: The building blocks of protein • Peptide bonds: Covalent bonds formed between amino acids during protein synthesis • Structure – Primary, secondary, tertiary, quartenary • Enzymes: Protein catalysts – – – – Lock-and-key model Active site Cofactors Coenzymes 2-32 Peptide Bonds 2-33 Protein Structure and Enzyme Action 2-34 Nucleic Acids: DNA and RNA • DNA: Deoxyribonucleic acid – Genetic material of cells copied from one generation to next – Composed of 2 strands of nucleotides • Each nucleotide contains one of the organic bases of adenine or guanine which are purines and thymine or cystosine which are pyrimidines • RNA: Ribonucleic acid – Similar to a single strand of DNA • Four different nucleotides make up organic bases except thymine is replaced with uracil (pyrimidine) 2-35 DNA Structure 2-36 Nucleotides and Nitrogenous Bases 2-37 Adenosine Triphosphate (ATP) • Energy currency of the body • Provides energy for other chemical reactions as anabolism or drive cell processes as muscle contraction • All energy-requiring chemical reactions stop when there is inadequate ATP 2-38