Chaper 5: Transport

Question 1

Explain the mechanism of active transport

Answer 1

• Can carry material in the direction opposing equilibrium

- Uses ATP and can transport molecules away from equilibrium

Question 2

Explain the mechanism of passive transport

Answer 2

-capable of carrying material only in the direction of equilibrium.

Question 3

Describe mechanisms by which the major solutes and water move across cell membranes

Answer 3

• Lipid solutes are hydrophobic and dissolve in the lipid interior of the membrane. Make their way from side of membrane where they are more concentrated to the side where they are less concentrated
• important ions (Na+, K+, Ca2+, and Cl-) move passively through ion channels.

Question 4

equilibrium

Answer 4

the state toward which an isolated system changes; has no input or output of energy or matter

Question 5

Voltage-gated channels

Answer 5

open and close in response to the voltage difference across a membrane; important in generation of nerve impulses

Question 6

stretch-gated channels

Answer 6

(tension-gated) - open or close in response to stretching or pulling forces that alter the physical tension on a membrane.

Question 7

phosphorylation-gated channels

Answer 7

respond to whether or not the channel proteins are phosphorylated; channels would be under control of kinases, which are controlled by second messengers

Question 8

ligand-gated channels

Answer 8

act as receptors of extracellular signal and as ion channels; close to passage of ions in absence of signal

Question 9

Relative concentrations of major inorganic cells

Answer 9

• More K+ inside a cell, and more Na+ outside a cell.

- Charge right up against the membrane is different from the charge of the ions crowding inside and outside the cell

Question 10

Explain the relationship between solute concentration and osmotic pressure

Answer 10

-low solute concentration is low osmotic pressure and vice versa

Question 11

facilitated diffusion

Answer 11

passive transport of polar organic solutes across cell membrane occurs by noncovalent and reversible binding of solutes to solute specific transporter proteins in membrane.

• always occurs in direction of electrochemical equilibrium
• transported faster

Question 12

Cotransport

Answer 12

When a cotransporter protein moves two solutes in linked fashion in one direction

Question 13

countertransport

Answer 13

When a countertransporter protein moves two solutes in obligatorily linked fashion in opposite direction

Question 14

Hyperosmotic

Answer 14

If solution A has a lower osmotic pressure than solution B, SOLUTION B is hyperosmotic to solution A

Question 15

Hyposmotic

Answer 15

If solution A has a lower osmotic pressure to solution B, SOLUTION A is hyposmotic to solution B.

Question 16

Na+ transport from water

Answer 16

• protons are pumped into water by ATPase in the apical membrane, and Na+ diffuses inward
• An Na+-K+-ATPase in the basolateral membrane pumps the Na+ out of the cell

Question 17

Cl- transport from water

Answer 17

• protons are pumped into water by ATPase and a countertransporter exchanges Cl- for HCO3- in the apical membrane
• HCO3- is replenished from waste CO2

Question 18

Electrochemical equilibrium

Answer 18

the condition in which the voltage difference balances the concentration gradient

Question 19

How is glucose moved out of the gut epithelial cells?

Answer 19

Facilitated diffusion