BSCI105 Final Exam Study Guide“What should we know from…”- Lecture 1 (Chapter 1)o Nothing Specific- Unit I: Chemical Basis of Lifeo Chemistry in Water (Ch. 2/3) Electron shells: Electrons occupy layers or “shells” around thenucleus of an atom. Each shell can hold a fixed number of electrons Orbitals: Electrons occupy orbitals within shells- Each orbital holds 2 electrons- Shells can have multiple orbitals Valence: Electrons in the outer shell, determine reactivity Bonds:- Covalent: Electron Sharing, takes considerable energy to make or break- Ionic: Weak, electron stripping interactions- Electronegativity: An atoms power to attract and hold electrons in their orbitals- Hydrogen Bonds: Occur between covalent compounds having hydrogen atoms in highly polar configurations Chemical Reactions:- Reactivity & Valence: Reactivity depends on unpaired electrons aka the Valence electrons in the outer shell- Making & Breaking Bonds: Chemical reaction occurs, uses or liberates energy. All atoms of the reactants mustbe accounted for in the products, reactions cannot create or destroy matter but can only rearrange it- Reversible: All chemical reactions are reversible, with the products of the forward reaction becoming the reactants for the reverse reaction. (Two opposite-headed arrows)- Equilibrium: The point at which the reactions offset one another exactly. Reactions are still going on, but with no net effect on the concentrations of reactants and products. Does not mean they are equal in concentrations. Properties of Water:- Polar molecule: unequal sharing of electrons, charge unevenly distributed (oxygen portion = partially negative, hydrogen portion = partially positive)- Hydrogen Bonding: When in it’s liquid form, its hydrogen bonds are very fragile and form, break, and re-form frequently.o Cohesion: due to hydrogen bonding contributes to the transport of water and dissolved nutrientsagainst gravity in plants. (Helps hold together the column of water within cells)o Adhesion: clinging of one substance to another, adhesion of water to cell walls by hydrogen bonds helps counter the downward pull of gravity. (Helps resist the downward pull of gravity)o Surface Tension: Measure of how difficult it is to stretch or break the surface of a liquid. Reasonwhy some animals can stand, walk, or run on water without breaking the surface- High Specific Heat: The amount of heat that must be absorbed or lost for 1g of that substance to change its temperature by 1°C. Because of its high specific heat relative to other materials, water will change its temperature less when it absorbs or loses a given amount of heat. - High heat of Vaporization: The quantity of heat a liquid must absorb for 1g of it to be converted from the liquid to the gaseous state. Emergent property related to hydrogen bonds. o Evaporative Cooling: As a liquid evaporates, thesurface of the liquid that remains behind cools down. Occurs because the “hottest” molecules, those with the greatest kinetic energy, are the most likely to leave as gas. (Cools us, cools the ocean)- pH (Acids & Bases): The amount of H+ ions is measured as pH, or concentration of hydrogen ions on alog scaleo The water molecule that loses a proton is a hydroxide ion (OH-) which has a charge of 1- andbinds to the other water molecule, forming a hydronium ion (H3O+)o The concentrations of H+ and OH- are equal in pure water, but adding acids and bases, disrupts this balance.o Acid: substance that increases the hydrogen ion concentration of a solution (donates addition H+ to the solution)o Base: substance that reduces the hydrogen ion concentration of a solution (reduces the H+ concentration, higher concentration of OH-)o Solutions with equal concentrations of H+ and OH- are neutralo Buffer: substance that minimizes changes in the concentrations of H+ and OH- in a solution Does so by accepting hydrogen ions from the solution when they are in excess, and donating hydrogen ions to the solution when they have been depleted. Carbon: The backbone of organic molecules- Diversity, Shapeo Contains 4 valence electrons making it capable offorming 4 bondso Orbitals avoid each other Tetrahedral shapes Creates geometric variationo Usually forms single or double covalent bondso Hydrocarbons: Organic molecules consisting of only carbon and hydrogen- Isomers: Compounds that have the same numbers of atoms of the same elements but different structures andhence different propertieso Structural: differ in the covalent arrangements of their atoms, as well as the different locations of the double bondso Geometric: (cis-trans) same covalent organization, but differ in arrangement around carbon backbone. Stable geometric isomers result from inflexibility of double bonds o Enantiomers: isomers that are “mirror images” of each other and that differ in shape due to the presence of an asymmetric carbon. Asymmetric carbon: one that is attached to four different atoms or groups of atoms- Functional Groups: “Side groups”o Increase molecular diversityo A few side groups are responsible for much of the diversity of biological moleculeso Alter the reactivity and chemical properties of organic moleculeso 7 groups: Hydroxyl- (-OH)- Alcohols- Polar- Forms hydrogen bonds with watermolecules, to help dissolve organiccompounds Carbonyl- (>CO)- Ketones- Aldehydes- Found in sugars Carboxyl- (-COOH)- Carboxylic Acids- Acidic properties due to acidic polarity Amino- (-NH2)- Amines- Acts as a base- Ionized with a charge of 1+, under cellular conditions Sulfhydryl- (-SH)- Thiols- React together to form covalent bonds, which stabilizes protein structure- “Crosslinks” Phosphate- (OPO3 2-)- Organic phosphates- Has the potential to react with water, releasing energy- Contributes negative charge to the molecule it is apart of Methyl- (-CH3)- Methylated compounds- Affects expression of genes- Affects shape and function of sex hormoneso Macromolecules (Ch. 5): Huge Monomers: Smaller molecules that are the remaining units that serve as building blocks of a polymer Polymers: Long molecules consisting of many similar or identical building blocks linked by covalent bonds - Dehydration synthesis: Process by which monomers are connected by a reaction in which two molecules arecovalently bonded to each other with the loss of a water molecule. One monomer provides a hydroxyl group (-OH), while the other provides a hydrogen atom (-H).-
View Full Document
Unlocking...