Biological Membranes and Structure

Flashcards covering the structure and functions of biological membranes, including the fluid-mosaic model and types of membrane proteins.

What is the primary role of the plasma membrane?

To separate the internal contents of a cell from its external environment.

What are the typical physical characteristics of a cell membrane?

It is thin (typically 5-10 nm) and somewhat fluid.

Besides the plasma membrane, what other types of membranes are found in eukaryotic cells?

Internal membranes that form organelles.

Name one vital cellular activity that occurs at the interfaces provided by biological membranes.

Selective uptake and export of ions and molecules, cell compartmentalization, protein sorting, anchoring of the cytoskeleton, production of energy intermediates, cell signaling, cell and nuclear division, or adhesion of cells to each other and to the extracellular matrix.

What are the two primary components that form the basic matrix and structure of biological membranes?

Phospholipids and proteins.

What is the name of the model that describes membrane structure as a mosaic of lipid, protein, and carbohydrate molecules exhibiting fluid properties?

The fluid-mosaic model.

What part of a phospholipid is found in the interior of the membrane, and what part is on the surface?

The hydrophobic (nonpolar) tails are in the interior, and the hydrophilic (polar) heads are on the surface.

What is a 'leaflet' in the context of a phospholipid bilayer?

One half of a phospholipid bilayer, such as the cytosolic leaflet or the extracellular leaflet.

Which type of carbohydrate-attached lipid is primarily found in the extracellular leaflet and contributes to cell surface recognition?

Glycolipids.

What are the three types of membrane proteins?

Transmembrane proteins, lipid-anchored proteins, and peripheral membrane proteins.

Which two types of membrane proteins are classified as integral membrane proteins?

Transmembrane proteins and lipid-anchored proteins.

How do transmembrane proteins associate with the membrane structure?

They span or traverse the entire membrane, with nonpolar amino acid segments embedded in the hydrophobic interior.

How do lipid-anchored proteins associate with the membrane?

They have a lipid molecule covalently attached to an amino acid side chain that is inserted into the hydrophobic portion of the membrane.

How do peripheral membrane proteins typically bind to the membrane?

They are noncovalently bound to regions of transmembrane proteins or to the polar head groups of phospholipids, often by hydrogen or ionic bonds.

Name three mechanisms by which biological membranes regulate the traffic of substances.

Simple diffusion, proteins that span the membrane, intercellular channels, exocytosis, and endocytosis.