# Lecture 4 Flashcards

1
Q

Explain water transport?

A

Water transport is completely passive
No water pumps exist
Water passes into cell with the use of aquaporins
simple diffusion = no saturation but has linear kinetics

2
Q

What is the definition of concentration?

A

the mass of a substance in a known volume

3
Q

How does water move?

A

Water can move across membranes and it is going to do so by going down its concentration gradient.

Water will move in the direction of high solute concentration until equilibrium.

4
Q

What are the two driving forces of water movement?

A
1. Osmotic force- water wanting to move to an area of high solute
2. Hydrostatic driving forces- the effect of gravity on the fluid across capillary endothelial cells
5
Q

What is the van’t Hoff equation?

A

This equation is used to calculate the osmotic pressure of a solution.

pie = nRTC

6
Q

What is water flux and what is the equation?

A

A difference in osmotic pressure between two compartments that leads to water movement

Jv = Kh A [RC (Ci - Co)]

7
Q

Describe osmosis?

A

The flow of water between two solutions that are separated by a semi-permeable membrane

water will flow from low osmolarity to high osmolarity

8
Q

What does the reflection coefficient (RC) represent?

A

it is a number between 0 and 1

0 indicates that the solute is totally permeable and exerts NO osmotic pressure differences

1 indicates that the solute is totally impermeable and therefore exerts an osmotic pressure on water flow.

9
Q

How is osmolarity different from tonicity?

A

Osmolarity is the total concentration of all particles in the solution

on the other hand, tonicity is only the concentration of active particles.

10
Q

What kind of particles contribute to tonicity?

A

ONLY impermeable particles will contribute to the tonicity and cause changes in cell volume

11
Q

What describes the volume change of a cell at equilibrium?

A

tonicity

Net water movement will be into the compartment that has the higher concentration of non-penetrating solutes.

12
Q

What kinds of solutes can penetrate the membrane?

A

glucose, urea, and glycerol

solutes will distribute to equilibrium

13
Q

What kinds of solutes cannot penetrate the membrane ?

A

sucrose, NaCl, KCl

water will move in to dilute solutes

these solutes determine tonicity!!!

14
Q

Explain iso-osmotic, hyperosmotic, and hypo-osmotic?

A

iso-osmotic is when the osmotic pressure is equal in both the solution and cell

hyperosmotic is when the solution has a greater osmotic pressure than the cell

hypo-osmotic pressure is when the solution has a less osmotic pressure compared to the cell

15
Q

Explain isotonic, hypertonic, and hypotonic?

A

isotonic is when the cell is at equilibrium and will not shrink or swell

hypertonic is when the cell shrinks because the non-penetrating solute concentration on the outside of the cell is greater than inside the cell

hypotonic is when the cell swells because the non-penetrating solute concentration on the outside of the cell is less than inside the cell

16
Q

150 mM of NaCl + 50 mM of glycerol

osmolarity? tonicity? water movement?

A

150 x 2 = 300 + 50 x 1 = 350

350 means hyperosmotic because normal is between 290 and 300

NaCl is cannot cross and glycerol can
the tonicity is isotonic because the NaCl osomolarity is 300 (normal)

The cell will, at first, shrink because water leaves cell but the glycerol will equilibrate and attract water (cell return to normal size)

17
Q

170 mM NaCl + 10mM glycerol

osmolarity? tonicity? water movement?

A

170 x 2 = 340 + 10 x 1 = 350

Hyperosmotic!

340 (NaCl) to high! Thus hypertonic

Water will leave the cell. glycerol affect on equilibrium is minimal!

18
Q

75 NaCl + 10 mM glycerol

osmolarity? tonicity? water movement?

A

75 x 2 =150 + 10 x 1 =160

hypo-osmotic!!!

150 (NaCl) = hypotonic!

Water will enter cell

19
Q

All hypo-osmotic solutions are?

A

hypotonic

20
Q

iso-osmotic solutions can be?

A

hypotonic or isotonic

21
Q

hyperosmotic solutions can be?

A

hypo, hyper, or isotonic

22
Q

5 percent dextrose in water

A

isotonic, but physiologically hypotonic

23
Q

10 percent dextrose in water

A

hypertonic

24
Q

0.45 percent saline

A

hypotonic

25
Q

0.9 percent saline

A

isotonic

26
Q

3.0 percent saline

A

hypertonic

27
Q

why use 5 percent dextrose in water?

A

Used to replace water loss and treat hypernatremia

170 cal and no electrolytes

28
Q

why use 10 percent dextrose in water?

A

provides free water

340 cal and no electrolytes

29
Q

why use 0.45 percent saline?

A

provides free water in addition to Na and Cl
used to replace hypotonic fluid loss

no cals

30
Q

why use 0.90 percent saline?

A

Used to expand intravascular volume and replace extracellular fluid loss

does not provide free water

may cause intravascular overload and hyperchloremic acidosis

31
Q

why use 3.0 percent saline?

A

Used to treat symptoms of hyponatremia

must be given slowly and with caution because it could lead to intravascular fluid overload and pulmonary edema