Membrane Transport

Question 1

What is selective permeability?

Answer 1

Membranes are selective permeable barriers that block hydrophilic molecules. small, uncharged or hydrophilic molecules freely cross membranes by simple diffusion. charged polar molecules require specialist proteins to allow them to cross the membrane

Question 2

What is passive transport?

Answer 2

Movement down a concentration gradient

Question 3

What is facilitated diffusion?

Answer 3

Allows movement down a concentration gradient via a membrane protein or an ion channel

Question 4

The GLUT Transporters?

Answer 4

GLUT 1 = in erythrocytes, low Km, high affinity, allows gluose uptake
GLUT 2 = in liver and pancreatic b-cells, high Km, low affinity, allows regulation of blood vessels
GLUT 3 = in neurones, low Km, high affinity
GLUT 4 = in muscle and adipocytes, regulated by insulin

Question 5

Types of Gated Channels?

Answer 5

Gated ion channels - allow facilitated diffusion of specific ions
Ligand gated channels - allow opening and closing
Voltage gated channels - open when change in membrane potential

Question 6

What is Active transport?

Answer 6

Where solutes move against a concentration gradient and require membrane proteins and ATP.
primary active transport directly involves ATP in the movement of the solute

Question 7

What is the Na+/K+ pump?

Answer 7

A tetramer (a2b2)
phosphorylated ATP causes conformational change which closes the the pump one side and opens it the other allowing ions K+ to bind and Na+  releases. hydrolysis of the phosphate group reverts back to normal releasing K+ into the cell

Question 8

What is Co-transport?

Answer 8

a pre-established gradient drives the transport of the solute against a gradient. ATP establishes the primary gradient

Question 9

What is SGLUT?

Answer 9

This is a Na+/glucose cotransport which allows glucose absorption from the intestine. Uses ATP hydrolysis o drive uptake of glucose into cells

Question 10

What is the Na+/Ca2+ transporter?

Answer 10

Ca2+ exported from the muscle cell against the gradient. this is an antiport, Na+ gradient established by Na+/K+ pump and ATP hydrolysis is used to drive the export of Ca2+ from cells

Question 11

Types of transport?

Answer 11

Antiport - molecules transport in opposite directions

Symport - Molecules travel in the same direction