The cholesterol forms weak attractive forces with multiple phospholipids in the bilayer. would this increase or decrease flexibility of the membrane?

This would increase the flexibility of the membrane.

Explanation:

Studies with isolated plasma membranes reveal that their most abundant components are phospholipids, cholesterol and proteins. These biological membranes are fluid like liquid paraffin. Cholesterol is one of the responsible for this cell membrane fluidity. This is because cholesterol molecules prevent carbon chains from interacting potently - which would result in a gelatinous state of the membrane. Therefore, we can conclude that if cholesterol forms weak attractive forces with multiple phospholipids in the bilayer, this increases membrane flexibility.

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