15-Plasma Membranes Flashcards
What is the role of the plasma membranes?
To separate cells inner components from the outside world
What are the three functions of the plasma membrane?
Receiving information
Import and export of molecules
Capacity for movement and expansion
What are the basic properties of plasma membranes?
2 ply sheets composed of lipids
5nm in thickness
proteins that control transport of nutrients into the cell, waste products out of the cell
PM aslo invloved in cell growth, movement, division
What is the role of the lipids in the PM?
Barrier
What is the role of proteins in the PM?
transport/signalling function
What is meant by amphipathic phospholipids?
Contain both hydrophyllic and hydrophobic parts
What is the role of lung surfactant?
Decreases surface tension and allows bubbles to form alveoli and keeps airway open
Describe the membrane fluidity of saturated lipids?
Highly rigid
tightly packed
Describe the membrane fluidity of unsaturated lipids?
More fluid
Less tightly packed
What is the role of cholesterol?
Fills the spaces between the phospholipids left by their kinks from the unsaturated hydrocarbon tails- decreases fluidity
Describe the membrane fluidity of unsaturated lipids plus cholesterol?
Less fluid
Increased membrane stiffness
Why is membrane fluidity important?
Allows membrane proteins to diffuse in the 2D plane of the membrane
This protein- protein interaction is key for cell signalling
Allows membrane lipids to move within the bi-layer
Allows membranes to fuse with each other and exchange contents
Ensures equal distribution of cell contents between daughter cells when a cells divides
What are flip-flop enzymes?
Enzymes that can move lipids across the bilayer
Why is it so important to maintain cell shape?
It is critical for red blood cell function
What is required for active trasnsport?
involves protein transporters and ion channels
