Membranes Flashcards
What is the fluid mosaic model?
Fluid refers to the phospholipids and proteins moving freely within the membrane laterally, and phospholipid also moving transversely.
Mosaic refers to proteins being embedded in the phospholipid bilayer in a random arrangement.
What are glycolipids?
Glycolipids are oligosaccharides covalently bonded to lipids
Where are peripheral proteins located?
Peripheral proteins occur on the surface of the phospholipid bilayer
How is peripheral proteins bound to the membrane?
Peripheral proteins are bound to the membrane by hydrogen and ionic bonds between the hydrophilic polar phosphate head and polar R groups of amino acids on the surface of the protein
Where are integral proteins located?
Integral proteins either span part or whole of the phospholipid bilayer. Integral proteins that span the whole of the phospholipid bilayer are known as transmembrane proteins.
How are integral proteins bound to the membrane?
Integral proteins are bound to the membrane by hydrogen and ionic bonds between the hydrophilic polar phosphate heads of the phospholipid and the polar R groups of amino acids on the surface of the protein. They are also bound to the hydrophobic core of the membrane by hydrophobic interactions between the hydrophobic non polar hydrocarbon tails and the non polar R groups of amino acids on the surface of the protein.
How does greater proportion of unsaturated hydrocarbon tails affect fluidity of membrane?
The greater the proportion of phospholipids containing unsaturated hydrocarbon tails, the less closely packed the phospholipid molecules are resulting in less fluidity.
How does amount of cholesterol affect fluidity of membrane?
The greater the amount of cholesterol in the membrane, the less closely packed the hydrocarbon tails are resulting in less fluidity
How does length of hydrocarbon tails affect fluidiity of membrane?
The longer the hydrocarbon tails, the more closely packed they are resulting in greater fluidity.
Why can non-polar, uncharged molecules pass through the membrane via diffusion?
Non-polar and uncharged molecules can pass through the hydrophobic core of the phospholipid bilayer via diffusion
Why can’t polar, charged molecules pass through the membrane via simple diffusion?
Polar and charged molecules cannot pass through the hydrophobic core of the phospholipid bilayer and can only pass through via specific membrane channels embedded in the membrane.
What is facilitated diffusion?
Facilitated diffusion is the net movement of molecules from a region of higher concentration to a region of lower concentration, down a concentration gradient, across the cell membrane via a specific transport protein.
What are transport proteins?
Transport proteins are transmembrane proteins that forms a hydrophilic channel for molecules to pass through
What is the function of cell surface membrane?
Cell surface membrane provides a boundary between the contents of the cell and the external environment to maintain a constant internal environment for the cell.
What is the function of membrane within the cell?
Membrane within cells forms a boundary between the cytoplasm and specific content within the membrane bound organelle. Such compartmentalisation allows a constant internal environment to be maintained within each organelle.
