Diffusion and Membrane Transport Flashcards
What is Diffusion?
Movement of substances from an are of high to low concentration
What is flow?
The amount of substance moving per time (mol/sec)
What is flux (j) ?
The rate of flow per unit of area (mol/sec/cm^2)
Flow/Area
Flux depends on the _______________.
Concentration gradient
What factors affect the rate of diffusion of a substance?
Directly Proportional:
- Concentration
- Surface Area of the membrane
- Lipid Solubility
Inversely Proportional:
- Molecular Weight
- Distance/Thickness
Why do particles take longer to diffuse across large distances?
Because individual particles are always randomly changing directions
Flow = _____ x ______
Flux x Area, j x A
The displacement of particles is about……………..
s= (2Dt)^1/2 Where s=displacement D=diffusion constant t= time
Permeability, P, consists of ___________, __________________ and ____________
Thickness
Diffusion Coefficient
Solubility
Flux = __ x ________
P x ( [x1] - [x2] ) P = Permeability [x1] and [x2] = concentrations
Flux = __ x _____/____
Flux = D x ( [x1] - [x2] ) / s D = diffusion constant s = displacement
The body is made of about __% water
55%
1/3 of the body’s water is ______________
Extracellular
2/3 of the body’s water is ______________
Intracellular
Na and Cl are generally __________ the cell
Outside
K is generally _________ the cell
Inside
Endo/Exocytosis are examples of _______ transport and and can move substances ________________________.
Active
Against their concentration gradient
Briefly describe vesicle formation:
- Substance binds to a receptor
- Binding triggers invagination into a Clathrin coated pit
- Actin and Myosin pinch off the vesicle
What is the difference between a pore and a channel?
Pores are generally always open whereas a channel is something that can be opened or closed
What are the 3 classes of gated channels?
Voltage - open in response to voltage change
Ligand - opens in response to a chemical bonding
Mechanical/Stretch - respond to movement
What are gap junctions?
Pores between cells that allow small polar molecules to diffuse directly between the cells
How are gap junctions formed?
Transmembrane protein called Connexon binds with a Connexon in an adjacent cell forming a tube
How can we change permeability?
Opening and Closing gated channels
What is osmotic pressure?
The pressure needed to stop osmosis from happening. It’s abbreviated as π
What’s the formula for osmotic pressure?
π = RT * ΔC ΔC = change in concentration of water (Osmolarity) R = Universal Gas Equation T = Temperature in Kelvin (+270.15)
1mOsmol is equivalent to _____ mmHg
19.3mmHg
If you put a cell in a Hypotonic Solution it will _______
Crenate
If you put a cell in a Hypertonic Solution it will _______
Expand/Burst
What is a Hypotonic Solution?
A solution that has a low osmotic pressure than a reference solution
What is a Hypertonic Solution?
A solution that has a high osmotic pressure than a reference solution
Hyposmotic cells _______
Swell
Hyperosmotic cells _______
Crenate
