Applicable for A-Level, IB, DSE, AP-Level Exams
The Fluid Mosaic Model describes fluid nature of the phospholipid bilayer, which composes of cell membranes. The presence of cholesteral maintains the stability and horizontal and lateral movement of the bilayer. The presence of channel and carrier proteins allow for the faciliated diffusion or active transport of non-lipid soluble molecules.
Diffusion is the movement of molecules or ions from an area of high concentration to an area of low concentration down a concentration gradient.
Osmosis is the movement of water from an area of higher water potential to an area of lower water potential.
Active transport is the usage of carrier proteins to transfer molecules or ions from an area of low concentration to an area of low concentration using energy from the hydrlysis of ATP to ADP and Pi.
Glucose is absorbed by the complex process involving carrier and channel proteins. The sodium-potassium pump helps transport 3 Na+ out and 2 K+ in. The higher concentration of Na+ carries glucose into the epithelial cell along a symport carrier protein. Glucose then moves into the blood by facilitated diffusion through an uniport.