1.4 MEMBRANE TRANSPORT

Question 1

Simple diffusion (passive transport)

Answer 1

The net movement of molecules from a region of high concentration to a region of low concentration

Question 2

Facilitated diffusion (passive transport)

Answer 2

the passive movement of molecules across the cell membrane via the aid of a membrane protein (transmembrane proteins)

Question 3

Transmembrane proteins

Answer 3

ultilised by large, polar molecules and ions

Question 4

Osmosis

Answer 4

the net movement of water molecules across a semi-permeable membrane from a region of low solute concentration to a region of high solute concentration

Question 5

Aquaporins

Answer 5

water channels

Question 6

Osmolarity

Answer 6

measure of solute concentration

Question 7

Hypertonic

Answer 7

High osmolarity solution (high solute conct. → gains water)

Question 8

Hypotonic

Answer 8

Low osmolarity solution (low solute conct. → loses water)

Question 9

Isotonic

Answer 9

Same osmolarity solution (same solute conct. → no net water flow)

Question 10

Active transport

Answer 10

uses energy to move molecules against concentration gradient (uses ATP)

Question 11

Steps in Active transport

Answer 11

1. the specific solute will bind to the protein pump on one side of the membrane
2. The hydrolysis of ATP (to ADP + Pi) causes a conformational change in the protein pump
3. The solute molecule is translocated across the membrane & released

Question 12

Active transport is carried out by?

Answer 12

globular proteins in membranes → pump proteins

Question 13

Sodium Potassium pump

Answer 13

integral protein that exchanges 3 sodium ions (out of the cell) with 2 potassium ions (into the cell)

Question 14

Steps in Sodium Potassium pump

Answer 14

1. Three sodium ions bind to intracellular sites on the sodium-potassium pump
2. A phosphate group is transferred to the pump via the hydrolysis of ATP
3. The pump undergoes a conformational change, translocating sodium across the membrane
4. The conformational change exposes two potassium binding sites on the extracellular surface of the pump
5. The phosphate group is released which causes the pump to return to its original conformation
6. This translocates the potassium across the membrane, completing the ion exchange