biology: digestive system

• What is the definition of ingestion in the alimentary canal?

  The intake of food through the mouth.
• What is digestion in the context of the alimentary canal?

  The physical or chemical breakdown of larger food molecules into smaller and soluble molecules that can be absorbed by body cells.
• What is absorption in the alimentary canal?

  The uptake of digested food substances into body cells.
• What does assimilation refer to in digestion?

  Digested food substances are converted into new protoplasm or used for energy.
• What is egestion in the alimentary canal?


  The removal of undigested food waste from the body.
• What are the main functions of the mouth in digestion?

  • Chews food (mechanical digestion)
  • Breaks food into smaller pieces, increasing surface area for enzymes
  • Secretes saliva containing salivary amylase to break down starch into maltose
  • Rolls food into a bolus to be swallowed
• What is the pH level of the mouth?

  7
• What digestive enzyme is found in saliva?

  Salivary amylase
• What is the function of the oesophagus in digestion?

  • Pushes food from the mouth into the stomach
• What is the pH level of the oesophagus?

  7
• What are the main functions of the stomach in digestion?

  • Secretes gastric juice containing hydrochloric acid and pepsin
  • pepsin breaks down protein into short polypeptides
  • Churns food, mixing it with gastric juice (mechanical digestion)
• What is the pH level of the stomach?

  2
• What digestive enzyme is secreted by gastric glands?


  Protease
• What are the main functions of the small intestine in digestion?

  • Very long, allowing more time for absorption
  • Has many folds, increasing surface area to volume ratio
  • Contains three parts: Duodenum (mainly digestion), Jejunum (some digestion and absorption), Ileum (mainly absorption)
• What is the pH level of the small intestine?

  1. 9
• What enzymes are secreted by the epithelial cells of the small intestine?

  • Intestinal Lipase: fats -> glycerol + fatty acids
  • Maltase: maltose -> glucose + glucose
  • Protease: short polypeptides -> amino acids
• What is the function of the gall bladder in digestion?


  • Stores bile
  • Bile is secreted into the duodenum via the bile duct
  • Bile salts emulsify large fat droplets into smaller ones
• What is the pH level of bile?

  Alkaline (>7)
• What are the functions of the pancreas in digestion?


  • Secretes pancreatic juice containing LAP enzymes
  • Pancreatic Lipase: fats -> glycerol + fatty acids
  • Pancreatic Amylase: starch -> maltose
  • Protease: proteins -> short polypeptides
• What is the pH level of pancreatic juice?


  Alkaline (>7)
• What are the main functions of the large intestine?

  • Absorbs water and mineral salts
  • Temporarily stores undigested food (faeces) in the rectum
• What is the pH level of the large intestine?

  7
• What is the function of the anus in digestion?


  • Expels faeces from the body
• What are the main enzymes involved in digestion and their sources?

  • Amylase (salivary): Salivary glands, digests starch
  • Protease: Gastric glands, digests proteins
  • Lipase (pancreatic): Pancreas, digests triglycerides
  • Maltase: Epithelial cells, digests maltose
• What is the definition of peristalsis?

  Rhythmic, wave-like muscular contractions in the wall of the alimentary canal that moves food forward.
• How does peristalsis work in the alimentary canal?

  • Circular muscles contract while longitudinal muscles relax to push food forward.
  • Circular muscles relax while longitudinal muscles contract to allow food to pass through.
  • Circular and longitudinal muscles are antagonistic.
• What are the adaptations of villi for fast absorption?

  • Finger-like projections increase surface area to volume ratio.
  • Lined with a one-cell-thick layer of epithelial cells to minimize diffusion distance for absorption.
  • Epithelial cells have microvilli to further increase surface area.
  • Many blood capillaries in the villi for constant transport of absorbed substances away the villi to maintain a steep concentration gradient.
• What is the role of the hepatic portal vein?

  It transports glucose and amino acids from the small intestine to the liver.
• What happens to glucose and amino acids in the liver?


  • Glucose is converted to glycogen and stored in the liver and muscles.
  • Amino acids are transported around the body for assimilation.
  • Deamination occurs, converting excess amino groups into urea.
• What are the functions of the liver?


  • Detoxification of harmful substances.
  • Breakdown of hormones.
  • Bile production.
  • Deamination of amino acids.
  • Regulation of blood glucose levels.
• What are the short-term effects of excessive alcohol consumption?


  Alcohol slows brain functions and increases reaction time.
• What are the long-term effects of excessive alcohol consumption?


  • Addiction leading to neglect of social responsibilities.
  • Increased risk of stomach ulcers.
  • Liver damage, including cirrhosis and liver failure.
  • Brain damage, including dementia and impaired fetal brain development during pregnancy.
• 
  

  stomach pepsin

  pancreatic trypsin

  intestinal erepsin
• How does pH affect enzyme activity?

  pH can denature enzymes, optimize enzyme activity, alter substrate binding, and regulate enzyme stability.
• What is the optimal pH range for most enzymes?

  Most enzymes have an optimal pH range, usually between pH 6.5 and pH 8.5.