lecture 2: Fundamentals of Cell Biology: Membrane Structure

Flashcards covering key terms and definitions related to membrane structure in cell biology.

Plasma Membrane

The membrane that encloses the cell, defining its boundaries and maintaining the essential differences between the cytosol and the extracellular environment.

Lipid Bilayer

A double layer of lipids that forms the fundamental structure of the cell membrane.

Amphiphilic

Molecules that contain both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts.

Phospholipid

The most abundant type of lipid in cell membranes, composed of a glycerol backbone, two fatty acids, and a phosphate group.

Sphingolipid

A type of lipid found in cell membranes, built from a sphingosine backbone and often involved in cell signaling.

Sterols

Rigid ring structures related to steroids but containing a single polar hydroxyl group and a short nonpolar hydrocarbon chain. A class of lipids that includes cholesterol, which helps maintain membrane fluidity and stability.

Transmembrane Protein

Proteins that span the entire lipid bilayer, allowing for interactions with both the internal and external environments of the cell. (eg, receptors and channels)

Glycoprotein

A protein that has carbohydrate chains attached to it, often found on the exterior surface of the cell membrane.

Flippase

An enzyme that moves selective phospholipids unidirectionally from one side of a bilayer to the other, maintaining asymmetry.

Scramblase

A membrane protein that facilitates the non-selective movement of phospholipids between the two leaflets of a membrane bilayer.

Fluidity

The ability of lipid molecules to move laterally within the membrane, influenced by lipid composition and temperature.

Lipid Asymmetry

The unequal distribution of different types of lipids in the inner and outer leaflets of a membrane bilayer, critical for cell membrane function.

membranes of organelles

maintains the difference between the contents of each organelle and the cytosol (eg nucleus, ER, mitochondria)

Glycerophospholipids

the main phospholipids in animal cell membranes that consist of a glycerol backbone, two fatty acid tails, and a phosphate group, playing a crucial role in membrane structure and function.

Micelles

cylinder shaped apmphilic molecules with hydrophilic heads facing outward and hydrophobic tails inward, facilitating the formation of lipid bilayers.

Exocytosis

the secretory pathway that delivers newly synthesized proteins and lipids from the ER to the golgi apparatus, endosomes and the plasma membrane via transport vesicles

Membrane proteins

perform most of the membrane’s specific tasks and therfore give each type of cell membrane its functional properties. attatched to a monolayer either by an amphiphilic alpha helix or by one or more covalently linked lipid chains

peripheral membrane proteins

not directly attatched to the lipid bilayer, they associate with the membrane's surface through interactions with integral proteins or lipids, playing roles in signaling and maintaining the cell's shape.

hydropathy index

the free energy needed to transfer successive segments of a polypeptide chain from a nonpolar solvent to water

Beta barrel membrane proteins

arranged as cylinders that form pores in membranes, allowing the passage of ions and small molecules. Outside amino acids are hydrophilic

Detergents

small amphiphilic molecules of various structures, can disrupt the lipid bilayer and liberate proteins in a soluble form