Humans

• A balanced diet includes appropriate proportions of carbohydrates, proteins, lipids, vitamins, minerals and water
• Bile is produced in the liver and stored in the gall bladder
• Carbohydrates provide energy, and are found in bread, potatoes and sugars
• Lipids provide energy stores, and are found in butter, cheese and vegetable oils
• Proteins are required for growth and repair, and are found in meat, fish and pulses
• Vitamin A is needed for night vision, without it you get night blindness, and it's found in carrots and cod liver oil
• Vitamin C is needed for strong tissues, without it you get scurvy, and it is found in fresh fruit and vegetables, most notably citrus fruits
• Vitamin D is needed for strong bones, without it you get rickets, and it is found in cod liver oil, milk and eggs
• Calcium is needed for strong bones and teeth, without it you get rickets and it is found in milk
• Iron is needed to make haemoglobin for new red blood cells, without it you get anaemia and it is found in red meat, liver and vegetables
• Water has many functions, mainly the action of being a solvent to transport substances, without it you get dehydrated
• Fibre helps move waste through the gut, without it you get constipated and it is found in bran, fruit and vegetables
• Amount of energy required increases towards adulthood for growth and muscle development
• Amount of energy required increases with activity level as more energy is needed to allow muscle contractions to facilitate exercise via respiration
• Amount of energy required by Females during pregnancy will increase as more energy is needed to support the growth of developing fetus, and the large mass that the Mother will carry around
• The alimentary canal follows the path of the mouth, salivary glands, oesophagus, stomach, passing the gall bladder and pancreas in the duodenum, the ileum, the colon and rectum
• In the mouth:

  • Mechanical digestion occurs
  • Large food is turned into a bolus to provide large surface area to volume ratio for salivary Amylase to break down Starch in food into Glucose
  • Saliva lubricates bolus for easy swallow
• In the oesophagus:

  • Peristalsis (wave-like contractions) occurs to push bolus down the tube towards Stomach
• In the stomach

  • Peristalsis continues mechanical digestion, and enzymes begin chemical digestion
  • Hydrochloric acid maintains Optimum pH to increase rate of enzyme activity and metabolic reactions
• In the small intestine:

  • Lined with Villi to absorb digested soluble molecules into the circulatory system for use
• In the large intestine:

  • Absorbs Water from undigested food to produce faeces (stored in the Rectum and removed through the Anus)
• In the pancreas:

  • Synthesises pancreatic enzymes (Amylase, Protease, and Lipase)
  • Secretes pancreatic enzymes into the Stomach and Small intestine for digestion
• What is the process that pushes food through the alimentary canal?

  Peristalsis
• What causes peristalsis to occur?

  Rhythmic contraction and relaxation of muscles
• Which system controls the muscles involved in peristalsis?

  Nervous system
• What is the role of circular muscles in the esophagus?

  They change the radius of the esophagus
• What is the function of longitudinal muscles in the esophagus?

  They change the length of the esophagus
• What happens when longitudinal muscles contract where the food bolus is located?

  It moves the bolus along the gut
• How does the contraction of circular muscles affect the food bolus?


  It constricts the gut to prevent backflow
• What is the overall effect of wave-like muscle contractions during peristalsis?


  They push the food bolus from mouth to anus
• Starch -(amylase)-> maltose -(maltase)-> glucose
• Protein -(protease)-> amino acids
• Lipids -(lipase)-> glycerol and fatty acids
• What is the optimum pH range for enzymes in the small intestine?

  8-14
• Why do enzymes in the small intestine require alkaline conditions?

  To function optimally and increase metabolic reactions
• What creates an acidic environment in the stomach?

  Hydrochloric acid
• How does bile affect hydrochloric acid in the stomach?

  Bile neutralizes hydrochloric acid
• What is the purpose of bile in digestion?

  To maintain alkaline conditions for enzyme activity
• Why is emulsification of lipids important in digestion?

  It increases surface area for faster breakdown
• What does bile do to large lipid molecules?

  Emulsifies them into small droplets