digestive system pg 240 280 n.
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Digestive System pg 240-280. Process of breaking down food so its small enough to absorb Digestive Tract (alimentary canal) Open ended, mostly one way tube Approximately 6 ½ - 9 m long in an adult Consists of accessory glands that secrete digestive juices as well 4 stages

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digestive system pg 240 280
Digestive System pg 240-280
  • Process of breaking down food so its small enough to absorb
  • Digestive Tract (alimentary canal)
    • Open ended, mostly one way tube
    • Approximately 6 ½ - 9 m long in an adult
    • Consists of accessory glands that secrete digestive juices as well
  • 4 stages
    • Ingestion-taking nutrients in
    • Digestion- physical and chemical breakdown of nutrients
    • Absorption-Transport of nutrients to the tissues of body
    • Egestion- removal of indigestible
principle structures
Principle Structures

Add the structures of the digestive system to Digestive Dave(pg 259)

pathway of digestion
Pathway of Digestion
  • Food travels through mouth down esophagus, to stomach into smallintestine to largeintestine through rectum and out anus
  • Not all organs actually “see” food, accessory organs secrete enzymes to aid in chemical digestion (liver, gall bladder, salivary glands, appendix, pancreas)
  • Nutrients digested (Chemical’s of Life)
    • Carbohydrates, Lipids (Fats) and Proteins
  • Peristalsis (series of wave like movements) moves the food
essential nutrients chemicals for life
Essential Nutrients: Chemicals for Life
  • Carbohydrates
  • Proteins
  • Lipids (Fats)
carbohydrates 242 244
Carbohydrates (242-244)
  • Function
    • Primary source of energy for cells
    • Structural material for plant cell walls
  • Source
    • Can’t make so must eat PLANTS (photosynthesis)
    • Test for Carbs in food by adding Benedicts or Iodine solution
    • Make up the bulk of our diets
  • Building Blocks
    • Monosaccharide (sugar units)
    • Carbon, Hydrogen, Oxygen (1:2:1 ratio)
carbohydrates cont
Carbohydrates cont.
  • Types
    • Monosaccharide (single sugar unit)
      • Glucose (human blood), fructose (plant), ribose (DNA)
    • Disaccharides (2 single sugar unit bonded together)
      • Maltose (malt sugar), lactose(milk sugar), sucrose (table sugar)
    • Polysaccharides (more than 2 single sugar units bonded together)
      • Starch(plants store energy), cellulose (plant cell walls), glycogen (animals store energy)




proteins 249 251
Proteins (249-251)
  • Function
    • Not a primary energy source
    • Structural components of cell
      • Cell organelles
      • Part of muscles, nerves, skin and hair
      • Antibodies and enzymes
  • Building Blocks
    • amino acids
    • Made up elements Carbon, Hydrogen and Oxygen, Nitrogen and Sulfur
proteins cont
Proteins cont.
  • Source
    • Once you ingest and digest they are broken back down into amino acids and carried away in blood
    • 8 essential amino acids we have to ingest
  • Types
    • histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan, valine

Amino Acids






lipids fats pg 246 249
Lipids (Fats) (pg 246-249)
  • Function
    • Energy storage
    • Structural component of cell
    • Cushions delicate organs
    • Carries vitamins such as A D E K
    • Raw materials for hormones and other body chemicals
    • Insulation
  • Building Blocks
    • Glycerol and fatty acids
    • Made with elements of Carbon, Hydrogen, Oxygen
lipids fats cont
Lipids (Fats) cont.
  • Source
    • Get lipids through plant oils and animal fats
  • Types
    • 3 Types
      • Triglyceride
        • Glycerol and three fatty acids
        • Animal fat (Saturated=hard to break down) solid at room temp
        • Plant oil (Unsaturated = easy to break down) liquid at room temp
      • Phospholipids
        • Glycerol and phosphate group
      • Waxes
        • long chain of fatty acid and long chain of alcohols or carbon rings


Animal fat vs Plant oil


enzymes pg 254 258
Enzymes (pg 254-258)
  • What are they?
    • Proteins that play a vital role in production of chemicals during complex, multistep reactions in the human body (metabolic pathways)
    • Approximately 200,000 different reactions in that 20 different enzymes assist with
    • Names of enzymes end in –ASE
    • 3 major groups of enzymes each responsible for breaking down a specific nutrient
      • Carbohydrates-Carbohydrases (Maltose-Maltase)
      • Proteins-Proteases
      • Lipids-Lipases
    • Has two important sites for binding: an active and regulatory site
enzyme structure pg 254 or 257
Enzyme Structure (pg 254 or 257)





