What is in a lipid raft?

What is in a lipid raft?

Rafts are small platforms, composed of sphingolipids and cholesterol in the outer exoplasmic leaflet, connected to phospholipids and cholesterol in the inner cytoplasmic leaflet of the lipid bilayer. These assemblies are fluid but more ordered and tightly packed than the surrounding bilayer.

What is the purpose of a lipid raft?

Lipid rafts influence membrane fluidity and membrane protein trafficking, thereby regulating neurotransmission and receptor trafficking. Lipid rafts are more ordered and tightly packed than the surrounding bilayer, but float freely within the membrane bilayer.

How do you detect a lipid raft?

Probably, the most direct method to study lipid rafts is based on monitoring chemical (lipid) composition of the cell membranes with mass spectrometry (Boxer et al., 2009, Kraft et al., 2006, Lozano et al., 2013). However, this method works under ultra-high vacuum and with freeze-dried samples.

Do lipid rafts exist?

Tiny structures made of lipid molecules and proteins have been believed to wander within the membrane of a cell, much like rafts on the water. This “raft hypothesis” has been widely accepted, but now scientists at TU Wien (Vienna) have shown that in living cells these lipid rafts do not exist.

What is a lipid raft MCAT?

lipid raft: an area in the membrane where there is a high concentration of cholesterol, and a different composition of carbohydrates, proteins and other lipids compared to the rest of the membrane.

Does cholesterol stabilize lipid rafts?

Rafts also appear to be enriched in cholesterol and lipids with saturated fatty acids, especially sphingolipids, which would lead to regions of enhanced packing and reduced fluidity. Cholesterol would stabilize packing in spaces created with lipids with large head groups.

How are lipid rafts formed?

Protein Lipidation and Lipid Rafts Lipid raft formation in the exoplasmic leaflet of the plasma membrane is driven by the tight packing of the long saturated acyl chains of sphingolipids with cholesterol.

What is lipid raft in biology?

Lipid rafts are plasma membrane microdomains enriched in cholesterol and sphingolipids that are involved in the lateral compartmentalization of molecules at the cell surface. Internalization of ligands and receptors by these domains occurs via a process defined as raft-dependent endocytosis.

Do lipid rafts increase membrane permeability?

Chol and SM are known to form self-associating lipid domains that have been termed rafts [10–13]. They are also present in high concentrations in the outer leaflet of apical membranes of barrier epithelia where they function to increase lipid order and reduce membrane permeability [9,14].

Do lipid rafts decrease fluidity?

Lipid rafts are specialized membrane microdomains that serve as organizing centers for assembly of signaling molecules, influence membrane fluidity and trafficking of membrane proteins, and regulate different cellular processes such as neurotransmission and receptor trafficking.