Biology-> diet and digestion

• Adaptations of length of instestine


  This gives plenty of time for digestion to be completed and for digested food to be absorbed as it slowly passes through
• What do epithelial cells have ?

  They contain mitochondria to provide energy for absorption against the concentration gradient
• How are food molecules absorbed ?

  Mainly by diffusion or by active transport
• How are fatty acids and glycerol absorbed ?

  They are absorbed into the lacteal and are transported a ay from the small intestine in the lymph
• What is there at the center of each villus ?


  An internal structure called a lacteal connected to the lymphatic system .
• What do the blood capillaries do ?

  They transport glucose and amino acids away from the small intestine in the blood
• What is there a dense network of what in each villus ?

  Blood capillaries
• How is the surface area further increases ?

  The outer membrane of each epithelial cell has microvilli which increased increases by 20 times exposed surface of the cell
• Adaptatios of lining epithelium membrane

  It's very thin as it is made of asimile layer of epithelial cells so fluids can rapidly pass through it .
• How is the internal surface greatly increased ?

  It's internal surface is greatly increased by circular folds, bearing thousands of tiny projections called villi
• What does the length provide

  A large absorbing surface to the digested food
• Ileum


  The longest part of the small intestine and between 2-4 meters long
• Where does most absorption happen

  ileum
• Absorption

  the molecules are small enough to pass through the walls of the small intestine into the blood. This is called absorption.
• What substances have been broken down in the duodenum ?

  Most carbohydrates have been broken down into simple sugars ,proteins to amino acids and fats to fatty acids and glycerol these molecules are small enough to pass through the walls of the small intestine into the blood. This is called absorption.
• What substance do goblet cells secrete

  Mucus
• Where is digestion completed ?

  In the duodenum
• In what conditions do enzymes in the small intestine work best in ?

  Alkaline conditions but the food is acidic after having been in the stomach
• what happens to food after it has been in the stomach ?


  It travels to the small intestine
• What does hydrochloric acid provide ?

  Provides the optimum conditions for Pepsin

  This enzyme works best in very acidic conditions and only breaks down proteins at an optimum ph of 2
• What does hydrochloric acid do ?

  It kills many harmful microorganisms that might have been swallowed along with the food . It does this by denaturing the enzymes in the harmful bacteria .
• What does the stomach produce ?

  Hydrochloric acid
• What conditions does trypsin require?

  It requires alkaline conditions
• What is trypsin responsible for ?

  Breaking down proteins to peptides .
• How is trypsin secreted ?

  In an inactive form which is changed to an active enzyme in the duodenum
• What is trypsin secreted by ?

  By the pancreas
• What does pepsin do and what conditions does it require ?

  It acts on proteins and breaks them down into smaller compounds called polypeptides . It requires acidic conditions low ph
• Where is pepsin secreted

  In the stomach
• What two different protease enzymes breakdown protein

  Pepsin and trypsin
• What does maltase do ?

  Catalyzes the breakdown of maltose into glucose on the membranes of the epithelium lining of the small intestine
• What does amylase do ?

  Catalyses the breakdown of starch into malotes in the mouth and the small intestine
• What do lipases catalyze the breakdown of ?

  Fats and oils into fatty acids and glycerol in the small intestine
• What do proteases catalyze the breakdown of ?

  Proteins into amino acids in the stomach and small intestine
• What do these enzymes do ?

  They are secreted and function in different parts of the alimentary canal
• What does lipase do ?

  Breaks down fats and oils to fatty acids and glycerol
• What does protease do ?

  Breaks down protein to amino acids
• What does amylase do ?

  Breaks down starch to simpler reducing sugars
• What does chemical digestion allow for food substances ?

  It allows them to be absorbed through the epithelium of the alimentary canal , thorough the walls of blood vessels and into the blood
• What is chemical digestion

  Breaking down large insoluble molecules into small soluble molecules .
• What does chemical digestion require


  Enzymes