Question

Membrane permeability is based on the basic chemical structure/nature of lipid membranes. What is the main property of the membrane that dictates what can and can not pass through the membrane.? Give three specific examples of biologically important molecules and how they are impacted by this property (ex - what can and can not pass through the membrane).

Answer 1

The membranes are composed of lipid bilayers. The hydrophilic heads are placed on the exterior sides and the hydrophilic tails are placed facing each other. Integral membrane proteins are interspersed throughout the membranes which provide structural support. Receptor ptoteins are also present on the exterior side.

The main property of the lipid membranes that dictate which substance can and cannot pass through the membrane is the hydrophobic (tail) and hydrophilic (head) nature of the lipids. Some of the examples of membrane transport include the following,

1. Hydrophobic molecules like oxygen, carbon dioxide, nitrogen and steroids pass easily through lipid bilayers
2. Small, uncharged polar molecules like water, glycerol, urea and ethanol also pass through the lipid membrane
3. Large, uncharged polar molecules like glucose and sucrose cannot pass through the lipid bilayers