DIFFUSION / OSMOSIS

•What does the prefix ‘homo’ mean?

•Same

HOMEOSTASIS•Homeostasis (aka Homoeostasis): the

tendency of a system to STAY THE SAME

•Our body is an example of a system

• There are two ways that homeostasis can be maintained:– Diffusion– Osmosis

OSMOSIS

• Osmosis is the movement of WATER from high to low concentration.

• Membranes (barriers) can be permeable Permeable (def.): allowing things (such as liquid or solids) to pass through

• What does the word ‘selective’ mean?

*Think of charter schools that are described as selectively enrolled students

So what does selective permeability mean?

SELECTIVE PERMEABILITY

•Selective Permeability: a PARTIALLY selective membrane that allows only CERTAIN things to go through

DIFFUSION • Diffusion is movement of solid, gases, and

other substances molecules (solutes) from high to low concentration.

PRACTICE/PREDICTION

3 TYPES OF CONCENTRATION • Hypertonic

• Hypotonic

• Isotonic

• Hyper = More

• Hypo = Less

• Iso = Same

concentration of solute outside of

the cell is EQUAL to the

concentration of solute inside the

cell.

H2O

H2O

Water MoleculeDissolved Molecule

ISOTONIC SOLUTION

HYPOTONIC SOLUTIONConcentration of solute is LOWER

(higher water concentration)

outside of the cell than the

concentration of solute inside the cell.

H2O

H2O

Water MoleculeDissolved Molecule

• In a HYPOtonic solution - The cell swells because more water goes in the cell. Less solutes outside of the cell, high concentration of solutes in the cell, so water moves in.

HYPERTONIC SOLUTION

Concentration of solute is HIGHER

(water concentration is lower) outside of

the cell than theConcentration of solute inside of the

cell

H2O

H2O

Water moleculeDissolved molecule

• In a HYPERtonic solution - The cell shrinks because water leaves the cell. High concentration of solids on the outside of the cell, so the cell loses water and shrinks.

What type of solution is this Hypo-, Hyper- or Iso- tonic?

Which way will the water move?

Hypotonic

Water moves INTO the cell

What type of solution is this Hypo-, Hyper- or Iso- tonic?

Which way will the water move?

Isotonic

Water moves at an EQUAL rate into and out ofthe cell

What type of solution is this Hypo-, Hyper- or Iso- tonic?

Which way will the water move?

Hypertonic

Water moves OUT of the cell

water

water

waterwater

Cell SWELLS

Cell stays the SAME

Cell Shrinks

ANIMAL CELL

PLANT CELL

Isotonic Hypotonic Hypertonic

Isotonic Hypotonic Hypertonic