fluid compartments

Question 1

define osmolarity

Answer 1

[aq] expressed as total no. solute particles per litre; e.g. NaCl (aq) dissociates into Na+ and Cl- so osmolarity is double

Question 2

osmolarity example: membrane permeable to H2O and solute

Answer 2

initial osmolarity: EC is less than IC; osmosis so water in; diffusion so solute out, reducing IC osmolarity; overall: [H2O] and [solute] IC=EC so no net change in volume

Question 3

osmolarity example: membrane permeable to H2O and solute 1, impermeable to solute 2

Answer 3

initial osmolarity: EC is less than IC; water in until osmolarity IC=EC; solute 1 out, decreasing IC osmolarity so cell swells

Question 4

osmolarity example: membrane permeable to H2O, impermeable to solute

Answer 4

initial osmolarity: EC is less than IC; osmosis so water in; cell bursts before osmolarity IC=EC

Question 5

define tonicity

Answer 5

“strength” of aq as it affects final cell volume, depending on permeability and solute composition

Question 6

define hypertonic

Answer 6

osmolarity of impermeant solutes out>in, so cell shrinks

Question 7

define hypotonic

Answer 7

osmolarity of impermeant solutes out less than in, so cell swells

Question 8

define isotonic

Answer 8

osmolarity of impermeant solutes out=in, so cell volume unchanged

Question 9

synthetic membrane: hydrophobic molecules, small uncharged polar molecules, large uncharged polar molecules and ions

Answer 9

hydrophobic molecules diffuse through, some small uncharged polar molecules diffuse through (majority don’t), almost all large uncharged polar molecules don’t diffuse through, ions don’t diffuse through

Question 10

synthetic membrane vs real cell

Answer 10

real cells have protein pumps capable of active transport (no net movement of Na+ so osmolarity IC=EC)