role of membrane separate ICF (intracellular compartment; contains 67% body water) from ECF (outside cells; 33% body water) material and allow exchange What is the role of the membrane? The majority of water in the body is found where? selectively permeable restrictive movement of molecules through the plasma membrane What does it mean when we describe the plasma membrane as being selectively permeable? extracellular matrix collagen & elastin meshwork linked to plasma membrane through integrins (glycoprotein adhesion molecules that extend from the cytoskeleton within cell through the plasma membrane into extracellular matrix) What is the role of integrins? Describe them. simple diffusion the passive movement of molecules (such as O2 and CO2) through a biological membrane's lipid bilayer...requires no membrane proteins...rate of diffusion is influenced by the concentration gradient, membrane permeability, temperature, and membrane surface area Describe simple diffusion. Does it use energy or require membrane proteins? What sort of substance can diffuse through the plasma membrane? What factors effect the rate of diffusion? small, non-polar molecule two characteristics more likely to make a substance diffuse through cell membrane; so molecules with a relatively high lipid solubility are capable of crossing the membrane directly across the lipid bilayer facilitated diffusion mediated transport in which a carrier (transmembrane protein) binds molecules on one side of a membrane and transports them to the other side by means of a conformational change...this transport (examples are monosaccharides and amino acids) is passive and its rate is determined by 1. transport rate of individual carriers 2. number of carriers in membrane; these carriers are specific