L1: CELL MEMBRANE&SOLUTE MOVEMENT

Body Fluid Compartments:
70kg person (x 60% or 2/3 body weight H2O) 42L H2O:

• 2/3 inside cells
• 1/3 outside cells : 20% plasma, 80%between cells

Stable composition: functional consequnces of the [ ] gradients on nerve cells:

• IN: HIGH: K+, LOW: Na+, Cl-, Ca++ (really low)
• OUT: LOW: K+, HIGH: Na+, Cl-, Ca++ (acts as a signalling molecule-->>important how muscles contract: CARDIAC)

Cell membrane function:

boundaries cellular components within cell, cells&environment, specialised for functions they perform, selective permeability

larger/charged molecules,need proteins--small/uncharged/polar molecules,no proteins, pass easily

Na+, K+, Cl-, glu/tryptophan, urea, glycerol, H2O/alcohols

LOW permeability HIGH permeability

Passive Transport

Diffusion: flow of particles (O2, CO2) <>> areas of ↓ [ ]

dependent on 1) [ ]gradients (may require E to establish them)

2) passive process/membrane impermeable to glu: proteins r required

Simple Diffusion: membrane, Osmosis (↑ H2O/ ↓osmolatiry-->> ↑osmolairty ↓H2O): porins,

Facilitated diffusion: transporters: carriers=integral membr. proteins where solutes bind changing shape protein&solute released on the other side of membrane down gradient

diffusion rate determined<>> ethanol ↑ permeability

NET FLUX

Active transport pumps (carriers) against gradient, requires ATP

direct use (HYDROLYSIS) of ATP-->>ADP+Pi: Primary active transport: from α subunit of Na+K+ATPase 3Na+ out, 2K+ in

Secondary active transport: nutrient absorption in gut oupled to Na+ transport