The types of fatty acids eaten will be reflected by the fatty acid composition in the plasma membranes (phospholipid fatty acids). When more of the fatty acids are saturated, and thus fairly straight, neighboring molecules can get closer making the membrane more crowded and less dynamic (fluid). When LDL receptors surface on the plasma membrane, they actually must migrate to anchoring sites (Figure 13.3). Once they are anchored they can then bind circulating LDLs and bring it into that cell. The LDL is then broken down and the cholesterol is available to that cell. Meanwhile the receptor is then able to resurface on the plasma membrane and migrate to the anchoring site. This process is often called LDL receptor cycling and the rate-limiting step is the LDL receptor migration from its surfacing site to its anchoring site. Therefore if the migration takes longer, the whole cycle takes longer and less LDL is removed from the blood throughout the day.
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