The Membrane Flashcards
All membranes are
fluid mosaics
All membranes have
phospholipids
proteins
carbohydrates
sterols (an exception)
what are some factors that affect membrane fluidity?
-high temperatures can cause an increase the fluidity which can cause the membrane to be more permeable
low temperature can decrease fluidity and make the membrane more thick (this can make the cell stop moving leading to death of the cell)
what are some factors that can affect membrane fluidity? (part 2)
-the type of phospholipid:
unsaturated fatty acids are more fluid because there double bonds allow them to be more flexible and movement
say that the membrane has reached very low temperatures, what can the cell do to help the membrane with movement?
the cell will add more double bonds to the fatty acids and this is done with the help of the desaturase enzyme
how can sterols help in maintaining optimal fluidity
in times of high temperature, sterols will decrease disruption by restraining the movement in membranes
in times of low temperatures, sterols will help prevent close packing of phospholipids
integral proteins pass
through the lipid bilayer
because integral proteins can pass through the entire lipid bilayer, what parts of the membrane can they both interact with?
hydrophobic regions & hydrophillic regions
peripheral membrane proteins only attach to
the surface of the membrane but they can bind to phospholipids or integral proteins
what carbohydrate is attached to integral membrane protein?
glycoproteins
what carbohydrate is attached to phospholipid?
glycolipid
what direction are glycoproteins and glycolipids facing?
carbohydrates always face outside of the cell (outside of the cytoplasm)
what are the functions of these carbphydrates?
cell-cell recognition
ex: when we get sick, the body can recognize that it is a virus and start fighting the bad bacteria right away
what causes membranes to be asymmetric ?
the lipid bilayer has different proteins and other components on one side and different components on the other side, causing an imbalance
on the outside face of the membrane:
carbohydrates are attached to lipids and proteins proteins anchor (attach) membrane to the extracellular matrix
on the inside face of the membrane:
proteins anchor the membrane to the cytoskeleton
on the inside face of the membrane:
proteins anchor the membrane to the cytoskeleton
the tendency of molecules to move down a concentration gradient?
diffusion
only small or non-polar molecules can move across the membrane
simple diffusion
why is the lipid bilary permeable to small, non-polar molecules?
because the core of the phospholipid bilayer is non-polar so it likes to only interact with non-polar things
can water pass through?
yes it can but its very difficult and is very slow
large molecules cannot simply pass through the lipid billayer so what is required to help move them through?
membrane proteins help carry these large molecules through the bilayer
diffusion of substances aided by membrane transport proteins
facilitated diffusion
is energy required for this diffusion?
NO! because its moving from a concentration of high to low
what are the type types of membrane proteins used to help these large molecules move through?
- Channel proteins
2. Carrier proteins
what do channel proteins do to move large molecules?
they form hydrophillic channels that allow specfific molecules to pass
ex: ions
what do carrier proteins do to help?
carrier proteins will change the shape when large polar molecules bind to carry the across the membrane
ex: glucose transport
what can’t and can cross the membrane ( osmosis)?
water can move through the membrane through osmosis , however the solutes cannot
