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50 Cards in this Set
- Front
- Back
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What is osmolarity?
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The concentration of osmotically active particles in a solution.
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What type of property is osmolarity?
How is it measured? |
Colligative - msrd via freezing point depression
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What is the formula for calculating osmolarity?
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Osmolarity = gC
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What is g? What is C?
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g = # of particles in solution
C = concentration |
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What are 2 solutions with the same calculated osmolarity called?
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Isosmotic
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What is the osmolarity of a 1 M NaCl solution?
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2 Osm/L
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What is osmosis?
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Flow of water across a semipermeable membrane from one compartment with low [solute] to high
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Why does water go from low solute conc to high?
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Because water wants to go where the salt is.
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What is the force exerted by presence of a solute in one compartment that is separated from another by a semipermeable membrane called?
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Osmotic pressure (pi)
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What will happen to the amount of water in each compartment as a result of osmotic pressure?
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-The compartment with solute will get higher amt of water
-The compartment with NO solute will have reduced water volume |
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What law describes osmotic pressure?
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Van't Hoff
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What is Van't Hoff's law?
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pi = gCRT
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What is g?
What is C? What is R? What is T? |
g = # of particles in solution
C = concentration R = gas constant .0821 T = absolute temp |
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What are 2 solutions with the same calculated osmotic pressure called?
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Isotonic
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In what direction will water flow when one compartment is hypertonic and one is hypotonic?
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From hypotonic to hypertonic
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What is colloid osmotic pressure? What is another name for it?
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The osmotic pressure created by plasma proteins; aka oncotic pressure.
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What is the Reflection coefficient?
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A number between 0 and 1 that describes the ease with which a solute permeates the membrane.
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Regarding the Reflection coefficient, what does 1 mean? What does 0 mean?
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1 = solute is IMPERMEABLE
0 = solute is COMPLETELY permeable |
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What is a specific example of a molecule with a reflection coefficient of nearly 1?
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Albumin
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What is a molecule with a reflection coefficient of almost zero?
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Urea
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So does Urea create osmotic pressure?
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No; it is an ineffective osmole.
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What is important to remember when giving IV's?
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Calculate the EFFECTIVE osmotic pressure
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How is EFFECTIVE osmotic pressure calculated?
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-Pi x Reflection coefficient
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WHY do we care so much about membranes, transport, and ion concentration gradients?
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Because they set up electrical potential differences that allow for ACTION POTENTIALS!!!
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What molecules allow for ion passage into/out of cells?
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Ion channels!
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What are ion channels again?
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Integral membrane proteins that span the entire membrane and are anchored to hydrophobic residues
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What allows for ion channels to effectively set up membrane potential differences?
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Their SELECTIVITY
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What 2 factors determine the selectivity of an ion channel?
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-Size of channel
-Charge distribution lining the channel |
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What will a small channel lined with negatively charged groups be selective for?
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Small cations
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What will a small channel lined with positively charged groups be selective for?
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Small anions
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Why aren't action potentials always occurring in cells?
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Because ion channels can be open or closed.
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What determines the conductance of an ion channel?
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The probability that the ion channel is open or closed.
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What results when an ion channel has a high probability of being open?
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High permeability of the ion for which that ion channel is selective.
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What controls the opening and closing of ion channels?
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Gates
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What are 2 types of gated channels?
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-Voltage gated channels
-Ligand gated channels |
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What opens or closes voltage gated channels?
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Changes in the membrane potential
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What opens the activation gate of the sodium channel in a nerve?
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Depolarization (increased positivity of the membrane potential)
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When during an action potential is the sodium channel activation gate open?
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During the AP upstroke
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What closes the inactivation gate of the Sodium channel?
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Depolarization does this too!
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How can the inactivation gate be shut AND the activation gate opened, both by depolarization?
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Well the inactivation gate is shut SLOWER so there is time for the sodium influx during the AP upstroke.
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When during the AP does the inactivation gate of the Sodium channels close?
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During the Repolarization phase
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What are 3 examples of 'ligands' that close/open ligand gated channels?
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-Neurotransmitters
-Hormones -2nd messengers |
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What is an example of a ligand gated ion channel?
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Nicotinic ACh receptors on Na/K channels at motor end plates
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What is a Diffusion potential?
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A potential difference generated by an ionic concentration gradient across a membrane.
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What MUST be able to occur in order for a diffusion potential to be established?
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The membrane must be permeable to the ion
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What determines the size of a diffusion potential?
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The size of the ionic concentration gradient
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What determines the SIGN of a diffusion potential?
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Whether the diffusing ion is pos or negatively charged.
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Do diffusing ions that set up diffusion potentials change the intra/extracellular concentrations of the particular ion?
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NO - the diffusion consists of very few ions actually crossing the membrane.
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What is an EQUILIBRIUM potential?
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The diffusion potential that exactly balances the tendency for diffusion caused by a concentration gradient.
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What happens when the chemical and electrical forces acting on an ion are EQUAL and OPPOSITE?
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The cell is at electrochemical equilibrium for that ion; no net diffusion occurs.
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