V8

Membrane fluidity (MF) is a parameter describing the freedom of movement of protein and lipid constituents within the cell membrane.

• consist of a sugar / carbohydrate covalently linked to a lipid moiety

• are expressed on the outer leaflets of biomembranes

• stabilize biological membranes by formation of hydrogen bonds with H2O

• act as cellular recognition site (blood type, immune system)

• can associate with specific proteins, growth factors other sugars

• form domains in lipid bilayer membranes together with cholesterol (rafts)

• are a functional group that is either part of lipid bilayers or interact with them

• can be a permanent or a transient part of bilayer membranes

• can penetrate the bilayer or associate with one side (transmembrane / monotopic)

• insert spontaneously into lipid bilayers due to electrostatic and hydrophilic / hydrophobic interaction

• are responsible for a large variety of cellular functions (signaling, transport, recognition, reactions)

• make up 1/3 of all human proteins and are targets for half of all drugs administered

In facilitated diffusion, molecules diffuse across the plasma membrane with assistance from membrane proteins.

• Molecule movement along Δc

• Facilitated transport proteins shield molecules from the hydrophobic bilayer core

• Transport of molecules that normally are not able to cross lipid bilayers (charged, polar)

• Types: Channel proteins, Carrier proteins

When two lipid-stabilized emulsion droplets are brought together, a lipid bilayer is forming between the emulsion droplets, which is called droplet interface bilayer (DIB).

• Facile production of bilayers for protein tests

• Controlled start of protein insertion

• Possibility of macroscopic droplets for simple optical analysis

In active transport, molecules are pumped against their concentration gradient with the assistance of membrane proteins.

• Energetic uphill transport of molecules

• Active transport is a process of energy conversion from chemical to potential energy

• Molecular transport by adenosine triphosphate (ATP)-fueled pump proteins

▪ Endocytosis is the process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane.

▪ Exocytosis describes the process of vesicles fusing with the plasma membrane to release their contents into the extracellular environment.