Phospholipids and Cholesterol.

https://www.youtube.com/watch?v=E0GEp3zgK7w

Whats the structure of a phospholipid

A phospholipid has a glycerol molecule bonded to two fatty acid molecules, the glycerol is also bonded to phosphate.

The phosphate is negatively charged, this part of the molecule is polar, and so the phosphate group is hydrophillic

How is phospholipid molecule represrnted

The head group is polar hydrophilic part of molecule, tails represent two fatty acid molecules (they are non polar and hydrophobic)

Why do phospholipids behave very differenntly in water ( phospholipid bilayer)

Due to hydrophilic and hydrophobic regions of the phospholipid molecule

In water, phospholipid molecules position themselves so that the hydrophilic head groups can interact with water molecules, while the hydrophobic tails cluster together , well away from water molecules. This is the phospholipid bilayer

Why is phospholipid bilayer useful

It allows phospholipids to form the membranes that we find both around cells and within cells

What is cholesterol

Part of a family of lipids called sterols.

Two key features of cholesterol

The hydroxyl group is hydrophilic, however rest of group is hydrophobic,

This means that cholesterol can insert into cell membranes,

the hydrophilic hydroxyl group on the cholesterol molecule can interact with head groups of phospholipids, while rest of cholesterol molecule can interact with hydrophobic fatty acid tails.

What are key roles of cholesterol

Used as starting point for a range of hormones, including oestrogen and testosterone

Cholesterol used in body to make vitamin D, takes place in skin in response to UV light.

Cholesterol used in liver to produce bile, bile increases rate of digestion of lipids by enzyme lipase.