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2.1.5 biological membranes > osmosis > Flashcards

osmosis Flashcards

1
Q

what is osmosis

A

the net diffusion of water molecules from a region of where are more water molecules to an area where there are fewer water molecules across a partially permeable membrane

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2
Q

what is a solute

A

a substance dissolved in a solvent to form a solution

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3
Q

what does the amount of solute in a certain volume of aqueous solution determine

A

the concentration

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4
Q

what is the solvent

A

the liquid in which solute molecules are dissolved in a solution

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5
Q

in aqueous solutions what is the solvent

A

water

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6
Q

what can easily pass through the phospholipid bilayer

A

water molecules

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7
Q

what are protein channels for water called

A

aquaporins

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8
Q

what do aquaporins allow water molecules to do

A

diffuse more rapidly through the bilayer

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9
Q

where is water present in cells

A

in the cytoplasm and the medium of cells as cells are surrounded by extracellular tissue fluid

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10
Q

what happens when solute molecules are added to water

A

the relative number of water molecules in the resulting solution is changed. if the solute molecules dissociate into charged ions (for e.g NaCl dissociating into Na+ and Cl- ions), they exert more effect on the number of water molecules than larger non ionic molecules.

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11
Q

what happens when solute molecules dissociate into charged ions

A

if the solute molecules dissociate into charged ions (for e.g NaCl dissociating into Na+ and Cl- ions), they exert more effect on the number of water molecules than larger non ionic molecules (glucose for e.g) this is because as NaCl molecules dissociate into Na+ and Cl- the number of particles in the solution doubles

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12
Q

how does osmosis occur in prokaryotic cells

A

water molecules can enter or leave them across the partially permeable plasma membrane. if they lose enough water, then their metabolism can’t proceed and they can’t reproduce.

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13
Q

what can adding salt or sugar to food do

A

preserve food and prevents spoilage as any bacteria can’t respire, grow or multiply as water is lost by the bacterial cells by osmosis.

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14
Q

what does penicillin prevent

A

some types of growing bacteria from synthesising their peptidoglycan wall. this makes them vulnerable to the effects of osmosis. if they swell up whilst water enters, they will burst

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15
Q

what is the net diffusion of water by osmosis determined by

A

the differences in water potential between two solutions connected by a partially permeable membrane

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16
Q

what is water potential

A

a measure of the tendency of water molecules to diffuse from one region to another

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17
Q

what is the unit for water potential

A

kilopascals

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18
Q

what is the water potential of pure water

A

0kPa - pure water has the highest water potential

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19
Q

what is the water potential of solutions

A

they have a lower water potential than pure water with a negative water potential

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20
Q

what is the water potential of a solution affected by

A

the amount of solute it contains
the greater the amount of solute, the lower the water potential

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21
Q

why does greater amount of solute lower the water potential

A

water molecules bind to the solute molecules reducing the number of water molecules that are free to diffuse

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22
Q

what is the solute potential

A

the contribution that solutes make to the water potential of a solution is the solute potential

23
Q

is the solute potential negative or positive

A

negative

24
Q

how do water molecules move if they are separated by a partially permeable membrane

A

they will move from the solution with a higher water potential to a solution with a lower water potential

25
Q

what happens when the water potential on both sides becomes equal

A

there will be no net osmosis, the water molecules still move randomly

26
Q

what happens to the solute potential as more solute molecules are added

A

water potential is lowered so the value becomes negative

27
Q

how else is the water potential of a solution affected

A

by the pressure applied to it

28
Q

how does pressure affect the water potential

A

greater pressure = higher water potential

29
Q

why is pressure potential always positive

A

due to the constant flow of water into the cell causing a force or pressure against the cell membrane or cell wall.

30
Q

why is solute potential always negative

A

When solute is dissolved in water, the amount of free water molecules reduces causing the kinetic energy of the molecules to reduce.

31
Q

what is the equation for water potential

A

solute potential + pressure potential

32
Q

what is osmotic concentration

A

refers to the amount of dissolved solutes in a solution

33
Q

what is another name for a concentration solution

A

a solution with a high osmotic concentration and a low water potential

34
Q

what is another name for dilute solution

A

a solution with a low osmotic concentration and a high water potential

35
Q

how do insoluble molecules affect osmotic concentration

A

they dont

36
Q

how does water move along the concentration gradient

A

it moves DOWN it

37
Q

which protein channel does water move through

A

aquaporins

38
Q

what does a partially permeable membrane result in

A

an uneven distribution across the membrane - it only lets small water molecules through

39
Q

what is an isotonic solution

A

any external solution that has the same solute concentration and water concentration compared to a cell. in an isotonic solution, no net movement of water will take place

40
Q

what is a hypertonic solution

A

any external solution that has a high solute concentration and low water concentration compared to a cell. in a hypertonic solution, the net movement of water will be out of the body and into the solution

41
Q

what is a hypotonic solution

A

any external solution that has a lower solute concentration compared to the intracellular solute concentration. when a red blood cell is placed in a hypotonic colution, there will be a net movement of water into the cell.

42
Q

in an animal cell, describe the movement of water in a isotonic solution

A

the water potential outside the cell is the same as the water potential of the cell cytoplasm. there is no net movement of water

43
Q

in an animal cell, describe the movement of water in a hypertonic solution

A

the water potential outside the cell is lower than the cell cytoplasm. water has therefore moved out of the cell.

44
Q

what happens if water moves out of an animal cell

A

the cell becomes crenated as the cytoplasm pulls away from the cell membrane

45
Q

in an animal cell, describe the movement of water in a hypotonic solution

A

the water potential outside the cell is higher than inside of the cell. water has therefore entered the cell.

46
Q

what happens if water moves into a plant cell

A

because the cell has no protective cell wall, it eventually bursts (lysis)

47
Q

which solutions have the same osmotic concentration as the cytoplasm

A

isotonic solutions

48
Q

which solutions have a lower osmotic concentration as the cytoplasm

A

hypotonic solutions

49
Q

which solutions have a higher osmotic concentration as the cytoplasm

A

hypertonic solutions

50
Q

in a plant cell, describe the movement of water in a hypertonic solution

A

the water potential outside the cell is lower than inside the cell. water has therefore moved out the cell

51
Q

what happens when water moves out of a plant cell

A

the cytoplasm has pulled away from the cell wall and the cell is plasmolysed

52
Q

in a plant cell, describe the movement of water in a hypotonic solution

A

the water potential outside the cell is higher than inside the cell. water has entered the cell.

53
Q

what happens when water moves into a plant cell

A

the cytoplasm is pushing against the cell wall and the cell is turgid

2.1.5 biological membranes (7 decks)

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