How to prepare for your annual encounter with confusion. Daylight Saving Time ends Sunday at 2 a.m., which means that weâre all going to spend a few minutes scratching our heads trying to figure out whether weâre gaining or losing an hour of sleep. Save yourself the trouble and let TIME break it down for you.
For example, plasma membrane proteins carry out functions as diverse as ferrying nutrients across the plasma membrane, receiving chemical signals from outside the cell, translating chemical signals into intracellular action, and sometimes anchoring the cell in a particular location (Figure 4).
Cell membranes are composed of a bimolecular layer of phospholipids and cholesterol, with hydrophilic and hydrophobic regions. Peripheral proteins move along the surfaces and integral proteins are embedded in the lipid bilayer. Some integral proteins extend through both layers (transmembrane proteins). Many of these are glycoproteins with surface carbohydrate units. The cell membrane is the site of the sodium ion pump which maintains cell volume by pumping sodium out of the cell. The outer plasma membrane is permeable to ions, but not to larger molecules. It is also the site for hormone-receptor and cell signal interaction.