Biological membranes

Membrane Functions

Include creating compartments, selective transport, communication, and acting as a scaffold for biochemical activities (energy transduction).

Plasma membrane

separate content of the cell from the extracellular media

Selective transport

Solutes must travel between compartments and with the exterior of the cell. 

communication

Between cells (signaling and cell-cell interaction) and between organelles to allow cells to respond to changes in a coordinated way

Self-seal

Ability of biological membranes to close back after being disturbed or perturbed.

what effects Fluidity (2)

Temp and Membrane composition affect fluidity

is the membrane fluid at high temp?

Yes

Longer fatty acids mean what?

less fluid

Adaptable

cells can change membrane composition using the same basic components

Dynamic

their basic composition can move inside

Semipermeable

Membranes allow the transport of certain substances while restricting others.

Membrane Components

Consist of lipids (phosphoglycerides, sphingolipids, sterols), proteins (transmembrane, anchored, peripheral), and saccharides.

Lipids

phosphoglycerides, sphingolipids, sterols

Phosphoglycerides

a lipid

1. Derivative of glycerol 3-phosphate

2. Two long fatty acid chains (varies by amount of carbons and degrees of saturation) and a polar head group 

Sphingolipids

1. Ceramide: sphingosine + fatty acid + amide bond

2. Two main classes:

   1. Sphingomyelins: ceramide + phosphate polar head group

   2. Glycosphingolipids: ceramide + sugar

Sterols

Are lipids

have a four-ring isoprenoid-based hydrocarbon with a hydroxyl group. This hydroxyl makes these lipids amphipathic as well but their polar region is much smaller

Transmembrane Protein

Protein that can cross from one side of the membrane to the other.

Anchored Protein

Protein anchored to the membrane via lipid modification.

Fatty acid, Cholesterol or GIP Covalently bound

Peripheral Protein

Associated with a transmembrane protein without covalent bonds, released using high salt.

Hydrogen bonds or electrostatic interactions involved

Hydrophobicity Plots

Used to display the distribution of polar and apolar residues along a protein sequence, identifying possible transmembrane regions.

Fluid Mosaic Model

Describes membranes as having a hydrophilic exterior, hydrophobic interior, and being dynamic, fluid, and semipermeable.

Domains

region of a membrane that has different properties from the membrane around it.

1. Membrane composition differs between concrete areas of the same leaflet, called domains. 

Leaflet

he lipid bilayer consists of two leaflets.

Membrane composition differs between two leaflets of the same membrane.

Differences in membrane composition

differs between different organisms and organelles by a number of factors such as the number of fatty acids and amount of kinks or unsaturations present.