Enzymes & Digestion

Enzymes & Digestion

1. Have a uniquely shaped active site

   • Substrate and active site collide
     • Substrate binds to active site
       • Enzyme acts as a catalyst to speed up the reaction to make the product

2. Works at its optimum when placed the the right conditions

   • If the PH is too low then the reaction rate will rise until the optimum is reached
     • If this exceeds the optimum level then the enzyme will begin to denature
       • When it denatures then the active site will change shape permanently
         • The substrate can no longer bind to the active site
   • The enzyme activity rate will rise as the temperature rises
     • When optimum temperature is reached the enzyme is working at its best.
       • If this exceed the optimum level then the enzyme will begin to denature
         • When it denatures the active site will change shape permanently
           • The substrate can no longer bind to the active site
   • When the substrate concentration is at the optimum all the enzymes are working at their maximum effiency
     • After the substrate concentration exceeds the optimum the activity rate plateaus
   • Each enzyme has a different optimum for PH, temperature and substrate concentration
   • Most enzymes in the human body have an optimum temperature of 40 °C
     • Food enters the mouth, and the large forms are broken down physically by chewing (Ingestion)
       • Enzymes are released from the glands and are used in catabolic reactions
       • Salivary amylase from the salivary glands chemically break down the food further
         • Peristalsis, the contraction of muscles in the digestive track, push the food down the oesophagus and into the stomach
           • Muscular contractions continue physical digestion in the stomach
             • Hydrochloric acid kills bacteria
             • Pepsin begins the digestion of proteins
               • Bile from the liver and gall bladder neutralize the acid and emulsifies the fat in the Duodenum, the first half of the small intestine
                 • Pancreatic amylase, lipase and endopeptidase digest carbohydrates (disascharides) into glucose (monosaccharides) and fats. Trypsin digest polypeptides (proteins) into amino acids (Digestion)
                   • Longitudinal and circular muscles in the small intestine mix the enzymes and the nutrients together
                     • The nutrients are then absorbed through the villi found around the illeum, the second half of the small intestine (Absorption)
                       • Water is then reclaimed in the large intestine leaving semi-solid faeces stored in the rectum
                         • The anus forces the faeces out of the body (Transport)
                       • Villi increase the surface area for absorption and have a rich blood supply because of the blood capillary
                         • The rich blood supply maintains a concentration gradient which allows nutrients to diffuse across the membrane
                           • Lymph vessels (Iacteals) close to the surface allow lipids to be easily absorbed.
                         • Epithelial cells, found on the surface of the villus have microvilli to increase the surface area even further
                           • This layers makes the diffusion path of digested food molecules shorter
                             • Diffusion is faster and more efficient.
                           • They also have a mitochondria to generate ATP for the active transport of digested food molecules
                           • Hydrophobic molecules cannot move through the membrane which means they need to use facilitated diffusion to move across the membrane
                             • For example, glucose is polar meaning its hydrophobic, so it moves across the membrane with a sodium ion through facilitated diffusion

3. Scientists attach enzymes to an insoluble material, these are called immobilized enzymes

   • Lactose-free Milk
     • Lactase is obtained from yeast or bacteria
       • Lactase is bound to alginate beads
         • Milk is repeatedly passed through the beads
           • The lactose is broken down into glucose and galactose
             • The immobilized enzymes is used repeatedly
             • The product is sweeter, lacotse-free milk
               • Sold to people who cannot natural make lipase, making them lactose intollerant
   • High Fructose Corn Syrup
     • Glucose isomerase is immobilised
       • This converts the glucose in the corn syrup to fructose, which makes it sweeter.
         • The immobilized enzyme is used repeatedly