AQA AS Biology

Revision for AS Bio on AQA

  • Created by: Annie
  • Created on: 23-12-11 17:35

The Digestive System- Mouth


  • mechanical digestion/teeth (increases SA for enzyme action)
  • chemical digestion/saliva (amylase breaks down starch into maltose, saliva is a lubricant)
  • swallowing is a reflex causing food to enter oesophogus

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The Digestive System- Muscles


  • muscles contract rythmically pushing bolos infront of peristaltic squeeze in oesophogus.
  • longitudinal and circular muscles and are an antagonistic pair- contracting in opposite timing.
  • sub mucosa is made up of elastic fibres, collagen, blood vessels and nerves (so it contracts in time). 
  • mucosa is supported by the sub mucosa, it is the layer in contact with the bolos, it is adaptable according to which organ it's in

Gastric gland in the mucosa of the stomach-

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The Digestive System- Duodenum (first 30cm of Smal


Villi and microvilli maximise uptake into cells:

  • efficient blood supply- cappillery in villi
  • short diffusion distance
  • Large SA 

Products of digestion are transported:

  • products of fat digestion are transported in lymph system
  • amino acids and glucose are transported in capillary bed

They re-enter cells to be:

  • re-constructed, e.g. amino acids turned back into protein
  • used directly- assimilation
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The Digestive System- Enzymes

·         Large molecules are hydrolysed by enzymes to produce smaller molecules that can be absorbed and assimilated.


  • Lipase (triglycerides -> fatty acids/ glycerol)
  • Protease (protein -> amino acids)
  • Amylase (starch -> maltose)


  • Protease - released from gastric glands in mucosa of stomach lining (which is folded so it can stretch)


  • Amylase - released from salivary glands
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The Digestive System- Bile


  • emulsifies fat (increases SA by turning it into droplets, increasing rate of lipase action)
  • Gall bladder stores bile
  • Bile duct is by the Gall bladder and pancreas (where lipase works on fat)
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V- Vena Cava

A- Atria (Right)

V- Ventricle (RIght)

A- Artery (Pulmonary- goes to the lungs)


V- Vein (Pulmonary- from the lungs)

A- Atria (Right)

V- Ventricle (Left)

A- Aorta (Artery that pumps around the body)

BICUSPID- Left (both have fewer letters)

Left ventricle wall is thicker as it pumps to the body.

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