Membranes L3 Flashcards
What drives transmembrane transport?
Dissipating a concentration gradient and increase entropy
How can you write out the Gibbs energy change
G = Go + RTln[X]i/[X]o
For uncharged species Keq= ?
1 because conc on both sides same at equilibrium
uncharged species Go=?
0
If conc inside is lower than conc outside of an uncharged species… (in terms of delta G)
delta G negative, spontaneous, exergonic transport occurs
What is a typical membrane potential for an animal cell?
-80mV
What is Gibbs change for CHARGED solute?
G = RTln[X]i/[X]o + zFEm
How can you predict the conc gradient that forms passively at Em?
Rearrange gibbs change for delta G =0
What is the full Nernst equation and the one at 20 degrees?
Em = RT/zF.ln[X]o/[X]i Em = 58/z.log[X]o/[X]i
What is the lipid partition coefficient?
amount dissolving in test lipid/ amount dissolving in water
Draw permeability coefficient vs lipid partition coefficient
Straight line with urea then water as outliers above curve
What is Fick’s first law?
Rate of diffusion of small uncharged solute = permeability coefficient x conc gradient
How is lipid permeability of cells good?
In anearobic resp in fungi and plants ethanol leaves cell down conc gradient
What is bad about lipid permeability?
Renders cell vulnerable to pollutants from industrial activities
What characteristics do protein-mediated transport reactions show? (4)
- Highly specific
- Rate can be inhibited by structurally similar solutes
- Rate higher than could be mediated by diffusion (proteins lower activation energy)
- Shows saturation kinetics
