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B3 REVISION NOTES

ACTIVE TRANSPORT

Substances get in and out of cells through1. Diffusion

2. Osmosis3. Active transport

A cell may need to take up a substance against the concentrationgradient. This involves energy and is called active transport.

It is the only one of the tree methods that requires energy.

EXCHANGE OF GASES IN THE LUNGS

The lungs are in the thorax and protected by the rib cage.

The lungs exchange carbon dioxide and oxygen with the atmosphere.

They have a large surface area and are moist.

Diffusion takes place much more quickly through a wet surface.

EXCHANGE IN THE GUT

Digested food is absorbed by the capillaries alongside the small intestine(gut).

The small intestine has a rich blood supply.

The surface area of the small intestine is greatly increased by villi.

Absorption by the bloom is by diffusion and active transport.

EXCHANGE OF MATERIALS IN OTHER ORGANISMS

Fish exchange oxygen through their gills.

Frogs exchange oxygen through their skin.

Insects exchange oxygen through holes in their sides leading to a series oftubes.

EXCHANGE IN PLANTS

Plants exchange gases through their leaves.

Plants take up water and minerals through their roots.

Leaves and roots have adaptations for efficient exchange of materials.

Plants respire all the time

During daylight hours enough oxygen is produced by photosynthesis, sodiffusion into the leaves is mainly of carbon dioxide.

At night oxygen diffuses into the leaves, as respiration is the only process

taking place.

TRANSPIRATION

Plants take up gases through stomata.

They take up water and can lose water through the stomata.

If plants lose too much water they wilt.

On hot days there is more energy causing the water to evaporate.

On dry days the air can hold more water.

On windy days any build up of humidity (water vapour) around the plantis blown away.

THE CIRCULATORY SYSTEM The heart pumps blood around the body.

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There are two separate circulation systems.

Arteries, veins and capillaries are the vessels involved in transportingblood.

TRANSPORT IN THE BLOOD Red blood cells transport oxygen.

Blood plasma transports carbon dioxide, urea and the products ofdigestion.

THE EFFECT OF EXXCERCISE ON THE BODY

During exercise muscles need more energy.

More glucose and oxygen need to be transported to the muscles.

To do this there are changed in heart rate, in breathing and in bloodsupple to the actively respiring muscle cells.

ANAEROBIC RESPIRATION Muscles can become fatigued after a long period of activity. They may berespiring anareobically as they cannot get enough oxygen.

Lactic acid id produced in anaerobic respiration. When the activity hasstopped lactic acid must be broken down. This is the cause of oxygendebt.

THE HUMAN KIDNEY

Chemical reaction in the body produce substances that aretoxic/poisonous e.g. urea.

The kidneys excrete substances that the body does not want.

The kidneys first filter substances out the blood. They then reabsorb thesubstance that the body needs.

Urea is made in the liver from excess amino acids.

DIALYSIS AN ARTIFICIAL KIDNEY

If your kidneys fail, you would die if no action were taken.

A dialysis machine does the work of the kidneys and keeps patients alive.

If a successful kidney transplant is carried out, then the dialysis machinewill no longer be necessary.

KIDNEY TRANSPLANTS

A diseased kidney can be replaced by a healthy kidney.

The healthy kidney must be a very good match.

The immune system has to be suppressed or it is likely to reject the newkidney.

GROWING MICROBES

On a small scale, microbes are grown on agar in Petri dishes.

Carbohydrate is the energy source for the microbes.

Special precautions are taken to grow microorganisms safely and asuncontaminated cultures.

In schools and colleges cultures are incubated at 25o.

FOOD PRODUCTION USING YEAST Yeast is a single-celled organism.

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Yeast is used in making bread and alcoholic drinks.

Yeast respires aerobically and anareobically.

The anaerobic respiration of yeast produces alcohol and carbon dioxide.

FOOD PRODUCTION USING BACTERIA

Bacteria are used t help produce cheese and yoghurt. In yoghurt production, bacteria convert lactose sugar into lactic acid.

LARGE-SCALE MICROBE PRODUCTION

Microorganisms can be grown on a large scale in industrial fermenters.

The conditions in a fermenter must be very carefully controlled.

A mycoprotein can be produced using the fungus Fusarium.

ANTIBIOTIC PRODUCTION

They are produced in Fermenters.

The mould penicillin produces the antibiotic.

BIOGAS

Biogas is mainly methane.

It is made up by the anaerobic fermentation of a wide range of wastesubstances and plant material containing carbohydrate.

Biogas can be made on a large and a small scale.

Many different microorganisms are involved in biogas production.

It is produced through fermentation microorganisms respireanareobically to produce the gas.

MORE BIOFUELS

Ethanol-based fuels can be produced by fermentation and used to powercars.

Microorganisms respire anareobically to produce the ethanol, using sugarsas the energy source.

The ethanol produced through the fermentation process has to be distilledbefore it can be used.