the functions of cell mebranes?

Question

the functions ,where are they found and any thing that accompany this concept

Answer 1

The cell membrane (also called the plasma membrane or plasmalemma) is a semipermeable lipid bilayer common to all living cells. It contains a variety of biological molecules, primarily proteins and lipids, which are involved in a vast array of cellular processes. It also serves as the attachment point for both the intracellular cytoskeleton and, if present, the cell wall. Robert Hooke was the first one to name the cells parts including the plasma membrane.

The cell membrane surrounds the cytoplasm of a cell and physically separates the intracellular components from the extracellular environment, there by serving a mechanical function similar to that of skin. This barrier is able to regulate what enters and exits the cell as it is selectively permeable - cells require a variety of substances to survive and the cell membrane serves as "gatekeeper" to what, and how much, enters and exits. The movement of substances across the membrane can be either passive, occurring without the input of cellular energy, or active, requiring the cell to expend energy moving it across the membrane.

Specific proteins embedded in the cell membrane act as molecular signals which allow cells to communicate with each other. Protein receptors are found ubiquitously and function to receive signals from both the environment and other cells. These signals are transduced into a form which the cell can use to directly effect a response. Other proteins on the surface of the cell membrane serve as "markers" which identify a cell to other cells. The interaction of these markers with their respective receptors forms the basis of cell-cell interaction in the immune system

In animal cells the cell membrane alone establishes a separation between interior and environment, whereas in fungi, bacteria, and plants an additional cell wall forms the outermost boundary. However, the cell wall plays mostly a mechanical support role rather than a role as a selective boundary. One of the key roles of the membrane is to maintain the cell potential. The functions of the cell membrane include, but are not limited to:

* Controlling what goes in and out of the cell.
* Anchoring of the cytoskeleton to provide shape to the cell
* Attaching to the extracellular matrix to help group cells together in the formation of tissues
* Transportation of particles by way of ion pumps, ion channels, and carrier proteins
* Containing receptors that allow chemical messages to pass between cells and systems
* Participation in enzyme activity important in such things as metabolism and immunity

New material is incorporated into the membrane, or deleted from it, by a variety of mechanisms:

* Fusion of intracellular vesicles with the membrane not only excretes the contents of the vesicle, but also incorporates the vesicle membrane's components into the cell membrane. The membrane may form blebs that pinch off to become vesicles.
* If a membrane is continuous with a tubular structure made of membrane material, then material from the tube can be drawn into the membrane continuously.
* Although the concentration of membrane components in the aqueous phase is low (stable membrane components have low solubility in water), exchange of molecules with this small reservoir is possible.

In all cases, the mechanical tension in the membrane has an effect on the rate of exchange. In some cells, usually having a smooth shape, the membrane tension and area are interrelated by elastic and dynamical mechanical properties, and the time-dependent interrelation is sometimes called homeostasis, area regulation or tension regulation.

Answer 2

Cells have a plasma membrane, composed of a double layer (bilayer) of phospholipids, with various proteins attached to it, or embedded in it. The specific functions of a membrane depend on the types of pholspholipids and proteins present. Generally, though, it acts as a selective barrier that nevertheless allows passage of needed oxygen and nutrients in and wastes out.

Answer 3

the membrane is specialized in that it contains specific proteins and lipid components that enable it to perform its unique roles for that cell or organelle. In essence membranes are essential for the integrity and function of the cell.

Answer 4

um, well . . in cells! of course, animal cells because plant cells have cell walls instead. Cell membranes primarily exist to let some stuff in or out (ions, water, etc.) and not other stuff (usually bigger) by diffusion. That's why they are referred to as semipermeable membranes. Pretty cool, actually.