Biochemistry : Biological Energetics
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Example Question #21 : Biological Energetics
If a red blood cell (RBC) is placed into a hypotonic solution, which of the following is most likely to occur?
The RBC will shrivel up and lyse
The RBC will remain unchanged
The RBC will fill with water and burst
The cell will use its mitochondria to counteract the change in tonicity
Osmotic pressure in the cell will increase
The RBC will fill with water and burst
If the RBC is placed into a hypotonic solution, water will rush into the cell because there is a higher osmotic pressure in the cell than outside of it. The osmotic pressure in the cell will actually decrease as water flows in from the outside. Red blood cells do not have mitochondria.
Example Question #21 : Biological Energetics
A drug has a pKa of 3.3. If the pH in the stomach is 1.5 and the pH in the small intestine is 6.0, where will more of the drug be absorbed? Why?
The intestines because the drug will be less polar and will be able to pass through the membrane more easily.
The stomach because the lower pH will make the drug more hydrophilic so that it can cross cellular membranes more easily.
The stomach because the drug will be less polar and will be able to pass through the membrane more easily.
The intestines because the higher pH will make the drug more hydrophobic so that it can cross cellular membranes more easily.
The drug will absorb equally in both areas because pH does not effect bioavailability.
The stomach because the drug will be less polar and will be able to pass through the membrane more easily.
The stomach: The lower pH will result in the drug being in the neutral form, and this less polar form will be able to pass through the membrane more easily and absorbed into the blood stream.
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