H1 Biology and H2 Biology

What is the role of Cholesterol in Cell Membranes?

Notes from the video ‘A Level H2 Biology Tuition and H1 Biology Tuition | Role of Cholesterol in Cell Membrane’:


In this Biology tutorial, we would learn the role of cholesterol in cell membranes.

Structure of Cholesterol

H2 Biology Tuition | H1 Biology Tuition | Cholesterol

Firstly, let’s look at the structure of cholesterol. A cholesterol molecule is a bulky molecule consisting of a polar OH group attached to a planar steroid ring structure with four fused steroid rings and a non-polar hydrocarbon tail.


Functions of Cholesterol

Cholesterol regulates membrane fluidity by preventing the membrane from being overly fluid at high temperatures by restricting the lateral movement of phospholipids. The membrane is also prevented from being overly firm at lower temperatures as cholesterol prevents the close packing of the hydrocarbon chains of the phospholipids, resulting in increased membrane fluidity.


Cholesterol also decreases membrane permeability by filling in the spaces between hydrocarbon chains of phospholipids, thus plugging any transient gaps which ions or small polar molecules may pass through.


Lastly, cholesterol increases the mechanical stability of the membrane.
Its rigid steroid ring structure interferes with the motions of the hydrocarbon chains of phospholipids, thus enhancing the mechanical stability of the membrane.

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