A cell’s plasma membrane acts as aboundary that let’s stuff in and out of the cell and governs interactions,which means it acts as a selectively permeable barrier between the cell and itsenvironment. Almost like a guard at a club that decides who goes in and whogoes out. The membrane is vital in allowing nutrients into the cell, andeliminating any wastes outside of the cell also protecting the cell from whatenters.
The plasma membrane is made up of carbohydrates, lipids, and proteins,which provides support for the cell. There is also an important transportmethod that occurs in the plasma membrane known as diffusion. Diffusion is apassive process in which no cellular energy or ATP is needed, and is driven bya substance diffusion down its concentration by movement along a concentrationgradient from an area of high concentration to low. AnatomyWhat is the structure of the plasmamembrane? Well the plasma membrane of a cell is composed of many differentparts including lipids (phospholipids and cholesterol), proteins, and carbohydrates.”The basic structural component of the plasma (cell) membrane is thephospholipid bilayer, which is composed of two layers of phospholipid molecules”(Sarikas 29). Another lipid component is cholesterol, which is very flexibleand adds to the fluidity of the membrane.
The phospholipid molecule is made upof a “head”, and a “tail”. The head is a hydrophilic molecule, or a moleculethat is attracted to water, where the tail is the opposite it is a hydrophobicmolecule which means it is not attracted to water, or repels water. Anothercomponent of the membrane is protein. There are two types of membrane proteins,integral and peripheral. “The plasma membrane has integral proteins that arefirmly inserted into the lipid bilayer and peripheral proteins that restloosely on the inner surface” (Sarikas 29). Carbohydrates are normally found onthe outside surface attached to a protein or lipid.
PhysiologyThe function of the plasma membraneis to control what enters and leaves the cell, allowing only selectedsubstances into the cell, it acts as a barrier to the cell. In the plasma membranediffusion can occur and the function of diffusion is to allow molecules smallenough to pass through the membrane and migrate from an area of highconcentration to low. There are four factors that can affect diffusion, temperature,concentration gradient, adding a catalyst, and concentration of solute.
Forexample when there is an increase in temperature molecules will move faster andthe diffusion rate will increase. When making Kool aid Cup A is water and theKool aid packet mixed together, Cup B has the same contents, but the cup is putunder a flame. Cup B will diffuse at a faster rate than Cup A because heat wasapplied. All molecules have kinetic energy which means they move in alldifferent directions at high speeds, the diffusion rate depends on the fourfactors. Diffusion does not require cellular energy, a molecule can effectivelydiffuse through the membrane if its lipid soluble, uncharged, and small enoughto pass through.