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Unit 1 ­ Biology and disease

Chapter 1 ­ Causes of disease

Microorganisms are single celled organism. Microorganisms which cause disease are called

For a microorganism to be considered a pathogen it must

Gain entry to the host
Colonise the tissues of the host
Resist the defences of the…

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Sunlight ­ The more exposed to sunlight, the greater the risk of skin cancer.

Lifestyle factors that contribute to coronary heart disease (CHD): -

High blood pressure ­ Excessive prolonged stress, certain diets and lack of exercise increase
high blood pressure.
Blood cholesterol levels ­ Can be lowered by…

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Polysaccharides are made up of many monosaccharides joined by glycosidic bonds that were formed
by condensation reactions. They are insoluble so good for storage. Some polysaccharides like starch
are used to give structural support to plant cells.

Starch can be detected as it turns the colour of iodine in potassium…

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The molecule which the enzyme works on is called the substrate. It forms an enzyme-substrate

Lock and key model ­ Enzymes are specific in the reactions they catalyse. The shape of the
substrate (key) exactly fits the active site of the enzyme (lock).

Induced fit model ­ The enzyme…

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The greater the resolving power of an electron microscope compared to a light microscope is due to
the electron beam having a shorter wavelength than light.

Eukaryotic cells have a distinct nucleus and possess membrane-bounded organelles, e.g. epithelial

Epithelial cells absorb and secrete.

Parts of a nucleus: -


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also labels them to be accurately sorted and sent to their correct destinations. Once sorted, the
modified proteins and lipids are transported in vesicles.

Functions of Golgi apparatus are to: -

Add carbohydrates to proteins to form glycoproteins.
Produce secretory enzymes.
Secrete carbohydrates.
Transport, modify and store lipids.
Form lysosomes.…

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All plasma membranes found around the inside cells have the same phospholipid bilayer structure.
What gives plasma membranes their different properties are the different substances they contain
especially proteins.

Functions of proteins in the membrane: -

Provide structural support
Act as carriers transporting water-soluble substance across the membrane.
Allow active…

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Glucose is absorbed through the walls of the small intestine. These are then folded and have villi. Villi
increase the surface area for diffusion. They are thin walled, reducing the distance over which
diffusion takes place. They are well supplied with blood vessels so that blood can carry away

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Damage to the epithelial cells lining the intestine.
Loss of microvilli due to toxins
Excessive secretion of water due to toxins.

To treat diarrhoea you need to rehydrate the patient. This can't be done by simple drinking water as
water is not being absorbed by the small intestine and water…

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Mycobacterium Bovis

The symptoms of tuberculosis are a persistent cough, tiredness, loss of appetite leading to weight
loss, fever and coughing up of blood may occur.

TB is spread through the air by droplets released into the air when infected individuals cough,
sneeze, laugh and talk. It takes close contact…










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