Cells and Tissues Flashcards
Describe the structure of the plasma membrane. how is this structure related to the transport of substances inside and outside of the cell?
The flexible plasma membrane is a fragile, transparate barrier that contains the cell contents and separates them from the surrounding environment.
The structure of the plasma membrane consists of two lipid (fat) layers arrange “tail to tail” in which protein molecules float. Most of the lipid portion is phospholipids, but a substantial amount of cholesterol is found in plasma membranes too. The polar “heads”of the phospholipids molecules are being hydrophilic and are attracted to water, the main component of both the intracellular and extracellular fluids, and so they lie on both the inner and outer surfaces of the membrane. Their nonpolar Tails being hydrophobic, avoid water, and line up in the center of the membrane.
The proteins scattered in the lipid bilayer are responsible for most of the specialized factions of the membrane. some proteins are enzymes. many of the proteins protruding from the cell exterior are receptors for hormones or other chemicals messengers or are binding sides for anchoring the cell to fibers or to other structures inside or outside the cell.
Most proteins that span the membrane are involved in transport. for example, some cluster together to form protein channels (tiny pores) through which water and small water-soluble molecules or ions can move. others act as carriers that bind to a substance and move it through the membrane.
