Lecture 1/29

• classification of carbohydrates is based on how many building blocks are in a molecule
• if the monosaccharide is reduced, then monosaccharide itself is oxidized
• polysaccharides are more than 2 sugars
• reduction - taking away oxygen or add proton
• reducing substance - reduces other compounds; take away oxygen/ add electron or add proton
• glucose - in order for body to use carbohydrate, must be broken down from a complex sugar -> monosaccharide -> glucose
• glucose exists in an alpha and beta form; our body can only utilize the alpha form
• disaccharides structurally are two monosaccharides linked together
• disaccharides can provide some nutrients only if broken apart; sometimes part of cell surface markers or antigens
• hydrolysis and dehydration synthesis require enzymes
• polysaccharides are defined as repeated glucose units
• if we have excess glucose, rest is stored as

  1. glycogen
  2. triglycerides and cholesterol
  3. amount of cholesterol stored determined by genetics
• metabolism

  • oral - saliva has only amylase, causes digestion chemically; physical digestion caused by chewing
• metabolism

  • stomach - HCl is secreted; denatures amylase and stops digestion of amylose; HCl activates other proteinase (enzyme that breaks down protein) called pepsin
• pepsin is the only enzyme working at decreased pH
• metabolism

  intestinal - chyme moved by stomach into intestine; acidic chyme is neutralized to neutral pH; amylase starts digestion again; what wasn't digested or catabolized in mouth is then catabolized

  • once broken down into monosaccharides, we absorb them (glucose, fructose, galactose)
• sucrase breaks down sucrose

  lactase breaks down lactose

  maltase breaks down maltose
• lactose intolerance - gas from bacteria breaking down lactose