Biol 1 - Digestive System

Notes on the digestive system - Unit 1 of AQA AS Biology

  • Created by: Stephanie
  • Created on: 10-05-12 19:36


Digestion : The breaking down of large molecules into small molecules
                   Polymers --> Monomers

Polymers are insoluble
So need to be hydrolysed into smaller molecules to be absorbed 

1 of 8


  • Uses waves of contractions to move food along called 'peristalsis'
  • Mucus is secreted from tissues in the walls for lubrication
2 of 8


  • Small sac with folds allowing expansion
  • Entrance and exit controlled by sphincters
  • Stomach walls secrete Gastric Juice; made of - HCL, Mucus and the precursor for pepsin
    -Pepsin (enzyme) hydrolyses breakdown of proteins and only works in acidic conditions (hence the HCL!)
  • Peristalsis of stomach churns food into 'Acid Chyme' 
3 of 8

Small Intestine (The Duodenum & Ileum)

  • Acid chyme moved along by peristalsis
  • In Duodenum chyme is neutralized by bile and panreatic juice
    -which breaks it into smaller moleucules
  • In the Ileum small molecules are absorbed by villi in intestinal epithelium (gut wall) 
4 of 8

Large Intestine (Colon)

  • Absorbs water, salts and minerals
  • Folded wall provides large surface area for absorption
5 of 8


  • Faeces stored and passed through sphincter muslces
6 of 8

Salivary Glands

  • Produce Saliva made of; salivary amylase, mucus and mineral salts
  • Salivary amylase (enzyme) breaks starch into maltose
  • Saliva also lubricates food
7 of 8


  • Secretes pancreatic juice into Duodenum via pancreatic duct
  • Juice contains amylase and other digestive enzymes
  • Also contains sodium hydroxide which neutralises acidity of HCL from stomach acid
8 of 8


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Human, animal and plant physiology resources »