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Nutrition in Man (How to test for presence of nutrients (Benedict's…

- - - - disaccharides (contains 2 monosaccharides)
        
        glucose + glucose = maltose (reducing sugar)
        
        reducing sugar: any sugar that is capable of acting as a reducing agent, gives a brick-red precipitate when boiled with Benedict's solution
        
        fructose + glucose = sucrose
        
        galactose + glucose = lactose (reducng sugar
      - monosaccharides (all are reducing sugars)
        
        glucose
        
        fructose
        
        galactose
      - polysaccharides (long chains of monosaccharides linked by glycosidic bands)
        
        starch
        
        branched chains of glucose molecules
        
        Function: energy storage in plants, stored in storage organs
        
        glycogen
        
        highly branched of glucose molecules
        
        Function: energy storage in animals, stored in liver and muscle tissues
        
        cellulose
        
        found in plants
        
        cannot be digested by the human body, acts as fiber to bind waste and is passed out
        
        linear chain of glucose molecules
        
        functions: connects cells to form tissues, controls shape of plant cells ; helps plant to remain stiff and strong, structural support
  - - - bonds between polypeptide chains cause the chain to fold and form proteins
- - - - is a protein
      - functions as a biological catalyst
      - alters or speeds up chemical reactions
        
        building up of complex substances
        
        break down of complex sunstances
      - remains unchanged at the end of the reaction
    - - an enzyme has a specific 3-D shape which contains an active site
      - only substrate with a 3-D shape complementary to that of the active site of the enzyme can fit into the enzyme and form an enzyme-substrate complex
      - chemical reactions will occur and the substrate is converted into products
      - the products detach from the active site ; the enzyme remains unchanged at the end of the reaction
      - 'lock': enzyme, 'key': substrate
    - - denaturation can be caused by: high temperatures relative to opimum, chemicals such as acids and alkalis
      - when an enzyme is denatured, there is a loss of shape of its active site
        
        the substrate can no longer fit into the active site to form an enzyme-substrate complex. Thus, no reaction can take place
      - at low temperatures, the enzymes are inactive. the KE is low. Hence, chances of the substrate molecules colliding with enzymes are very low.
        
        as temperature rises, the enzyme activity increases. the temperature rise increases the KE of molecules, increasing the chance of a collision which increases the rate of formation of an enzyme-substrate complex
        
        the temperature and pH at which the rate of enzyme reaction is the highest is called the optimum temp/pH.
        
        beyond the optimum temperature, the enzyme activity decreases as the high temperature breaks the bond within the enzyme and changes its 3-D shape. The active site is lost and the enzyme is denatured
        
        pH is the measure of the acidity/alkalinity of a solution
        
        enzymes work in a very narrow band of pH values
        
        extreme pH denatures enzymes. the acid or alkaline environment will break the bonds that hold the enzymes in its specific shape.
        
        shape of the active site is changed, the substrate cannot fit and no product is formed
- - - - salivary amylase in saliva chemically digests starch starch into maltose ; digestion starts
      - physical digestion ; chewing
      - saliva is mixed with food by tongue which softens it
      - tongue rolls food into boli
    - - food passes down by peristalsis and enters the stomach
    - - peristalsis mixes food with gastric juice ; a dilute solution of hydrochloric acid and pepsin (protease)
        
        acid provides an ideal environment for the enzyme to work in and kill bacteria
        
        protease breaks down proteins into polypeptides
      - hydrochloric acid denatures salivary amylase > environment is acidic, unsuitable environment for salivary amylase > no starch digestion
      - HA an acidic medium (optimum pH) for action of pepsin and kills micro-organisms in food
      - pepsin (protease): protein > polypeptides
      - the partially digested food is liquefied : forming chyme
    - - stores feces/waste
  - - - produces bile which emulsifies fats into smaller fat droplets ; physical digestion. Increases SA:VR for lipase to chemically digest it efficiently (bile is not an enzyme)
    - - produces pancreatic juice which contains digestive enzymes (eg. amylase, protease, lipase and trypsin)
    - - stores bile temporarily
      - releases bile into small intestine
  - - - Circular muscles: 1.(in front of bolus: relax) 2.(behind bolus: contract)
      - Longitudinal muscles: 1.(in front of bolus: contract) 2.(behind bolus: relax)
      - wall of gut dilates, allowing food to enter the lumen
      - wall of gut constricts, pushing food forward