09/13/07
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| Q: Buffers, buffers, buffers. What is a buffer? | A: A buffer is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid that cause a solution to resist changes in pH when an acid or base is added.
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| Q: How do buffers work? | A: Buffer systems minimize pH changes by converting stronger acids and bases into weaker acids and bases.
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| Q: When are buffers most effective? | A: Buffers are most effective when they're composed of equal amounts of weak acid and conjugate base. She also mention that you would want lots of each.
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| Q: What is meant by the following statement? The most effective buffering occurs in the portion of the titration curve that has a minimum slope. | A: It means the most effective buffering occurs within 1 pH unit above and below the value of pKa.
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| Q: A buffer can only compensate for an influx or removal of hydrogen ions within approximately 1 pH unit of its _______. | A: pKa.
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| Q: If the pH of a buffered solution changes from pKa to one unit below pKa, what happens to the concentration of [A-] to [HA]? | A: It goes from 1:1 to 1:10.
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| Q: True or false? More concentrated buffers are more effective. | A: True! They contain a greater total number of buffer molecules per unit volume and more is better.
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| Q: What does the Henderson-Hasselbalch equation describe? | A: The Henderson-Hasselbalch equation describes the dissociation characteristics of weak acids and bases and the effect on pH.
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| Q: What is the Henderson-Hasselbalch equation? | A: pH = pKa + log [A-]/[HA]
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| Q: If pH > pKa then _______ predominates. | A: Base.
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| Q: If pH < pKa then _______ predominates. | A: Acid.
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| Q: Name the four acid-buffer systems discussed in class. | A: The hemoglobin (Hb) buffer system, the protein buffer system, the bicarbonate buffer system, and the phosphate buffer system.
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| Q: In class, what was referred to as the most important acid-buffer system? | A: The bicarbonate buffer system, also called the carbonic acid-bicarbonate buffer system.
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| Q: What is the pH of a solution with a pKa of 3.86, [A-] of 1 molar, and [HA] of 10 molar? | A: 2.86. Create your own variation of this question and work through them.
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| Q: Why can the bicarbonate buffer system work effectively at physiologic pH with a pKa of 6.1? | A: Because C02 is a gas and can be exhaled by the lungs.
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| Q: The _______ buffer system is the only intracellular buffer system that can have an immediate effect on the pH of the extracellular fluid. | A: The hemoglobin (Hb) buffer system.
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| Q: No question here, just a reminder to study the figures at the bottom of page 1-10 & the top of page 1-11. | A: What are you looking here for? If there's no question, there's no answer. Go look at the figures.
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| Q: What is an aliphatic organic molecule? | A: They are carbon strucures that are straight or branched, with single or double bonds, but DO NOT contain a ring.
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| Q: What is an aromatic organic molecule? | A: They are carbon structures that contain cyclic structures, unsaturated.
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| Q: What is a hydrocarbon? | A: Chains of carbon atoms.
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| Q: Did you know? Attaching other atoms or groups to the carbon backbone of a hydrocarbon forms all other organic molecules? | A: Yah, I knew that too.
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| Q: Have you studies your functional groups lately? | A: You might want to take a look at them again.
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| Q: _______ is determined by propotion of polar / nonpolar groups & their positions in the molecules. | A: Solubility.
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| Q: What does the anagram OIL RIG stand for? | A: It refers to oxidation/reduction and the loss or gain of electrons... Oxidation Is Loss, Reduction Is Gain.
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| Q:_______ has occurred if a molecule gains an oxygen atom or losses hydrogen (electrons). | A: Oxidation.
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| Q: _______ has occured if a molecule loses an oxygen atom or gains hydrogen (electrons). | A: Reduction.
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PCC Biochemistry I
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