| Question | Answer |
| respiratory acidosis | CO2 (g) accumulates, giving rise to H2CO3, which dissociates to form H+ and HCO3 -. |
| hypoventilation | Inability to excrete CO2 rapidly enough to meet physiological needs. |
| respiratory alkalosis | Rise in plasma pH in the blood |
| hyperventilation | Breathing rate more rapid than necessary for normal CO2 elimination from the body. Can result in inappropriately low [CO2(g)] in the blood. Causing blood pH to rise |
| Overall equilibrium constant for ionization of H2CO3 in equilibrium with CO2(d) | KaKh = [H+][HCO3 -] / Kh[CO2(d)] |
| carbonic anhydrase | Enzyme that mediates hydration of CO2. Facilitates the equilibrium by rapidly catalyzing the reaction H2O + CO2(d) <--> H2CO3 |
| Bicarbonate Buffer System of Blood Plasma | Concentration of H2CO3 maintained through equilibrium with dissolved CO2, produced in tissues and available as gaseous in the lungs. Buffers concentration of H2CO3. Overall buffer system: CO2(d) + H2O <-Kh-> H2CO3. H2CO3 <-Ka-> H+ + HCO3 -. Where Kh = equilibrium constant for hydration of CO2 and Ka = first acid dissociation constant for H2CO3. |
| bicarbonate/carbonic acid couple | Buffer system of blood plasma. H2CO3 <--> H+ + HCO3 -. Concentration of H2CO3 small fraction of HCO3 - concentration, because pKa1 is 3.77. |
| imidazole group | Five-membered ring possessing two nitrogen atoms. |
| histidine | amino acid. Part of it’s structure is an imidazole group. pKa for dissociation of imidazole hydrogen is 6.04. Concentration of histidine low and pKa more than 1 pH away from prevailing intracellular pH. Only serves a minor role. May combine with other amino acids as in proteins or dipeptides that will increase the pKa substantially. |
| phosphate system | Buffer the intracellular fluid of cells at physiological pH because pK2 likes near pH value. Phosphate abundant anion in cells in both inorganic form and functional group |
| Bicarbonate/carbonic acid (HCO3 - / H2CO3) system | maintain extracellular fluid pH |
| Phosphate (HPO4 2- / H2PO4-) system and histidine system | maintain intracellular pH |
| molarity of a buffer | the sum of the concentrations of the acid and conjugate base forms |
| how do you choose a buffer system | based on closed pKa to desired pH |
| buffers | Solutions that tend to resist changes in their pH as acid or base is added. Composed of a weak acid and its conjugate base. Contains nearly equal amounts of acid and base (because, by definition, has pH near its pKa) Addition of H+ and OH- has little effect because they are absorbed by H+ + A- --> HA or OH- + HA --> A- + H2O |
| biological relevance of titration curves | Region of pKa, pH remains relatively unaffected as increments of OH- (or H+) are added. Acts as a buffer. |
| titration curve for polyprotic acid | Three dissociable H+ lost in discrete steps, each dissociation showing a characteristic pKa |
| titration curve | Adding incremental amounts of NaOH, plot the pH of the solution versus the amount of OH- added. Shapes of titration curves for weak acids identical |
| titration | Analytical method used to determine the amount of acid in a solution. Experimental method of determining pKa values of weak electrolytes: Where half the HAc has been neutralized, concentrations of HAc and Ac- are equal and pH = pKa for HAc. |
| Henderson-Hasselbalch equation | pH = pKa + log [A-]/[HA]. pH of a solution can be calculated, provided Ka and the concentrations of the weak acid HA and its conjugate base A- are known. Provides a general solution to the quantitative treatment of acid-base equilibria in biological systems. |
| ionization constant | Another name for Ka. States the extent to which a substance forms ions in water. |
| weak electrolytes | Substances with only a slight tendency to dissociate to form ions in solution. |
| Ka / acid dissociation constant | Ka = K[H2O] |
| what are some examples of strong electrolytes | salts, strong acids, strong bases |
| electrolyte | Substances capable of generation ions in solution and thereby causing an increase in electrical conductivity of the solution. |
| strong electrolytes | Substances that are almost completely dissociated to form ions in solution. |
| neutrality / neutral pH | pH = 7. No excess of acidity or basicity. |
| why is pH used widely in biological applications | H ion concentrations in biological fluids low |
| pKw = ? | = pH + pOH = 14 |
