Physiology

Question 1

Osmolarity

Answer 1

Osmolarity: total [] of ALL particles in solution.
Osmolarity=ΦnC
N-# of particles
C-concentration
Φ-osmotic coefficient (usually 1)

Question 2

Aquaporins

Answer 2

Integral proteins that functional as H20 channel.

Increase net flux of water across membrane.

Question 3

Movement of water is driven by…

Answer 3

Solute.
Movement of H20 is driven by movement of solute.
H20 moves towards area of high solute [] until equilibrium.

Question 4

Driving force for water movement (2)

Answer 4

1. Osmotic-water moves toward high [solute]

2. Hydrostatic driving forces-gravity on fluid across capillary endothelial cells.

Question 5

Van’t Hoff Equation

Answer 5

To calculate osmotic pressure of a sol’n.
π=nRTC

π-osmotic pressure
n-# of particles produced by a molecule
R-gas constant
T-temperature
C-concentration

Question 6

Water flux

Answer 6

A diff in osmotic pressure between two compartments can provide a driving force for water to flow.

Question 7

Osmosis

Answer 7

Flow of water caused by diff in [solute].

Driving force is a diff in osmotic pressure caused by presence of solute.

Depends on permeability of the membrane.

Question 8

Reflection coefficient

Answer 8

σ=1 : solute totally impermeable. Exerts osmotic pressure for water flow.

σ=0 : solute is totally permeable. No osmotic pressure.

Question 9

Tonicity

Answer 9

Tonicity: [] of only the osmotically ACTIVE particles

Only impermeable particles contribute and cause change in cell volume.

*Tonicity of a solution describes the volume change of a cell at equilibrium.

Question 10

Penetrating solutes VS Non-penetrating solutes (tonicity)

Answer 10

Penetrating solutes= can enter cell.
ie Glucose and urea
Solutes will distribute to equilibrium.

Non-penetrating solutes=cannot enter cell.
ie NaCl, KCl, sucrose
*Determines tonicity

Question 11

Osmolarity-
Isoosmotic

Hyperosmotic

Hypoosmotic

Answer 11

Isoosmotic: total osmotic pressure of sol’n=that of cell

Hyperosmotic: osmotic pressure of sol’n is > that of cell

Hypoosmotic: osmotic pressure of the sol’n

Question 12

Tonicity-
Isotonic
Hypertonic
Hypotonic

Answer 12

Isotonic: equilibrium. Non-penetrating solute [] on either side of the membrane is the same.

Hypertonic: cell shrink. Non-penetrating solute [] on outside > than inside cell

Hypotonic: cell swell. Non-penetrating solute [] is lower outside the cell.

Question 13

Typical value of plasma osmolarity

Answer 13

300 mOsm