[SCIENCE 10 reviewer 4th qrt]

• Carbohydrates


  Major source of energy for the body
• Carbohydrate-rich foods


  • Simple sugar
  • Starch
  • Figure 2
• Types of carbohydrates


  • Monosaccharides • Disaccharides •Polysaccharides
• Monosaccharide


  Simplest sugar and basic subunit of a carbohydrate
• Monosaccharides


  • White solids at room temperature
  • Have polar, hydroxyl (-OH) groups in their molecular structures
  • Very soluble in water
• Common monosaccharides


  • Glucose (dextrose)
  • Fructose
• Glucose and fructose have the same molecular formula (CHO) but different structural formulas
• Isomers


  Compounds with the same molecular formulas
• Glucose and fructose are isomers
• Though glucose and fructose have the same molecular formula, they cannot be used in the same way by cells in the body
• The arrangement of the C, H, and O atoms determines the shape and properties of each sugar
• For fats and lipids, their digestion is completed in the small intestine and is broken down primarily into fatty acids and glycerol
• Digestion of carbohydrates


  1. Broken down into monosaccharides

  2. Absorbed into blood

  3. Transported to cells

  4. Provides instant energy
• Eating too much, especially when tired

  Excess glucose stored in liver as glycogen
• It is very important to have a steady supply of glucose in the blood to maintain body functions
• Too much glucose in the blood

  • Pancreas secretes insulin
  • Insulin stimulates cells to absorb glucose and transform it into glycogen or fats
• Blood glucose drops


  • Pancreas secretes glucagon
  • Glucagon causes liver, muscles and fat to convert glycogen back to glucose
• Fructose


  • A monosaccharide found in fruits like grapes, apple or atis
  • The sweetest naturally occurring sugar
• Fructose as a sweetener

  Less fructose is needed to produce the same sweetness as table sugar
• Starchy food is widely distributed in the plant world, and its main constituent glucose is found in all plants and in the sap of trees
• Glucose is also found in glycogen that is produced in animal cells
• Disaccharides


  Sucrose is a disaccharide with the molecular formula C12H22O11
• Formation and breakdown of sucrose

  1. Condensation reaction - two molecules combine, one water molecule lost

  2. Hydrolysis reaction - bond between monosaccharides broken, one water molecule added
• When two glucose molecules are combined, maltose is formed and water is lost during the process
• Aaron Jay swears he will never drink milk again
• Lactose


  A disaccharide made up of galactose and glucose
• Lactase


  An enzyme necessary to break the bond between galactose and glucose in lactose
• Lactose intolerance


  Inability to digest milk products due to lack of lactase enzyme
• Lactose molecules are too large to be absorbed


  They continue through digestive system and are broken down by bacteria, producing gas
• Symptoms of lactose intolerance include bloating, gas, and diarrhea
• Aaron Jay concludes he may be lactose intolerant
• Digestible Disaccharides in Food

  • Sucrose (glucose-fructose)
  • Lactose (galactose-glucose)
  • Maltose (glucose-glucose)
• Formation of glycosidic bond between monosaccharides


  1. Combination reaction

  2. Water produced as side product
• Polysaccharides


  Large molecules that are made up of many smaller units that are joined together
• Polysaccharides


  • Starch
  • Glycogen
  • Cellulose
• Breakdown of starch


  1. Requires a water molecule to provide a hydrogen atom and a hydroxyl group to the site where the bond is broken

  2. With the help of enzymes in the digestive system, the glucose units can be separated from one another
• Glucose molecule separated from the rest of the starch polymer


  Can be absorbed and used as fuel by cells
• Since it takes time for glucose to be separated from the polysaccharide, it is released to the cells gradually
• The glucose from starch reaches muscle cells over a period of time providing energy as it is needed
• Athletes often eat meals rich in complex carbohydrates before an athletic event