Physiology Ex 1 - Osmosis

Question 1

Define Molarity

Answer 1

Molar concentration, amount concentration or substance concentration. Based on specific volume of the solution.

Question 2

Define molality

Answer 2

A measure of the concentration of a solute in a solution in terms of amount of substance in a specified amount of mass of the solvent. Moles solute / mass of solvent.

Question 3

What is the normal serum osmolality?

Answer 3

282 - 303 mOsm/kg

Question 4

Which is isosmotic with a cell?

a) 100 mM glucose solution
b) 100 mM sodium chloride solution
c) 100 mM calcium chloride solution

Answer 4

100 mM calcium chloride solution

300 mOsm (blood plasma is same)

Question 5

What is the osmolarity of a 100 mM glucose solution?

Answer 5

100 milliosmoles

Question 6

What is the osmolarity of a 100 mM sodium chloride solution?

Answer 6

200 milliosmoles

100 from Na+ and 100 from Cl-

Question 7

What is the osmolarity of a 100 mM calcium chloride solution?

Answer 7

300 milliosmoles

100 from Ca

200 from Cl₂ (100 x 2)

Question 8

What is the osmolarity of blood?

Answer 8

300 milliosmoles

Question 9

Osmolarity is related to the number of molecules in a solution?

T/F?

Answer 9

True

Question 10

How many milliosmoles in Glucose (formula weight 180.0)?

Answer 10

100

Formula weight = 180

18.0 g glucose/L = 100 mM glucose = 100 mOsm

Question 11

How many milliosmoles in NaCl (formula weight 58.5)?

Answer 11

200 mOsm

Formula weight 58.5 = 5.85 g NaCl/L = 100 mM NaCl

100 mEq/L Na+ and 100 mEq/L Cl- = 200 mOsm total

Question 12

What does vant Hoff’s Law refer to?

Answer 12

Osmotic pressure

Osmotic pressure = RTnc

where:

R = ideal gas constant

T = absolute temp (K)

n = # of particles formed by dissociation of a solute molecule

c = molar concentration of solute

Question 13

What is the formula for Effective osmotic pressure?

Answer 13

πeff = σRTnc

where:

σ = membrane permeability coefficient (0 = completely permeable, zero osmotic pressure because zero times anything = zero; 1 = impermeable)

Question 14

What type of membrane do you need for osmotic pressure?

Answer 14

A semi-permeable membrane. You have to take into account how permeable the membrane is.

Question 15

What is equilibrium potential?

Answer 15

Where the electrochemical forces acting on an individual ion balance out and the number of ions entering the cell equals the number exiting the cell

Na+ = +60 mV

K+ = -90 mV

Cl- = -70 mV

Question 16

What is the Nernst Equation and what does it describe?

Answer 16

It describes the relationship of the equilibrium potential of an ion and the ion concentration gradient.

E_ion = RT/ZF x ln([ion]₀ / [ion]₁)

Where:

R = gas constant

T = temp

Z = valence

F = Faraday’s constant

Question 17

What does the Hodgink-Katz-Goldman Equation describe?

Answer 17

the relationship of the membrane potential, the permeability of ions through the membrane, and the ion concentration gradients

Question 18

What is the resting membrane potential of a cardiac myocyte?

Answer 18

-90 mV

Question 19

What can diffuse through membranes?

Answer 19

Small, non-polar molecules/drugs (lipid soluble)

Question 20

What cannot diffuse through a membrane?

Answer 20

Polar (ionized, water soluble) molecules/drugs cannot diffuse through membranes unless there is a carrier

Question 21

The amount of ionized drug is affected by?

Answer 21

pH

Question 22

The pKa of a drug is the pH at which?

Answer 22

50% is ionized