Arrange the order of events for the internalization of ldl particles into cells:

1) a combination of cholesterol and apolipoprotein binds to ldl receptors and becomes internalized as endocytotic vesicles.
2) the environment of the endosome becomes acidic, which causes the ldl to dissociate from its receptor; additionally, the endosome fuses with a lysosome.
3) several endocytotic vesicles fuse to form an endosome.
4) the ldl particle is degraded by the lysosome.
5) ldl receptors migrate to the cell surface and cluster in clathrin-coated pits.

The correct answer is "5-1-3-2-4".

Explanation:

Internalization of LDL particles into cells, is needed to form the intracellular vesicles known as endosomes. The order of events that allow for this process are:

5) LDL receptors migrate to the cell surface and cluster in clathrin-coated pits. Clathrin acts directing the receptors to the cell membrane region where endosomes are formed.

1) A combination of cholesterol and apolipoprotein binds to LDL receptors and becomes internalized as endocytotic vesicles. Once the receptors are in the proper cell membrane region, cholesterol and apolipoprotein are bound and internalized.

3) Several endocytotic vesicles fuse to form an endosome.

2) The environment of the endosome becomes acidic, which causes the LDL to dissociate from its receptor; additionally, the endosome fuses with a lysosome. LDL should be dissociated from its receptor since it is going to be degraded in the following step.

4) The LDL particle is degraded by the lysosome. This takes place after endocytosis, when LDL particles are transported into lysosomes once they are fused, cleaving the cholesterol esters into cholesterol and fatty acids.