Types of Digestion

• Nutrients:

  Types:

  • Micronutrients - vitamins and minerals
  • Macronutrients - carbohydrates, proteins and lipids.
• Proteins

  • Consist of 100 or more amino acids
  • 2 amino acids joined together are known as a dipeptide
  • Then or more acids joined are known as polypeptide
• Lipids

  • Consists of 1 molecule of glycerol and 1-3 fatty acid molecules
• Carbohydrates

  • Polysaccharides - large numbers of simple sugars joined (e.g. glycogen and starch)
  • Disaccharides - 2 simple sugars joined (e.g. sucrose and lactose)
  • Monosaccharides - one simple sugar (e.g. glucose, galactose)
• Mechanical Digestion:

  • Breakdown of food into smaller particles without changing its chemical makeup.
• The Mouth

  • Immediately after food ingestion, the action of the jaw and teeth begin mechanical digestion
  • Known as mastication (chewing)
  • There are 4 types of teeth and each have different functions
• Stomach

  • Stomach contracts in variety of ways in a process called churning.
  • Here, the food is mixed with gastric juice to produce Chyme (thick, soupy liquid)
• Small intestine

  • The jejunum and ileum have muscular walls that push food along - peristalsis
  • Food id divided into smaller clumps and mixed - segmentation
  • Bile salts break lipids into smaller droplets (emulsification) in the jejunum and ileum
• Chemical Digestion:

  • The breakdown of large molecules into smaller molecules with a different chemical structure.
  • Usually involves an enzyme
•  

  Digestive enzymes (overview)

  • Salivary glands produce salivary amylase
  • Gastric juices in the stomach contains gastric protease
  • The pancreas produces pancreatic juice which contains:

  1. Pancreatic amylase
  2. Pancreatic protease
  3. Pancreatic lipases

  • Glands of the intestines produce:

  1. Intestinal amylase
  2. Intestinal protease
  3. Intestinal lipases
• Carbohydrates

  • In the mouth, salivary glands secrete saliva which contains a digestive enzyme - salivary amylase
  • Salivary amylase begins the chemical digestion of carbohydrates, breaking down starch into polysaccharides
  • Pancreatic amylase breaks down polysaccharides into disaccharides in the duodenum
  • Intestinal amylase breaks down disaccharides into monosaccharides in the jejunum and ileum.
• Protein

  • The stomach lining secretes gastric juice which contains hydrochloric acid, mucus and digestive enzymes.
  • The enzyme gastric protease (pepsin) breaks down the large proteins into shorter chains called polypeptides.
  • In the duodenum, pancreatic protease breaks down polypeptides into peptides.
  • In the jejunum and ileum, intestinal protease breaks down peptides into amino acids
• Lipids

  • Broken down by pancreatic lipases and intestinal lipases into fatty acids and glycerol.
  • Occurs on the jejunum and ileum.
• Vocab tips -

  • Amylases breaks down carbohydrates
  • Proteases breaks down proteins
  • Lipases breaks down lipids