Plasma membrane, fluid-mosaic model, lipid rafts, channels, pumps, active/passive transport.
Cell Membrane And Transport
Plasma membrane
Self-assembled phospholipid bilayer + integral/peripheral proteins separating cell from environment. ~5 nm thick; asymmetric leaflet…
Fluid-mosaic model (Singer-Nicolson)
Singer-Nicolson 1972: plasma membrane is a 2D fluid of laterally-diffusing lipids with proteins embedded like icebergs. Refined by…
Lipid raft
Nanoscale (10-200 nm) membrane domain enriched in sphingolipids + cholesterol + GPI-anchored proteins. Liquid-ordered phase; platforms for…
Ion channel
Integral membrane protein forming a selective aqueous pore for ion diffusion (10⁶-10⁸ ions/s). Gated by voltage, ligand, mechanical force,…
Voltage-gated ion channel
Channel that opens/closes in response to membrane voltage via charged voltage-sensor (S4 segment). Na+, K+, Ca²+, Cl− variants drive action…
Active transport
Transport against electrochemical gradient coupled to energy source. Primary (direct ATP use: P-type ATPases, ABC transporters) vs…
Na+/K+ ATPase
P-type pump exporting 3 Na+ / importing 2 K+ per ATP hydrolysed. Establishes resting membrane potential and Na+ gradient driving secondary…
Endocytosis
Membrane invagination internalising extracellular material. Clathrin-mediated (receptor-mediated, LDL, transferrin), caveolin-mediated,…
Facilitated diffusion
Passive transport via channel or carrier protein down concentration gradient. GLUT family (glucose), aquaporins (water). Saturation…
Membrane potential
Voltage across plasma membrane set by ion gradients + selective permeability. Nernst: E = (RT/zF) ln([out]/[in]); Goldman-Hodgkin-Katz for…
Goldman-Hodgkin-Katz multi-ion membrane equation
GHK voltage equation V_m = (RT/F) ln[(P_K[K]_o + P_Na[Na]_o + P_Cl[Cl]_i)/(P_K[K]_i + P_Na[Na]_i + P_Cl[Cl]_o)] is the steady-state of the…
Carrier-mediated saturable transport
Facilitated transport via membrane carriers obeys Michaelis-Menten-type kinetics J = J_max [S]/(K_m+[S]); saturation distinguishes…
Fluid mosaic model (1972)
Singer-Nicolson 1972 fluid-mosaic: lipid-bilayer with embedded integral + peripheral proteins; lateral diffusion ~10^-8 cm^2/s; lipid rafts…
Na+/K+-ATPase (Skou 1957)
J C Skou 1957 (Nobel 1997): 3 Na+ out + 2 K+ in per ATP; ouabain inhibitor; cardiotonic glycoside target; basis of resting…
Aquaporin (Agre 2003)
Agre 2003 (Nobel 2003) AQP1 6-pass channel; selectively permeable to H2O via NPA motif single-file; AQP2 V2-vasopressin renal; AQP4 brain…
Patch-clamp (Neher-Sakmann 1976)
Neher-Sakmann 1976 (Nobel 1991): giga-seal patch-clamp records pA single-channel currents; voltage-clamp + current-clamp + cell-attached +…
GLUT family (Mueckler 1985)
Mueckler 1985 GLUT1 cloning: 12-TM facilitative-diffusion sugar carriers; GLUT1 erythrocyte/brain, GLUT2 liver/pancreas, GLUT3 neuron,…
Clathrin endocytosis (Pearse 1976)
Pearse 1976 clathrin triskelion + Schmid-Smythe clathrin-mediated-endocytosis: AP2-adaptor + dynamin-GTPase scission; receptor-mediated…
Membrane potential (Bernstein 1902)
J Bernstein 1902 membrane-potential theory; foundational; modern Goldman-Hodgkin-Katz extension; nernst potential per ion.
MDR (Juliano-Ling 1976)
Juliano-Ling 1976 P-glycoprotein multidrug-resistance; modern ABC-transporter superfamily + cancer-chemoresistance.
SNARE (Rothman 2013)
J Rothman + R Schekman + T Sudhof Nobel 2013 SNARE-mediated exocytosis; modern Munc18 + Munc13 priming.
Ca2+ signaling (Clapham 2007)
D Clapham 2007 'Calcium signaling' Cell review; modern store-operated entry + IP3R + RyR.
Gap junctions (Revel 1967)
Revel-Karnovsky 1967 + Loewenstein 1968 gap-junctions; modern connexin-26 + 43 deafness + cardiac-arrhythmia.
BAR domains (McMahon 2005)
McMahon 2005 + Frost 2008 BAR-domain membrane-curvature sensors; modern endocytosis + filopodia + dynamin.