Phospholipid Bilayer Flashcards
What is the phospholipid bilayer?
A structural component that isolates the cells components (organelles) from extracellular environments
What are lipids made up of?
Glycerol, carboxyl group, fatty acid and a double bond.
What is the phospholipid bilayer made up of?
Fatty acid non-polar tails (hydrophobic) and phosphate polar heads (hydrophillic)
What are the main functions of the lipid bilayer?
- Maintain an internal environment which differs from extracellular environment
- Allows the cell to control what enters/exits via transporter proteins.
- Mediates communication inside and outside the cell using protein receptors for cell recognition and signalling
- Gives the cell specificity in shape e.g. red blood cell allows larger surface area due to concave shape.
What facilitates non-polar molecules and non-lipid soluble passing through the membrane?
Transmembrane proteins - the cell can control gene expression of what proteins should be transcribed. e.g. if low on glucose it will switch on genes for a protein that facilitates glucose passage
What else is found in lipid bilayers?
Cholesterol, glycoproteins and antigens
What is the role of cholesterol?
Stabilises the structures of mammalian membranes, it raises the melting point if under high temperatures and at low temperatures it inserts between the phospholipids to prevent stiffening.
What are the role of glycoproteins?
Play a role in cell signalling and act as receptors for hormones
What are the role of antigens?
Cell recognition molecules and play a role in immunity and the ability to identify foreign molecules
Why is it referred to as the fluid mosaic model?
Because the phospholipids are not fixed and are free to move around within the bilayer, the mosaic refers to the proteins fixed within the layers that appear like a mosaic.
What does selectively permeable mean?
Allows certain molecules in and other out
