Outline of Campbell Biology Chapter 9

VIII. CATABOLISM OF OTHER MOLECULES

  1. Introduction
    1. Respiration is flexible in the fuels it can oxidize to make ATP.
    2. Organisms obtain most calories from fats, proteins, disaccharides and polysaccharides.
    3. These complex molecules must be enzymatically hydrolyzed into simpler molecules or monomers that can enter an intermediate reaction of glycolysis or the Krebs cycle.
  2. Carbohydrates
    1. Glycolysis can accept a wide range of carbohydrates for catabolism.
    2. Starch is hydrolyzed to glucose in the digestive tract of animals.
    3. In between meals, the liver hydrolyzes glycogen to glucose.
    4. Enzymes in the small intestine break down disaccharides to glucose or other monosaccharides.
  3. Proteins
    1. Proteins are hydrolyzed to amino acids.
    2. Organisms synthesize new proteins from some of these amino acids.
    3. Excess amino acids are enzymatically converted to intermediates of glycolysis and the Krebs cycle. Common intermediates are pyruvic acid, acetyl CoA and alpha-ketoglutaric acid.
    4. This conversion process deaminates amino acids, and the resulting nitrogenous wastes are excreted.
  4. Fats
    1. Fats are excellent fuels because they are rich in hydrogens with high energy electrons.
    2. Oxidation of one gram of fat produces twice as much ATP as a gram of carbohydrate.
    3. Fat sources may be from the diet or from storage cells in the body.
    4. Fats are digested into glycerol and fatty acids.
    5. Glycerol can be converted to glyceraldehyde phosphate, an intermediate of glycolysis.
    6. Fatty acids are converted into acetyl Ca which can enter the Krebs cycle.