BIOL 2050 1st Edition Lecture 4Outline of Last Lecture I. Vaccinesa. Herd ImmunityII. PolioOutline of Current Lecture Chapter 2III. Octet RuleIV. Chemical Bondsa. Ionic Bondsb. Hydrogen Bonds c. Covalent BondsV. Molecular FunctionVI. Chemical ReactionsChapter 3VII. Watera. Unique Propertiesb. Acids and BasesCurrent LectureChapter 2Octet Rule: Distribution of valence electrons between atoms byI. Gaining an electron from another atomII. Losing an electron to another atomIII. Sharing electrons with another atomChemical Bonds: attractions that hold atoms with incomplete valence shells together when electrons are shared between these atoms.I. Covalent Bonds: sharing of a pair of valence electrons by two atoms.a. Shared electrons count as part of each atom’s valence shellThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Molecule: consists of two or more atoms held together by covalent bondsValence: bonding capacity of an atomElectronegativity: an atom’s attraction for the electrons in a covalent bond.Types of bondsa) Nonpolar Covalent Bonds: shares electron equallyb) Polar Covalent Bonds: one atoms is more electronegative, and the atoms do not share the electron equally.a. Unequal sharing causes a partial positive or negative chargeII. Ionic Bondsa. After the transfer of an electron between two atoms, both atoms have charges. These charged atoms are called ions.i. Cation: positively charged ionii. Anion: negatively charged ioniii. Ionic Bond: attraction between an anion and a cation1. Ionic Compounds: compounds formed by ionic bonds III. Weak Bondsa. Ionic Bondsb. Hydrogen Bondsi. When a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom.1. Very important in waterc. Van der Waals Interactionsi. Attractions between molecules that are close together as a result of a “hot spot”, or collection of positive or negative charges.Molecular Functiond. Shape of a molecule is important to its functioni. Determined y the positions of its atoms’ valence electronsii. Biological molecules recognize and interact with other molecules based on shapeChemical Reactionse. Chemical Reactions: the making and breaking of chemical bondsi. Reactants: the starting moleculeii. Products: the final molecules of a chemical reaction1. Example: Photosynthesisiii. Chemical Equilibrium: reached when the forward and reverse reaction rates are equalChapter 3Water I. Biological MediumII. Cells are 70-90% waterIII. Polar Molecule: opposite ends have opposite chargesUnique PropertiesI. Heat StorageII. Ice FormationIII. High Heat of VaporizationProperties that facilitate an environment for life:I. Cohesive behaviora. Cohesion: collectively hydrogen bonds hold water molecules togetherb. Adhesion: attraction between different substancesc. Surface Tension: measures how hard it is to break the surface ofa liquid.II. Ability to moderate temperaturea. Water absorbs heat from warmer air and releases stored heat to cooler air with only a slight change in its own temperature.b. Kinetic Energy: energy of motionc. Heat: the measure of the total amount of kinetic energy due to molecular motiond. Temperature: measures the intensity of heat due to the average kinetic energy of molecules.i. Calorie: amount of heat required to raise the temperature of one gram of water by one degree Celsius.ii. Heat Vaporization: the heat a liquid must absorb for onegram to be converted to gasiii. Evaporative Cooling: as a liquid evaporates, its remaining surface coolsIII. Expansion upon freezing a. Ice floats because hydrogen bonds make ice less dense IV. Versatility as a solventa. Solution: liquid that is a homogeneous mixture of substancesb. Solvent: dissolving agent of a solutionc. Solute: substance that is dissolvedd. Aqueous Solution: water is the solventV. Other Propertiesa. Hydrophilic: substance that has an affinity for waterb. Hydrophobic: substance that does not have an attraction to water.c. Colloid: stable suspension of fine particles in a liquidd. Molecular Mass: sum of all masses of all atoms in a moleculeMolarity: number of moles of solute per liter of solutionAcids and BasesVI. Hydrogen Ion (H+)VII. Hydronium Ion: water molecule with an extra proton VIII. Hydroxide Ion: water molecule that lost a proton IX. Acid: any substance that increases the H+ concentration of a solution.a. less than seven on the pH scale X. Base: any substance that reduces the H+ concentration in a solution.b. more than seven on the pH