Describe the fluid mosaic model in terms of membrane structure
- Lipid bilayer with imbedded membrane proteins
- Membrane & lipid = 50:50 (held by H bonds)
- Barrier to entry/exit of polar substances
- Proteins are regulating “gatekeepers”
How does the molecular structure of the membrane result in selective permeability
Permeability is determined by membrane proteins for transport, electrochemical gradient, permeability of molecules to membrane
How does the composition of different fluid compartments act to store energy?
Cells use ~30% of resting energy to maintain conc and electrical gradients - these gradients represent stored energy
What is the function of the cell membrane?
Provides a protective barrier that surrounds cytoplasm of cell
What are integral proteins
- Extend into or completely across membrane
- Amphipathic
What are peripheral proteins
- Proteins attached to either inner or outer surface of membrane
- Easily removed
What are integral proteins?
- Extend into or completely across membrane
- Amphipathic: nonpolar amino acids in helices in core / hydrophilic ends interact with aqueous solution
What are peripheral proteins?
- Proteins attached to either inner or outer surface of membrane
- Easily removed
What are the functions of membrane proteins? (6)
- ION CHANNELS
- TRANSPORT PROTEINS
- Receptor proteins
- Cell identity markers
- Links to other cells
- Act as enzymes
What are the functions of membrane proteins? (6)
- ION CHANNELS
- MEDIATE PROTEIN TRANSPORT
- Receptor proteins
- Cell identity markers
- Links to other cells
- Act as enzymes
What is the lipid bilayer permeable to?
- Nonpolar, uncharged molecules (O2, N2, benzene)
- Lipid-soluble molecules (fatty acids, etc.)
- Small uncharged molecules (H2O, CO2, urea, glycerol)
What is the lipid bilayer impermeable to?
- Large uncharged polar molecules
- Impermeable ions (Na, K, Cl, Ca, H)
What are the laws of diffusion?
Transport from high to low conc until equilibrium reached
- Greater the difference in conc = faster
- Larger/thicker = slower
- Smaller distance = faster
Non-charged molecules will diffuse up/down conc gradient?
Down
The movement of ions is determined by_?
Sum of electrical and chemical gradient (sometimes these are in opposite) = electrochemical gradient
What makes an electrical gradient/membrane potential?
Cells can maintain a difference in charged ions between inside and outside of membrane - due to selective permeability
