Pathogens must be able to:

  •  gain entry to host cells
  •  colonise the tissue of the host
  • resist the defence of the host
  •  cause damage to host tissue.

Microorganisms gain entry of the host through: The gas exchange system or digestive system.

The body has natural defence mechanisms such as:

  • Mucus layer on exchange surface
  • Enzymes that break down pathogens
  • Production of stomach acid


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  • Created by: charlotte
  • Created on: 11-03-13 10:51


Pathogen is a microorganism that causes disease:

  •  it must gain entry to host
  •  colonise the tissue of host
  •  resist the defence of the host
  •  cause damage to host tissues.

Microorganisms gain entry through host by gas exchange system (breathing) or digestive system (consumption.)

Body has natural defences such as:

  • Muscus layer on exchange surface
  • Enzymes that break down pathogens
  • Production of stomach acid.
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Life style and health


  • A measue of the probability hat damage will occur as a result of a given hazzord.

Risk factors of cancer:

  • Diet
  • obesity
  • physical activity
  • sunlight

Risk of coronory heart disease:

  • High fat
  • smoking
  • increase blood pressure
  • obesity
  • diet
  • lack of excercies
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Enzymes and digestion


The physical breakdown of large insoluble molecules by enzymes to produce smaller soluble molecules to be used in the body.

  • Oesophagus- muscular wall moves food from mouth to stomach
  • Stomach- contrains HCL, contains mucus to prevent it being digested by its own enzyme
  • Small intestine- absorb products of digestion into bloodstream, contains micro villi for SA
  • Large intestine- absorb water
  • Rectum- faeces stored

Physical breakdown- teeth and churning in stomach

Chemical- enzymes hydrolyse molecules


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Carbohydrates and monosaccharides

  • Monomer- Individual chain
  • Polymer- a repeating chain or monomers

Monosacharides- Glucose

Test for reducing sugar:

  • Add water, an equal vol of benedicts
  • heat
  • Colour change from blue to brick red when present

Glucose + Glucose = Maltose (Hydrolysed by Maltase) Glucose + Fructose = Sucrose (Hydrolysed by Sucrase Glucose + Galactose = Lactose (Hydrolysed by Lactase)

Glycosidic bond occurs between monosaccharides to bond them.

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Condensation reaction joins molecule by water
Hydrolysis splits molecules with water

Test for none reducing sugars:

  • Do a nomral benedicts tset before hand, no colour change, so remains blue carryout recucing test.
  • Prepare new sample, adding HCL
  • Place in boiling water and neautralise with hydrogencarbonate
  • Add benedicts again, boil again. If changes to red reducing sugars present.

Polysacharides are made of many monosacharides

Test for starch:

  • Add iodine, colour change from brown to black if present
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Carbohydrate digestion

  • Salivary amylase hydrolyses starch to maltose, food is then swallowed in the stomach where amylase is denatured. Pancreatic amylase hydrolysesremaining starch to maltose.
  • Cells in the small intestine produce maltase which hydrolyese the maltose into α glucose.

Lactose intollerance

When you are born you have alot of lactase the break down the lactose, as you get older the amount of lactase is reduced. Some people the level is decreased so much they are unable to digest milk, causing diarrhoea.

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Enzymes are catalysts that lower the activation energy.

Lock and key model:

  • They have an active site thats complimentary to the substrate
  • when the enzyme binds to it, a substrate complex is formed
  • enzyme causes a change to the substrate breaking hydrogen bond
  • Altering bonds causes a change in shape, so leaves the active site

Induced fit model: Substrate is thought to change shape of enzyme, it molds to form shape of substrate. Works same way as lock and key.

Factors affecting enzyme activity:

  • Temperature
  • concentration
  • kinetic energy
  • pH
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