Biology & Disease AQA Unit 1

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  • Created by: Sobia Ali
  • Created on: 03-05-12 08:58
Preview of Biology & Disease AQA Unit 1

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Pathogens can penetrate through:
Gas exchange system
Digestive system
Gas exchange:
Pathogens trapped in mucus ling lung epithelium
Cilia hair beat & move the mucus up trachea to mouth to be removed
Pathogens enter through damage skin and enter bloodstream
Blood clots to prevent pathogens from entering but some enter before the clot
Digestive system:
Bacteria from food can be killed by stomach acid
Some pathogens survive and enter gut wall to invade cells and cause disease
Pathogens cause disease by a) producing toxins and b) damaging
Bacteria release toxins in body to prevent certain functions from happening
Pathogens can physically damage host cells by
Replicating inside cells & bursting them when released
Breaking down nutrients in cells for their own use
Rupturing them to release nutrients inside them

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The immune system
Antigens trigger immune response:
If antigens found on cells are foreign
Phagocytes engulf pathogens:
Phagocytes recognise antigen on pathogen
Phagocytes engulfs pathogen
Pathogen now contained in phagocytic vacuole
Lysosomes fuses and lysozyme breaks down the pathogen
Phagocyte presents the pathogens antigen n its surface to activate other immune
system cells
Phagocytes activate T-cells:
T-cells have protein on its surface that bind to antigen
Activates other T-cells
T-cells activate B-cells:
When antibody on surface of B-cells bind to complementary antigen it bind to…read more

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Vaccines and antibodies
Help reduce the primary response
Contain antigens which cause body to produce memory cells against pathogen
Protects individual and reduces occurrence of disease
People not vaccinated protected as less to catch from-herd immunity
Can be injected or taken orally (broken down by enzymes or too large to be
absorbed into blood)
Booster cells given later in life to make sure memory cells produced
Antigenic variation:
Because changes in genes some pathogens can change surface antigens
So when infected second time memory…read more

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The digestive system
Polymers(large complex molecules in food are made up of monomers(small
basic molecular unit)
Carbohydrate monomers are called monosaccharide-contain CHO
Protein monomer are amino acids-contain chon
Polymers insoluble-need to add water to break bonds so they are small
soluble molecules
Parts of digestive system:
Oesophagus: transports food from mouth to stomach by peristalsis, mucus
secreted to lubricate food's passage downwards
Stomach: folds and expands to be able to hold food, entrance and exit is controlled
by sphincter muscles, stomach wall produces gastric…read more

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Monomers- amino acids : Dipeptide- 2 amino acids join together
Polypeptide- more than two amino acids joint together
Protein- one or more polypeptide
Diff. amino acids have diff.…read more

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Made from monosaccharide containing CHO
Monomers- glucose fructose and galactose
Joined by condensation-molecule of water is released and glycosidic bond forms
between two monosaccharide
Disaccharide- two mono... join and polysaccharide more than two mono... join
Lactose intolerant:
Don't have enough lactase to break down lactose
Undigested lactose id fermented by bacteria and cause intestinal complaints e.g.
Milk can be artificially treated with purified lactase
Benedict's test:
Reducing sugars- add Benedict's reagent to sample and heat it.…read more

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Enzyme action
Biological catalysts:
Catalyse metabolic reactions ­ enzymes highly specific due to their tertiary structures
Lower activation energy
Often make reactions happen at lower temp.…read more

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Factors affecting enzyme action
More heat=more kinetic energy molecules move faster
Energy of collisions increase so number of successful collisions increase
If temp.…read more

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Animal cell structure
Plasma membrane:
Made of lipids and proteins and regulates the movement of substances into and out
of cells.…read more



 A well presented and written set of notes that  summarises the key facts of the  topics for the AQA unit on health and disease, that covers spread of disease, immunology, digestion, enzymes, lung function, protein and carbohydrates. Get these included as part of your work and build on them by including  well annotated diagrams to help illustrate some of the key points.


This is a fantastic resource!!! Everything covered is in great detail and I would highly recommend this to anyone doing A level Biology.

Ben Leitch

This is so so good thanks so much fab ***

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