Lipoproteins are found in the blood and lymphatic circulation. Inside them is a shell of lipids, totally apolar, TG triglycerides and CE cholesterides, esters of cholesterol. 

These apolar lipids can only circulate if they are surrounded by amphipathic lipids. 

Also found is a protein portion, the apoproteins, present in multiple copies with the function of helping to keep the lipoproteins in solution. 

The apolar part of these amphipathic lipids is contained in the core, while the outer part is polar, consisting of phospholipids and free cholesterol. 

Fatty acids and lysophospholipids that can circulate bound to albumin are found in lipoproteins.

The 4 families of lipoproteins are:

• Chylomicrons
• VLDL
• LDL
• HDL

Dal punto di vista delle dimensioni i chilomicroni sono i più grandi e sono chiamati così perché arrivano anche ad 1 micron, e chilo perché si trovano nel chilo che è contenuto nell’intestino.

Passando da VLDL ad HDL le dimensioni si riducono.