L3

Question 1

osmosis

Answer 1

the passive diffusion of H20

Water flows from high to low

Question 2

hypertonic vs hypotonic solution

Answer 2

hyper: solute concentration is greater outside than inside; cell loses water

hypo: solute concentration is less outside than inside; cell swells

Question 3

isotonic solution

Answer 3

solute concentration is the same as that inside the cell no net water movement across the plasma membrane

Question 4

aquaporins form…

Answer 4

forms a channel in the membrane

H20 diffuses both directions (net movement is from high to low)

does NOT use alternating access (substrate is very small)

has a narrow channel with a selectivity filter (only allows very small and polar molecule)

Question 5

what happens to cell in each of 3 conditions: isotonic/hypotonic/hypertonic

Answer 5

isotonic - cell remains intact
hypotonic - cell swells/explodes
hypertonic - cell shrivels

Question 6

strategy for dealing with water imbalance: Paramecium contractile vacuole

Answer 6

-cytoplasm has a higher solute concentration than its surrounding environment

-water leaks into cell by osmosis

-water is collected in vacuoles, vacuoles contract to expel water back to the environment

aquaporins wouldn’t be found on the cell surface membrane - that would allow more water to enter the cell; aquaporins are leading to/around the contractile vacuoles

Question 7

facilitated diffusion: an alternating access mechanism

Answer 7

uniport by a carrier protein (one substrate at a time)

allows PASSIVE movement of sugars into cells from circulation

specific example: Glut-5 functions in fac. diff. of fructose

Question 8

ask tutor

Answer 8

Question 9

poll q

Answer 9