. At the isoelectric point of a polyampholytic protein, the protelh W A. Have no
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. At the isoelectric point of a polyampholytic protein, the protelh W A. Have no charged groups B. Be surrounded by a counterion atmosphere, effectively neutralizing the protein C. H D. Be more soluble in solutions of low ionic strength E. None of the above ave an even distribution of charge and tend to self associate and precipitate out of solution 14. Bicarbonate is a crucial buffer in the body and is usually present in body fluids as sodium bicarbor (sodium being the main positive ion in extracellular fluids). (enzyme-catalyzed) pKa = 6.14 What features of sodium bicarbonate contribute to its effectiveness as a biological buffer? A. The bicarbonate ion (HCOs) can combine with a proton (H') to form carbonic acid (HCOs). th absorbing protons from solution and raising blood pH B. Carbonic acid, which can be formed from CO2 and water, can dissociate into H+ and ???'in 0 to provide Ht and lower blood pH C. Carbonic acid, which can be formed from bicarbonate, is converted to CO2 and water via a very enzymatic reaction D. CO2, being volatile, can be rapidly expelled from the body at varying rates by respiration E. All of the above 15. The bicarbonate buffering system of blood can respond quickly to mild metabolic acidosis (undesire decrease in blood pH) by A. Expelling CO2 in the lung B. Retaining HCOs in the kidney C. Excreting H* in the kidney D. Direct buffering action of the H CO, central intermediate E. Retaining CO2 in the lungs At pH 6.2, what can we say about the two N atoms within the imidazole side chain of histidine? A. They will both be protonated thus, both N-atoms can serve as H-bond donors B. One N is protonated thus, it can serve as a nucleophile and donor for hydrogen bonding, while t 16. other is unprotonated and can serve as an electrophile and H-bond acceptor C. They are both deprotonated and will be H-bonding acceptors D. One is protonated, the other is deprotonated but their chemistry in this state is unreactive E. None of the above 4Explanation / Answer
13. C. Polyampholytic proteins are polymeric protein systems composed of monomers of varying charge which can self aggregate at isoelectric point.
14. E. All of the above.
15. A. Expelling CO2 in the lung.
16. D. One is protonated, the other is deprotonated but their chemistry in this state is unreactive.
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