Membrane Structure Lecture Notes

Flashcards for reviewing membrane structure and function.

Membrane Composition

Biological membranes are composed of lipid bilayers that are impermeable to polar or charged molecules.

Hydrophobic Effect in Membrane Formation

The hydrophobic effect drives membrane formation, causing amphipathic molecules to assemble due to non-covalent interactions.

Membrane Asymmetry

Membranes are asymmetric and composed of lipids and proteins, which may or may not have carbohydrates covalently bound (PTMs).

Role of Membrane Proteins

Membrane proteins play key roles in the transport of molecules and transduction of information across the membrane.

Membrane Fluidity

Membrane components can move rapidly in the plane of the membrane.

Membrane Mosaic

Membranes are a diverse mixture of lipids, embedded and peripheral proteins, and carbohydrates on the surface.

FRAP

Fluorescence Recovery After Photobleaching. A technique used to measure the mobility of molecules in a membrane.

Single-molecule tracking fluorescence microscopy

A method used to monitor the movement of fluorescent molecules throughout the membrane.

Lipid Rafts

Regions within the membrane where proteins or lipids may spend more time interacting.

Membrane Leaflet Composition

The two leaflets of the membrane have very different lipid and protein compositions.

Glycosylation

A form of post-translational modification mediated by enzymes and is important for membrane insertion and cell recognition, i.e. the addition of sugars to lipids and proteins.

Flippases and Floppases

Enzymes that help drive the movement of lipids from one membrane to the other using ATP hydrolysis.

Scramblases

Enzymes that move all lipids down their concentration gradient, producing a symmetrical membrane.

Lipids

Class of molecules involved in providing structural support for cells and organelles, storage of carbons for energy, and can play a role in information transduction and signalling.

Lipid Self-Assembly

Spontaneously aggregate in water to bury their hydrophobic groups while polar groups interact with water.

Triacylglycerides

Lipids used for energy storage.

Phospholipids, Sphingolipids, Glycolipids, Sterols

Lipids used for structural purposes.

Eicosanoids, Sterols

Lipids used for signalling purposes.

Saturated Fatty Acids

Fatty acyl chains that contain no double bonds.

Unsaturated Fatty Acids

Fatty acyl chains that contain double bonds.

Omega-3 and Omega-6 Fatty Acids

Polyunsaturated fatty acids that humans cannot synthesize and must obtain from their diet.

Phase Transition

The melting of membrane lipids that describes the change from a gel-like solid phase to the liquid crystalline phase.

Melting Temperature (Tm)

An index of membrane fluidity.

Tri-acyl-glycerols (TAGs)

The dehydrated storage form of lipids found primarily in adipocyte cells.

Amphipathic molecules

Molecules created by attaching fatty acyl chains to polar (OH, sugar, phosphate) head groups.

Cholesterol

Steroid found in membranes that modulates membrane fluidity.

Peripheral Membrane Proteins

Adhere to the surface of lipid membranes or integral membrane proteins through non-covalent interactions.

Integral Membrane Proteins

Proteins that completely span the membrane (ie. transmembrane segments, TMs).

Lipid Anchored Proteins

Proteins that have lipid chains are covalently attached to amino acid functional groups and side chains.

Detergents

Amphipathic molecules that can help form micelles around the hydrophobic regions of a membrane protein, helping with solubilization.