Transport across membranes

Question 1

how/what type of solutes move across membranes?

Answer 1

Some solutes (small uncharged molecules) move by simple diffusion across a membrane, some require active transport (large charged molecules)

Question 2

what is diffusion?

Answer 2

• the movement of a solute from an area of high concentration to an area of low concentration
• Move down the concentration gradient

Question 3

what is a concentration gradient?

Answer 3

difference in concentration of a solute across a membrane

Question 4

what is facilitated diffusion?

Answer 4

• diffusion across a membrane through protein transporters; requires energy
• building of a gradient

Question 5

what is osmosis?

Answer 5

movement of water across a selectively permeable barrier from an area of lower solute concentration to an area of higher solute concentration

Question 6

what are isotonic solutions?

Answer 6

solutions that have the same concentrations of solute

Question 7

what is a hypertonic solution?

Answer 7

is a solution that has a greater solute concentration than the one it is being compared to

Question 8

what is a hypotonic solution?

Answer 8

is a solution that has less solute concentration than the one it is being compared to

Question 9

what is crenation?

Answer 9

when an animal cell is placed in a hypertonic solution, water leaves the cell and causes it to shrink

Question 10

what is lysing?

Answer 10

when an animal cell is placed in a hypotonic solution, water enters the cell, eventually causing it to explode
because it does not have a cell wall to hold it together

Question 11

what is it when a plant cell is flaccid?

Answer 11

when a plant cell is placed in an isotonic solution, it becomes flaccid. meaning there is no water pressure to keep it rigid. can be seen when plants are wilting

Question 12

what is plasmolysis?

Answer 12

when a plant cell is placed in a hypertonic solution, water leaves the cell, and the plasma membrane pulls away from the cell wall

Question 13

what does it mean when a plant cell is turgid?

Answer 13

when a plant cell is placed in a hypotonic solution, water enters the cell, and causes it to become rigid
Plants happy place
Cell wall prevents from exploding

Question 14

what are solution tonicitys

Answer 14

isotonic, hypertonic, hypotonic

Question 15

what is a dialysis membrane (tubing)?

Answer 15

is an artificial membrane that allows only molecules of a certain size to cross

Question 16

in the dialysis tube experiment, which molecules were small enough to diffuse by simple diffusion across a dialysis membrane? glucose, starch, I2KI, water?
how could we tell?

Answer 16

Glucose:
moved from inside –> outside
we could tell because of glucose test strips
Iodine:
moved from outisde –> inside
we could tell because of the colour change, when starch and iodine come in contact, they turn purple
Starch:
did not move
we can tell because if it was able to move outside of the membrane we would have seen a colour change when it reacted with the iodine, but the iodine went from dark yellow to lighter yellow (indicating the concentration got lower)