1. What is the meaning behind the PHOSPHOLIPIDS’ chant?
Phospholipids make up most of the cell membrane, in a phospholipid bilayer. Phospholipid molecules form two layers, with the hydrophilic (water loving) head facing the extracellular fluid and the cytosol (intracellular) fluid, and the hydrophobic (not water loving) tails facing one another. The cell membrane is constructed in such a way that it is semipermeable, and allows oxygen, CO2 and lipid soluble molecules through easily, while other molecules like glucose, amino acids, water, and ions cannot pass through quite as easily. That is the meaning behind the chant “some things can pass, others cannot!”.
2. Why is H2O concerned about the aquaporin shutting down? What are aquaporins and how are they involved in plasma membrane transport? In addition to the use of aquaporins, what is another way H2O can cross the plasma membrane? Is this second way sufficient? Explain your answer.
Since aquaporins are water channels which contain transport proteins that allow facilitated diffusion of water across the cell membrane, H20 is concerned it won’t be able to get across if those transport proteins are on strike. H2O crosses the plasma membrane via osmosis – also known as the diffusion of water across a cell membrane, and aquaporins are the “main route” for water entering and exiting the cell. Osmosis moves water in the direction of higher solute concentrations, (thus trying to dilute the solute). Professor Tosol went onto explain that water can also pass directly through the phospholipids as they shift around “due to the fluidic nature” of the bilayer. This “direct diffusion” isn’t as efficient, or sufficient, as the use of aquaporins.
3. Both GLUCOSE and AMINO ACID claim to have a special relationship with their respective transport proteins. What is the basis for their claims?
The transport proteins that carry those molecules across