L12 Membrane Transport

Question 1

what is passive diffusion?

Answer 1

movement directly through the membrane- done my small hydrophobic, molecules like gases and steroid someone’s as well as by small uncharged polar molecules like water and urea. and glycerol

Question 2

what cannot move via passive diffusion

Answer 2

large polar molecules like glucose and sucrose have low permeability and require proteins to cross. charged ions have no permeability and require a protein to cross

Question 3

what is the driving force behind passive diffusion

Answer 3

electrochemical gradient. until equilibrium is reached.

Question 4

what are the 3 types of facilitated diffusion.

Answer 4

channels
gated channel s
uniporters

all facilitated transport of solute down its conc gradient until equilibrium

Question 5

describe gated channels and give an example of one

Answer 5

more specific than non gated channels- ENaC- epithelia sodium channel- almost all gated channels are ion channels. the functional components is a gate, sensors and selective filter

Question 6

describe and name a group of carrier mediated facilitated difussion?

Answer 6

GLUT family
1- RBC
2- intestine
4- skeletal and cardiac muscle

they have an inner and outer gate!

Question 7

what is saturation kinetics?

Answer 7

the flux of flow with carrier mediated diffusion is much greater than if predicted by passive diffusion,

Question 8

name the 2 types of secondary active transport

Answer 8

symporters and antiporters

use the kinetic energy provided by the electrical chemical gradient of one molecule to move another

Question 9

give an example of a symporter?

Answer 9

SGLT- Na+ glucose co trasnporter

Question 10

what are the 4 main types of active transporters

Answer 10

P-type ATPase
F ATPase
V-ATPase
ABC transporters

Question 11

what active transporters in seen in excess in MDR cancer cells

Answer 11

P-glycoprotein ABC type- effluxes compounds like cancer drugs out the cell

Question 12

describe how CFTR uses ATP

Answer 12

ATP hydrolysis causes conformational change in the CFTR then the channel opens allows movement of cl- down its electrochemical gradient

Question 13

which fluid compartment in the body contains the most fluid

Answer 13

intracellular fluid- 25L 40% of body weight

Question 14

describe the differences between the plasma, interstitial fluid and the intracellular fluid

Answer 14

o Interstitial fluid and plasma re similar but ECF and ICF are markedly different
 In plasma NA+ is the major cation and cl- and HCO3- are the major anions
 In interstitial fluid are similar to plasma but there is little protein
 Intracellular fluid has higher concentrations of K+ and Mg+ than ECF

Question 15

What is ASL and where is it?

Answer 15

Airway surface liquid

thin layer of watery solution that lies between the lumen of the airway and the epithelial cells.

Question 16

what happens if there are defects in the ASL like in Cf?

Answer 16

lack of cilia beating and inhibition of the muocilliary transport as the thick mucus is too thick to move as it becomes dehydrated due to no CFTR proteins. mucus continues to be secreted and builds up.