MCP 25: Solute Transport

Question 1

extrinsic proteins

Answer 1

proteins attached to membrane

Question 2

intrinsic proteins

Answer 2

proteins embedded in a membrane; may be anchored by cytoskeletal proteins; cannot be removed without destroying membrane

Question 3

diffusion

Answer 3

the transport of molecules from an area of high concentration to an area of low concentration; water, hydrophobic molecules (nitrogen, oxygen, CO2, benzene) or small nonpolar molecules (H2O, urea, maybe glucose) can passively diffuse through the membrane without ion channels; ions CANNOT move through membrane without channels.

Question 4

flux

Answer 4

the movement of ions from high to low concentration, measured in amount of particles per time

Question 5

Fick’s law

Answer 5

Ji=DiA(C1-C2)/x; concentration gradient and flux related linearly

Question 6

Fick’s law applied to plasma membrane

Answer 6

Jx=Px(Xo-Xi); where Xo and Xi represent concentrations of molecules inside and outside the cell, P is the permeability constant

Question 7

permeability coefficient for Fick’s law

Answer 7

based on 4 things 1.) partition coefficient 2.) diffusion coefficient 3.) membrane thickness 4.) area over which diffusion occurs

Question 8

saturation kinetics and solute transport

Answer 8

facilitated diffusion or primary/secondary transport; shows saturation kinetics

Question 9

active transport

Answer 9

uses energy either directly or indirectly from ATP to move molecules against their concentration gradient

Question 10

antiport

Answer 10

molecules moving in opposite directions, ATP used indirectly

Question 11

symport

Answer 11

molecules moving in same direction, ATP used indirectly

Question 12

V class ATPase

Answer 12

in vesicles, stores chemicals in high concentration

Question 13

P class ATPase

Answer 13

Na/K pump or Ca2+ transporter

Question 14

F class ATPase

Answer 14

ATP synthases on inner mitochondrial membrane

Question 15

Gut epithelial cell glucose transport mechanism

Answer 15

Na+/K+ ATP pump on blood/epithelial cell membrane keeps extracellular Na+ high, intracellular Na+ low. Glucose/Na+ symporter on lumen/epithelial cell membrane allows glucose to enter cell via secondary active transport because of low intracellular Na+ concentration. Glucose moves into blood via facilitated diffusion if concentration gradient permits.

Question 16

pore (non-gated channel)

Answer 16

leakage channel, allow molecule to move through via simple diffusion, CREATE RESTING MEMBRANE POTENTIAL OF CELL!!!

Question 17

channel (gated pore)

Answer 17

gated by a door and responsible for action and synaptic potentials

Question 18

Na+/K+ pump

Answer 18

pumps 3 Na+ out of cell and 2 K+ into cell, against concentration gradients

Question 19

electrogenic

Answer 19

creates positive charge outside cell and negative charge inside cell (i.e. Na+/K- sodium pump)

Question 20

types of gated channels

Answer 20

voltage, ligand, mechanical, temperature, and water

Question 21

p-loop

Answer 21

where the ion binds loosely on a voltage gated ion channel, 5 transmembrane domain on voltage gated ion channels

Question 22

tetramer channels

Answer 22

Na+, Ca++ and K+ channels–4 subunits (each containing 6 transmembrane helices)

Question 23

components of a typical ion channel

Answer 23

1.) gate 2.) ion selectivity filter 3.) glycoproteins 4.) anchoring proteins 5.) voltage sensor or ligand binding site

Question 24

components of voltage-gated channels

Answer 24

6 domains of transmembrane helices, the 5th domains is known as the P loop at is the site for loose ion binding

Question 25

membrane voltage

Answer 25

charge separation across membrane

Question 26

partition constant

Answer 26

ratio of a molecule’s solubility in oil to its solubility in water; high number is more lipophilic and results in a great ability to cross hydrophobic core of plasma membrane

Question 27

carrier mediated transport

Answer 27

primary or secondary active transport

Question 28

facilitated diffusion

Answer 28

pass transport through pore or channel; technically Vmax exists but concentration of ions in biological systems too high for Vmax to ever be reached; faster that passive transport at low ion concentrations

Question 29

respiratory pump

Answer 29

H+ ions flow down concentration gradient, releasing energy to drive ATP production

Question 30

ion channel selectivity

Answer 30

based on size and loose binding for specific ion

Question 31

pentamer channels

Answer 31

nicotinic ACh receptor channel

Question 32

hexamer channels

Answer 32

connexons that make up gap junction