Nutrition

• Digestion in the mouth

  Food to further mechanically digest
• Oesophagus


  Moves food to stomach by peristalsis
• Digestion in the stomach

  1. Food churned

  2. Gastric acid secreted

  3. Pepsinogen converted to pepsin

  4. Mucus added

  5. Mechanical digestion
• Digestion in the duodenum

  1. Bile and secretions from Brunner's glands neutralise stomach acid

  2. Pancreatic amylase hydrolyses remaining starch to maltose
• Digestion in the ileum

  1. Epithelial cells hydrolyse disaccharides into monosaccharides

  2. Monosaccharides absorbed into bloodstream
• Digestion in the colon

  1. Water, mineral ions and vitamins absorbed

  2. Indigestible food, undigested cellulose, sloughed off cells and bacteria stored and then egested
• Amylase


  Converts starch to maltose
• Pepsin


  Digests proteins
• Trypsinogen


  Converted to trypsin by enterokinase
• Exopeptidases


  Hydrolyse peptides into amino acids
• Epithelial cells absorb monosaccharides
• What is the term for the feeding structure found in organisms like Hydra?

  Tentacle
• What type of nutrition do multicellular organisms like Hydra use?


  Nutrition in multicellular organisms
• What is the inner layer of cells in a developing embryo called?

  Endoderm
• What is the function of the hollow body cavity in organisms like Hydra?


  It is where digestion occurs
• What is the jelly-like substance found in organisms like Hydra?

  Jelly layer
• What type of environment do Hydra inhabit?


  Fresh water
• How do Hydra capture their prey?


  Using tentacles with stinging cells
• What type of digestive system do Hydra have?


  Undifferentiated digestive system
• How do Hydra digest their prey?


  Prey is moved into the hollow body cavity through the mouth
• What happens to the products of digestion in Hydra?


  They are absorbed into body cells
• How many openings does the digestive system of Hydra have?


  One opening
• What is the structure of the digestive system in most animals?


  A tube with two openings
• What are the two openings in the digestive system of most animals?

  Mouth and anus
• What are the four main functions of the human digestive system?


  Ingestion, digestion, absorption, egestion
• What is mechanical digestion?


  Cutting and crushing food to increase surface area
• What is chemical digestion?


  Breakdown of food using digestive enzymes
• What role does bile play in digestion?


  It aids in the chemical digestion of fats
• What is peristalsis?


  A wave of muscular contractions that moves food along the gut
• What aids peristalsis in the intestines?


  Dietary fibre
• What are the functions of the human gut?


  1. Ingestion: Taking food into the body through the mouth.
  2. Digestion: Breakdown of large insoluble molecules into soluble molecules.
  3. Absorption: Passage of small soluble molecules through the gut wall into the blood.
  4. Egestion: Elimination of indigestible waste.
• What are the steps of peristalsis?


  1. Contraction of circular muscles behind food.
  2. Contraction of longitudinal muscles ahead of food.
  3. Contraction in circular muscle layer forces food forward.
• What are the functions of parts of the digestive system?

  • Mouth: Ingestion, mechanical digestion of food.
  • Oesophagus: Carries food to the stomach.
  • Stomach: Mechanical and chemical digestion of food.
  • Duodenum: Receives pancreatic juice and bile, chemical digestion.
  • Ileum: Absorption of digested food.
  • Colon: Absorption of water.
  • Rectum: Storage of faeces, site of egestion.
• What is the role of the food vacuole in unicellular organisms?


  It surrounds large food molecules for digestion
• How do unicellular organisms like Amoeba obtain nutrients?


  Through diffusion, facilitated diffusion, and active transport
• What happens to food vacuoles after they fuse with lysosomes?


  The contents are digested by hydrolytic enzymes
• How are indigestible remains egested in unicellular organisms?


  By exocytosis
• What is the primary function of the contractile vacuole in unicellular organisms?


  Regulating water balance
• Why must food be digested in humans?

  Food molecules are too large to pass through the membrane
• What is the role of salivary amylase in digestion?


  It chemically digests starch in the mouth