Cell structure & organisation Flashcards
are there any bonds holding the PL bilayer?
no. they naturally form this configuration due to their nature of hydrophilic and hydrophobic components
phospholipids remain in the same position and cannot move. is this correct?
no. they are able to move horizontally around the membrane. (just not vertically)
a phospholipid with more saturated fatty acids will have more fluidity. is this correct?
yes. the fact that they have a double bond that causes a bend in the structure means PLs are less able to pack tightly together, increasing fluidity
a PL bilayer which is less fluidity has more of which type of fatty acid in the PLs?
unsaturated
besides saturated fatty acids, what else helps with fluidity in PL bilayers? how?
cholesterol. this does so by binding to the hydrophobic regions of the PL and holding PLs apart from each other, so they are not tightly packed together
when the temperature increases, how does cholesterol maintain the PL bilayer structure?
it holds phospholipids together so they do not move too far apart
when the temp decreases, how does cholesterol ensure that the cell membrane doesn’t get too rigid?
prevents phospholipids from packing tightly together
cholesterol is only a polar molecule. t/f and explain
f.
it is amphipathic (both polar and non polar regions)
has a hydrophilic head that associates with the hydrophilic region of the PL and a hydrophobic tail
cell membranes are mosaic in appearance.. what does this mean?
contains a mixture of lipids and proteins, which has the appearance of a mosaic
types of membrane proteins
integral and peripheral
integral proteins are…
embedded in the bilayer and are permanently associated with the membrane- hydrophobic regions of molecule associate with hydrophobic region of bilayer
peripheral proteins are…
not permanently attached to the membrane, only found on one side of the membrane and are interacting with something attached to the membrane, such as a fatty acid
molecules that are……… ……… or ………. are able to pass easily through the membrane
small, uncharged, non polar
some molecules are still able to pass through the membrane but it is more difficult… what properties do they have?
they are small but charged/polar. large molecules are not able to pass through the membrane easily
purpose of enzymes on the surface of membrane
facilitates the conversion of one molecule to another
