Membrane structure Flashcards
What is the purpose of membranes?
- Separate the contents of the cell from its environment
- Separate different organelles each other and the cytosol
What is compartmentalisation and why is it important?
The formation of separate membrane bound areas in a cell. Important because there are many different and incompatible reactions going on in a cell. Having reactions in separate parts of the cells allows for specific conditions to be met.
What is the plasma membrane?
The cell surface membrane that separates the cell from the external environment
How do phospholipid bilayers play a part in membrane formation?
The hydrophilic phosphate heads are on the outside of the membrane, interacting with the aqueous environment and shielding the hydrophobic fatty acid tails into the middle of the membrane
Why is the model known as the fluid mosaic model?
Phospholipids are free to move in the membrane, relative to each other (fluid)
Proteins are embedded into the membrane, with various shapes and sizes (mosaic)
What is the difference between intrinsic and extrinsic proteins?
Intrinsic- span the membrane from one side to the other
Extrinsic- only on one side of the membrane
What is the purpose of cholesterol in the membrane?
Adds stability/ regulates fluidity and permeability
Packs the spaces between the phospholipids, which helps to reduce the movement of water soluble molecules in the membrane
What is a glycoprotein?
Intrinsic proteins with an attached carbohydrate chain.
Cell adhesion
Receptors for chemical signals/ cell signaling
What is a glycolipid?
Lipid with an attached carbohydrate chain
Cell recognition
What is a channel protein?
Intrinsic protein
Involved in transport of polar molecules/ions down a concentration gradient through a membrane
What is a carrier protein?
Intrinsic protein
Involved in passive and active transport through a membrane
Usually requires the protein changing shape
How does temperature affect membrane structure?
Temperature increased-phospholipids have more KE- move more-membrane is more fluid- membrane begins to lose its structure(more permeable)-cell breaks down completely
Carrier and channel proteins will be denatured- affects transport across the membrane
How do solvents affect membrane structure?
Organic solvents which are less polar than water/ non polar (eg alcohol) dissolve the membrane.
Pure/very strong alcohol solutions destroy cells (toxic)
Non polar alcohol molecules enter the cell membrane and disrupt the position of phospholipids- membrane becomes more fluid and permeable
