Mod2-Obj2: Passive transport and active transport

Question 1

Types of transport: Passive transport

Answer 1

No energy (ATP) required

• Substances move down concentration gradient
• Simple and facilitated diffusion

Question 2

Types of transport: Active transport

Answer 2

Requires ATP

-Primary active transport

Question 3

Concentration gradients

Answer 3

Atoms and molecules move from an area of high concentration to an are of low concentration

• Down or along a concentration gradient
• Once equilibrium is reached, there is no further net movement

Question 4

Simple diffusion

Answer 4

Movement in and out of cell, no ATP required

• Solutes move down concentration gradient
• High to low
• Speed is influenced by size, the smaller the molecule the faster the rate of diffusion
• Lipid-soluble substance

Question 5

Facilitated diffusion

Answer 5

Assisted movement in and out of cell, no ATP required
-Solutes move down concentration gradient
-High to low
-Carrier proteins to faciliate the passage of lipid-insoluble (polar) solutes across the plasma membrane i.e.) glucose
-Protein channels
+leakage channels and gated channels
i.e.) sodium (Na+) and potassium (K+)

Question 6

Carrier-mediated facilitated diffusion

Answer 6

Via protein carrier specific for one chemical; binding of substrate causes transport protein to change shape

Question 7

Channel-mediated facilitated diffusion

Answer 7

Through a channel protein; mostly ions selected on basis of size and charge

Question 8

Leakage channel

Answer 8

Are always open and simply allow ions or water to move according to concentration gradients

Question 9

Gated channel

Answer 9

Are controlled (opened or closed) by chemical or electrical signals

Question 10

Facilitated diffusion: Voltage gated channels

Answer 10

Voltage-gated channels open in response to changes in t membrane potential

Question 11

Osmosis

Answer 11

Net diffusion of water through a selectively permeable membrane, from an area where there is more water, to an area where there is less

• One solute molecule, displaces one water molecules
• Water moves from an area where there is less solute, to an area where there is more solute, to balance out the concentration gradient
• Through an aquaporin or through the lipid bilayer

Question 12

Diffusion and osmosis are…

Answer 12

Passive and non-energy requiring

Question 13

Tonicity

Answer 13

The ability of a solution to affect cell shape by altering water volume

Question 14

Tonicity: Isotonic solution

Answer 14

Same concentration of solutes and water

-No change in volume or shape

Question 15

Tonicity: Hypertonic solution

Answer 15

Higher concentration of solutes, lower concentration of water
-Cell volume decreases, cell shrinks

Question 16

Tonicity: Hypotonic solution

Answer 16

Lower concentration of solutes, higher concentration of water
-Cell volume increases, cell swells

Question 17

Tonicity: Clinical importance

Answer 17

• Never use plain water in an IV drip, as net movement of water inside and outside of a cell should not occur
• Use saline in an IV drip
• Never drink sea water
• You drink water when thirsty

Question 18

Primary active transport

Answer 18

Plasma membrane can actively move substances against their concentration gradients

• Low to high
• Mediated by carrier proteins (uses ATP to drive movement)
• Maintains concentration differences either side of membrane

Question 19

Hydrolysis of ATP changes…

Answer 19

Shape of carrier protein
-Pump solutes (ions) 
E.g.) K+/Na+ pump
-Moves Na+ out of the cell 
-Move K+ into the cell 
-Maintains membrane potential

Question 20

Endocytosis and Exocytosis

Answer 20

Used to move particles too large to cross the membrane

-Involves vesicles and the cell membrane

Question 21

Endocytosis

Answer 21

Into the cell (phagocytosis and pinocytosis)

Question 22

Exocytosis

Answer 22

Out of the cell (i.e. proteins from golgi apparatus)