I need help with those questions. It’s Microbiology. Why is the plasma membrane
ID: 193202 • Letter: I
Question
I need help with those questions. It’s Microbiology.Why is the plasma membrane considered the external boundary of the cell, even though other structures outside of the plasma membrane are considered part of the cellular anatomy? In 1985, a 0.5 mm cell was discovered in surgeonfish and named Epulopiscium fishelsoni. It was presumed to be a protozoan. In 1993, researchers determined that Epulopiscium was actually a Gram postive bacterium. What do you suppose caused the initial identification of this organism as a protozoan? What evidence would change the characterization of this organism? A 0.1 ml sample is removed from a sample diluted 1 X 10-5 and is placed on an agar plate, spread for distribution, and incubated. The next day, there are 124 colonies on the plate. How many bacteria were present per ml in the original sample?
Explanation / Answer
(1)
Cell membranes serve as barriers and gatekeepers. The cell membrane is semi-permeable in nature and forms a barrier across which certain molecules and chemicals cannot diffuse. As a result of this property, the cell membranes restrict diffusion of highly charged molecules, such as ions, and large molecules, such as sugars and amino acids. It lest small polar molecules such as O2 and CO2 to pass through.
Cell wall although present as the outermost structure works only to provide rigidity for a cell.