Membranes Flashcards
What are the functions of a cell membrane?
- Selective barrier to the passage of molecules
- Detecting Chemical signals
- Anchoring cells to adjacent cells and to the extracellular matrix of connective tissue proteins
How thick are cell membranes?
6-10mm
What are are membranes mostly comprised of?
phospholipids
How are phospholipids organised in the plasma membrane?
In a bilayer with the non-polar fatty acid chains in the middle
What else does the plasma membrane contain that intracellular membranes do not contain much of?
Cholesterol
What are the two classes of membrane proteins?
Integral and Peripheral
What does it mean for phospholipids to be amphipathic?
They have both hydrophobic and hydrophilic parts
What are the 3 types of junctions that cells are physically joined by?
Desmosomes
Tight Junctions
Gap Junctions
What are integrins?
Transmembrane proteins which bind to specific proteins in the ECM and link them to membrane proteins on adjacent cells
What are Desmosomes?
Dense plaque accumulation along cytoplasmic surface that serve as anchoring points for cadherins, which link up and bind to cadherins in adjacent cells
What is the function of a desmosome?
Hold adjacent cells firmly together in areas that are subject to considerable stretching such as the skin
What is a tight junction?
Where two adjacent plasma membranes join so no extracellular space remains between them
What is a gap junction?
where Connexins from the two membranes join, forming small protein lined channels lining the cytosol of the two cells
what is Diffusion?
random thermal motion causing movement from one location to another
what is flux?
The amount of material crossing a surface in a unit of time
