Topic 2: Cell Physiology 1 - Membrane Transport (Passive) Continued

Question 1

What is osmotic pressure?

Answer 1

• pressure that must be applied to PREVENT movement of water from a pure H2O solution (s1) across a semipermeable membrane, into another solution (S2)

Question 2

What is S2 has a high solute concentration?

Answer 2

• aka low water concentration
• then more water will move into S2
• requires pressure to stop water from moving into S2

Question 3

What is the rule of osmotic pressure? (2)

Answer 3

• the greater [solute] in solution, the greater osmotic pressure and lower [H2O]
• because water wants to move down CG

Question 4

What happens if S1 and S2 are pure water?

Answer 4

• no pressure required to prevent water movement bc no gradient
• therefore S1, S2 OP is 0

Question 5

What does osmotic pressure measure?

Answer 5

• concentration of solute of a solution

Question 6

What does high osmotic pressure mean?

Answer 6

• high [solute]
• low [H2O]

Question 7

What is tonicity?

Answer 7

• response of a cell immersed in a solution

Question 8

What does tonicity depend on? (2)

Answer 8

• solute concentration and permeability of cell membrane to solute

Question 9

What is a hypotonic solution? (2)

Answer 9

• ECF has a lower osmotic pressure (higher [H2O] than ICF (cytosol))
• cell swells (takes in water) and may burst

Question 10

What is a hypertonic solution? (2)

Answer 10

• ECF has higher OP (lower [H2O] than ICF (cytosol))
• cell shrinks (loses H2O)

Question 11

What is an isotonic solution? (3)

Answer 11

• ECF and ICF have equal OP
• cell neither swells or shrinks
  RBC - all [solutes] within equals a 0.9% saline solution (normal saline)

Question 12

What are the uses of tonicity in the body? (2)

Answer 12

• injecting 10% sucrose solution (hypertonic) will move water to blood stream
• ex. use to lower brain edema (swelling)

Question 13

What is the role of osmosis in [solute] regulation?

Answer 13

• concentration of solutes in body fluids must be maintained within narrow limits or cells will die

Question 14

What are the major body fluids? (3)

Answer 14

ECF:
- blood plasma
- interstitial fluid (ISF)
lymph in lecture

• ICF

Question 15

Give an example of osmosis role in solute regulation in terms of sweating (3)

Answer 15

1. body loses H2O when sweating
2. increased [blood] therefore blood OP increases
3. fluid moves from tissue to blood

Question 16

What is the response when you lose water when sweating? (2)

Answer 16

• thirst
• decreased renal H2O loss which leads to decreased urine production

Question 17

What is bulk flow?

Answer 17

• movement of fluids (and solutes) due to a pressure gradient (high pressure to low pressure)

Question 18

Bulk flow includes hydrostatic pressure. What is that?

Answer 18

• pressure of a fluid pressing against a surface
  ex. cell membrane, blood vessel wall (= BP)

Question 19

How is a capillary an example of bulk flow? (2)

Answer 19

• if blood has higher pressure that ISF, fluid flows out of capillary (filtration)
• if ISF has higher P than blood, fluid flows from ISF to capillary (absorption)