Cell Membranes Flashcards
Where are plasma membranes found?
Cells, organelles and vesicles
What are the functions of a plasma membrane?
- form a barrier between 2 environments
- control exchange of substances between environments
- allows different conditions to be established and maintained
What is the difference between a plasma membrane and a cell surface membrane?
A cell surface membrane envelopes the cytoplasm of a cell
Plasma membrane can be found anywhere
What is the cell surface membrane made from?
Phospholipids
What is the structure of a phospholipid?
Hydrophilic head:
Phosphate with phosphoester bond
Hydrophobic tail:
Glycerol wire ester bond
Attached to 2 fatty acids
What is the fluid mosaic model?
Molecules within the phospholipid bilayer fit like a mosaic and are free to move within the layer
What does the fluidity of the bilayer depend upon?
Temperature and presence of cholersterol molecules
Phospholipid
- arranged in bilayer
- hydrophilic head points out
- hydrophobic tail faces in
- form total waterproof barrier around the cell/organelle/vacuole
Extrinsic protein
- proteins on the outside of the cell
- receptors
- enzymes
Intrinsic protein
- proteins that goes all the way through the bilayer
- allows water soluble molecules to pass into or out of cell
- channel proteins or
- molecules can entry by facilitated diffusion
Glycoprotein
- protein with carbohydrate chain coming off of it
- recognition of self
- helps cell stick to each other to form tissues
Glycolipid
- carbohydrate chain attached to phospholipid molecules
- self recognition
- maintains stability of cell membrane
Cholesterol
- molecule sits within the phospholipid bilayer
- bind to tails of phospholipids, causing them to pack more closely together- restricts movements (less fluid more rigid)
- maintain integrity and fluidity of cell membrane (shape)
What molecules can pass through the phospholipid bilayer?
Small molecules e.g. oxygen and carbon dioxide
And lipid soluble molecules
What properties should a drug have to enter a cell quickly?
Small molecules and lipid soluble