Nutrition

• what is nutrition?


  the process by which an organism obtains energy to carry out life functions and to create/maintain structur.
• What is holozoic nutrition?

  Holozoic nutrition is a type of nutrition in which organisms ingest and digest solid food particles by endocytosis.
• Endocytosis?

  Ingestion of large food molecules eg bacteria then surrounded by membranes to form vacuoles. Vacuoles fuse with lysosomes to digest vacuol content, products are then absorbed into the cell membrane.
• What are hydra?

  Multicellular fresh water animals. Same phylum as jellyfish. Cylindrical in shape and have tentacles at top of body to paralyse prey.
• Why must food by digested?

  Nutrient absorption- smaller soluble molecules can be dissolved into blood and travel to cells to be assimilated into molecules needed in body cells. Food molecules are made smaller to cross membranes
• Ingestion definition?

  Taking food into the body through the mouth.
• Digestion definition?

  The breakdown of large insoluble molecules into soluble molecules that are then small enough to be absorbed by the blood. Two types.
• What is mechanical digestion?

  Cutting and crushing by teeth and muscle contractions of the gut wall to increase the surface area for enzymes to act on.
• What is chemical digestion?

  Breakdown using digestive enzymes. Examples including bile and stomach acid.
• What is absorption?

  The passage of small soluble molecules and ions through the gut wall into the blood.
• What is elimination?

  The elimination of indigestible waste eg cellulose
• order these processes: Egestion, ingestion, digestion, absorption?

  Ingestion, Digestion, Absorption, Egestion
• Describe the gut?

  A long, hollow muscular tube. Allows the movement of its contents in one direction only. Each section is specialised. Food is propelled along the gut by peristalsis.
• What is peristalsis?

  The wave of muscular contractions and relaxations of the gut wall which propel the contents along the whole length of the gut. Circular muscles contract behind the bolus of food then relax after the wave of contraction has passed. Dietary fibre aids peristalsis in the intestines
• Describe the process of digestion?

  Mouth to begin mechanical digestion and chemical digestion of starch. Through the oesophagus to the stomach. Stomach has mechanical digestion through muscle walls and chemical digestion. Duodenum is first part of small intestine and digests lipids. Ileum digests carbohydrate, lipid and proteins, then egested through the anus.
• Where is pancreatic fluid and bile produced?

  Pancreas and gall bladder
• Which organ absorbs digested food?

  Small intestine (ileum)
• Which organ absorbs water?

  Colon
• Name the 4 tissue layers surrounding the lumen of the gut?

  Mucosa, submucosa, muscularis, serosa
• What is the role of the mucosa?

  Lines the gut, epithelium secretes mucus to lubricate and protect mucosa. Secretes digestive juices and absorbs digested food.
• What is the role of the submucosa?

  Connective tissue contains blood and lymph vessels to remove the absorbed products of digestion. Also contains the nerves to coordinate peristalsis
• What is the role of the muscularis?

  Coordinate waves of contraction to push the bolts of food through the alimentary canal.
• What is the role of the serosa?

  Made of collegen and contains tough connective tissue to protect gut wall. Helps to reduce friction during peristalsis.
• Outermost layer of gut wall?

  Serosa
• How are carbohydrates hydrolysed?

  Starch+ amylase = maltose

  Maltose + maltase = alpha glucose
• How are proteins hydrolysed?

  Polypeptides -> dipeptides -> amino acids
• The role of endopeptidases?

  Hydrolyse peptide bonds within the protein molecule
• The role of exopeptidases?

  Hydrolyse peptide bonds at the terminal ends of polypeptides.
• How are fats hydrolysed?

  Lipase to create products of fatty acids and glycerol
• What is the role of bicarbonate ions in the saliva?

  create slightly alkaline pH (optimum) for amylase
• What is the role of the epiglottis in the oesophagus?

  A layer of tissue preventing food from entering the trachea.
• What contracts for the bolus of food to remain in the stomach?

  sphincter muscles
• What is in the gastric (pancreatic) juice?

  Mucus, hydrochloric acid and pepsin
• Where is bile produced, stored and passed?

  Made in the liver, stored in the gall bladder and passed into the duodenum via the bile duct.
• Why does bile contain bile salts?

  Bile salts are hydrophobic and hydrophilic and emulsify lipids into smaller droplets to increase surface area for lipase action.
• What is trypsinogen?

  Inactive enzyme converted into the endopeptidase trypsin by enterokinase
• What feature of the ileum helps increase surface are?

  Villi
• What are the two adaptations of columnar epithelial cells?

  Have microvilli for a large surface area for absorption of the products of digestion and many mitochondria to produce ATP for active transport.
• Stomach Muscle Walls


  Contract and relax to churn and mix food with digestive enzymes
• How does cartilage differ from the submucosa?

  Cartilage lacks blood vessels, lymph vessels, and nerves, and is not found in the mucous membrane or submucosa.