Further Biology Revision Notes

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Further Biology
Exchange of materials
Active transport
Substances are sometimes absorbed against a concentration gradient by active transport.
Active transport uses energy from respiration.
Cells can absorb ions from very dilute solutions and move molecules through cell membranes
using active transport.
Exchange of gases in the lungs
Your breathing system takes air into and out of your body.
Oxygen from the air diffuses into your bloodstream and carbon dioxide diffuses out.
The alveoli of the lungs provide a very large, moist surface area with a rich blood supply and
thin walls to make diffusion as effective as possible.
Exchange in the gut
The villi in the small intestine provide a large surface area with an extensive network of
capillaries. This makes them well adapted to absorb the products of digestion by diffusion
and active transport.
In material exchanges, the surface area : volume ration is always important ­ a big surface
area is vital for successful diffusion.

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Exchange of materials in other organisms
Whatever the organism, gas and solute exchange depends on a large surface area, moist
surfaces, short diffusion distances and a large concentration gradient.
This is shown in the two examples taught:
o Gas exchange in a fish,
o Gas exchange in an insect.
Exchange in plants
Plants have stomata which allow them to obtain carbon dioxide from the atmosphere.
Carbon dioxide enters the leaf by diffusion.…read more

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Transporting substances around the body
The circulatory system
The body transport system consists off the blood vessels, the heart and the blood.
The three main type of blood vessels are:
o Arteries,
o Veins,
o Capillaries.
Blood Vessels Distinctive features
Artery
They have thick walls and a thick layer of
muscle and elastic fibres, with a small lumen.
Your arteries carry blood away from your heart
to the organs of your body. This is usually
oxygenated blood so it is bright red.…read more

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Human beings have a double circulation.
The heart works as a pump, moving blood around the body.
Transport in the blood
Your blood is the main transport medium of your body.
Your blood plasma transport dissolved food molecules, minerals, carbon dioxide and urea.
Your red blood cells are adapted to transport oxygen from your lungs to the organs of your
body.
Red blood cells are biconcave discs which have no nucleus and are packed with the red
pigment haemoglobin.…read more

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Anaerobic respiration
If muscles work hard for a long time they become fatigued and don't contract properly. If
they don't get enough oxygen they will respire anaerobically.
Anaerobic respiration is respiration without oxygen. Glucose is broken down to form lactic
acid, water and a small amount of energy.
After exercise, oxygen is still needed to break down the lactic acid which has built up. The
amount of oxygen needed is known as the oxygen debt.…read more

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Kidney transplants
In a kidney transplant diseased or damaged kidneys are replaced with a healthy kidney from
a donor.
The donor kidney may be rejected by the recipient's immune system. To try and prevent
rejection the tissue types of the donor and the recipient are matched as closely as possible
and immunosuppressant drugs are used.
Microbiology
Growing microbes
Microorganisms can be grown in an agar culture medium with a carbohydrate energy source
and various minerals, vitamins and proteins.…read more

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Food production using bacteria
Bacteria are used in making both yoghurt and chees.
In the production of yoghurt a started culture of bacteria acts on warm milk. Lactose is
converted to lactic acid in a lactic fermentation reaction. This changes the texture and taste
of the milk to make yoghurt.
On cheese-making a different starter culture is added to warm milk giving a lactic
fermentation which results in solid curds and liquid whey.…read more

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Ethanol based fuels can be produced by the anaerobic fermentation of sugar cane juices and
from glucose derived from maize starch by the action of the enzyme carbohydrase.
Ethanol is distilled from the fermentation products and can be used as a fuel in motor vehicles
on its own or mixed with petrol to produce gasohol.…read more

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