carbs & proteins

• Ingestion


  The process of taking in food through the mouth
• Digestion


  1. Mechanical and chemical breakdown of food

  2. Carbohydrates, proteins, and lipids are broken down for absorption

  3. Reduced to simpler particles prior to absorption

  4. Different organs play specific roles
• Mouth


  • Amylase begins to breakdown starches into maltose
  • Food then travels from the esophagus to the stomach
  • Stomach's acidity inhibits the enzymatic reaction
• Duodenum (Small Intestine)


  • Chyme mixes with the digestive secretion of the pancreas, liver, and gallbladder
  • Amylase-containing pancreatic juices resumes digestion of starch and glycogen into maltose
  • The disaccharides are further broken down into monosaccharides by enzymes: maltases, sucrases, and lactases
• Digestion of Carbohydrates in Duodenum

  1. Maltase breaks down maltose to glucose

  2. Other disaccharides sucrose and lactose are broken down by sucrase and lactase, respectively

  3. Lactase breaks down lactose into glucose and galactose

  4. Resulting monosaccharides are transported from intestinal epithelium into the bloodstream
• Absorption of Carbohydrates


  • Monosaccharides are end products of carbohydrate digestion
  • These monosaccharides are then absorbed across the membrane of the small intestine
  • Transported to the liver or throughout the body
• Absorption of Fructose


  Fructose is used in energy production by converting it to glucose, then potentially glycogen
• Factors Affecting Absorption of Carbohydrates

  • Food matrix and foods eaten at the same time influence carbohydrate absorption
• Glycemic Index


  • A numbering scale used to rank carbohydrate-rich foods as "high GI", "low GI", "medium GI"
  • Digestion and absorption rate of carbohydrate-containing foods
  • Rate of increasing glucose in blood
• Factors Affecting Absorption of Carbohydrates

  • High glycemic foods are more quickly digested, cause large increase in blood glucose levels
  • Low glycemic foods are slowly digested
  • Cooking - least cooked foods are digested more slowly compared to more cooked or processed foods
  • Fiber slows down digestion of carbohydrates
  • Fats and proteins eaten with carbs help slow down digestion and reduces its GI
  • Acids in foods slow down the time it takes for the stomach to empty itself
• Digestion of Proteins


  1. Pepsin breaks down the intact protein into peptides in the stomach

  2. Stomach continues to churn the partially digested proteins into a uniform mixture, chyme

  3. Chyme then enters the duodenum and enzymes produced by the pancreas are secreted

  4. Trypsin elastase, carboxypeptidase and chymotrypsin are released to the duodenum

  5. Peptidases aid to further breakdown of peptides into single amino acids

  6. Carboxypeptidases, dipeptidases and amino peptidase reduce peptides into free amino acids

  7. Amino acids are then transported into the bloodstream by diffusion into the walls of the small intestine
• • Steps in Protein Digestion:
  • 1. In the stomach, pepsin breaks down proteins into fragments called, peptides.
  • 2. Protein-digesting enzymes are secreted from the pancreas into the small intestine.
  • 3. In the small intestine, various enzymes break down large peptides into smaller peptides, and then into individual amino acids.
  • 4. Amino acids are absorbed in the bloodstream via small intestine