Biology B3 Revision notes

Parts in red are Higher topics

HideShow resource information
  • Created by: Bhavik
  • Created on: 13-05-11 11:32
Preview of Biology B3 Revision notes

First 422 words of the document:

Biology Revision notes
Biology revision notes
There are two main ways which dissolved substances move into and out of cells.
Diffusion is when they move from a high concentration to a low concentration.
Active transport is from a low concentration to a high concentration. Against the
concentration gradient through a partially permeable membrane.
Solute molecules are moved through the partially permeable membrane by the use
of a transport protein.
The solute is recognised and grabbed by the transport protein.
Protein rotates in membrane and releases the solute inside the cell and then rotates
back again.
The energy comes from cellular respiration. This means that lots of mitochondria are
required for active transport.
It happens in roots, the kidney and in salt glands of marine and sea birds/animals
Your lungs are in the upper part of your body in the THORAX. The thorax contains the
When you breathe the diaphragm flattens from its normal dome shape this pulls air
into the lungs. Then when you breathe out the ribs move down and in pushing the air
Your lungs are adapted to make gas exchange more efficient by having clusters of
alveoli which have a large surface area. They are kept moist so gasses can dissolve in
the water and diffuse easier.
They also have a rich blood supply to maintain a concentration gradient both
directions. Oxygen is constantly removed into the blood and more carbon dioxide is
constantly delivered into the lungs. As a result, gas exchange takes place along the
steepest concentration gradients possible making it rapid and effective. The layer of
cells between the air and the lungs and blood capillaries is also very thin, this lets
diffusion take place over the shortest possible distance.
In the gut both diffusion and active transport are used to move molecules from the
small intestine into the bloodstream.
Diffusion can only happen when the food molecules are dissolved in water.
The digested food molecules are then small enough to pass freely through the walls
of the small intestine into the blood vessels. They move in this direction because
there is a very high concentration of food molecules in the gut and a much lower
concentration in the blood. In other words, the move into the blood along a steep
concentration gradient.
Bhavik BarochiaPage 1

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Biology Revision notes
The lining of the small intestine is folded into thousands of tiny projections known as
villi. These increase the uptake of digested food by diffusion. Only a certain number of
molecules can diffuse over a given surface areas of the gut lining at one time.…read more

Page 3

Preview of page 3

Here's a taster:

Biology Revision notes
Also there are many air spaces inside the leaf allowing the carbon dioxide to come
into contact with lots of cells. This provides a large SA
Leaves lose water through evaporation. If Co2 could diffuse in and out freely, water
vapour would be lost very quickly.
The leaf cells don't need co2 all the time. When it's dark they don't need carbon
dioxide because they are not photosynthesising. So leaves are adapte to only allow
co2 in when needed.…read more

Page 4

Preview of page 4

Here's a taster:

Biology Revision notes
The stomata will close which stops photosynthesis and risks overheating. The plant
will remain wilted until the temperature drops, the sun goes or it rains.
The transport system is absolutely vital to supply the needs of your body cells and to
remove the waste material they produce. The blood vessels, the heart and the blood
are the 3 main elements.
Humans have a double circulatory system. One carries blood from the heart to the
lungs and to the heart again.…read more

Page 5

Preview of page 5

Here's a taster:

Biology Revision notes
The blood is a complex mixture of cells and liequid which carries a huge range
of substances around the body.…read more

Page 6

Preview of page 6

Here's a taster:

Biology Revision notes
The muscles use a lot of energy. Muscles need a lot of energy, for example
the heart.
Your muscles also contain glycogen stores which can be converted to glucose
when needed.
Glucose + oxygen Carbon dioxide + water + energy
When you are resting your muscles use up a little energy but when you're
exercising your muscles contract much faster and harder which means that
they need more glucose and oxygen.…read more

Page 7

Preview of page 7

Here's a taster:

Biology Revision notes
Kidneys also maintain the balance of water in your body. Too much water in
the blood would case the cells to have too much water in them, too little
water in the blood would meant that not enough water can move out the cell
and it becomes too much for the cell to handle.
If you're short of water, your kidneys conserve it. If you produce very little
urine, most of the water is saved for use in the body.…read more

Page 8

Preview of page 8

Here's a taster:

Biology Revision notes
Most people go to hospital for dialysis but in 1964 home dialysis machines
were made available so that patients didn't have to spend endless time in
Kidney transplants are where are where a kidney from another patient or body
and transplanted into the closest match. The kidney would come from a
donor and if all goes well would replace the non working kidneys in their job in
the recipient.…read more

Page 9

Preview of page 9

Here's a taster:

Biology Revision notes
Another way to grow microorganisms is using a culture flask but for either
method warmth and oxygen is needed.
There's always a risk of mutation occurring when culturing bacteria, and a
dangerous pathogen could be made.
Contamination from external sources must be avoided and also health and
safety procedures must be carried out strictly.
One of the microorganism which is most useful to people is yeast. Yeasts are
single celled organisms. They reproduce asexually.…read more

Page 10

Preview of page 10

Here's a taster:

Biology Revision notes
Milk very rapidly goes off and tastes disgusting however milk can be changed
into food which can last for much longer. These changes depend on the use
of microorganisms
Yogurt is a staple part of the diet in the Middle East and has been for a very
long time and only recently has come into fashion in the UK. Cheese however
has been used all over the world for a very long time.…read more


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »