Low density lipoproteins
Low density Lipoproteins (LDL) is a cholestryl ester which is the form in which cholesterol is transported in blood [1][2].
These lipoproteins serve as useful molecules for maintaining the blood composition of cholesterol, keeping it within normal range as high cholesterol levels can lead to blood vessels being blocked and result in atherosclerotic plaque which can lead to strokes.
LDL maintain blood cholesterol level by binding with LDL receptors on cell surface membranes which can then be internalized into cell by Receptor Mediated Endocytosis.
Process of Import:
- LDL receptors are expressed on the surface of cell membrane.
- Internal signals within cell cause production of clathirin coated pits, which internalize LDL receptors along with any LDL molecules that have bound to them.
- Clatherin coated pits shed their coat and deliver their contents to Early Endosome. Low pH in endosomes result in LDL molecules being released from their receptors and passed onto Lysosomes.
- LDL receptors are recycled back to cell surface membrane to be reused whilst discharged LDL molecules remain in lysosome.
- Cholestryl Esters in LDL are hydrolysed to free cholesterol molecules which can then be used by cell in other biochemical reaction, such as formation of cell membrane for example.
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