Bio Chem Lecture 3 Diffusion&Osmosis

8/3/2019 Bio Chem Lecture 3 Diffusion&Osmosis

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Unit 3 Lecture 3


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DiffusionDiffusion movement of substances from an area of

high concentration to an area of low concentration

yworks to balance the concentration gradients ofsubstances

y ex: perfume in a room, dye in a glass of water


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Diffusion contdConcentration Gradient difference in

concentration of a substance over a certain area

y with/down the gradient = particles move from areaof high conc. to low conc.

y typical diffusion; natural movement

y against the gradient = particles move from area of

low conc. to high conc.

y non-natural movement; requires E


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Diffusion contdDynamic Equilibrium a balance of the distribution of

particles in an area acknowledging the constant

movement of the particlesy dynamic opposite of sta(tic/sis)

y indicates constant change


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Diffusion contdDiffusion often occurs through one of two types of

membranes:

y permeable membraney allows all molecules [solute, solvent, or other

particle] to pass through

y semi/selectively permeable membrane

y allows only certain substances to pass through

ywhich type of membrane do cells have?


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Diffusion DrawingsProblem: In a membrane selectively permeable to X

molecules, there are:

y 4 particles of X [3 left, 1 right]y 12 particles of O [2 left, 10 right]

Based on the given information,

y identify & understand the type of membrane

y draw before & after beaker with membrane


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Problem: In a membrane selectively permeable to X molecules,

there are:4 particles of X [3 left, 1 right]; 12 particles of O [2 left, 10 right]



y draw before & after beakers with membrane


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before beaker:

y under beaker, record # of particles per side

y draw # particles in beaker

X = 3 X= 1

O = 2 O = 10


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before beaker:

y determine directions of particle movement

X = 3 X= 1

O = 2 O = 10


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before beaker:

y above, draw arrows specifying how particles will move

X = 3 X= 1

O = 2 O = 10


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before beaker:

y large arrow = larger movement [specify type of particle]

X = 3 X= 1

O = 2 O = 10

X


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before beaker:

y small arrow = smaller movement [specify type of particle]

X = 3 X= 1

O = 2 O = 10

X


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after beaker:

y under beaker, record new # of particles per side

X = 3 X= 1

O = 2 O = 10

X

X = 2 X= 2

O = 2 O = 10


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after beaker:

y draw # of particles in beakers

X = 3 X= 1

O = 2 O = 10

X

X = 2 X= 2

O = 2 O = 10


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after beaker:

y draw appropriate arrows [specify type of particle]

X = 3 X= 1

O = 2 O = 10

X

X = 2 X= 2

O = 2 O = 10

X


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OsmosisOsmosis diffusion of water across a selectively

permeable membrane

ymembrane allows ONLY water to go throughy solute particles NEVER move

ywater must be used to reach dynamic equilibrium

y more water moves to where there is more solute


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Osmosis contdy Ex:

ywhich has the higher concentration of solute?

y how can you make the concentrations equal?

y 5 scoops of lemonade in a pitcher

filled with 8 ounces of water

y 5 scoops of lemonade in a pitcher

filled with 1 gallon of water


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Osmosis DrawingsProblem: With a membrane selectively permeable

to water, there are:

y 4 particles of X [3 left, 1 right]



y draw before & after tubes with membrane


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P

roblem: With a membrane selectively permeable to water, thereare: 4 particles of X [3 left, 1 right]



y draw before & after tubes with membrane


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P


before tube:

y under tube, record # of particles per side

y draw # particles in tube

X = 3 X= 1


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P


before tube:

y determine directions of particle movement

X = 3 X= 1


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P


before tube:

y above, draw arrows specifying how particles will move

X = 3 X= 1


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P


before tube:

y large arrow = larger movement [specify type of particle]

X = 3 X= 1

H2O


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P


before tube:

y small arrow = smaller movement [specify type of particle]

X = 3 X= 1

H2O


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Problem: With a membrane selectively permeable to water, there

are: 4 particles of X [3 left, 1 right]

after tube:

y under tube, record # of particles per side

X = 3 X= 1

H2O

X = 3 X= 1


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after tube:

y draw # of particles in beakers AND water level

X = 3 X= 1

H2O

X = 3 X= 1


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after tube:

y draw appropriate arrows [specify type of particle]

X = 3 X= 1

H2O

X = 3 X= 1

H2O


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What happens to cells?Hypertonic Solution solution outside of the cell has a

higher concentration of solute than inside of the cell.

y

hyper = more than normalywater moves out of cell

y cell shrinks

Why is this bad for the cell?


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What happens to cells? contdIsotonic Solution solution outside of the cell has the

same concentration as the solution inside of the cell.

y

concentrations are equaly cell remains the same size


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What happens to cells? contdHypotonic Solution solution outside of the cell has a

lower concentration of solute than inside of the cell.

y

hypo = less than normalywater moves into the cell

y cell swells [possibly bursts]

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Bio Chem Lecture 3 Diffusion&Osmosis