2.2 Membrane Structure & Function Flashcards
fluid mosaic model
the idea that a biological membrane consists of a fluid phospholipid bilayer in which proteins are embedded and float freely
how is our current view of membrane structure based on the fluid mosaic model?
This model proposes that membranes are not rigid, with molecules locked into place. Instead, membranes consist of lipid molecules in which proteins are embedded and float freely. Membranes are described as a fluid because the lipid and protein molecules are generally free to move laterally within the two layers.
glycolipid
any membrane lipid that is bound to a carbohydrate
glycoprotein
a membrane component that contains a sugar, or carbohydrate, bound to an amino acid
what are the dominant lipids found in membranes?
phospholipids
phospholipid
contains 2 fatty acids tails, which are usually linked to glycerol, a phosphate group and a compound (e.g. choline)
why is the composition of phospholipids important?
This composition is important for membrane function. The fatty acid tails of a phospholipid are very hydrophobic (nonpolar), whereas the phosphate-containing head group is charged and hydrophilic (polar).
when added to an aqueous solution, what do phospholipids form?
phospholipids form a bilayer or a structure that is 2 lipid molecules thick
what is the dynamic nature of the lipid bilayer dependent on?
how densely the individual lipid molecules can pack together
sterol
a type of steroid with an OH group at one end and a non-polar hydrocarbon chain at the other
integral membrane protein
a protein that is embedded in the lipid bilayer
peripheral membrane protein
a protein on the surface of the membrane
When comparing the outside and inside halves of a cell membrane’s phospholipid bilayer, the composition of lipids on the two surfaces is asymmetrical.
(a) Describe how membranes are asymmetric
(b) Why is membrane asymmetry an important characteristic in cell membranes?
(a) The membranes are asymmetrical because the proteins and other components of
one half of the lipid bilayer differ from those that make up the other half.
(b) Membrane asymmetry reflects the differences in functions performed by each half of
the membrane.
How does the structure of the plasma membrane facilitate its function?
The phospholipids on the bilayer are oriented so that their hydrophilic heads point
outwards towards the aqueous external environment and inward towards the aqueous
cytosol of the cell.
The hydrophobic tails point towards the interior of the membrane.
This prevents most polar or ionic substances from diffusing through.
what is meant by membrane fluidity
“Membrane fluidity” is the dynamic nature of the membrane, which allows for it to be flexible. That is, membrane lipids undergo free movement on their side of the bilayer.
