Lecture 9 Flashcards
Differentiate between the terms osmole, osmolarity, osmolality and tonicity. List the typical value and normal range for plasma osmolality.
Osmole: conc of solutes in fluid
Osmolarity: total conc of ALL particles in solution
Osmolality:
Tonicity: total conc of ONLY OSMOTICALLY ACTIVE particles in solution; volume change in equilibrium
Plasma osmolality: 300 mOsm
Describe the role of water channels (aquaporins) in facilitating the movement of water across biological membranes.
Aquaporins allow water to transport passively (simple diffusion) through the membrane. Shows linear kinetics
Water flows from low solute to high solute (wants to dilute)
Understand how regulation of the concentrations of K+, Cl-, and other Na+ solutes influence cell volume.
Reflection coefficient of 1: solutes not permeable = water flux; water conc gradient
Reflection coefficient of 0: solutes permeable = no flux; no water conc gradient
Non penetrating:
KCL
NaCl
Penetrating:
glucose
urea
Understand that movement of water is driven by solute movement.
Water will move from low solute to high solute
When is a solution:
iso-osmotic
hypo-osmotic
hyper-osmotic
Iso-osmotic: total osmotic pressure of solution is equal to the cell
Hypo-osmotic: solution has less osmotic pressure than the cell
Hyper-osmotic: solution has great osmotic greater than the cell
When is a solution
iso-tonic
hypo-tonic
hyper-tonic
Isotonic: at equilibrium it causes the cell to neither swell or shrink
Hypotonic: causes cell to swell
- Non-penetrating solute concentration on the outside of the cell is lower than on the
inside
Hypertonic: causes cell to shrink
- Non-penetrating solute concentration on the outside of the cell is higher than on the
inside
Rules about osmotic solutions
- All hypo-osmotic solutions are hypotonic
- Iso-osmotic solutions can be hypo or isotonic
- Hyper-osmotic solutions can be hypo-, iso-, or hyper-tonic depending on the ratio of non-penetrating solutes
between the 2 compartments
