(DSM6) Osmosis

Question 1

What is the equation for osmolarity?

DSA6 LO3

Answer 1

Osmolarity = g x [C]

Where:

g = the number of particles the solute dissociates into in solution

[C] = the molarity of the solute

Question 2

What do the terms isosmotic, hyposmotic, and hyperosmotic mean?

DSM6 LO3

Answer 2

Isosmotic:

-solution in question has the same osmolality as the solution it is being compared to

Hyposmotic:

-solution in question has a lower osmolality than the solution being compared to

Hyperosmotic:

-solution in question has a higher osmolality than the solution being compared to

Question 3

What is the reflection coefficient?

What is its range and what does its value indicate?

DSA LO3

Answer 3

Reflection coefficient represents a solutes premeability to a cell membrane.

Values range from 0 to 1 with 0 being completely permeable and 1 being not permable at all.

Question 4

What is the average osmolality of the human body and what is the normal range?

DSA6 LO3

Answer 4

Average:

-290 mOsm

Normal range:

-270-300 mOsm

Question 5

What solution of sodium chloride is isosmotic to the human body?

DSA6 LO3

Answer 5

0.9% NaCl, also refered to as normal saline

Question 6

What is the formula for estimated osmolality?

DSA6 LO4

Answer 6

Estimated osmolality = 2[Na] + [glucose]/18 + [BUN]/2.8

Question 7

What happens to a cell with normal osmolarity when exposed to a solution that is isosmotic, hyposmotic, and hyperosmotic?

DSA6 LO5

Answer 7

Isosmotic:

-cell volume unchanged

Hyposmotic:

-cell volume increases

Hyperosmotic:

-cell volume decreases

Question 8

What do isotonic, hypotonic, and hypertonic mean?

How does tonicity relate to osmolarity?

DSA6 LO6

Answer 8

Isotonic:

-will not affect the volume of an RBC

Hypotonic:

-will increase the volume of an RBC

Hypertonic:

-will decrease the volume of an RBC

Tonicity and osmolartiy are similar if the reflection coefficient of the solute is close to 1. They are disimilar if the refelction coefficient is close to 0.