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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…

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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…

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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…

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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…

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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. variable groups:

Forms by condensation reaction

Structural levels:
Primary- sequence of amino acids- peptide bonds
Secondary- Hydrogen bonds form…

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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…

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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.
Substrate fits into active site of enzyme and forms enzyme-substrate complex

Lock & key model:
Substrate fits into active site of enzyme and…

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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. raised too much the vibrations can break bonds that hold enzyme in shape
Active site then changes and substrate no longer fits enzyme denatured


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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. Receptor molecules allow it to respond to chemicals like hormones

Surrounded by nuclear envelope(double membrane) containing pores
Contains chromatin (made from proteins & DNA-to control the cells activity)…




 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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