Full B3 Revision Notes for AQA

I made these notes using my own work and various other sources to help me revise for my B3 exam, I hope they are useful.

To the best of my knowledge it contains all the topics needed for the 2011 syllabus, sorry that some areas are less detailed than others but I did not bother to describe in detail the topics I knew very well.


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  • Created by: Zoe
  • Created on: 15-05-11 14:08
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Material Exchange

Diffusion and osmosis
Diffusion is the process by which molecules spread from areas of high concentration to
areas of low concentration along a concentration gradient. It is a passive process due to
the random movement of particles.

When all the particles are evenly spread it is called…

Page 2

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The Gut
Once food has been broken down in the gut the useful substances must be transferred
to the blood. This happens in the small intestine.

It works because there is a high concentration of food molecules in the gut, and a low
concentration of food molecules in the blood…

Page 3

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What is transpiration?

Transpiration is the loss of water vapour through the surface of the leaves.

As water is lost through the stomata, it is pulled up through the xylem.

This movement is known as the transpiration stream.

Hot conditions ­ increases the rate of evaporation.

Dry conditions ­ increases…

Page 4

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Transporting substances around the body

The Circulatory System
The human circulatory system has two different blood systems so is
called a double circulation.

One system transports blood from the heart to the lungs and back

The other takes blood around the rest of the body.

Blood vessels:

Arteries carry…

Page 5

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Blood Transport
The liquid part of our blood is called plasma. It contains:

Cell Function
Red Blood Cells Transport
White Blood Cells Immune system
Platelets Blood clotting
Carbon dioxide is carried in the plasma. Oxygen is carried in the red blood cells.

Urea, is carried by the plasma to the…

Page 6

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The Kidneys
The kidneys filter the blood and reabsorb what is needed. Example; All sugar is
reabsorbed by active transport, but water and dissolved mineral ions are selectively
absorbed. Urine concentration depends on how much you have taken in and giving out.


- The blood is filtered through partially…

Page 7

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Harmful microorganisms are known as pathogens.

To grow microbes in a lab we use a culture medium which contains carbohydrates,
mineral ions and sometimes proteins in an agar jelly which is first sterilised, warmed to
add the nutrients then poured into a sterilised petri dish and left to cool.…

Page 8

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Other bacteria and food
How to make yoghurt:

1. adding a culture of the right type of bacteria to warm
2. keeping the mixture warm so the bacteria grow
reproduce and ferment
3. as the bacteria break down the lactose, lactic acid is
produces (this gives yoghurt the

Page 9

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Industrial fermenters have:

- Oxygen so the microorganisms can respire.
- Stirrers to keep the temperature constant and make sure oxygen and food
supply are evenly spread.
- A water cooled jacket to remove excess heat from respiration.
- Measuring devices to maintain constant conditions (i.e. pH and temperature)


Page 10

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Is a carbon neutral fuel because the plants take in the same amount of carbon dioxide
that they release when burnt.

The starches in the plant must first be broken down by enzymes before being
fermented. Ethanol does not produce carbon monoxide or sulphur dioxide.

It can be combined…


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