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Chemical Basis of Life Chapter 2 Chemistry - study of matter Biochemistry-chemistry of organisms 2.1: Introduction Why study chemistry in an Anatomy and Physiology class? - Body functions depend on cellular functions - Cellular functions result from chemical changes - Biochemistry helps to explain physiological processes 2 2.2: Structure of Matter Matter – anything that takes up space and has mass (weight). It is composed of elements. Elements – composed of chemically identical atoms: • Bulk elements – required by the body in large amounts • Trace elements - required by the body in small amounts • Ultratrace elements – required by the body in very minute amounts Atoms – smallest particle of an element 3 Structure of Matter A. Atoms-basic unit 1. Nucleus a. proton- “+”, 1 amu b. neutron- no charge, 1 amu 2. Energy Levels/Shells a. electron- “-”, 0 amu 2,8,8 • All atoms are electrically neutral because the # of p+ = # of e-. • Atomic number = # of protons. • Atomic weight = # of protons + neutrons. • Isotopes-atoms of the same element having different atomic masses. • Radioactive isotopes-an isotope which easily loses subatomic particles. Molecules and Compounds Molecule – particle formed when two or more atoms chemically combine Compound – particle formed when two or more atoms of different elements chemically combine Molecular formulas – depict the elements present and the number of each atom present in the molecule H2 C6H12O6 H2O 8 Bonding of Atoms: Ions Ion • An atom that gains or loses electrons to become stable • An electrically charged atom Cation • A positively charged ion • Formed when an atom loses electrons 11p+ 12n0 17p+ 18n0 Anion • A negatively charged ion • Formed when an atom gains electrons Sodium atom (Na) Chlorine atom (Cl) (a) Separate atoms If a sodium atom loses an electron to a chlorine atom, the sodium atom becomes a sodium ion (Na+), and the chlorine atom becomes a chloride ion (Cl–). 9 Covalent Bonding • occurs when the atoms forming the bond SHARE one or more pairs of electrons • this results in MOLECULES • Each “dash” represents a pair of shared electrons (single covalent bond) Bonding of Atoms: Structural Formula • Structural formulas show how atoms bond and are arranged in various molecules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H H H H2 O O O2 H O H2O O C CO2 13 O Bonding of Atoms: Polar Molecules Polar Molecules • Molecule with a slightly negative end and a slightly positive end • Results when electrons are not shared equally in covalent bonds Slightly negative end • Water is an important polar molecule Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) Slightly positive ends 14 Hydrogen Bonds Hydrogen Bonds • A weak attraction between the positive end of one polar molecule and the negative end of another polar molecule • Formed between water molecules • Important for protein and nucleic acid structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H H O H O H O H O H H O (b) Hydrogen bonds H H H 15 Chemical Reactions Chemical reactions occur when chemical bonds form or break among atoms, ions, or molecules Reactants are the starting materials of the reaction - the atoms, ions, or molecules Products are substances formed at the end of the chemical reaction NaCl Na+ + ClReactant Products 17 Chemical Reactions • SYNTHESIS - “A + B---> AB” Ex: H2 + O2---> H2O • DECOMPOSITION - “AB ---> A + B” Ex: 2H2O ---> 2H2 + O2 • EXCHANGE - “AB + CD ---> AD + CB” Ex: HCl + NaOH ---> NaCl + H2O • Many reactions are reversible Ex: A + B <---> AB Acids, Bases, and Salts Electrolytes – substances that release ions in water NaCl Na+ + ClAcids – electrolytes that dissociate to release hydrogen ions in water HCl H+ + ClBases – substances that release ions that can combine with hydrogen ions NaOH Na+ + OHSalts – electrolytes formed by the reaction between an acid and a base HCl + NaOH H2O + NaCl 19 + H pH-measurement of the concentration of a solution 0<---------7---------->14 acidic alkaline (basic) distilled water is neutral, having a pH of 7.0 blood pH = 7.4 if below--->acidosis if above--->alkalosis pH scale ranges from 0 - 14 Figure 02.10 Chemistry of Cells Organic -contain C & H Inorganic-don’t contain both C & H 2.3: Chemical Constituents of Cells Organic v. Inorganic Molecules Organic molecules • Contain C and H • Usually larger than inorganic molecules • Dissolve in water and organic liquids • Carbohydrates, proteins, lipids, and nucleic acids Inorganic molecules • Generally do not contain C • Usually smaller than organic molecules • Usually dissociate in water, forming ions • Water, oxygen, carbon dioxide, and inorganic salts 24 Inorganic substances (usually electrolytes) Water 2/3 of wt. Oxygen Carbon dioxide Inorganic Salts (electrolyte balance) Organic Compounds Organic compounds almost always have covalent bonds. The four types we will discuss are: 1. Carbohydrates • contain C, H, O---H:O ratio is 2:1 Ex: C6H12O6 C12H22O11 • provide immediate energy source • short-term energy storage • carbon is in short chains or RINGS • Monosaccharides (simple sugars) examples are: glucose, fructose, galactose, ribose, deoxyribose • Disaccharides (double sugars): examples are sucrose, lactose, maltose. These are each made of 2 rings of carbons (2 simple sugars joined together. • Polysaccharides: examples are starch, glycogen (animal starch), and cellulose. These are made of many rings of carbon (many simple sugars joined together). Figure 02.12 2. Lipids • provide long-term energy storage • water insoluble (either the entire molecule or part of the molecule) • cell structure, vitamins, hormones • types: fats, phospholipids, cholesterol Fats (animal fats, oils) • made of C,H,&O, but H:O ratio is MUCH greater than 2:1 (C57H110O6) • Each molecule is called a triglyceride, and is made of 1 glycerol and 3 fatty acids. • An unsaturated fat has at least one carbon to carbon double or triple bond in its fatty acids, and it is usually liquid--good. • A saturated fat has no C=C or triple, usually solid--bad. Phospholipids • major component of cell membranes • Each molecule is made of 1 glycerol, 2 fatty acids, and 1 phosphoric acid • partially water insoluble Cholesterol • important in cell membranes and as source of steroid hormones • partially water insoluble 3. Proteins • structural component of cells, some hormones, transporters, enzymes • Each molecule is made of a LONG chain of amino acids. This chain takes on a 3dimensional shape due to hydrogen bonding between the amino acids. • Denaturization-results from the breaking of H-bonds---alters shape--destroys function Animation: Protein Denaturation Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 46 4. Nucleic Acids • DNA, RNA • made of chains of nucleotides--each nucleotide is made of: 5-C sugar, phosphate, and nitrogenous base • DNA-found in chromosomes-provides code for protein production (genes) • RNA-helps in protein production Figure 02.21