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1. Passive TransportA. Diffusion

B. Gradients

C. Osmosis

D. Hypotonic

E. Hypertonic

F. Isotonic

2. Active Transport (energy expenditure, direction)

A. Endocytosis (phagocytosis )

B. Exocytosis

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1. Define diffusion

1. Define gradient

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1. Define diffusion:

The movement of molecules from an

area in which they are highly

concentrated to an area in which they

are less concentrated.

2. Define gradient:

An increase or decrease in the amount

of a concentration observed in passing

from one point or moment to another.

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• Draw a diagram of an

example of diffusion we

saw in class.

Remember:

tea bag,

food coloring drops,

sugar cubes,

etc.

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The diffusion of water through a semi-permeable

membrane.

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• French botanist working with

plant cells between 1824 and

1830.

• He looked for cells in animals,

but was unable to find any.

• He also discovered and

named the phenomenon of

osmosis, which is the

passage of a liquid through a

semi-permeable membrane.

• First to carefully study

respiration and light sensitivity

in plants.

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• Surface area to volume ratio

• Concentration gradient

• Size of molecule(s)

• Same things effecting diffusion.

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Size matters

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• The surface of a cell (membrane) is where it exchanges

materials and its external environment.

• This surface must allow sufficient exchange to support the

contents of the cell.

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As an object increases in size its volume increases as the cube of its linear dimensions while surface area increases as the square.

This ratio limits how large cells can be.

These cubes illustrate the surface area to volume ratio of a small object is larger than that of a large object of similar shape.

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Cell Dimensions(cm)

Surface Area(cm2)

Volume(cm3)

RatioSurface area to Volume

1 2 x 2 x 2 (2x2x6) = 24 (23) = 8 24:8

2

3

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CellDimensions

(cm)Surface Area

(cm2)Volume(cm3)

RatioSurface area to

Volume

1 2 x 2 x 2(2x2x6) =

24(23) = 8

24:83

2 4 x 4 x 4(4 x 4 x6) =

96(43) = 64

96:641.5

3 8 x 8 x 8(8 x 8 x 6)

= 384(83) = 512

384:5120.75

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Controlling what comes in and out.

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are

• Semi-permeable / Permeable (Selectively)

• Membranes regulate passage of material in and out of cell.

• Double layer of lipid with proteins scattered throughout

• Oxygen & Carbon Dioxide can dissolve in lipids

• Water cannot dissolve, must be passed through protein carrier

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Two layers

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• Some proteins actively use energy from the Adenosine Triphosphate (ATPs) in the cell.

• Proteins drag molecules from area of low concentration to areas of high concentration (work against diffusion).

• An example of this is the sodium/potassium pump.

Here the energy of a phosphate (shown in red) is used to exchange sodium atoms for potassium atoms.

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Diffusion of water through a semi-permeable membrane

• Water is 70-95% of living cells

• Cell has no control over osmosis, dependanton water concentration

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• This experiment demonstrates the process of osmosis.

• Water flows through a semi-permeable membrane into a sugar solution, diluting the solution.

• The sugar molecules cannot pass through the membrane, so the water outside remains pure.

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3 Solution Conditions• Isotonic — equal, the

same

• Hypotonic —under

• Hypertonic —above, over

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Solution

Typev

Concentration

Amount

Cell Results

Hypotonic

Water in cell is

high solution

surrounding cell

is low.

Cell will swell

Isotonic

Exactly the same

concentration of

water and

solution.

No change

Hypertoni

c

Water in cell less

than solution

surrounding cell.

Cell will shrivel

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Hypotonic Isotonic Hypertonic

"HYPO" means

less

"ISO" means the

same

"HYPER" means

more

There are less solute

(salt) molecules outside

the cell, since salt

sucks, water will move

into the cell.

The water will move

back in forth but it won't

have any result on the

overall amount of water

on either side.

There are more solute

(salt) molecules outside

the cell, which causes

the water to be sucked

in that direction.

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• Hypotonic Solution

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When push comes to shove

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Two types of active transport

1. Endocytosis — endo means internal; within

— cyt means cell

2. Exocytosis — exo means external; from outside

— cyt means cell

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Involves moving material through the plasma

membrane and incorporation of the bulk

material into a vacuole.

a)Phagocytosis involves the

engulfing of solid materials.

b)Pinocytosis involves the engulfing

of liquid materials.

Endocytosis

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Is the expulsion of solid or liquid materials

by expulsion.

Exocytosis

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