4 - Membrane Transport

Question 1

What are the dominant ions in the ECF and ICF?

Answer 1

ECF - Na

ICF - K

Question 2

How do you work out osmolality if you know the sodium and potassium concentration?

Answer 2

Double it, can assume same amount of Cl as other ions

Question 3

What transport requires ATP and what doesnt?

Answer 3

No ATP: Osmosis, Diffusion

ATP: Phagocytosis, Pinocytosis, Active

Question 4

Why is facilitated diffusion faster than normal?

Answer 4

Don’t have to worry about the thickness of the membrane

Question 5

What are the main points of Fick’s law?

Answer 5

Diffusion is proportional to SA of barrier and inversely proportional to thickness.

Concentration gradient is driving force of net diffusion

Flux is 0 when no concentration gradient

Question 6

Does Na+/K+ ATPase affect membrane potential?

Answer 6

No, swapping exact same charges

Question 7

How do large molecules enter the cell?

Answer 7

Endocytosis, Phagocytosis, Pinocytosis

ACTIVE

Question 8

What is the structure of an aquaporin and what is it’s function?

Answer 8

• 6 TM Alpha helices
• Narrow inner cavity with hydrophilic AA
• Centre of channel +vely charged residues to prevent entry of H+ ions
• Molecules go through single file really fast
• In tissues associated with movement of fluid

Question 9

What does it mean having a high osmotic pressure?

Answer 9

High solute concentration, would take a lot of force to resist the water entering the solution

Question 10

What is osmolality and what are the units?

Answer 10

When the concentration of a solution is expressed as the number of solute particles per kg of water

280-310 mOsm/kg normally