BRS Chapter 1

Question 1

What is the diffusion equation?

Answer 1

J = -PA (C1 - C2)

J = Flux (mmol/sec)
P = Permeability (cm/sec)
A = Area (cm^2)
C1, C2 = Concentrations (mmol/L)

Question 2

What does the minus (-) sign in the diffusion indicate?

Answer 2

It tells you the direction of low (from high concentration to low concentration)

Question 3

Explain the variable, P, in the diffusion equation.

Answer 3

P = permeability

Tells you how easy it is for a solute to diffuse through a membrane

Question 4

Which is more rapid? Simple diffusion or facilitated diffusion?

Answer 4

Facilitated diffusion, because there are attractions that occur to “facilitate” it across the membrane faster.

Question 5

What are the characteristics that distinguish carrier-mediated transport?

Answer 5

1. Stereospecifity (D-glucose vs. L-glucose)
2. Saturation (Tm, Vmax) - the transport rate increases as the concentration of the solute increases, until all of the channels become occupied with the solute.
3. Competition - structurally related solutes compete for a limited number of channels

Question 6

What is the ATPase that pushes Ca2+ against its concentration gradient into the SER called?

Answer 6

SERCA (Ca2+-ATPase)

Question 7

What is the equation for osmolarity?

Answer 7

Osmolarity = gC

g = number of particles in solution (ex. 2 for NaCl)
C = concentration (mol/L)

Question 8

What is another name for the equation in calculating osmotic pressure?

Answer 8

van’t Hoff’s Law

Question 9

What is the equation for osmotic pressure?

Answer 9

π = iMRT

i = number of dissociated particles
M = concentration of solute
R = 0.0821 L-atm/mol-K
T = temperature in Kelvin

Question 10

When does the osmotic pressure increase?

Answer 10

When the solute concentration increases

Question 11

What does the conductance of a channel depend on?

Answer 11

The probability that the channel will be in the open state

Question 12

Write the Nernst Equation:

Answer 12

Eion = -60 mV / z * log( [ion in] / [ion out] )

E = equilibrium potential (mV)
z = charge on the ion (+1 for Na+, +2 for Ca2+, -1 for Cl-)
ion in/out = concentrations of the ion

Question 13

Why is the resting membrane potential at -70mV?

Answer 13

Because there is a high resting conductance from open K+ channels and 0 conductance from closed Na+ channels.

Question 14

List 2 toxins that block voltage-sensitive Na+ channels.

Answer 14

Tetrodotoxin (TTX) and Lidocaine

Question 15

What does increase the diameter of an axon do to the resistance to the propagated electrical signal?

Answer 15

It decreases the internal resistance