A patient went to the doctor for a general checkup and the doctor asked for seve

Question

A patient went to the doctor for a general checkup and the doctor asked for several tests. The results of the analysis showed that the patient had extremely high levels of cholesterol in blood, which put him in high risk of having a heart attack. Next, the doctor ordered a second analysis, which confirmed that the LDL receptor was expressed in the plasma membrane of the cells. Give two different reasons that could explain the high level of cholesterol in blood despite the existence of the LDL receptor in plasma membrane.

Explanation / Answer

LDL receptors which mediates the endocytosis of cholesterol rich ,it is a cell surface receptors that recognise the apolipoprotein B which is embbeded in the outer layer of the phospholipids .These are present in the clatherin coated pits on thecell surface which when bounded to LDL cholesterol via adaptin are pinched off to the form the clatherin coated vesicle from the cell ,This allows LDL -cholesterol to bound and internalized in a process called exocytosis .so LDL it occurs in all cells especially liver cells except the erythrocytes .

Two different reasons ;

1.mutation in the gene LDRL which encodes for the LDL receptors which is seen in the people with the famailial hypercholestrimeia .

2. LDLR is not transported from the endoplasmic reticulum to the golgi apparatus for expression on the cell surface

3. LDLR receptors may not be able to recyle back to cell surface .

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