Membrane Structure and Function Lecture Notes

Practice vocabulary flashcards covering the organisation, historical models, lipid composition, and protein functions of biological membranes based on the Week 2 lecture notes.

Fluid Mosaic Model

The model for membrane structure proposed by Singer and Nicolson in 1973, describing the membrane as a mosaic of protein molecules in a fluid bilayer of phospholipids.

Amphipathic

A property of molecules, such as phospholipids, that possess both a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail.

Ernst Overton (1890s)

A scientist who discovered that lipid-soluble substances crossed cell barriers easily, concluding that lipids are a key component of the cell membrane.

Gorter and Grendel (1925)

Researchers who used a Langmuir Trough to show that the area occupied by extracted lipids was twice the surface area of erythrocytes, confirming the bilayer organization.

Sandwich Model

A model proposed by Davson and Danielli in 1935 suggesting that the lipid bilayer is coated on both sides by layers of proteins.

Phosphoglycerides

A primary class of membrane phospholipids that includes Phosphatidylcholine, Phosphatidylserine, and Phosphatidylethanolamine.

Hydrophobic Forces

Effects where water forces non-polar groups together to minimize their disruptive impact on the hydrogen-bonded network.

Van der Waals Forces

Weak bonding interactions occurring between any two atoms at very short distances due to fluctuating electrical charges.

Membrane Asymmetry

The unequal distribution of phospholipids between the two sides of the bilayer; for example, Phosphatidylcholine is typically exoplasmic while Phosphatidylserine is cytosolic.

Scramblases

Non-specific phospholipid translocators that transfer phospholipids from one side of the $ER$ membrane bilayer to the other to ensure equal growth.

Flippases

Head-group specific phospholipid translocators responsible for transferring Phosphatidylserine ($PS$) and Phosphatidylethanolamine ($PE$) from the exoplasmic to the cytosolic side.

Floppases

Translocators that move phospholipids from the cytoplasmic face to the exoplasmic face in an energy-dependent process.

Cholesterol

A rigid planar steroid ring structure found abundantly in eukaryotic membranes that stabilizes the bilayer and regulates membrane fluidity.

Integral Membrane Proteins

Proteins that are embedded within or span across the lipid bilayer, such as Bacteriorhodopsin.

Peripheral Membrane Proteins

Proteins that are located on the surface of the lipid bilayer and do not extend into the hydrophobic core.

FRAP (Fluorescence Recovery After Photobleaching)

An experimental technique used to demonstrate the lateral diffusion and movement of membrane lipids by measuring the recovery of fluorescence in a bleached area.

Phase Transition

The change of a membrane between an ordered gel phase and a disordered liquid-crystalline phase, occurring at a specific temperature.

Palmitic Acid

A saturated fatty acid with $16$ carbons and $0$ double bonds, possessing a melting point of $63^{\text{o}}C$.

Oleic Acid

An unsaturated fatty acid with $18$ carbons and $1$ double bond, possessing a melting point of $+16^{\text{o}}C$.

Tight Junctions

Cell structures that can restrict the lateral movement of membrane proteins, maintaining membrane polarity in areas like the gut.

Hereditary Spherocytosis

An inherited hemolytic disorder affecting $1:2000$ individuals, caused by mutations in cytoskeletal proteins like Ankyrin or Spectrin, resulting in spherical erythrocytes.