BSCI105 Final Exam Study Guide What should we know from Lecture 1 Chapter 1 o Nothing Specific Unit I Chemical Basis of Life o Chemistry in Water Ch 2 3 Electron shells Electrons occupy layers or shells around the nucleus 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 must be 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 nutrients against 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 Reason why 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 the surface 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 a log scale o The water molecule that loses a proton is a hydroxide ion OH which has a charge of 1 and binds 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 neutral o 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 Shape o Contains 4 valence electrons making it capable of forming 4 bonds o Orbitals avoid each other Tetrahedral shapes Creates geometric variation o Usually forms single or double covalent bonds o 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 and hence different properties o Structural differ in the covalent arrangements of their atoms as well as the different locations of the double bonds o 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 diversity o A few side groups are responsible for much of the diversity of biological molecules o Alter the reactivity and chemical properties of organic molecules o 7 groups Hydroxyl OH Alcohols Polar Forms hydrogen bonds with water molecules to help dissolve organic compounds 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 Organic phosphates Has the potential to react with OPO3 2 Methyl water releasing energy Contributes negative charge to the molecule it is apart of CH3 Methylated compounds Affects expression of genes Affects shape and function of sex hormones o 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 are covalently 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 Hydrolysis Process by which polymers are disassembled to monomers the reverse of the dehydration reaction The bond between the monomers is broken by the addition of a water molecule with the hydrogen from the water attaching to one molecule and the hydroxyl group attaching to the adjacent monomer
View Full Document
Unlocking...