Microbiology Daily Newsletter

January 21, 2014

The Prokaryotic Cell Membrane

At first glance, the prokaryotic cell shows less complexity than the eukaryotic cell. The obvious two differences are size and absence of internal membranes. These two aspects of cells actually go hand in hand. It deals with the concept of the surface area to volume ratio. Basically, because prokaryotic cells lack internal membranes, their size is limited. Eukaryotic cells on the other hand can be larger because of internal compartmentalization.

But why is surface area so important? Two reasons should come to mind:

the ability to acquire nutrients and release waste.
the membrane is a key player in many metabolic functions (e.g., electron transport chains).

In general biology, the cellular membrane (and internal membranes) are focused on because of their importance. They are the defining structure of the cell. The cell membrane defines the internal vs. the external environment. The types of receptors, channels, pores and enzymes a cell puts on their membrane shows the capabilities and metabolic features of a cell. For instance, if a cell is going to use lactose, it has to have a mechanism to bring lactose across the cell membrane.

Also remember that cells will create concentration gradients across membranes. You may remember the Sodium/Potassium gradient or the Proton Motive Force. Both of these are electrochemical gradients, and are critical to the survival of cells.

Today's Challenge: Cell membrane structure

You may recall that the cell membrane is described as a fluid mosaic: Proteins floating in a sea of lipids. Today, think back on the membrane. Why is the membrane so critical to the life of the cell? What reactions have to take place around the membrane? How important is membrane composition? What happens when you change fatty acids, or in the case of Archaea, the type of lipids used in the membrane? What can we learn from the study of membranes? The above questions do not have to be answered individually. They are there for you to consider as you build your forum reply.

For more information on cell membranes, go to the Essentials of Cell Biology eBook published by Scitable by Nature.
For more information on archaea, look at the Encyclopedia of Life article on Archaea .