Cell Membranes and Polarity Flashcards
Describe lipid bilayer
Hydrophilic cytoplasmic side, hydrophobic interior, hydrophillic ECM side
Lipid-protein interactions are:
Noncovalent. Allows for fluidity amongst them
Miscelle is made when….What is its double FA counterpart called?
- Put strands of SINGLE FA chains in polar environment
2. Liposome. Becomes a sphere. Hydrophillic exterior, hydrophobic interior.
What’s a phosphoglyceride?
Glycerol backbone, 2 FA’s attached (one is not saturated, so it’s kinked to increase fluidity), and phosphate group (- charge) = polar head.
Phosphatidyl serine:
Has net (-). Kind of phosphoglyceride.
Phosphatidyl-ethanolamine and Phosphatidyl Choline
phosphoglycerides, both have neutral charge
Sphingomyelin:
derived from sphingosine, has 2FA’s and AMINE group
Cholesterol = ?
Sterol, POLAR because it HAS an OH. Located at membrane surface. Rigid ring structure stiffens some parts of membrane, but aliphatic components keep the FA’s apart.
Glycolipids = ?
has 2FA’s and sugar (charged or uncharged) intsead of phosphate (looks like sphingosine)
Give description of composition of lipid membrane:
Cholesterol + sphingomylin = less internal part of plasma membrane
Phosphatidyl ethanolamine + phosphatidyl choline = internal part of membrane
Glycolipid: not much lie in internal membrane
Protein distribution = asymmetric between the two sides of the layer.
Bacteria have cholesterol (T/F)
F: Bacteria (and plants) have a cell wall, which has no cholesterol.
How often does the membrane move?
Lateral diffusion (left and right movement) as well as rotations = quite common. However, very little flipping
Describe relative locations of different proteins in the layer.
Phosphotidyl serine: alwasy internal in order to participate in kinase receptor mech
Phosphatidyl choline, sphingolipids, and glycolipids = ECM side.
Cholesterol = both sides
What is a lipid raft?
NON-random lipid distribution in inner or outer membrane. Cholesterol + sphingomyelin. Thicker FA chain consistency.
What can be used for signaling purposes?
phosphatidylinositol (PiP2 cleaved to iP3)
What is an integral membrane protein?
Permanent in membrane. Stretch of hydrophobic AA. In case of alpha helix, 100% internal. In case of barrel beta sheet, hydrophobic exterior with hydrophobic interior.
Peripheral membrane proteins = ?
Proteins attached covalently but can be removed. Can also be used for signaling.
Name some protein membrane attachments
Amide linkages and thioester linkages with cystein. Both are reversible.
So, what crosses the membrane?
Hydrophobic molecules (O2, CO2, N2, steroids). All else, small or large will not pass.
Describe a channel transporter
Transports ions, not very specific, flow = down concentration gradient. no energy needed. FAST transfer.
Tetrotodoxin = Na+ channel blocker.
Lidocaine = anesthetic, treats tachy heart
K+ blockers: treats arrhythmias.
Nicotinic acetylcholine receptor: Na+/K+ channel at neuromuscular jxn.
Curere: antagonist for Ach.
Describe a carrier
Binds molecule on one side, switch conformation (physical change, not chemical), release solute on other side. No energy needed. Medium speed.
Uniport: 1 molecule transport. Ex: Glut1 (glucose transporter)
Synport: transports 2 molecules at once, one of which is going against its concentration gradient. FASTER than DIFFUSION. Ex: Na+-Glucose, where glucose is going against. Overcome Na+ cell saturation by using Na/K pumps to pump out excess Na+ from the cell.
Describe a pump transporter
Transfer AGAINST gradient. Need ATP, Slowest.
P-Type: cleaves ATP to phosphorylate itself and change conformation. Pumps ions.
Ex: Pushes Ca2+ into SER for muscle contraction.
EX: Na+/K+ pump, which shoves both molecules against concentration gradient (Na_ exits the cell, K+ enters)
ABC: ATP Binding Cassette: uses 2 atpases, transports small molecules. Both binding sites need atp. Sends molecules outside cell.
Ex: ABC transporters (MOLECULES, not IONS, except in case of CFTR) helps with tumor’s drug resistance. once it multiplies, no drug can help.
What determines rate of carrier transport?
Km, and flip rate (Vmax)
