Human Digestive System

• What is the function of the digestive system?

  To break down food into a form that can be absorbed by cells.
• What are the main organs of the digestive system?

  1. Glands (salivary glands and pancreas)
  2. Stomach
  3. Small intestine
  4. Liver
  5. Large intestine
• What role do glands play in digestion?

  They produce digestive juices containing enzymes that break down food.
• What is the function of the stomach in digestion?

  It produces hydrochloric acid to kill bacteria and provide optimum pH for enzymes.
• What happens in the small intestine?

  Soluble molecules are absorbed into the blood.
• What is the role of the liver in digestion?

  It produces bile which is stored in the gallbladder, which helps with the digestion of lipids.
• What does the large intestine do?

  It absorbs water from undigested food to produce faeces.
• What are enzymes and their functions?

  • Biological catalysts that increase reaction rates.
  • Break down large molecules and join small ones.
  • Protein molecules with a specific active site for substrate binding.
• What is the Lock and Key Hypothesis?

  It explains how the substrate fits into the enzyme's active site to form an enzyme-substrate complex.
• Why do enzymes require an optimum temperature?

  Because their activity increases with temperature up to a certain point, after which they denature.
• What happens to enzymes at high temperatures?

  They denature, changing the shape of the active site and preventing substrate binding.
• What is the optimum pH for most enzymes?

  7, although some enzymes have a lower optimum pH.
• What is the effect of pH on enzyme activity?

  Extreme pH levels can denature enzymes, changing the shape of the active site.
• What are the types of enzymes and their functions?

  1. Carbohydrases: Convert carbohydrates into simple sugars (e.g., amylase).
  2. Proteases: Convert proteins into amino acids (e.g., pepsin).
  3. Lipases: Convert lipids into fatty acids and glycerol.
• What tests can be used to identify carbohydrates, proteins, and lipids?

  Benedict's test for sugars, iodine test for starch, Biuret test for proteins, and emulsion test for lipids.
• What are the two roles of bile in digestion?

  To neutralize hydrochloric acid and emulsify fats.
• How can the rate of enzymatic reactions be investigated?

  By measuring the time taken for a product to form at different pH levels.
• Where do faeces pass out of your body?


  The rectum and anus
• Name the grey label and its function in the digestive system

  Salivary gland- contains enzymes which break down foods

  
• Name the yellow label and its function in the digestive system

  Oesaphagus- Transports the food from the mouth to stomach

  
• Name the black label and its function in the digestive system

  Liver- produces bile which helps with the digestion of lipids

  
• Name the red label and its function in the digestive system

  Stomach- produces hydrochloric acid to kill bacteria and provides the optimum pH for the protease enzyme to work

  
• Name the green label and its function in the digestive system:

  Gall badder: stores bile

  
• Name the pink label and its function:

  Pancreas- produce digestive enzymes to break down foods

  
• Name the Blue label and its function: 


  Large intestine- absorbs water from undigested food to produce faeces

  
• Name the purple label and its function in the digestive system:

  Small intestine- where soluble molecules are absorbed into the blood

  
• Name the orange label and its function in the digestive system:

  Rectum- where faeces pass through to be excreted

  
• Explain what is happening here

  The shape of the substrate (key) is complementary to the shape of the active site (lock), so when they bond it forms an enzyme-substrate complex

  
• Explain what is happening here:

  Once bound, the reaction takes place

  
• Explain what is happening here:

  The reaction has taken place and so products are released from the surface of the enzyme and the enzyme can be used again

  
• What does amylase break down starch into?


  Maltose
• Where is amylase produced?


  Salivary glands and pancreas and small intestine
• Where is pepsin produced?


  Stomach, other forms can be found in pancreas and in small intestine
• Where is lipase produced?


  Pancreas and small intestines
• What do lipases convert lipids into?


  Fatty acids and glycerol.
• Where do soluble glucose, amino acids, fatty acids and glycerol pass into?


  They pass into the bloodstream to be carried to all the cells around the body
• What colour does the solution turn to when there is sugars present in Benedict’s test?


  Brick red
• What colour does the solution turn to when there is starch present in iodine ?


  Blue-black
• What colour does the biuret test turn when there is protein present?


  Purple
• What happens when there is lipids present in an emulsion test?


  A cloudy layer