Lecture 16 Flashcards
Membrane structure is held together by:
Hydrogen bonds
Lipids rarely flip flop between membrane leaflets therefore the lipid composition of the leaflets can be asymmetric. T/F?
True
How does lipid tail length affect the fluidity of the membrane?
The longer the tail, the less fluid the membrane
How does the number of double bonds affect the fluidity of the membrane?
More double bonds increases fluidity
How does the amount of cholesterol affect membrane fluidity?
More cholesterol decreases fluidity
Integral proteins are:
Proteins that extend into or completely across cell membrane (transmembrane)
Peripheral proteins:
Attached to either the inner or outer surface of cell membrane and are easily removed from it.
Integral proteins polarity:
amphipathic
Functions of membrane proteins (x6)
Receptor, cell identity markers, linkers, enzymes, ion channels, transporters
Channel proteins:
Allow specific substances to move through water filled pore.
Transport proteins:
Transport specific substances across membrane by changing shpa.e Amino acids enter body cells via transporters.
Selective permeability of membrane: (x4)
Permeable to nonpolar, uncharged molecules. Permeable to lipid soluble molecules. Permeable to small uncharged polar molecules.
Impermeability of membrane:
-Impermeable to large uncharged polar molecules.
Impermeable to ions.
The greater the difference in concentration between the 2 sides of the membrane, the ______ the rate of diffusion.
faster
The higher the temperature, the _____ the rate of diffusion
faster
An increase in surface area, _______ the rate of diffusion
increases
Increasing diffusion distance, ___ rate of diffusion
slows
What is 1 outcome of a cell increasing the membrane area available for diffusion?
increases diffusion
How does membrane thickness affect diffusion
Slows
Diffusion is very fast over ___ distances
small
Movement of ions will be influenced by the _____ _____
electrical gradient
What enables a difference in concentration gradient across the membrane to be established?
The selective permeability. The difference in charged ions between the inside and outside of membrane establishing an electrical gradient.
Osmosis:
diffusion of water across membranes.
Osmosis only occurs when:
Only occurs if membrane is permeable to water but not to certain solutes.
Define Pw, Pd, and Pf.
Pw = membrane permeability to water. Pd - permeability of lipid bilayer. Pf- permeability of water channel/aquaporins.
Pw eq
Pw = Pd + Pf. Pf > Pd
Water channels are also called
aquaporins
Properties of Pd
Small, mercury insensitive, temp dependent
Properties of Pf
Large, mercury sensitive, temperature independent
Osmotic pressure is:
the pressure applied by a solution to prevent the inward flow of water across a semi-permeable membrane
If the solution has the same osmolarity it is:
isosmotic
If the solution has a lower osmolarity it is
hyposmotic
If the solution has a higher osmolarity it is:
hyperosmotic
What kind of solution causes cell swelling and lysis?
Hypotonic
What kind of solution causes cell shrinkage (crenation)?
Hypertonic