| pH | negative log of the hydrogen ion concentration pH = -log [H+] pH scale: Based on negative logarithms, low pH values represent high H+ concentrations. |
| Kw / Ion product of water | Concentration of H2O in pure water Reciprocal relationship between H+ and OH- concentrations in aqueous solutions |
| Amount of H3O+ or OH- in 1 L of pure H2O at 25ºC is | 1 x 10^-7 mol |
| Amount of H3O+ or OH- in 1 L of pure H2O at 25ºC is | 1 x 10^-7 mol |
| what ways do cells prevent losing or gaining fluid through osmosis | Cell walls, extracellular fluids of comparable osmolarity and storage of substances (eg amino acids and sugars) in polymeric form |
| colligative properties | Characteristic changes in behavior due to the influence of solute on water Depend only on the number of solute particles per unit volume of solvent Effects: freezing point depression, boiling point elevation, vapor pressure lowering, osmotic pressure effects Solute imposes more order so more difficult for it to assume crystalline structure or leave Solution will draw solvent across an osmotic barrier from high concentration to low concentration |
| why do solutes influence water's properties | Solutes fix water surrounding them (regardless of polar or nonpolar) because limited orientation that neighboring H2O molecules can assume |
| micelles | Clusters of amphipathic molecules |
| examples of amphiphilic molecules | Salts of fatty acids: carboxylate functional group hydrates, long hydrophobic tails insoluble. |
| amphiphilic molecules | Compounds containing both strongly polar and strongly nonpolar groups. In water, hydrophobic tails join together as polar functions hydrated. |
| clathrate | H-bonded water network rearranged toward formation of a local cage structure surrounding each solute molecule. Accompanied by significant ordering (negative entropy). H2O next to solvent have limited structural options. Straddle nonpolar solute so two of three H-bonding vectors available (tangential to solute). Allows H2O to retain H-bonding possibilities because no H-bond acceptor/donator directed towards solute. |
| describe water and nonpolar solvents | Nonpolar solutes: do not H bond. Only sparingly soluble in water. Dissolving nonpolar solutes needs significant reorganization of water surrounding the solute |
| describe water and polar solutes | Nonionic but polar compounds can form H bonds with water. Polar interactions stronger than intermolecular attractions because H bonds stronger than van der Waals forces and weak H bonds. |
| what is the equation for dielectric constants | F = e1e2/Dr^2 where F is force, r is distance and e1 and e2 are the charges of the two ions. |
| describe water's dielectric constant | Water has high D. Attractions between H2O and ions is stronger than between ions. |
| dielectric constant | The ability of a substance to surround ions in dipole interactions and diminish their attraction for each other. D. What ionization in solution depends on. |
| hydration | Interaction between water molecules and ions. |
| what is H2O an excellent solvent for? | salts, nonionic but polar substances and carbonyl-containing molecules |
| hydration shells | water molecules surrounding ions. Stable structures but also dynamic. |
| what is water's structure in liquid | Disorderly bonded network. Many (at least half) of H bonds in liquid are in nonideal orientations. This makes liquid lack the structured order of ice. Each molecule connected to every other in fluid network of H bonds. Strain because of nonideal hydrogen bonds in liquid state. Creates kinetic situation in which H2O molecules can switch H-bond allegiances, creating fluidity |
| what is water's structure in ice | crystalline form of water, each H2O molecular has four nearest neighbors to which it is hydrogen bonded (tetrahedral symmetry). H bonds form space-filling, three-dimensional network. Bonds directional and straight. H bonds hold water molecules apart. Some H bonds break in melting that maintain crystal structure. Liquid molecules can actually pack closer together. |
| what is H2O's structure and how does it affect its properties | bent. makes it polar. Can be both H donor and acceptor in hydrogen bonds |
| what ability is crucial to the understanding of water's properties | hydrogen bonds |
| in what stage is the maximum density of water found? | liquid (negative volume of melting) |
| what are some of the unexpected properties of water? | High boiling point, melting point, heat of vaporization and surface tension. |
55 cards - created jan 8, 12:38pm