Topic 2 - CELL PHYSIOLOGY I (Passive Transport)

Question 1

Membrane Transport

Answer 1

• movement of material between the ICF and ECF

Question 2

Solute

Answer 2

substance dissolved in a solution

Question 3

solvent

Answer 3

substance solute is dissolved in

example: water

Question 4

name the 2 types of transport

Answer 4

1. Passive Transport
2. Active Processes

Question 5

Passive Transport

list the general facts

Answer 5

• no energy required (no ATP)
• movement from a high to low concentration (i.e. down its concentration gradient)
• the greater the difference in concentration = the more molecules want to move

Question 6

Passive Transport

name the 5 types

Answer 6

1. simple diffusion (solute movement)
2. fascilitated diffusion (solute movement)
3. fascilitated transport (solute movement)
4. osmosis (solvent movement)
5. bulk flow

Question 7

passive transport

simple diffusion

Answer 7

solute crosses through cell membrane bilayer, therefore small, lipid soluble (O₂, CO₂, etc)

Question 8

passive transport

fascilitated diffusion

Answer 8

ions diffuse through membrane via protein channels

Question 9

passive transport

fascilitated transport

Answer 9

• large, charged or water-soluble molecules
• moves across membrane using a specific carrier protein
  
  • must bind to protein to be transported
• e.g. glucose into liver or skeletal muscle

Question 10

osmosis

Answer 10

movement of H₂O across semipermeable membrane (permeable to H₂O) due to [H₂O] difference via pores (channels) or across the membrane bilayer

Question 11

Osmosis

high [H₂O] = ?

Answer 11

low [solute] - dilute solution

Question 12

Osmosis

low [H₂O] = ?

Answer 12

high [solute] - concentrated solution

Question 13

Osmosis

[solute] depends on what?

Answer 13

the number of ions or molecules, not the type

Question 14

Osmotic Pressure (OP)

Answer 14

pressure that must be applied to prevent movement of H₂O from pure H₂O solution (S1) across a semipermeable membrane into another solution (S2)

Question 15

Osmotic Pressure

What happens if S2 has high [salt], low [H₂O] ?

Answer 15

then more H₂O will move into it ⇒ requires pressure to stop it moving into S2

therefore, the greater the [salt] in S2, the greater the OP and lower [H₂O] ⇒ water will want to move in (down its gradient)

Question 16

Osmotic pressure

If S2 = pure H₂O, what happens?

Answer 16

No pressure is required to prevent H₂O movement (no gradient

therefore, S2 OP = 0

Question 17

OP is used for what?

Answer 17

OP is used as a measure of the [Solute] of a solution

Question 18

high OP = ?

Answer 18

high [solute], low [H₂O]

Question 19

Tonicity

list 2 characteristics

Answer 19

• response of a cell immersed in a solution
• depends on [solute] (and permeability of cell membrane to the solute)

Question 20

tonicity

list the 3 classifications

Answer 20

1. hypotonic solution
2. hypertonic solution
3. isotonic solution

Question 21

tonicity: hypotonic solution

name 3 characteristics

Answer 21

1. ECF has lower OP than ICF (cytosol)
2. cell swells (takes in water)
3. swelling can rupture cell = lysis
   
   • if a red cell = “hemolysis”

Question 22

Tonicity: Hypertonic Solution

list 2 characteristics

Answer 22

1. ECF has higher OP than ICF (cytosol)
2. cell shrinks (loses H₂O)

Question 23

Tonicity: Isotonic solution

list 3 characteristics

Answer 23

• ECF and ICF have equal OP
• cell neither swells nor shrinks
• rbc - [all solutes] in ICF = 0.9% saline solution (=normal saline)

Question 24

What are the uses of Tonicity

Answer 24

injecting 10% sucrose solution (hypertonic) will draw water into blood from tissues

example: use to decrease brain edema (swelling)

Question 25

1. what is the osmosis role in [solute] regulation?
2. list the major body fluids

Answer 25

1. concentration of solutes in body fluids must be maintained within narrow limits or cells will die
2. major body fluids:

• ECFs: blood plasma, Interstital Fluid
• ICF

Question 26

Give an example of [solute] regulation

Answer 26

if body loses H₂O (e.g. sweat) ⇒ [blood] increases

therefore, blood osmotic pressure increases ⇒ which causes fluid to move from tissues into blood

response = thirst and decreased renal H₂O loss which leads to decreased urine production

Question 27

Bulk Flow

Answer 27

movement of fluid (including solutes) due to a pressure gradient (high pressure to low pressure

Question 28

Hydrostatic pressure refers to what type of membrane transport? What is hydrostatic pressure?

Answer 28

• refers to Bulk Flow
• hydrostatic pressure is a pressure of a fluid pressing against a surface

Question 29

give 2 examples of hydrostatic pressure

Answer 29

1. cell membrane, blood vessel wall (= blood pressure)
2. capillary - if blood has higher pressure than ISF, fluid flows out of capillary (= filtration)