lecture 6

Question 1

Passive diffusion of particles

Answer 1

Molecules are in continuous random
motion
• Tend to become evenly distributed over
time (i.e. steady state or equilibrium)
• Known as diffusion
• Concentration gradient (chemical)
• Net diffusion

Question 2

Net diffusion….

Answer 2

Net diffusion and movement of molecules
down the concentration gradient (from
high to low concentrations)

Question 3

Fick’s law of diffusion:

Answer 3

• The collective influence of factors on the
rate of net diffusion of a substance across
a membrane
• The magnitude (or steepness) of the
concentration gradient
• The surface area of the membrane
across which diffusion is taking place
• The lipid solubility of the substance
• The molecular weight of the
substance
• The distance through which diffusion
must take place

Question 4

Passive diffusion of ions

Answer 4

Are electrically charged and other than concentration gradient, there movement Is affected by there electrical charge A difference in charge between two adjacent areas thus produces an
electrical gradient
• The combinatorial effect of the concentration and electrical gradients on
the ion forms the electrochemical gradient

Question 5

Osmosis

Answer 5

Can readily go through the plasma membrane and slip between the PL molecules.

Movement of water when
a selectively permeable membrane
separates two unequal solute
concentrations (and unequal water
concentration

Or through aquaporins

Driving force is the concentration gradient

Net diffusion for water is known as osmosis

Question 6

Osmatic pressure

Answer 6

The osmotic pressure of a solution (a “pulling” pressure) is a
measure of the tendency for water to move into that solution
because of the concentration of non-penetrating solutes and water

Question 7

Hydrostatic pressure

Answer 7

Hydrostatic (fluid) pressure is the pressure exerted by a standing,
or stationary, fluid on an object—in this case, the membrane