OBJ - Acid-Base Balance Flashcards
Define acids and bases in reference to the H+ and OH-
- Acid = + donors; H+ or HA
- tendency for a compound to lose protons to solution
- Base = + acceptors; HO-, or A-
- tendency for a compound to pick up protons to solution
Distinguish between a strong acid and a weak acid-base conjugate
Strong acid fully dissociates in water (much more negative pKa/smaller exponent)
Weak acid partially dissociates in water (smaller pKa/larger exponent)
HA <-> A:- & H+ HA = weak acid; A- = CB
Define pH, and show its relationship with hydrogen ion concentration
pH = negative log of H+ concentration
Explain what pKa is, and show its relationship to Ka
Ka = ionization/dissociation constant; pKa = negative log of Ka
less negative #(higher exponent) = weaker the acid
more negative (smaller exponent) = stronger acid
Use the Hendersen-Hasselbalch equation to explain the relationship between pH and pKa.
log 1 = 0
@ midpoint pH = pK;
pH where buffer resists change most/is most effective
but capacity is based on molar concentrations
Describe what is meant by the ion product of water
rate of dissociation of H & OH for water
Kw = 1.0E-14 @ 25 degrees C
Explain what a buffer is, and why weak acids and bases are better biological buffers than strong acids and bases
combination of a Conjugate ACid Base Pair (WA/CB or WB/CA) that work together to resist pH changes by not fully dissociating & having an equilibrium of HA & A- in solution together; very flat titration curve
SA/SB fully dissociate & have a very steep titration curve
Describe the concept of titration, interpret a titration curve, and identify compounds with dissociable groups from their respective titration curves
Titration - neutralizing an acid by adding base & continually checking the pH
SA titration curve - very steep in the middle
WA titration curve = very flat => GREAT BUFFER when pH ~pKa - buffering is best (strength is ~ to concentrations of each)
Explain the significance of the pKa of a buffer with respect to buffering capacity
buffer capacity is ~ to molar concentrations of WA & CB is solution, no place on curve
where pH = pKa there is about +/- 1 pH point for which it will buffer; want a pKa close to biological systems
List biological compounds known to have significant buffering capacity inside our body
Blood = pH 7.4 (6.8-7.8 is survivable)
Intracellular pH = 7.10 (6.9-7.4) Stomach Acid
Physiological buffers:
- Bicarbonate: Blood
- CO2 + H2O + Carbonic Anydrase H2CO3 (slipped/fleeting intermediate) HCO3- + H+
- Protein: AA have ionizable side chain (histadine) that can act as WA/WB
- Phosphate: cell’s cytoplasmic compartments; works with bicarbonate buffer system
- H2PO4- HPO4– + H+
Describe how the bicarbonate buffer system works to maintain a constant pH in our blood and tissues
Bicarb Buffer system = pKa 3.8
Carbonic anhydrase & CO2 produced by cellular metabolism
LCP - adapts to tissue CO2 increase, carbonic anhydrase in RBC catalyze conversion, dissolving CO2 in H2O to bedissolved in blood Kidney can reabsorbs/excrete H+ & HCO3- to keep at homeostasis
Distinguish between a closed and an open buffer system and evaluate the importance of our blood buffering system in the context of that concept.
- Closed: can be added but not removed
- Reactions slow becuase end products are not eliminated & can reach an EQL
- ex: Phosphate buffer system = closed inside cell; Inorganic Chem beaker & titrations
- Open:a system that can get rid of one of the buffer components; think LCP; better buffers because pH can remain relatively more constant
- The end products of acid buffering reactions are continuously eliminated from the body by the lungs and kidneys, allowing these reactions to continue **without being slowed by the accumulation of end products **
- ex: Bicarb system
*Proton pump inhibitor
Omeprazole/Prilosec/Zegerid inhibits proton pumps in stomach that maintain stomach’s low pH to minimize acidity & prevent GERD
