Stages in the Digestive Process

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Stages in the Digestive Process

• movement propels food through the digestive
  system
• secretion release of digestive juices
• digestion breakdown of food into molecular
  components small enough to cross the plasma
  membrane
• absorption passage of the molecules into the
  body's interior and their passage throughout the
  body
• assimilation becomes part of the body
• elimination removal of undigested food and
  wastes

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• Go to page 47 of study guide. You must be able
  to draw a diagram of the digestive system

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Enzymes Page 47 sg

• Catalyze the breakdown of food into
  macromolecules
• proteins
• fats
• carbohydrates

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Review of enzymes sg 14,15
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Enzymes. (When in doubt answer with enzymes)

• Enzyme protein -as a biological
  catalyst. speed up and regulate metabolic
  reactions.
• Catalyst speeds up rate of reaction without
  itself being consumed. ( may be used again)

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• A look at the biochemical pathways which are
  controlled by the action of enzymes.
• Animations (go to biochemical pathways)

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Activation energy

• decrease activation energy.
• reactions at a faster rate.
• http//www-medlib.med.utah.edu/NetBiochem/movies/l
  oacten.mov

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Anatomy of an enzyme
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Enzymes are substrate specific
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Enzymes are substrate specific

• Substrate reactants in an enzyme catalyzed
  reaction.
• Active site small portion of enzyme molecule
  which actually binds the substrate.

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The active site is the catalytic center.

• An enzyme substrate complex forms with hydrogen
  and ionic bonds
• The substrate is converted to product
• The enzyme releases the product
• The enzyme is available for the next reaction
• Animation of Enzyme Reaction

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• Animation of Enzyme Action
• http//ull.chemistry.uakron.edu/genobc/animations/
  enzyme.mov

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Enzymes of digestion sg 47

• Amylase
• Example Salivary amylase
• Source salivary glands
• Substrate Starch
• Products Maltose
• Optimum pH 7

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• Protease
• Example pepsin
• Source wall of stomach
• Substrate proteins
• Products small polypeptides
• Optimum pH 1.5

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• Lipase
• Example pancreatic lipase
• Source pancreas
• Substrate triglycerides ( fats and oils)
• Products fatty acids and glycerol
• Optimum pH 7

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Review of macromolecules sg 12 13
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Condensation Reaction

• loss of a water molecule, also known as
  dehydration synthesis.
• Dehydration Synthesis-Hydrolysis

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Hydrolysis

• Means - to break with water. This occurs in the
  digestive tract.
• Dehydration Synthesis-Hydrolysis
• Biology I Interactive Animations (go to
  biochemistry section)

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Monosaccharides

• Glucose most common

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Glucose comes in different shapes

• Linear and ring forms

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Disaccharide

• two monosaccharides joined by glycosidic linkage,
  a covalent bond formed during dehydration
  reactions Dehydration Synthesis-Hydrolysis (go
  to carbohydrate synthesis)

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Common Disaccharides
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Storage Polysaccharides

• Starch is a common PolySac of plants. Consisting
  of glucose molecules

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Lipids- Diverse hydrophobic molecules

• a molecule of glycerol (on the right) and
• three molecules of fatty acids.

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Structure of Fatty Acid
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The glycerol and fatty acid join

• This results in a ester linkage.

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Function of fats

• energy storage molecules
• Energy store ( 9 cal. Per gram
• Adipose
• Insulation
• Buoyancy

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• hydrophobic hydrophilic
• molecule that is both hydrophilic and hydrophobic
  is called amphipathic.

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Proteins ( topic pages 66-68)
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Polymers of amino acids are called peptides

• Carboxyl and amino group.
• R chain

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• Functions
• hormones
• storage (egg whites of birds, reptiles seeds)
• transport (hemoglobin)
• contractile (muscle)
• protective (antibodies)
• membrane proteins (receptors, membrane transport,
  antigens)
• structural
• toxins (botulism, diphtheria)

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Coming together to make a peptide bond.

• Animation of Peptide Bond Formation

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Intermolecular bonding sg 66, 67,68

• Interactive Concepts in Biochemistry -
  Interactive Animations
• You must be able to draw the digestive system.
  Mouth, esophagus, stomach, small intestine, large
  intestine, anus, liver, pancreas and gallbladder.

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Function of the stomach.P 47 sg
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• Stomach walls contract
• secretes
• mucous
• HCl
• protease
• HCl kills bacteria, acids denature enzymes
• Protease (pepsin) breaks polypeptides
• Medical Animation Library Digestion

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• pepsin is secreted, it is in its inactive form
  called pepsinogen.
• pepsinogen is converted to its active form pepsin
  when in the stomach exposure to HCL,
• The lining of the stomach is not affected by
  pepsin because pepsin acts only on proteins
  (mostly collagen, found in animal tissues), and
  the stomach is covered with mucus.

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• Hydrochloric acid (HCl) lowers pH of the gastric
  contents to about 2. . Low pH also stops
  salivary amylase promotes activity of pepsin.
• Pepsin is a hydrolytic enzyme that acts on
  proteins to produce peptides.
• pepsin protein
  H2O ? peptides

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• The contents of the stomach leave as an acidic
  chyme.
• This mixture is washed with bicarbonate as it
  enters the small intestines.

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Small Intestines

• Human small intestine is a coiled muscular tube
  about three meters long.

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• Pancreatic juice released into small intestines,
  contains protease, amylase, and lipase
• Nucleases are released and digest DNA/RNA in
  foods eaten.
• Macromolecules are absorbed

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• Digestion within the small intestine produces a
  mixture of disaccharides, peptides, fatty acids,
  and monoglycerides. The final digestion and
  absorption of these substances occurs in the
  villi,

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• Hole's Human Anatomy Physiology  Animation
  Activities go to small intestine digestion
• Small Intestine Histology
• Nest slide is villi page 47 sg
• You must be able to draw this

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Fig. 7.10c,d, p. 125
epithelium
villi
blood capillaries
lymph vessel
connective tissue
vesicles
artery
vein
lymph vessel
Villi on one of the folds, longitudinal section
One villus
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• increase the surface area
• The apical (exposed) surface of the epithelial
  cells of each villus is covered with microvilli
  (also known as a "brush border")

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The Large Intestine

• The large intestine colon, cecum, appendix, and
  rectum.
• Material is mostly indigestible residue and
  liquid.
• Movements are due to involuntary contractions, (
  peristaltic wave)

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• http//www.uclan.ac.uk/facs/health/nursing/sonic/s
  cenarios/uclananim/wholebodyzoom.swf