lec 2. intro Flashcards
composition of cell membranes
55% proteins, 42% lipids, 3% carbs
ionic composition of ICF and ECF
ICF - high in K+, PO4-, proteins
ECF - high in Na+, Ca+, HCO3-, Cl-
how molecules are transported across membranes
lipid soluble -> diffusion
small molecules and ions -> transport proteins
large molecules -> endo/exocytosis
types of transporters
carriers -> passive, move down concentration gradient
pumps -> active (require ATP)
channels -> passive, gated
Na+/K+ ATPase
type of pump ubiquitous electrogenic tetramer (2alpha, 2beta) 3 Na+ out, 2 K+ in
ubiquitous
found in lots of cells
electrogenic
charge generated
facilitated diffusion
helped across the membrane with transport carriers
saturation
carriers have maximum turnover rate (limit on how fast it can transport), and there are a maximum number of transporters in the membrane
diffusion can be secondary active, meaning…
EX. Glucose/Na+ cotransporter requires the active Na/K ATPase to set up driving force first
classifications of carriers
uniporter - carries one thing
symporter - carries two things in same directions
antiporter - carries two things in opposite direction
conductive
when ions flow through a channel and create a current
patch clamp technique
The patch pipette is sealed tightly onto the membrane. Ion channels under the patch pipette can detected by measuring current flow with a silver electrode in the salt solution in the pipette. Everything is measured with respect to a control bath.
in whole cell configuration, a patch of the membrane is gone and the cell is washed out with the solution. the total current flow across the cell membrane can be measured
KcsA
bacterial K+ channel, homologue to Kir
4 subunits with pore in the middle
structural differences between molecular channels
Kv - 4 subunits, 6 TMD = 24 total
Nav - 1 subunits, 24 TMD = 24 total
