Insulin is a hydrophilic ligand that is incapable of traveling across the hydrophobic plasma membrane unassisted. Because of this, insulin must use a protein receptor located on the plasma membrane to communicate with cells. These receptor proteins on the transmembrane are made by transmembrane polyribosomes and is part of the glucose transport channel that acts as a ‘lock and key’ model. Once activated by the process of phosphorylation, the phosphate groups on the interior part of the receptor are released into the cell’s cytoplasm.
These phosphate groups then travel to insulin-response substrates resulting in a cascade response which helps regulate cell differentiation, growth, and metabolism (Chang, 1994).
The microscopic villi located on the lumen of the intestine are covered by closely connected epithelial cells that separates the blood from the rest of the body. These finger-like projections on the epithelium helps to increase surface area by encouraging the cell to maximize the enzymatic activity that assists with the uptake of minerals and nutrients (Lumen, n.
d.). The surface of the microscopic villi is covered with a glycoprotein-polysaccharide called glycocalyx that promotes increased surface area by acting as cell-adhesion molecules helping to anchor digestive enzymes and binding substances for nutrient absorption.
Lumen explains that the blood vessels surrounding the lymphatic vessels and capillaries are connected to each villi so when lymphocytes are directed to the epithelium it stimulates an immune response causing inflammation. (n.d.). The inflammatory response caused by the immune system leads to decreased surface area which restricts the intestine’s ability to absorb minerals and nutrients by reducing the number of tight junctions where nutrients can travel through the plasma membrane.