  • What do they do?
    • Interact with substrate to lower amount of energy needed for the reaction to occur (activation energy)
    • Increase chance reactions occur by bringing molecules together in the “right” way
    • Substrates (carbs, lipids, proteins) bind to active site and then enzyme helps the substrate line up and bind with other molecules
    • Lock and Key-specific substrates only combine with specific enzymes
factors that affect enzymes
Factors that affect enzymes
  • If enzyme is altered in any way then will not function properly due to change in shape
factors that affect enzymes1
Factors that affect Enzymes
  • pH
    • 3 D shape of enzyme is altered because bonds between amino acids that make it up are changed
    • Some enzymes work better in acidic conditions (0-7) and other better in basic (7-14)
factors that affect enzymes2
Factors that affect Enzymes
  • Substrate concentration
    • If there is too much substrate and not enough enzyme then the rate at which reaction will occur will slow down
    • Substrate has to wait until enzymes are available for use
factors that affect enzymes3
Factors that affect Enzymes
  • Temperature
    • Heat up molecules they move faster and collide more therefore more products will be formed
    • Too hot can cause permanent damage to the shape of the enzyme and its active site
factors that affect enzymes4
Factors that affect Enzymes
  • Competitive Inhibition
    • Other molecules that are similar to substrate “beat” the substrate to the active site and prohibit the substrate from binding to enzyme
regulating enzyme activity
Regulating Enzyme Activity
  • Allosteric activity is way the body controls reactions to avoid accumulation of unneeded chemicals, controlled by body’s demand for chemicals
  • Two process involved
    • Feedback inhibition (turn production off)
    • Precursor activity (turn production on)
feedback inhibition
Feedback Inhibition
  • TOO MUCH final product
  • Excess final product will bind to initial enzymes regulatory site therefore changing shape and function of enzyme
  • Reaction will be “shut off”
precursor activity
Precursor Activity
  • TOO MUCH initial reactant
  • Excess initial reactant will bind with last enzyme’s regulatory site, change its shape and its function
  • “turn up” the reaction
digestion lets get specific


Describe the chemical and physical processing of matter through the digestive system.

mouth pg 260
Mouth (pg 260)

Physical digestion

  • Teeth chew, grind and rip food
  • Increase food surface area for chemical digestion
  • “Bolus”

Chemical digestion

  • Taste, smell and sight of food promotes secretion of saliva produced by the salivary glands (3 sets)
  • Saliva contains:
    • Mucin- protects the mouth and dissolves food
    • Buffer- neutralize acids
    • Antibacterial agents- kill pathogens
    • SALIVARY AMYLASE- breaks polysaccharides (starches) into midsize sugar unit chains


  • Nothing is absorb in the mouth
pharynx and esophagus
Pharynx and Esophagus
  • Pathway to stomach
  • Air and food travel down the pharynx but then directed by epiglottis
stomach pg 261
Stomach (pg 261)

Food storage and initial protein digestion

Physical digestion

  • The lower esophageal sphincter relaxes to allow bolus into the 3 layers of contracting muscle before it passes highly acidic chyme through the pyloric sphincter to the small intestine


  • The presence of the bolus promotes the secretion of gastric juices from cells in the stomach
  • Gastric Juice contains:
    • Protective coating/alkaline mucus- stops the HCl from digesting the stomach
    • HCl- pH of 2.0, kills pathogens, dismantles tissues holding food together
    • PEPSINOGENS-converted by HCL into PEPSIN which breaks proteins down into polypeptides


  • Water
  • Specific vitamins
  • Certain medicines
  • Alcohol
small intestine and pancreas pg 264 265
Small Intestine and Pancreas (pg 264-265)

Food does not pass through the pancreas but it works closely with the small intestine to help it digest food

Physical digestion

  • By the time chyme reaches the 7 m long intestine there is no longer any need for the physical breakdown of the food
small intestine and pancreas
Small Intestine and Pancreas

Chemical digestion

  • Most chemical digestion occurs here and is triggered by the arrival of the extremely low pH of the chyme
  • The small intestine secretes a number of different chemicals

1. SECRETIN- converted from prosecretin this chemical travels via the bloodstream to the pancreas to promote release of pancreatic fluid

4. EREPSIN- this protein digesting enzyme breaks short chain polypeptides into amino acids

6.DISACCARDIESASES (e.g. maltase, surceases, lactases)- finish the what the mouth and pancreas started and breaks disaccharides (lactose, maltose, sucrose) into monosaccharide (glucose, fructose, galactose)


SECRETIN arrives via the blood stream from the small intestine and stimulates the pancreas to release pancreatic fluid

    • Pancreatic fluid contains:

5. PANCREATIC AMYLASE- continues the mouths digestion of mid size sugar chains and breaks them down to disaccharides

2. BICARBONATE IONS (HCO3)- neutralize the acid from the stomach

3. TRYPSINOGEN- protein digesting enzyme that is converted to TRYPSIN to finish what the stomach started and gets protein from long polypeptides to short polypeptides

7. LIPASE – enzymes that break down lipids

small intestine and pancreas2
Small Intestine and Pancreas


  • Most absorption of nutrients occurs here
  • Finger-like projections called villi increase the highly folded small intestine up to 10 fold
  • Capillary networks transport amino acids and monosaccharides and Lacteals transport the fatty acids and glycerol
liver and gallbladder pg 267 268
Liver and Gallbladder (pg 267-268)
  • Food does not travel here but aid in fat digestion
  • Liver has many functions (see handout)

Physical digestion

  • Liver produces bile which is stored in the gallbladder
  • Bile released when fats are present in small intestine
  • Bile physically breaks down fat droplets
large intestine pg 268
Large Intestine (pg 268)
  • Indigestible material (cellulose, fibre etc) wait, bulk and build up before excreted

Physical digestion

  • No more digestion

Chemical digestion

  • No more digestion


  • Water
  • Inorganic salts
  • Vitamins
digestive disorders
Digestive Disorders
  • Deficiencies can severely affect our ability to function
  • Most disorders either affect the nutritional state of the body or its salt and water content
  • Examples include ulcers, inflammatory bowel disease (IBS), hepatitis, cirrhosis and gallstones