MEMBRANE TRANSPORT

Question 1

ACTIVE TRANSPORT

Answer 1

• requires energy
• charged ions
• metabolites, glucose
• low to high concentration
• uses carrier proteins/ cell channels

Question 2

OSMOSIS

Answer 2

net diffusion of water across a membrane to a higher solute concentration (water moves down concentration gradient)

Question 3

WHEN DOES OSMOSIS OCCUR?

Answer 3

• a membrane separates two solutions with different solute concentrations
• concentrations of free water molecules on both sides of membrane are different

Question 4

HYDRATION SHELLS

Answer 4

• water molecules that surround the charged solute molecules
• the side with a higher solute conc. has more water molecules in hydration shells thus less free water molecules

Question 5

OSMOTIC CONCENTRATION

Answer 5

concentration of all solutes in a solution determines osmotic concentration of solution

Question 6

HYPERTONIC VS HYPOTONIC

Answer 6

HYPERTONIC - higher solute concentration
HYPOTONIC - lower solute concentration
ISOTONIC - same osmotic concentration

Question 7

AQUAPORINS

Answer 7

• facilitate osmosis
• channels in cell membrane that regulate water in cell
• allows water movement, stops ions

Question 8

OSMOTIC PRESSURE

Answer 8

• force needed to stop osmotic flow
• cell in hypotonic solution gains water causing it to swell - creates pressure
• if membrane strong enough cell reaches counterbalance of osmotic pressure driving water in + hydrostatic pressure forcing water out
• animals cells must be isotonic

Question 9

MAINTAINING OSMOTIC BALANCE

Answer 9

• some cells use extrication where water is ejected through contractile vacuoles
• isosmotic regulation, extrusion, turgor

Question 10

CARRIER PROTEINS USED IN ACTIVE TRANSPORT

Answer 10

• ANTIPORTER - move two molecules in opposite directions
• UNIPORTER - moves one molecule at a time
• SYMPORTER - moves two molecules in same direction

Question 11

ATP-DEPENDENT MEMBRANE TRANSPORTERS

Answer 11

• P type ATPases (undergo phosphorylation, transport calcium, sodium + potassium)
• F type ATPases (proton transporters in mitochondria + bacteria)
• V type ATPases (in lysosomes)
• A type ATPases (anion transporters)
• ABC transporters

Question 12

SODIUM-POTASSIUM PUMP

Answer 12

• direct use of ATP for active transport
• antiporter (moves 3 Na out of cell + 2 K in to the cell against conc. gradients)
• ATP changes confirmation of the carrier protein
• > 1/3 of cell energy in a cell that’s not actively dividing is used in active transport of Na + K

Question 13

COUPLED TRANSPORT

Answer 13

• uses ATP indirectly
• uses energy released when a molecule moves by diffusion to supply energy to active transport of another molecule
• symporter used
  e. g. glucose-Na symporter captures the energy from Na diffusion to move glucose against conc. gradient

Question 14

COTRANSPORT

Answer 14

both molecules moving in same direction across membrane + transporter is symporter

Question 15

COUNTER-TRANSPORT

Answer 15

inward movement of Na is coupled with outward movement of another substance e.g. calcium + hydrogen

Question 16

BULK TRANSPORT

Answer 16

• substances that cells require for growth are mostly large, polar molecules that cannot cross through hydrophobic lipid bilayer barrier
• endocytosis + exocytosis