Flashcards in Topic 5 - chapter 11 Membrane structure Deck (46)
The lipid bilayer is a ...-dimensional fluid
The fluidity of a lipid bilayer depends on its ...? Which 3 factors?
- phospholipid tail length
- phospholipid saturation level
- presence of cholesterol
T or F - the lipid bilayer is symmetrical
false - asymmetrical
What are the most abundant lipids in cell membranes? Whatis the most common membrane lipid?
phospholipids (head linked to rest of lipid via phosphate group)
In the membrane lipid phosphatidylcholine, what makes up the hydrophilic & hydrophobic regions?
hydrophilic (polar head) - phosphate & choline
hydrophobic (non-polar tail) - hydrocarbon tail
What are 3 different types of membrane lipids? egs...
phospholipid - phosphatidylserine
sterol - cholesterol
glycolipid - galactoserebroside
Which polar molecule can dissolve in water?
Which polar molecule can not dissolve in water?
What is the difference between amphipathic and hydrophobic?
amphipathic molecules will always form a bilayer in water and spontaneously form sealed compartments
Lipid asymmetry is preserved during ...?
Why is the lipid bilayer considered two-dimensional?
- phospholipids form spherical liposomes in water
- membrane behaves like a fluid
- not much 'flip-flopping'
Approximate thickness of lipid membrane?
3 main functions of plasma membranes...
- receiving info from from environment via receptor proteins
- import & export of small molecules via transport proteins
- cell growth & movement due to flexibility of membrane
What is the hydrophilic/hydrophobic part of phosphatidylserine?
hydrophilic - serinephosphate
hydrophobic - hydrocarbon chain
What is the hydrophilic part of cholesterol?
What is the hydrophilic part of galactocerebroside?
sugar (galactose) & -OH group
Size range of cell vesicles membranes can form?
25nm - 1mm
Which ways can phospholipids move within the plane of the membrane?
What is meant by fluidity of a cell?
the ease with which lipid molecules move within the plane of the bilayer
Which structure(s) mainly affect membrane bilayer fluidity? Which 2 factors of those structures?
nature of the hydrocarbon tails:
- length (the shorter, the more fluid)
- number of double bonds (the more, the more fluid)
What is saturated and unsaturated?
based on number of hydrogen bonds attached to the carbon tail
saturated - fatty acid tail with no double bonds and full complement of hydrogen atoms
unsaturated - has at least one double bond thus does not have maximal hydrogen atoms
Usual hydrocarbon tail length?
18 - 20 carbon atoms
How does cholesterol fit into the lipid bilayer?
in animal cells, cholesterol fits in between the kinked gaps left by double bonds thus stiffening the bilayer and making it less permeable
Why is membrane fluidity so important?
- enables rapid diffusion of proteins
- enables protein interactions with one another
- enables membrane lipids & proteins to diffuse to other regions of the cell
- allows membranes to fuse with one another & mix their molecules
- ensures membrane molecules are distributed evenly between daughter cells during cell division
In eukaryotic cells, what are phospholipids made from?
enzymes bound to ER membrane
What enables the transfer of phospholipid molecules from one monolayer to another ('flip-flopping')?
Glycolipids are mainly located where? Their sugar groups?
in the plasma membrane and are found ONLY in the noncytosolic half of the bilayer
their sugar groups are exposed to the exterior of the cell forming a protective carb coating surrounding most animal cells
List 4 functions that membrane proteins serve
Transporters - protein example & function...?
transporters - Na+ pump: actively pumps Na+ out of cells and K+ into cells