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In order to conduct the day-to-day activities of daily life, all cells must transfer essential ions and small molecules across semi-permeable plasma membranes. Ions are atoms or molecules with a net positive or negative charge

To fulfill the requirements of life, cells exchange gases, such as oxygen and carbon dioxide; excrete waste products; and take in particles of food, water and minerals.

The exchange takes place between the inner cell and its surrounding extra-cellular fluid.

At the end of this article, students should be able to:
1. its-properties cytoplasm, cell sap, lymph and blood
6. Describe the mechanisms of transportation in various animals
7. Compare and contrast various mechanisms of transportation
8. Demonstrate and Define diffusion
2. Explain the inadequacy of diffusion alone as a transport system for complex organisms
3. Explain the necessity of a transport system in complex organisms
4. Identify source of materials and where they are transported to
5. Discuss the different types of transportation media such as the flow of materials in plant

MEANING OF TRANSPORT SYSTEM AND OSMO-REGULATION

Transport system in plants and animals refers to the movement of metabolic materials from various parts of the organisms where they are produced or obtained to the parts where they are either used, stored or removed from the body.

HOW OSMOSIS AND DIFFUSION HELP IN TRANSPORT SYSTEM

Diffusion is the process by which molecules or ions of a substance (i.e. gases and liquids) move from a region of high concentration to a region of low concentration until they are evenly distributed.

The substance involved in diffusion may be liquid, gases or solid.

factors affecting or controlling diffusion within the body system

The rate or speed of diffusion is controlled by a number of factors which are:

1. State of matter:

diffusion varies with the three states of matter. The diffusion of gases is more faster than that of liquids because the gas molecules are freer and therefore faster than liquid molecules.

Molecular size:

the nature or the size of the molecules affect diffusion. In general, the smaller the molecules, the faster the rate of diffusion while the larger the molecules the slower the rate of diffusion.

2. Differences in concentration: for diffusion to take place in a medium, there must be differences in the concentration of the substance in two areas osmosis and Diffusion

The greater the differences in the concentration of the molecules, the greater the rate of diffusion.

3. Temperature: high temperature increases the speed at which molecles move. Thus, the higher the temperature, the faster the rate of diffusion.

Experiment to demonstrate diffusion in liquids

Take a beaker and fill it with distilled water. Use pipette to deliver small quantity of potassium permanganate solution gently at the bottom of the beaker and leave it to stand for few minutes.

The purple colour of the potassium permanganate solution starts to spread outside.

Eventually, the colour spreads evenly throughout the water medium so that the water have the same shade of purple colour.

Experiment to demonstrate diffusion in gases

Take a bottle of ammonia solution, open the bottle and move some distance away from the bottle and wait for some time.

The small the air to perceive the odour. The smell of the ammonia gas shows that diffusion of ammonia has taken place.

importance of diffusion to flowering plants

Diffusion is important to flowering plants in the following ways:
1. Movement of carbon dioxide through the stomata of the leaves during respiration.

2. There is movement of carbon dioxide through the stomata into the leaves during photosynthesis.

3. Water vapour leaving the leaves during respiration.

4. Movement of oxygen into the leaves through the stomata during respiration.

Importance of diffusion to animals

Diffusion plays important roles in the life of animals through the following processes

1. There is intake of oxygen or nutrients from mother to foetus (embryo) through placenta.

2. Gaseous exchange in mammals occurs in the lungs during respiration

.
3. Gaseous exchange in many cells and organisms e.g. Amoeba takes in oxygen and gets rid of carbon dioxide by diffusion.

4. There is movement of carbon dioxide from the lung capillaries into the air sac.

diffusion in nature or non-living conditions

Diffusion is also very important in nature or non-living conditions through the following processes of osmosis and Diffusion
1. The smell or odour of perfume from a person or a corner of a room.
2. Diffusion of molecules (gases and liquids) in iodine, potassium permanganate and copper sulphate solutions.
3. The spread of insecticide in a room.
4. The spread of smell of gases released from the anus.

WHAT IS OSMOSIS AND HOW IT HELPS IN TRANSPORT SYSTEM

Osmosis is the flow of water or solvent molecules from a region of dilute or a weaker solutions to a region of concentrated or stronger solution through a selectively or differentially permeable membrane. It should be noted that osmosis is a special form of diffusion.

Conditions necessary for osmosis to take place

There are three major conditions which are necessary for osmosis to take place. These are:

1. Presence of a stronger solution e.g. sugar or salt solution.

2. Presence of a weaker solution e.g. distilled water.

3. Presence of a selectively or differentially permeable membrane.

how Living cells serves as osmometre

In osmosis, there are usually two solutions which are separated by a differentially permeable membrane in osmosis and Diffusion

The weaker solution is said to be hypotonic while the stronger solution is said to be hypertonic. When both solutions have the same concentration, they are said to be isotonic.  

1. Hypotonic;

when a cell of a living plant or animals is surrounded by pure water or solution whose solute concentration is lower, water passes into the cells by osmosis. The solution is therefore said to be hypotonic.

2. Isotonic: when the solute concentration of the cell and its surrounding medium are the same, the solution is said to be isotonic.

Hypertonic: when the cell is surrounded by a stronger solution, water will be lost by the cell. The shrinking of the cell is as a result of the surrounding solution being hypertonic.

In living cells when water moves across the membrane into a solution of higher concentration, a pressure is created in the cell, this pressure is called osmotic pressure under osmosis and Diffusion

3. The solution is said to exert a higher osmotic pressure than the weaker solution. Osmotic pressure is a force that draws in water into the cell. The pressure which a solution can potentially exert is called its osmotic potential osmosis and Diffusion

What is osmoregulation?

is the control of fluctuations in the concentration of substances in cell fluids by special devices such as the contractile vacuole in amoeba. osmosis and Diffusion

NEED FOR TRANSPORTATION OSMOSIS AND DIFFUSION

The need for osmosis and Diffusion  transportation in living organisms include:

1. Transport is necessary for every cell of the organism to obtain all the essential materials for its metabolism, e.g. nutrients, oxygen and water.

2. It is also necessary to remove and dispose metabolic wastes, e.g. carbon dioxide, water and urea.

3. In plants, transport is necessary to move mineral salt and water from the roots to the stems and leaves.

4. Transport is also required to move hormones in plants and animals from where they are produced to the area of need.

5. Glucose from the leaves and storage organs are some of the substances being regularly transported in plants.
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