Chapter 7.3- Digestion

• physical digestion


  large pieces of food broken down into smaller pieces- done by the teeth but churning movements in stomach also helps; doesn't change chemical components of food
• chemical digestion


  large moolecules in food are broken into smaller ones- involves chemical reactions and are catalyzed by enzymes; soluble in water so they can be absorbed into cells
• large molecules, their enzymes, and products

  - starch: amylase --> simple reducing sugar

  - protein: protease --> amino acids

  - fat: lipase --> fatty acids and glycerol
• enamel


  very strong material covering a tooth that is the hardest substance made by animals; can be dissolved by acids- bacteria feed on sweet food on teeth and produce acids, dissolving it and causing tooth decay
• dentine


  below the enamel, it is a living tissue that is quite hard, like bone, and contains a living cytoplasm
• middle of the tooth


  has nerves and blood vessels that supply the cytoplasm in the dentine with nutrients and oxygen
• cement


  material that holds teeth in the gums; has fibres growing out of it, attaching the tooth to the bone in the jaw but allowing it to move while chewing
• Four Types of teeth

  incisors, canines, premolars, molars
• incisors


  sharp edges, chisel-shaped teeth at the front of the mouth; used to bite off pieces of the food
• canines


  pointed teeth at either side of the incisors; used like the incisors and are used to kill prey in carnivores
• premolars


  teeth with broad, ridged surfaces, found between canines and molars; used for grinding food to increase surface area
• molars


  teeth similar to premolars but are larger with broad, ridged surfaces; found towards the back of the mouthlmouth used for gringing food to increase surface areagrinding
• chemical digestion

  enzymes can more easily make contact with the food after mechanical digestion
• optimum temperature and ph for stomach enzymes

  38°C and pH of 2 due to the presence of HCl in the stomach; enzymes in duodenum work a bit above pH 7
• maltose


  reducing sugar made of 2 glucose molecules joined together
• epithelium


  a tissue that covers a surface in an animal; for example, an epithelium covers the inside of the wall of the human alimentary canal
• pepsin


  a protease enzyme secreted in gastric juice; optimum pH is 2
• trypsin


  protease enzyme secreted by the pancreas; works in the duodenum
• emulsifiers


  breaks down large drops of fat or oil into smaller droplets, increasing their surface area and allowing them to mix with watery liquids
• Plaque


  coating of bacteria found on teeth
• gum disease


  bacteria in plaque can infect gums, causing them to swell and inflame, bleeding when brushing; infection in root can cause teeth to become loose