Biology 105
Biology of Exercise
Spring 2003

2/12/03 - Post class outline

Learning objectives:

• How are foods converted into useable energy?
• How is the level of glucose in the body regulated?

Diagrams.

• Overview of carbohydrate digestion, absorption, and metabolism
• Insulin and glucagon actions
• Anaerobic and aerobic metabolism during exercise
• Glycemic index table (external, from Gatorade Sports Science Institute paper) (choose pdf to print)

Overview of carbohydrate metabolism

• digestion
• absorption
• storage as glycogen
• aerobic metabolism
• anaerobic metabolism

Sugar chemistry

• monosaccharides
  • glucose
  • fructose
  • galactose
• disaccharides
  • sucrose = glucose + fructose (digestion catalyzed by sucrase)
  • lactose = glucose + galactose (digestion catalyzed by lactase)
    • Lactose intolerance is caused by low levels of lactase in adults.
• polysaccharides (100-1000 monosaccharides)
  • starch (found in plants)
  • glycogen (found in animals)
  • digestion to disaccharides catalyzed by amylase

The glycemic index

• A measurement of amount of increase in blood glucose level after eating a particular food.
• Comparison to a glucose (or sometimes white bread).
  • glucose set at 100%
  • high values indicate large increase in glucose
  • foods that lead to large increases in blood glucose have high values.
• Factors that influence glycemic index.
  • availability of digestive enzymes
  • size of food particle (smaller leads to higher GI)
  • absorption rate
  • mechanical or thermal preprocessing (leads to higher GI)
  • presence of fat or protein in meal (leads to lower GI)

Insulin and glucagon are part of a hormonal control system that regulates blood glucose.

Anaerobic vs aerobic metabolism of glucose