Answer:
Te correct answer is "Being transported by specific carrier proteins".
Step-by-step explanation:
Cholesterol is one of the most important lipids in our body. It is useful for membrane formation and for sexual and suprarenal hormone synthesis. The organism obtains cholesterol from food and liver production. It goes to the blood where it is transported by lipoproteins to its final destiny.
In the intestine, cholesterol is absorbed in three phases:
- intraluminal phase: in this phase micellar formation is necessary for cholesterol absorption. Micellar solubilization is a transport way for cholesterol to diffuse through the mucus barrier that covers intestine surface microvilli. Once there cholesterol is available for intestinal cells.
- mucose phase: in this phase cholesterol pass from the lumen to the cytoplasm of the intestinal cells, and when necessary, from the cytoplasm to the intestinal lumen. In the cells´ membrane, there are proteins that transport cholesterol to and from the interior of the cell.
- Intracellular phase: In the intestinal cell cholesterol is sent to the endoplasmic reticulum where it is reesterified to be transported in the blood. As cholesterol is insoluble it is packaged in lipoproteins to be transported.
Each lipoprotein has a union site that is specific for a target membrane receptor. Lipoproteins get in the target cells by endocytosis mediated by the specific receptors. Once in the interior of the cell cholesterol is taken from the lipoprotein by breaking the ester link, and then they reesterify it to include it in the membrane.