Diffusion and Membrane Transport

Question 1

What is Diffusion?

Answer 1

Movement of substances from an are of high to low concentration

Question 2

What is flow?

Answer 2

The amount of substance moving per time (mol/sec)

Question 3

What is flux (j) ?

Answer 3

The rate of flow per unit of area (mol/sec/cm^2)

Flow/Area

Question 4

Flux depends on the _______________.

Answer 4

Concentration gradient

Question 5

What factors affect the rate of diffusion of a substance?

Answer 5

Directly Proportional:

• Concentration
• Surface Area of the membrane
• Lipid Solubility

Inversely Proportional:

• Molecular Weight
• Distance/Thickness

Question 6

Why do particles take longer to diffuse across large distances?

Answer 6

Because individual particles are always randomly changing directions

Question 7

Flow = _____ x ______

Answer 7

Flux x Area, j x A

Question 8

The displacement of particles is about……………..

Answer 8

s= (2Dt)^1/2
Where 
s=displacement
D=diffusion constant
t= time

Question 9

Permeability, P, consists of ___________, __________________ and ____________

Answer 9

Thickness
Diffusion Coefficient
Solubility

Question 10

Flux = __ x ________

Answer 10

P x ( [x1] - [x2] )
P = Permeability
[x1] and [x2] = concentrations

Question 11

Flux = __ x _____/____

Answer 11

Flux = D x ( [x1] - [x2] ) / s 
D = diffusion constant
s = displacement

Question 12

The body is made of about __% water

Answer 12

55%

Question 13

1/3 of the body’s water is ______________

Answer 13

Extracellular

Question 14

2/3 of the body’s water is ______________

Answer 14

Intracellular

Question 15

Na and Cl are generally __________ the cell

Answer 15

Outside

Question 16

K is generally _________ the cell

Answer 16

Inside

Question 17

Endo/Exocytosis are examples of _______ transport and and can move substances ________________________.

Answer 17

Active

Against their concentration gradient

Question 18

Briefly describe vesicle formation:

Answer 18

1. Substance binds to a receptor
2. Binding triggers invagination into a Clathrin coated pit
3. Actin and Myosin pinch off the vesicle

Question 19

What is the difference between a pore and a channel?

Answer 19

Pores are generally always open whereas a channel is something that can be opened or closed

Question 20

What are the 3 classes of gated channels?

Answer 20

Voltage - open in response to voltage change
Ligand - opens in response to a chemical bonding
Mechanical/Stretch - respond to movement

Question 21

What are gap junctions?

Answer 21

Pores between cells that allow small polar molecules to diffuse directly between the cells

Question 22

How are gap junctions formed?

Answer 22

Transmembrane protein called Connexon binds with a Connexon in an adjacent cell forming a tube

Question 23

How can we change permeability?

Answer 23

Opening and Closing gated channels

Question 24

What is osmotic pressure?

Answer 24

The pressure needed to stop osmosis from happening. It’s abbreviated as π

Question 25

What’s the formula for osmotic pressure?

Answer 25

π = RT * ΔC
ΔC = change in concentration of water (Osmolarity)
R = Universal Gas Equation
T = Temperature in Kelvin (+270.15)

Question 26

1mOsmol is equivalent to _____ mmHg

Answer 26

19.3mmHg

Question 27

If you put a cell in a Hypotonic Solution it will _______

Answer 27

Crenate

Question 28

If you put a cell in a Hypertonic Solution it will _______

Answer 28

Expand/Burst

Question 29

What is a Hypotonic Solution?

Answer 29

A solution that has a low osmotic pressure than a reference solution

Question 30

What is a Hypertonic Solution?

Answer 30

A solution that has a high osmotic pressure than a reference solution

Question 31

Hyposmotic cells _______

Answer 31

Swell

Question 32

Hyperosmotic cells _______

Answer 32

Crenate