Quiz 10

Question 1

transport across biological membranes

Answer 1

*transport vital for all life forms
*cells must import nutrients and export waste
- all cells maintain concentration gradients across plasma and other membranes

Question 2

transporters

Answer 2

• movement of polar, water soluble molecule or ion across the hydrophobic interior of a membrane
• are integral membrane proteins

Question 3

four modes of membrane transport

Answer 3

1. passive diffusion
2. facilitated diffusion
3. active transport
4. secondary active transport

Question 4

passive diffusion

Answer 4

• transported species from down their conc gradient [high to low]
  uncharged: depends on conc of both sides
  charged: concentration and the charge on particle and electrical potential difference across membrane

Question 5

facilitated diffusion

Answer 5

• proteins facilitate transport, increasing the rates of transport
  1. solute flows only in favored direction
  2. transport displays saturation kinetics

Question 6

single channels

Answer 6

can be formed from dimers, trimers, tetramers or pentamers of protein subunits

Question 7

multimeric assemblies

Answer 7

in which each subunit has its own pore are knows. many are facilitated diffusion channels, that set up an electrical potential difference across the membrane

Question 8

potassium channel

Answer 8

combines high selectivity with high conduction rates.

Question 9

active transport

Answer 9

used when transport must flow against the thermodynamic potential of the solutes
- energy source and transport machinery are “coupled”
- energy source may be ATP or light

Question 10

sodium potassium pump

Answer 10

• maintains intracellular Na low and K high
• ATP hydrolysis drives Na+ out and K+ in
• 3 Na ions are moved from the inside to outside the cell while 2 potassium ions are moved from the outside to the inside of the cell
• cardiac glycosides inhibit by binding to outside part of the transporter

Question 11

ouabin

Answer 11

• one of the class of cardio tonic steroids.
• cardiac glycoside

Question 12

secondary active transport

Answer 12

• the gradients of H+, Na+ and other cations and anions previously established by ATPases can then be used for secondary active transport of various substrates

Question 13

secondary active transport **

Answer 13

• symports: moving in same direction
• antiports: move in opposite directions
  [ions and transported amino sugar]

Question 14

AcrB

Answer 14

• multi-drug resistance [MDR] transporter in e. coli
• as protons flow spontaneously inwards through AcrB in the E. coli inner membrane, drug molecules are driven outward