1.3 Membrane Structure Flashcards
What is the structure of a phospholipid? (head)
Consist of a polar head (hydrophilic) composed of a glycerol and a phosphate molecule
What is the structure of a phospholipid? (body)
Consist of two non-polar tails (hydrophobic) composed of fatty acid (hydrocarbon) chains
What are phospholipids named in terms of water?
phospholipids contain both hydrophilic (water-loving) and lipophilic (fat-loving) regions, they are classed as amphipathic
What can phospholipids spontaneously form?
Phospholipids spontaneously arrange into a bilayer
How are the phospholipids arranged in the plasma membrane?
The hydrophobic tail regions face inwards and are shielded from the surrounding polar fluids, while the two hydrophilic head regions associate with the cytosolic and extracellular fluids respectively
What holds the bilayer together?
The bilayer is held together by weak hydrophobic interactions between the tails
What effect do the Hydrophilic / hydrophobic layers have on the passage of substances?
Hydrophilic / hydrophobic layers restrict the passage of many substances
What does it mean that the membrane is fluid, in terms of phospholipids?
Individual phospholipids can move within the bilayer, allowing for membrane fluidity and flexibility
Why does the membrane need to be fluid?
This fluidity allows for the spontaneous breaking and reforming of membranes (endocytosis / exocytosis)
What is embedded in the phospholipid bilayer?
Phospholipid bilayers are embedded with proteins, which may be either permanently or temporarily attached to the membrane
What does it mean if a protein is integral?
Integral proteins are permanently attached to the membrane and are typically transmembrane (they span across the bilayer)
What does it mean if a protein is peripheral?
Peripheral proteins are temporarily attached by non-covalent interactions and associate with one surface of the membrane
According to which factor are membrane proteins arranged?
The amino acids of a membrane protein are localised according to polarity
How are non-polar amino acids localised?
Non-polar (hydrophobic) amino acids associate directly with the lipid bilayer
How are polar amino acids localised?
Polar (hydrophilic) amino acids are located internally and face aqueous solutions
What 2 structures can transmembrane proteins have?
Single helices / helical bundles
Beta barrels (common in channel proteins)
What 6 functions can membrane proteins have?
Junctions Enzymes Transport Recognition Anchorage Transduction
What do membrane proteins associated with junctions do?
Serve to connect and join two cells together
What do membrane proteins associated with enzymes do?
Fixing to membranes localises metabolic pathways
What do membrane proteins associated with transport do?
Responsible for facilitated diffusion and active transport