Flashcards in Membrane Structure: Ch.10 Deck (22):
What are the three main components of a cell?
1. cytoplasm: contents of the cell outside of the nucleus
2. cytosol: aqueous part of the cytoplasm
3. lumen: inside of the organelles
What are cellular function that occur at membranes?
2. scaffold for biochemical activities (ETC)
3. selectively permeable barrier (H2O)
4. transporting solutes
5. responding to external signals
6. interactions between cells
What are the two main functions of cell membranes?
1. divide cell into compartments
2. control movement of molecules
What is the lipid bilayer? Describe a phospholipid
-a basic unit; fluid structure
-hydrophilic/polar head, 2 hydrophobic/nonpolar tails
What happens to phospholipids in an aqueous environment?
-they spontaneously self-associate into a bilayer
What is an artificial lipid bilayer called? Describe its properties/uses.
-called a liposome
1. lipid properties
2. membrane protein properties
3. delivery into cells
-it is energetically favourable when it has a sphere-shape (sealed compartment)
Which is the most abundant lipid component?
What does a kink in the tail indicate?
that it is unsaturated; contains a cis double bond
What are the effects of having steroids as a lipid component?
-decreases the mobility of phospholipid tails
-plasma membrane is less permeable
- steroids have a rigid ring structure
What are glycolipids and where are they found? Where are they synthesized?
-glycolipids are sugar groups attached to the lipid molecules
-found in outer leaflet of plasma membrane, not in inner
-found in some organelles
-synthesized on the luminal face of Golgi
Describe phospholipid diffusion.
-rapidly diffuse laterally within each leaflet; flexion and rotation
-rarely move from one leaflet to another (flip flop)
What three factors affect membrane fluidity?
1. temperature: bilayer becomes rigid at low temps (gel)
2. phospholipid saturation: presence of cis double bonds allows membrane to remain fluid at low temps
3. length of phospholipid tails: shorter tails increase fluidity because they interact less
Rapid flip flop from one leaflet to the other occurs with the help of __________ _________. Why is this necessary?
- necessary because phospholipids are synthesized in the cytosolic leaflet of ER
Describe the asymmetry of the lipid bilayer?
-glycolipids face the lumen, found on outer leaflet of PM and protect cell from harsh environments
-specific phospholipids found on cytosolic leaflet of PM; can bind to cytosolic proteins
Are transmembrane proteins hydrophilic, hydrophobic or amphiphilic?
-they are amphiphilic
-hydrophilic domains are aqueous
-hydrophobic membrane spans domain
-AA side chains are nonpolar
Describe the single pass and multi pass of transmembrane proteins. Which proteins go through conformational change and which have ion channels?
single pass: 1) single alpha helix; no conformational change
multi pass: 2) multiple alpha helices; has ion channels and goes through conformational change to regulate permeability
3) rolled up beta sheet (beta barrel); rigid, has an aqueous pore; do not go through conformational change but has some channels
Proteins can be anchored on ______ face by an amphiphilic alpha helix because of the _______ _____
(cell membrane proteins on one side)
What are 3 types of lipid-anchored membrane proteins? What are their functions?
1. fatty acid chain anchor
2. prenyl anchor
3. GPI anchor
1 and 2: functions are to direct the protein to the cytosolic face; enzymes add the anchor
3: synthesizes in ER; end up on cell surface instead of cytosol
Which proteins are bound on either face? and what kind of interactions with other membrane proteins do they make?
peripheral membrane proteins make non-covalent interactions with other membrane proteins; don't span the lipid bilayer
What are the differences between extraction techniques of peripheral and integral membrane proteins?
-peripheral membrane proteins use gentle extraction that does NOT destroy lipid bilayer
-integral membrane proteins destroy membrane with detergents to extract the protein
What technique bleaches a small area by laser beam?
FRAP: Fluorescence Recovery After Photobleaching
-measures the green fluorescent protein movement into a bleached area
-measures the mobility of a population of protein molecules rather than an individual protein