Digestive System

• Biochemistry & Digestion
• The majority of compounds we obtain from food fall into three categories: Carbohydrates, Lipids, Proteins
• Each of these substances plays an important role in our body; furthermore, each substance is broken down by our body in different ways
• Vitamins & minerals also required, but in much smaller amounts
• Carbohydrates


  A diverse group of molecules that are composed of carbon, hydrogen, and oxygen atoms, often arranged in a 1:2:1 ratio
• Carbohydrates


  The main role is to provide energy for the body, we are unable to synthesize them ourselves so we must obtain them from other sources (food)
• Types of Carbohydrates


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Monosaccharides


  A single sugar unit, often referred to as "sugars", can switch between chain and cyclic forms
• Monosaccharides


  • Fructose
  • Glucose
  • Galactose
• Disaccharides


  Formed by the "linking together" of monosaccharides through dehydration synthesis, contain two sugar units and more than 7 carbon atoms
• Disaccharides


  • Sucrose
  • Maltose
  • Lactose
• Polysaccharides


  "Complex carbohydrates" with many simple sugars linked together, examples include starch and cellulose
• Cellulose is more difficult for our bodies to break down than simple sugars; offer little energy as a result, but are a good source of fibre
• Animals store carbohydrates in the form of a polysaccharide: glycogen
• Over 50% of the organic carbon in the biosphere is tied up as cellulose (in the form of starch)
• Lipids are also composed of carbon, hydrogen, and oxygen atoms, but arranged into molecules called "fatty acids"
• Lipids


  Act to store energy, are a component of our cell membranes, help carry vitamins, and play a role in hormone synthesis
• Saturated Fatty Acids


  Carbon chain consists only of single bonds, leading to a more "rectangular" shape, tend to be solids at room temperature and are more difficult to break down
• Unsaturated Fatty Acids


  At least one double bond in the carbon chain leads to a "kinked" shape, tend to be liquids at room temperature and are easier to break down
• Hydrogenation is used to convert unsaturated fats (i.e. oils) into saturated fats (i.e. butter)
• Lipids


  • Triglycerides
  • Phospholipids
  • Cholesterol
• Trans fats are a type of chemically altered unsaturated fatty acid high in LDL ("bad") cholesterol, studies have linked their presence to heart disease
• Proteins


  Composed of carbon, hydrogen, oxygen, and nitrogen, arranged into molecules called "amino acids"
• Proteins do NOT provide energy for our cells, they play many other important roles in our bodies
• Proteins


  • Lysozyme
  • Integrin
  • Collagen
  • Hemoglobin
• Enzyme


  A protein catalyst that permits chemical reactions to process at low temperatures
• Catalyst


  A chemical that increases the rate of chemical reactions without altering the products or being altered itself
• Substrate


  A molecule on which an enzyme works
• Active site


  The area of an enzyme that combines with the substrate
• Cofactor


  An inorganic ion that helps an enzyme combine with a substrate molecule
• Coenzyme


  An organic molecule synthesized from a vitamin that helps an enzyme to combine with a substrate molecule
• Enzymes act by DECREASING the activation energy of reactants
• Factors influencing enzyme action


  • Temperature
  • pH
  • Substrate concentration
• The digestive system has two main divisions: Accessory Organs and Digestive Tract/Alimentary Canal
• Stages of the digestive process


  • Ingestion
  • Digestion
  • Absorption
  • Egestion
• Organs of the digestive system


  • Mouth
  • Esophagus
  • Stomach
  • Small Intestine
  • Large Intestine
  • Rectum
  • Anus
  • Salivary Glands
  • Liver
  • Gallbladder
  • Pancreas
• Organs that actually handle food


  • Salivary glands
  • Liver
  • Gallbladder
  • Pancreas
• Organs of the Digestive Tract/Alimentary Canal


  • Mouth
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
• Digestive Process


  1. Ingestion: the taking in of nutrients

  2. Digestion: the breakdown of complex molecules into smaller components by enzymes

  3. Absorption: the transport of digested nutrients to the cells of the body

  4. Egestion: the removal of food waste from the body
• Organs of the Digestive System


  • Salivary Glands
  • Stomach
  • Pancreas
  • Large Intestine
  • Small Intestine
  • Appendix
  • Gallbladder
  • Liver
  • Esophagus
  • Mouth