membrane transport

Question 1

what moves with simple diffusion

Answer 1

O2, CO2, small hydrophobic molecules

Question 2

examples of molecules that move by facilitated diffusion

Answer 2

small uncharged polar molecule
- H2O, urea, glycerol
large uncharged polar molecules
- glucose, sucrose
ions in ion channels

Question 3

role of facilitated diffusion in cells

Answer 3

transport of inorganic ions & small molecules
regulate intracellular ions
uptake nutrients into the cells
excrete waste from the cells

Question 4

types of protein in facilitated diffusion

Answer 4

channels - discriminates mainly on size and charge

uniporter carrier proteins - binding of solutes involved is required

Question 5

for charged particles what can effect the movement into the cell

Answer 5

charge difference (electrochemical gradient) will alter ability

Question 6

key features of ion channels

Answer 6

• ion selectivity
• driven by conc/electrochemical gradient
• may be regulated

Question 7

examples of ways ion channels can be regulated

Answer 7

• voltage gated
• ligand gated
• mechanically gated

Question 8

what are K+ leak channels in cells

Answer 8

ion channels selective to K+ that are always open and allow K+ to move out of the cell to regulate action potential

Question 9

what type of protein carriers are glucose transports (Glut2) in the gut epithelia

Answer 9

uniporter carrier proteins

Question 10

how do uniporter carrier proteins work to move particles across membrane (using Glut 2)

Answer 10

flipping movement of the carrier protein.
alteration between two conformations

Question 11

what are features of glucose transports (Glut 2) in gut epithelia

Answer 11

• highly selective to glucose
• protein passes through membrane 12 times
• relatively slow movement

Question 12

types of active transport systems in cells

Answer 12

1. ATP-driven pumps (directly hydrolysis of ATP)
2. Coupled transporters (coupling 1 against with another going with its gradient)
3. light-driven pumps (direct energy derived from light)

Question 13

role of electrochemical gradients for cells

Answer 13

• drive transport across membrane
• electrical forces
• maintain osmotic balance

Question 14

key features of Na+/K+ ATPase

Answer 14

1. consumes 1/3 cells energy
2. expel 3 Na+ out and 2K+ into cell
3. acts as an enzyme to hydrolyse ATP -> ADP to provide energy for enzyme change of shape

Question 15

what is the process of ATPase cycle work?

Question 16

what are coupled transporters

Answer 16

proteins where one ion is going down its concentration gradient allows another molecule to move against the concentration gradient

Question 17

compare symport and antiport coupled transporters

Answer 17

SYMPORT - both in same direction
ANTIPORT - in opposite direction

Question 18

process of Na+ / glucose symporter

Answer 18

Na+ electrochemical gradient drives the movement of glucose against its gradient.

Question 19

process where glucose is uptaken into cells

Answer 19

• in epithelial gut cells
  1. primary active transport of Na+ out of cell through Na/K pump
  2. symporter with Na+ glucose
  3. glucose transporters into blood (facilitated diffusion)

Question 20

where are Na+/ Ca2+ antiporters found

Answer 20

in cardiac muscles

Question 21

what is the role of Na+/Ca2+ antiporter proteins

Answer 21

alteration of Ca2+ conc in allows a contraction to be triggered

reduced [Ca2+] = reduced contraction

Question 22

role of Na+/ glucose co-transporter (SGLT 1)

Answer 22

reduces blood glucose levels preventing it being reuptake from urine