Cell Biology

Front 1

Prokaryotic cell membranes

Back 1

Prokaryotic cell membranes:

- surrounded by a single plasma membrane, but no internal membrane sub-compartments

- 100s of proteins integral to cell function

- ATP synthesis

- initiation of DNA replication

- membrane transport proteins

Front 2

Eukaryotic cell membranes

Back 2

Eukaryotic cell membranes:

- plasma membrane surrounding cell are studded with proteins:

-- membrane transport proteins

-- receptors for chemical signaling

-- adhesion molecules (to extracellular components & cytoskeleton)

- plasma membrane typically composes <1% of total surface area of all eukaryotic cell components

-- biomembranes also found w/in cytoplasm surrounding organelles

- Double membrane = 2 layers (by-layers) = 2 phospholipid by-layers (each one has 2 leaflets = cytosolic leaflet and ectoplasmic leaflet) 4 leaflets in total

- The most abundant lipid components in most membranes are phospholipids, which are amphipathic molecules (i.e., they have a hydrophilic and a hydrophobic part)

Front 3

Lipid Layers (Leaflet)

Back 3

--> Each lipid layer is called a leaflet

Double membrane = 2 layers (by-layers) = 2 phospholipid by-layers (each one has 2 leaflets = cytosolic leaflet and ectoplasmic leaflet) 4 leaflets in total

Example:

LEAFLETS

The OUTER MITOCHONDRIAL membrane has 2 leaflets
The INNER MITOCHONDRIAL membrane has 2 leaflets

- The outer leaflet of the OUTER mitochondrial membrane faces the cytoplasm of the cell, therefore, it is the CYTOPLASMIC leaflet
- The inner leaflet of the OUTER mitochondrial membrane faces the interior of the mitochondria (inter-membrane space) , therefore, this is the EXOPLASMIC leaflet
- The outer leaflet of the INNER mitochondrial membrane is facing the inter-membrane space as well, therefore, this is the EXOPLASMIC leaflet
- The inner leaflet of the INNER mitochondrial membrane is facing the matrix of the mitochondria, this will be the CYTOSOLIC leaflet

Front 4

Functions of the Membrane

Back 4

- Shape to the cell and organelles

- Stability

--- hydrophobic & van der Waals interactions between lipid chains provides strength that allows membrane to retain its architecture

- Selectively-permeable barrier

- Concept of tonicity (concentration of solute)

--- Isotonic ( no net solute movement, no change in concentration, but water still moves in both directions)

--- Hypertonic

--- Hypotonic