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Biology B3 Notes(Hope They Help Leave A Comment)


Unit 1: Exchange of Materials
Unit 2: Transporting Substances Around the Body
Unit 3: Microbiology

B3-1 : Exchange of Materials

Active Transport

Two of the main ways in which diffused substances are transported across cells
areosmosis and diffusion. Diffusion is the…

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blood, even though that is against a gradient. Active transport is also used in marine birds and
reptiles, because they consume large amounts of salt when they drink water, and as the kidneys
cannot get rid of it all, they have salt glands which use active transport. Without the ability…

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The lungs have been adapted especially for making gas exchange more efficient. They are made
up of clusters of alveoli, which are tiny air sacs with large surface areas, and are kept moist.
They also have a rich blood supply, which maintains a concentration gradient in both directions.
Carbon dioxide…

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concentration in the blood, so the process here is diffusion. They move along a very steep
concentration gradient.

The lining of the small intestine is folded into thousands of tiny villi. These greatly increase the
uptake of digested food by diffusion. This is because only a certain amount of digested…

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it is needed. Most of the gas exchange takes place in the tracheoles, tiny tubes which are freely
permeable to gases. They are moist and constantly have air pumped in and out of them by the
insect to maintain a steady concentration gradient.

Material Exchange in Plants
All plants require…

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B3-2 : Transporting Substances Around the Body

The Circulatory System

The blood circulation system we have is made up of three main components: blood vessels,
the heart and theblood. It is made up of two different blood systems ­ adouble circulation. The
diagram shows that one transports blood from the…

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Theveins carry blood towards the heart, usually low in oxygen and hence are deep purple-red in
colour. No pulse in veins, but they do contain valves usually which prevent the backflow of

The capillaries are found in junctions between the arteries and veins. These are found in huge

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Red blood cells are the most common cell type in the human body. There are around 5 million
per each square milimetre of blood. The function of red blood cells is to pick up oxygen from the
lungs and deliver it to cells and tissues where it is needed. Their…

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oxygen being brought into the body and picked up by red blood cells ­ and this oxygen is carried
to the exercising muscles

Exercise is definitely very beneficial to us when done regularly. Regular exercise increases the
size of both the heart and the lungs, and they develop a bigger…

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Urine contains waste urea along with excess mineral ions and water not needed by the body.
The quantaties vary depending on how much you have taken in and given out. For example, on a
hot day if you drink little and exercise a lot, you will produce very little urine,…


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