Question

HELP PLEASE!! TIMED!!! | Low-density lipoproteins (LDLs) in the blood are taken up by receiving cells through receptor-mediated endocytosis. In familial hypercholesterolemia (FH), the receptor proteins for LDLs (LDLr) on receiving cells are defective or absent, and patients develop atherosclerosis due to high levels of LDLs in the bloodstream. To find a cure for FH by gene therapy, scientists created models of FH that produce similar phenotypes in animals. By re-introducing a normal receptor protein for LDLs (LDLr) into the cells that make these receptors in the animal model, scientists could reduce the level of LDLs and the impact of the disease.

How would the reintroduction of LDLr correct the deleterious effects of hypercholesterolemia?

A) The LDL receptor will incorporate the LDLs into the cell membrane and reduce the free LDLs in the blood.

B) The LDL receptor can promote the disposal of LDLs as waste, effectively lowering the level of free LDLs in the blood.

C) The LDL receptor will bind and neutralize the free LDLs in the blood and prevent them from forming plaques in the blood vessels.

D) The LDL receptor will help internalize excessive LDLs into receiving cells, where they can be broken into smaller molecules.

Answer 1

Reintroducing LDL receptors corrects familial hypercholesterolemia by allowing cells to internalize and break down LDLs, which are high in cholesterol, thus preventing their buildup and the risk of atherosclerosis. The correct option number is D.

Step-by-step explanation:

The reintroduction of LDL receptors (LDLr) would correct the deleterious effects of familial hypercholesterolemia (FH) by enabling cells to clear low-density lipoproteins (LDLs) from the bloodstream. When the functional LDL receptor is present, it allows cells to bind and internalize LDLs through a process called receptor-mediated endocytosis. This action facilitates the removal of LDL particles, which are rich in cholesterol, thereby preventing their accumulation and the subsequent formation of arterial plaques.

The correct answer to how the reintroduction of LDLr would correct the effects of FH is D) The LDL receptor will help internalize excessive LDLs into receiving cells, where they can be broken into smaller molecules. This process reduces the high levels of circulating LDLs, which is crucial in lowering the risk of atherosclerosis associated with high levels of LDL cholesterol. Thus, reintroducing a normal LDL receptor protein has the potential to significantly improve cholesterol regulation in individuals with FH.