Membrane Flashcards
What do membranes do?
Receive info, import and export small molecules, and have the capacity for movement and expansion.
What is the membrane structure?
Lipid bilayer with lipids and proteins interacting noncovalently.
What are the different types of membrane lipids and what characteristic do they share?
Glycolipid, cholesterol, phospholipid, all are amphiphilic.
Describe cholesterol and its role
reduces membrane permeability to small molecules. Role in fluidity is temperature dependent .
How do monolayers in plasma membrane move?
Monolayers (leaflets) commonly diffuse laterally but transverse movement (flip flop) is rare.
How is saturation related to fluidity?
Unsaturated hydrocarbon chains reduce membrane thickness and Shorter hydrocarbon chains makes membrane more fluid due to fewer interactions.
How did experiment between mouse and human cells show diffusion of proteins in membrane?
When they were mixed, the labeled proteins mixed and moved around.
Describe FRAP
Used to measure the rate of diffusion of lipids and proteins in the membrane
Higher rate of diffusion means a quicker rate of fluorescence return
How is mobility of proteins restricted in cell?
• Protein aggregation •
Tethering to a protein inside the cell •
Tethering to a protein outside the cell •
Cell-cell interactions •
Tight junctions •
Cytoskeletal Network
Where does phospholipid synthase occur?
In the ER
What do scramblases do?
They randomly distribute phospholipids in either direction toward equilibrium.
What do flippases and floppases do?
Move phospholipids from outer to cytosolic leaflet or vice versa, requires ATP unlike scramblase
What do membrane proteins do and what are their types.
They perform the tasks of the membrane. Integral and Peripheral Membrane Proteins.
Describe single vs multipass transmembrane alpha helices.
Single pass are mostly nonpolar with no proline. Multipass may have a mix of hydrophobic and hydrophilic, or be entirely hydrophobic depending on structure.
How many amino acids needed to span membrane as a helix?
20-30
Describe beta barrels.
H bonding between B strands, can’t be identified by hydropathy plot since only 10 amino acids required for B strand to cross membrane.
Where are oligosaccharides added in membrane?
Non cytosolic side of lipids and proteins.
Describe permeability of the lipid bilayer.
Small hydrophobic molecules like CO2 easily diffuse. Small uncharged polar molecules like H2O diffuse but with more difficulty. Large uncharged polar molecules like glucose hard to diffuse. Ions can not diffuse.
Describe diffusion and the difference between passive and active transport.
Diffusion is the movement down a gradient.
Passive uses a channel or transporter but no energy needed.
Active transport requires energy.
What are channel proteins?
Water filled pores through which solutes can diffuse.
How do transporters work?
They alternate between two conformations to mediate transport.
What are the types of transporters?
Uniport (One transported molecule), Symport (two molecules together), Antiport(one molecule on each opposite side.)
What is glut1-glucose transporter?
A passive transport uniporter that transports glucose to the cytosol.
What is the chloride bicarbonate exchanger?
A passive transport antiporter that uses Cl- and other molecules to cause exhalation and movement of CO2.
