Digestive System

• Basic Activities of the digestive system:

  • ingestion of food and water
  • Mechanical and chemical digestion
  • movement of food along the alimentary canal
  • absorption of digested food
  • elimination of material that is not absorbed
• Vitamins, mineral and water molecules are small enough to pass though the differentially permeable membrane.
• Proteins are broken down into amino acids
• Carbohydrates are broken down into simple sugars
• Fats are broken down into fatty acids and glycerol
• What is mechanical digestion?

  the physical breakdown of food
• examples of mechanical digestion:

  • teeth cutting, tearing and grinding food
  • Churning action in the stomach
  • bile
• Mechanical digestion increases the total surface area of food, which speeds up digestion.
• What is chemical digestion?

  The use of enzymes to break large, complex molecules into small, simpler molecules.
• Carbohydrates split into monosaccharides eg. glucose, fructose, galactose
• Proteins are split into peptides and amino acids
• Lipids are split into fatty acids and glycerol
• Nucleic acids are split into nucleotides
• polysaccharides are large carbohydrate molecules formed when many simple sugars join together
• Monosaccharides are simple sugars
• Examples of monosaccharides

  • glucose
  • fructose
  • galactose
• Disaccharides are two simple sugars joined together
• Examples of disaccharides

  • sucrose
  • maltose
  • lactose
• what are the 6 groups of nutrients

  1. carbohydrates
  2. lipids
  3. proteins
  4. water
  5. vitamins
  6. minerals
• lipids are broken down into fatty acids and glycerol
• Proteins are organic compounds that are made of many amino acids
• An amino acid is an amino group and a carboxyl group and can be joined by a peptide bond
• shorter length of Amino acids include dipeptides (2 amino acids joined) and polypeptides (more than 10 amino acids joined)
• each lipid molecule consists of one molecule of glycerol an up to 3 molecules of fatty acid molecules.
• Liver produces bile which is stored in the gall bladder and released into the small intestine.
• oesophagus carries food from mouth to stomach
• Types of teeth and their function

  • incisors - cutting and biting
  • canines - tearing
  • premolars - crushing and grinding
  • molars - crushing and grinding
• saliva is secreted by 3 pairs of salivary glands in the mouth and contains mucus and salivary amylase
• peristalsis is the movement of food though the alimentary canal by muscular contractions.
• the mucosa is the lining of the stomach which is specialised for the secretion of gastric juice via gastric glands located in narrow, tube-like structures called gastric pits.