BIO 201 Chapter 1 Notes Dr Sonja Pyott Chemical Basis of Life Part I Concept 1 Matter consists of elements and compounds I Terms to know Element Compound Essential element Trace element Chemical symbol II Some elements are essential to life examples oxygen carbon hydrogen and nitrogen Concept 2 Subatomic structure determines the chemical behavior of an element I Terms to know Atom Subatomic particles Proton Neutron Electron Atomic nucleus Atomic number Atomic mass Isotope Valence electrons Electron shells Electron orbitals II Summary of subatomic particles and properties Subatomic particle Proton Neutron Properties Positively charged subatomic Protons and neutrons are particle packaged in the atomic nucleus Number in an atom identifies the element and determines the Total number of protons atomic number and neutrons determines Neutrally charged subatomic the atomic mass particle Page 1 of 4 BIO 201 Chapter 1 Notes Dr Sonja Pyott Differences in number yield different isotopes Negatively charged subatomic particle Electron Arranged in shells of different energy levels that orbit the atomic nucleus Configuration of the Differences in number changes the valence electrons charge of the element determines the chemical behavior of that element Concept 3 Chemical bonds between atoms form molecules I Terms to know Chemical bond Molecule Molecular formula Covalent bond Single and double bonds Electronegativity Polar covalent bonds Nonpolar covalent bonds Ionic bonds Ion Cation Anion Hydrogen bonds Van der Waals interactions II Types of chemical bonds A Covalent bonds A strong chemical bond in which two atoms share one or more pairs of valence electrons Example H2O Differences in electronegativity can create polar bonds in which electrons are shared unequally B Ionic bonds A chemical bond resulting from the attraction of oppositely charged ions Page 2 of 4 BIO 201 Chapter 1 Notes Dr Sonja Pyott Example salts like NaCl C Weak chemical bonds Include hydrogen bonds and van der Waals interactions Although individual weak bonds are as their name suggests relatively weak their summative effect can be very strong III Chemical bonds impart a molecule with a three dimensional shape that is important to its function within the cell Concept 4 Chemical reactions make and break chemical bonds I Terms to know Chemical equation Reactants Products Chemical equilibrium II Reactions are drawn as chemical equations with reactants starting materials on the left and products on the right III Reactions have direction given by the arrow separating the reactants and products and rate speed at which reactants are converted to products IV Some reactions are reversible and the point at which the forward and reverse reactions occur at the same rate is called the chemical equilibrium Concept 5 Water has unique chemical properties that support life I Terms to know Cohesion Adhesion Surface tension Specific heat Evaporative cooling Aqueous solution Solvent Solute Molarity Page 3 of 4 BIO 201 Chapter 1 Notes Dr Sonja Pyott Hydrogen ion Hydroxide ion Acid Base Buffer II The polarity of water results in hydrogen bonding between water molecules III Hydrogen bonding of water provides it with unique chemical properties that support life including the ability of water to Readily dissolve polar molecules Display cohesion Moderate temperature Expand when frozen IV Dissociation of water leads to acidic and basic conditions Water can spontaneously dissociate into H a proton or hydrogen ion and OH a hydroxide ion Acids are substances that increase the concentration of H in solution For example in water HCl dissociates into H and CL increasing the concentration of H Bases are substances that reduce the concentration of H in solution For example in water NaOH dissociates into Na and OH The hydroxide ion readily accepts protons in solution and decreases their concentration V The pH scale is used to measure acidity and basicity and is logarithmic Logarithmic scales like the Decibel scale or the Richter scale are especially useful for describing phenomena that span large value ranges Because pH is a logarithmic scale differences in values are not linear For example a solution that has a pH of 2 is 10 times more acidic than a solution with a pH of 3 and 100 times more acidic than a solution with a pH of 4 VI Buffers Small changes in pH can have disastrous consequences for cells Cell use substances called buffers to resist changes in pH and to maintain pH within vary narrow ranges Page 4 of 4