Chap 6: Movement through Membranes

Solute

A substance which is dissolved, e.g. salt, sugar, coffee.

Solvent

A liquid that is capable of dissolving substances, e.g. water (known as the universal solvent)

Solution

Mixture of solute and solvent, e.g. salt water, mi wadi.

Hypotonic solution

A solution with a low solute concentration, e.g. weak dilute.

Isotonic solution

When two solutions have equal solute concentrations, e.g. isotonic sports drinks have the same concentration as bodily fluids.

Hypertonic solution

A solution with a high solute concentration, i.e. is concentrated/strong, e.g. espresso

Selectively permeable

Allows some substances to pass through, e.g. water, oxygen, carbon dioxide, but do not allow others, e.g. sugars, proteins, salts, unless needed.

Permeable

Allows all substances to pass through

Non-permeable

Does not allow any substances to pass through

Diffusion

The movement of molecules from a region of high concentration to a region of low concentration across a semi-permeable membrane. Passive transport method, and takes place along a concentration gradient, i.e. high to low

Passive transport

No energy is required for this process

Everyday examples of diffusion

Smells- baked bread, perfume. Coffee or sugar granules. Gas exchange

Gaseous Exchange Animals

Oxygen leaves the alveolus across one cell, i.e. diffusion. O2 enters a capillary and is taken to where respiration occurs.

Osmosis

The movement of water molecules from a region of high water concentration to a region of high low water concentration across a semi permeable membrane.

Amoeba

If amoeba becomes hypertonic inside, it will draw water across its membrane by osmosis, i.e. carrying out osmoregulation.

Osmoregulation

The control or regulation of water content of blood and cells.

Animal cell in a solution of the same concentration

Water will move in and out at the same rate and cell will remain intact.

Animal cell in a solution less concentrated

Water from outside will move into the cell and may cause it to burst or die.

Animal cell in a more concentrated solution

Water will leave the animal cell and the cell will shrivel up and die.

In a hypertonic solution

Red blood cells shrivelled

In an isotonic solution

Balanced

In a hypotonic solution

Incredibly turgid