Structure and Function of Plasma membrane Flashcards
What are the 4 Major components of a Eukaryotic Cell?
Plasma Membrane
Nucleus
Membrane-Bound organell
Cytoskeleton
What does the Plasma membrane do?
Defines boundaries of the cell
Why must the Plasma membrane physically seperate the interior of cell from surrounding enviroment?
For regulation and to keep desirable substances in the cell
What are the 6 functions of The Plasma Membrane?
Barrier - entry/exit of substances Site Metabolic Activities - mitochondria Ion transport - nerve impulses Cell signalling - communication Cell shape - eg erythrocytes Cell-Cell interaction - adhesion molecules
What are the 3 identities of the Existence of Plasma membrane?
1) Cell swelling (hypotonic less concentrated) & Shrinking (hypertonic more concentrated)
2) Escape of Cell contents (if ruptured)
3) Compartments (most internal organelles, chemical activities)
Who and When discovered the PM?
Robertson in 60’s - Unit membrane
Who and What model discovered in the 70’s?
Singer and Nicholson - Fluid Mosaic Model
How was the Unit membrane found by Robertson?
Used Osmium to stane the membrane and found railroad track structure
Describe Robertsons Railroad track structure?
Trilaminer consisting of 2 Dark lines (outer inner layer) containing polar head group
Seperated by Central Light space containing hydrophobic tail of lipid molecules
What did Electron Microscopy studies find?
Cells are seperated by thin PM that retains cell contents
What does Fluid Mosaic Model consist of?
2 Fluid layers of lipid and Proteins within or on Lipids
Describe the Structure of the Plasma Membrane?
Lipid molecules 50% of mass, Asymmetrically distributed, Amphiphilic with hydrophilic head and hydrophobic tail
What are the 3 Common types of Membrane Lipid Fluids?
Phospholipids
Glycolipids
Sterols
Describe Structure of Phospholipids?
2 Hydrocarbon tails - fatty acids
Tails differ in length between 14-24 carbon
Cis-double bonds in 1 tail creating Kink
Why do Phospholipid Molecules Aggregate?
Keep Hydrophobic tails in the interior and Expose Hydrophilic heads to water
What are the 2 types of Aggregation styles?
Cone shaped
Cylinder shaped
Describe Cone shaped aggregation?
Lipid molecules in a single chain form micelles
Describe Cylinder shaped aggregation?
Phospholipid molecules (double tailed) form bilayer
What is a Glycerol Based Phospholipid called?
Phosphoglyceride
What are the 4 Main types of Phosphoglycerides in PM?
Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine (-)
Phosphatidylinositol
Why is Phosphatidylserine Negative?
Activates certain enzymes with negative charge during apoptosis so PM modify and express on outer of membrane so macrophages recognize and remove out of system
What is the Main type of Sphingolipid in PM?
Spingomyelin
Describe the Phospholipid structure?
Polar head (such as choline, ethanolamine, serine, inositol)
Lipid backbone
Glycerol or Spinogosine based
How are Glycolipids formed?
By the Addition of a CHO group to lipids
