Cell Membranes: Structure and Composition

Flashcards covering the roles, composition, fluidity, and structural models of cell membranes based on Dr. Alessandro Siani's lecture.

Barrier

A role of the cell membrane that separates the intracellular space from the external environment.

Cell signalling

A function of the cell membrane allowing outside messages such as hormones or growth factors to modulate cellular function.

Cell recognition

A process allowing cells to recognize and interact with other cells and the extracellular matrix.

Homeostasis

The dynamic maintenance of a controlled and stable environment within the cell by the membrane.

Phospholipids

Molecules with a polar, hydrophilic "head" and hydrophobic fatty acid "tails" that vary in chain length and saturation.

Amphipathic molecules

Molecules that possess both hydrophilic and hydrophobic regions, such as phospholipids.

Micelles

Structures formed by a single layer of amphipathic molecules in aqueous solutions.

Liposomes

Bilayer structures formed by amphipathic molecules in aqueous solutions, often used in drug delivery.

Phospholipid Bilayer

A structure formed by hydrophobic interactions between nonpolar tails and hydrophilic interactions between polar heads and water.

Fluid Mosaic Model

A model proposed by Singer and Nicolson describing the membrane as a phospholipid bilayer "lake" in which proteins "float."

Lateral drift

The movement where most lipids and some proteins shift sideways within the membrane bilayer.

Flippases

Transmembrane proteins that help move lipids from the extracellular to the intracellular layer.

Floppases

Transmembrane proteins that help move lipids from the intracellular to the extracellular layer.

Cholesterol

A steroid that restrains phospholipid movement at warm temperatures ($37^\circ\text{C}$) and prevents tight packing at cool temperatures.

Glycolipids

Membrane lipids linked to carbohydrates, generally located on the extracellular side and involved in cell signalling.

Lipid rafts

Clusters of glycolipids and cholesterol that play key roles in cell signalling and protein trafficking.

Membrane asymmetry

The structural and functional distinction between the inside and outside faces of cell membranes.

Peripheral proteins

Proteins that are bound to the surface of the cell membrane.

Integral proteins

Proteins that penetrate the hydrophobic core of the membrane.

Transmembrane proteins

Integral proteins that span across the entire membrane.

Alpha helices

Common structural coils formed by stretches of nonpolar amino acids in the hydrophobic regions of integral proteins.

Glycoproteins

Membrane proteins with covalently linked carbohydrate residues, usually located on the extracellular side.

Receptors

Specialized membrane proteins that bind specific molecules called ligands to send messages inside the cell.

Freeze-fracture

A specialized preparation technique that splits a membrane along the middle of the phospholipid bilayer.

Fluorescence microscopy

An imaging technique used to visualize membrane components like lipid rafts or receptors using fluorescently labelled markers.