Health Science 20 Notes

• Molecules in the Body

  • Carbohydrates
  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Carbohydrates


  • Organic molecules that contain both hydrogen and carbon
  • Source of energy
  • Examples include starches, bread, pasta
• Monosaccharides


  • Simple sugars made from one molecule of sugar, each molecule is made from a ring of carbon atoms
  • Small molecules that break down easily to provide a fast source of energy
• Monosaccharides


  • Glucose
  • Fructose
  • Galactose
• Disaccharides


  • Made from two molecules of sugar, provide a fast source of energy
  • Examples include sucrose (table sugar), lactose (milk sugar)
• Polysaccharides


  • Made from three or more sugar molecules, release energy more slowly
  • Used for energy storage in plants, animals, and humans
• Plants, animals, and humans use a special type of starch called "glycogen" for energy storage
• Glycogen has different bonds between the glucose molecules, making it harder to break down than starch
• Cellulose is used to provide structural support in plants, forming the cell walls
• When small carbs join to form larger carbs


  A weaker molecule is released
• Process of small carbs joining to form larger carbs

  Called "dehydration synthesis"
• When a complete carb is broken into simple sugars

  A water molecule is required
• Process of breaking a complete carb into simple sugars

  Called "hydrolysis"
• Functions of organic molecules

  • Source of energy in our diet
  • Energy storage in the body
  • Building cell membranes and hormones
  • Bringing fat-soluble vitamins
• One gram of lipids contains over twice as much energy as one gram of carbs, so the body stores most energy as fat
• Lipids


  Fats, waxes, oils
• Lipids are made from

  Glycerol and fatty acids
• Forms of lipids


  • Saturated fats
  • Monounsaturated fats
  • Polyunsaturated fats
• Saturated fats


  Linked to arteriosclerosis (hardening of the arteries)
• Monounsaturated fats


  Have one double bond between carbon atoms of the chain
• Polyunsaturated fats


  Have more than one double bond in the chain of the fatty acid
• Unsaturated fats can contain essential fatty acids
• When unsaturated fat is twisted into a ring shape, it is called a "steroid". Steroids are lipids used to build hormones like testosterone and estrogen
• Proteins


  • Proteins have a specific shape and sequence of amino acids
  • Proteins are used as catalysts in biochemical reactions
  • Enzymes control the rate of a chemical reaction but are not used up by themselves
• Every chemical reaction in the body has its own unique enzyme
• A reaction might occur without an enzyme, but it won't be at the right speed
• Many disorders are caused by the body's lack of an enzyme (e.g., lactose intolerance)
• An enzyme works by binding to a molecule called a substrate on an area of the enzyme called the "active site" (based on the "lock and key theory")
• Some enzymes require a special group called "coenzymes" to attach to them in order to operate
• Coenzymes are usually vitamins & minerals
• Nucleic Acids are molecules that store information
• DNA (Deoxyribonucleic Acid) makes up the chromosomes inside the nucleus of every cell and carries instructions for making proteins
• RNA (Ribonucleic Acid) travels outside the nucleus where it builds proteins based on information from DNA
• Both DNA and RNA are made from chains of molecules called "nucleotides" which consist of a phosphate, a sugar (either deoxyribose or ribose), and a nitrogen-bearing base
• DNA is a double-stranded molecule twisted into a double helix shape, containing 4 bases that only bond in specific pairs: Cytosine-Guanine, Adenine-Thymine
• RNA is a single-stranded molecule with the base Uracil replacing Thymine
• Digestion involves mechanical and chemical processes where food is broken down into simpler forms for absorption
• Digestion


  1. Mechanical digestion: physically crushing food

  2. Chemical digestion: acids and enzymes breaking down food
• Digestion


  1. Digestion starts in the mouth where the tongue and teeth mechanically digest carbs, fats, proteins

  2. Saliva contains enzymes that begin to break down complex carbs into simple sugars

  3. Chewed food passes down the esophagus to the stomach

  4. The stomach mixes its contents with acids that digest proteins, and enzymes break down lipids

  5. Partially digested food moves into the small intestine where enzymes from the liver, pancreas, and gall bladder digest all three biomolecules

  6. Digested food is absorbed by structures called "villi"

  7. The waste passes into the large intestine where water is absorbed