Digestion of a Big Mac

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					                         Digestion of a Big Mac

1. Ingestion into the buccal cavity – (pH 7)
     a. Mechanical Digestion:
          i. Teeth – tear and grind up the Big Mac. This allows for greater
             surface area.
     b. Chemical Digestion
          i. Salivary glands – secrete saliva into the mouth. This saliva
             contains AMYLASE which is an enzyme that breaks down
             starch (bun; sauce) into maltose.
         ii. Also with saliva there is mucous, which helps the movement of
             the bolus down the esophagus. (Bolus is the food once
             digestion in the mouth has taken place).

  - Peristalsis is muscle contractions that move the food down the
    esophagus past the cardiac sphincter into the stomach cavity.

2. Stomach – (pH 1 – acidic)
     a. Mechanical Digestion:
         i. Churning and mixes the food to create chyme.

     b. Chemical Digestion:
           i. HCl – this breaks down bacteria and creates an acidic
              environment in the stomach.
          ii. Muscous – mucin – protects the stomach lining from the
         iii. Pepsin – an enzyme that breaks down proteins into proteases
              and peptones. This works in the stomach! This would
              breakdown the meat (some cheese) in the Big Mac.
         iv. Renin – this is more for infants and it breaks down milk.

  - The chyme is moved out of the stomach through the pyloric sphincter
    is opened when a specific acid level is reached and parts of the chyme is
    squirted out into the small intestine (duodenum).
3. Small Intestine – (pH 7)

   a. Sodium bicarbonate – is dropped in by the pancreas to neutralize
      the chyme from the stomach.
   b. Bile – comes from the liver (stored in gallbladder) emulsifies fats.
      (Big Mac = meat, cheese, bun, sauce etc…)
   c. Pancreatic Juices –
         i. Trypsin – breaks down proteins and components into
            polypeptides (Meat)

         ii. Chymotrypsin – specific proteins into polypeptides.

         iii. Amylopsin – starch broken down into maltose (bun;sauce)

         iv. Steapsin – emulsified fats into glycerol and 3 fatty acids.

              i. We can start absorption of fats now.

    a. Intestinal Juices:
         a. Peptidase – breaks down polypeptides to dipeptides to amino
            acids. (Meat)
         b. Maltase – breaks down maltose to 2 glucose (absorption can
            occur) – Bun and sauce
         c. Sucrase – breaks down sucrose to glucose and fructose ( bun
            and sauce) – can now be absorbed
         d. Lactase – breaks down lactose to glucose and galactose and
            they can then be absorbed (bun, cheese and sauce)
         e. Lipase breaks down emulsified fats into fatty acids and glycerol.
            ( they can then be absorbed – sauce and meat).

  - The food will then move through the jejunum into the large intestine.
  - The large intestine does most of the absorption of the nutrients,
    minerals, vitamins and water.

Lastly – egestion of the waste!
Overall Midterm Review

 Cell Cycle – mitosis is a component of the cell cycle, but it also includes
     o Interphase – G1 - carries out metabolic activities (making proteins)
       – proteins and organelles duplicated. S – DNA replication and G2 –
       cell growth.

 Proteins – made of amino acids. They are used to build necessary
  components of the cell. A specific example of a protein is an enzyme.
  Proteins can be denatured under different pH, temperature, and
  chemicals. Once the protein is denatured it becomes useless.

 DNA – deoxyribonucleic acid – contains our genetic information. Double
  helix – looks like a ladder. Phosphate and sugar make the sides of the
  ladder and the rungs are composed of nitrogenous bases. The bases are
  held to their complimentary strand via hydrogen bonds
     o Nucleotides – sugar, phosphate and nitrogenous base
     o Nitrogenous bases – A, T, C and G and U (only for RNA).
           A bonds with Tin DNA
           A bonds with U in RNA
           C and G bond always
           Purines and pryimidine - bond together.

 Monohybrid Cross – Punnett Squares looking at ONE trait.
   o Genotype – is the alleles of the organisms
   o Phenotype – is the visual characteristics of the organisms.
   o 3:1 ratio is phenotype for a cross of two heterozygous individuals.
   o 1:2:1 ratio is genotypic for a cross of two heterozygous individuals.
   o Recessive allele – only expressed when there are two.
   o Dominant allele – always expressed when in the genotype.

 Beyond Mendel –
    o Incomplete Dominance – When you get a mixture of the two
      alleles in the heterozygous individual. I.e. Red x white will produce
      pink offspring. There is no true dominant allele.
    o Co-dominance – When both alleles are equally dominant so that
      you will see both traits in the offspring. So brown fur (BB) white fur
      (WW) cats will produce brown and white cats (BW).
    o Multiple Alleles – when the gene/trait has more than two alleles
      that code for it. Blood types (ABO)

 Gas Exchange – occurs in the alveoli when they come into contact with
  the capillaries. Oxygen comes into the body and carbon dioxide goes out
  of the body.
     o Carbon Monoxide Poisoning – asphyxiation due to lack of oxygen.

 Brain Commands and Systems – Medulla Oblongata

 Deoxygenated Blood – travels in the veins, except for the pulmonary
  artery. Gets dumped into the right atrium of the heart.

 Oxygenated Blood – travels in the arteries, except for the pulmonary
  veins. Dumped into the left atrium of the heart.

 Digestive System

Shared By:
Jun Wang Jun Wang Dr
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