BIOL203 Lesson 4

• Calories


  A unit that measures energy
• Calorie


  Measure of how much energy it takes to raise 1kg of water 1°C; calorie with lowercase "c" is the measure of energy it takes to raise 1g of water 1 degree
• Kilocalorie

  1000 calories
• Outside of the North America, nutrition facts are listed in kJ (4.22 kJ = 1 kcal)
• Energy in food

  Stored within the C-H bonds, Fat = 9 kcal/g, Protein = 4 kcal/g, Carbohydrate = 4 kcal/g
• Simple Carbohydrates

  • Monosaccharides (glucose, fructose, galactose)
  • Disaccharides (lactose, sucrose, maltose)
  • Sugar alcohols (alternative sweeteners)
• Monosaccharides


  All have the same chemical formula but arrangements of atoms differ
• Glucose


  Most important monosaccharide, source for red blood cells and cells
• Fructose


  Abundant in fruits and honey
• Galactose


  Less sweet, found in milk
• Disaccharides

  Composed of two monosaccharide units, one unit of glucose always present
• Sucrose


  Table sugar, abundant in cane plant (glucose + fructose)
• Raw sugar and brown sugar are carbohydrates that are less processed and maintain more minerals and vitamins than table sugar
• Added sugars


  Caloric sweeteners added to foods during processing, preparation or at the table, do not include naturally occurring sugars found in fruits and milk products
• Consuming more than 4-12 tsp of added sugar per day is considered toxic
• What is high fructose corn syrup?


  Commercialized in the 1970s, they took grains containing endosperm and starch, broke them down into singular glucose molecules and chemically converted them into fructose
• Bacteria in the mouth produce acids that erode tooth enamel, causing cavities, from sugar stuck in crevices
• Alternative sweeteners


  Intensely sweet, provide no energy per serving, usually made by chemically modifying a molecule of sucrose
• Sugar alcohols (e.g. erythritol, xylitol, mannitol) are not fully absorbed by the intestinal tract and can cause diarrhea if consumed in large amounts
• Complex Carbohydrates

  • Polysaccharides
  • Glycogen
  • Starch
• Glycogen


  We absorb glucose; form of short-term energy storage
• Starch


  • Different properties depending on where it is stored in plants, determines consistency and flavor
  • Gelatinization temperature: starch granules unfold and bind to water molecules allowing sauce to thicken
  • Storage form of glucose in plants
• Amylopectin

  Type of starch; Quickly digested to glucose due to a high amount of free ends allowing enzymes to bind to it
• Amylose

  Type of starch; Slowly digested to glucose
• Most starch-containing foods are a combination of amylopectin and amylose
• High-starch foods like potatoes, rice, and pasta are easier to mash, fry, etc. compared to low-starch foods
• Glycogen


  Animal version of starch; We absorb glucose, stored in liver and muscle tissues, broken down to release glucose for energy

  • Liver and muscle tissues have limited storage space; extra sugar is stored as fat in adipose tissues
• Fiber

  • Soluble
  • Insoluble
• Soluble fiber


  Dissolves in water, forms viscous gels, fermented by bacteria in the large intestine
• Soluble fiber

  • Health benefits: lowers cholesterol, improves bowel health, reduces risk of cardiovascular disease, type 2 diabetes, obesity
• Insoluble fiber


  Not fermented in the large intestine, promotes bowel movements and prevents diverticulosis
• Digestion and absorption of carbohydrates

  1. Starch and disaccharides digested to monosaccharides (glucose, fructose, galactose)

  2. Absorbed by epithelial cells in the small intestine

  3. Transported to the liver where all monosaccharides are converted to glucose

  4. Glucose is used to build glycogen
• Lactose intolerance


  Inability to completely digest lactose due to insufficient lactase enzyme, results in gas, abdominal discomfort, and diarrhea
• Infants and children produce large amounts of lactase, but 70% of people become lactose intolerant as they age
• Carbohydrate metabolism

  1. After a carb-rich meal, blood glucose rises (state of hyperglycemia)

  2. Pancreas releases insulin to allow cells to take up glucose

  3. Insulin binds to cells allowing glucose entry

  4. Excess glucose is stored as glycogen in the liver and muscles

  5. Low blood sugar stimulates the pancreas to release glucagon, which breaks down glycogen to release glucose
• Type 1 diabetes


  Autoimmune disease that destroys insulin-producing cells in the pancreas
• Type 2 diabetes

  Chronic disease where insulin is not effectively used, can lead to pancreas shutting down
• Gestational diabetes


  Form of diabetes that occurs during pregnancy
• Carbohydrate intake recommendations (DRI)

  • RDA = 130g (minimum)
  • AMDR = 45-65% (225-325g)
  • Approximately 300g per day should come from pulses, vegetables, and whole grains
  • Dietary fibre intake should be proportional to calorie intake, at least 14g/1000 kcal
• The average Canadian only consumes about half the recommended amount of dietary fiber