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.


HideShow resource information
  • Created by: Zoe
  • Created on: 15-05-11 14:08
Preview of Full B3 Revision Notes for AQA

First 186 words of the document:

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 equilibrium.
Osmosis is the diffusion of water across a partially permeable membrane from areas of
low concentration to areas of high concentration. (I.e. to where there is less water, it
Active Transport is a process which moves molecules against a concentration gradient,
it requires energy. It is controlled by proteins.
The Lungs
The lungs remove waste carbon dioxide from respiration, and transfer oxygen into the
Gas exchange takes place in the alveoli.
The Alveoli:
Have an enormous surface area ­ to
increase rate of diffusion.
Moist lining ­ to dissolve gases.
Very thin walls ­ to allow molecules to
pass through easily.
A copious blood supply ­ to keep the
concentration gradient.

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

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 ­ diffusion.
The lining of the small intestine is made of tiny villi; these increase the surface area
which increases the rate of diffusion.…read more

Page 3

Preview of page 3

Here's a taster:

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 the concentration gradient of water.
Windy ­ removes the humid air around the plant and so increases the concentration gradient.
When plants wilt they are reducing the water loss because they reduce the surface
area.…read more

Page 4

Preview of page 4

Here's a taster:

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 blood away from the heart, it is usually oxygenated blood. Your pulse is
the arteries stretching as blood is forced through them.…read more

Page 5

Preview of page 5

Here's a taster:

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 kidneys. Digested food is carried by the plasma.
Biconcave discs to increase the
surface area.
Haemoglobin; pigments which can
carry oxygen.
No Nucleus means more room for
haemoglobin and diffusion.…read more

Page 6

Preview of page 6

Here's a taster:

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 permeable membranes.
- Then through dialysis fluid which contains the perfect concentration of
substances to ensure diffusion of waste substances into the fluid, but glucose
remains in the blood.…read more

Page 7

Preview of page 7

Here's a taster:

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. The dishes
need to be kept warm and oxygenated for good growth.
To prevent cross contamination
1.…read more

Page 8

Preview of page 8

Here's a taster:

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
sharp, tangy taste) ­ this process is lactic fermentation
4. the lactic acid causes the milk to clot and solidify to form
a yoghurt
5.…read more

Page 9

Preview of page 9

Here's a taster:

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)
A fungus known as FUSARIUM.
It requires aerobic conditions. It is usually produced in batches.
It serves as a high-protein, low-fat meat substitute.
Alexander Fleming discovered penicillin.…read more

Page 10

Preview of page 10

Here's a taster:

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 with petrol to make Gasohol. This reduces carbon emissions.…read more


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »