BIOL 439

• What type of metabolites will be emphasized in this course?

  Secondary metabolites (2º)
• Why are secondary metabolites considered important?


  They have significant ecological, economic, and pharmacological uses
• How are secondary metabolites produced?


  They are produced along offshoots of primary pathways
• What often induces the production of secondary metabolites?


  Varying environmental conditions
• What is the dividing line between primary and secondary metabolism?


  The dividing line is not clear
• How are primary and secondary metabolism connected?


  Primary metabolism provides the chemical building blocks for secondary metabolites
• What are the three major biosynthetic pathways for secondary metabolites?


  • Shikimic Acid Pathway
  • Mevalonate (isoprenoid) Pathway
  • Acetate-Malonate Pathway
• What is the Shikimic Acid Pathway responsible for?


  It is responsible for the biosynthesis of aromatic amino acids and alkaloids
• Which compounds are produced by the Shikimic Acid Pathway?


  Phenolics, lignans, flavonoids, and alkaloids
• Name two examples of alkaloids produced by the Shikimic Acid Pathway.


  Caffeine and morphine
• What does the Mevalonate (isoprenoid) Pathway produce?


  It produces terpenes, steroids, and carotenoids
• What is the starting molecule for the Mevalonate Pathway?


  Acetyl Co-A
• What does the Acetate-Malonate Pathway biosynthesize?


  It biosynthesizes fatty acids and lipids
• What is the first step in the Acetate-Malonate Pathway?


  Acetate is converted to acyl-CoA
• What are the three criteria that help distinguish secondary metabolites?


  • Restricted distribution mainly in plants and microorganisms
  • Formed along special biosynthetic pathways
  • Usually considered marginal or non-essential to primary life processes
• What are some biological functions of secondary metabolites?


  • Attract pollinators
  • Repel predators
  • Act as phytoalexins (antibiotics)
  • Reduce competition (allelopathy)
  • Detoxify harmful compounds
  • Serve as storage products
• Name a natural product from the isoprenoid pathway used in medicine.


  Vitamin E (alpha-tocopherol)
• What is the role of antioxidants like Vitamin E and Beta-carotene?


  They are effective scavengers and quenchers of reactive oxygen
• What are some examples of insecticides derived from natural products?

  Nicotine and pyrethrins
• What is a potential risk of consuming certain plant products?

  They may contain substances that can cause illness or be carcinogenic
• What can trigger large increases in the production of natural pesticides?


  Environmental stress or attacks by organisms
• What is the balance in our natural food supply regarding cancer-causing and cancer-inhibiting substances?


  • There is a balance between cancer-causing and cancer-inhibiting substances in fruits and vegetables.
• What caution should be taken when bi-engineering disease-resistant varieties?


  They may become too toxic for human consumption
• How many natural products have been identified from plants?


  More than 16,000
• What is the status of screening land-plant species for natural products?


  Only 5-10% of all land-plant species have been screened
• How does environmental change affect secondary metabolism?


  It induces different levels of secondary metabolism
• What is isomerism?


  Different molecules with the same chemical formula
• Why is isomerism important in natural product and environmental biochemistry?


  Many natural compounds have complex structures with many chiral centers
• How do enzymes add groups in a stereochemical manner?


  They add groups in a specific orientation
• What is an example of a structural isomer?


  1. methylpropane and n-butane
• What are optical isomers characterized by?


  Having one or more chiral centers
• What is a racemic mixture?


  A mixture with equal amounts of enantiomers
• How do enantiomers differ in their interaction with enzymes?


  They have identical chemical reactivities except in the presence of another stereoisomer
• What do enzymes do in metabolic reactions?


  They speed up reactions that are thermodynamically and mechanistically possible
• What is the role of enzymes in primary and secondary metabolism?


  They control reactions in both primary and secondary metabolism
• What are the six large classes of enzymes established in 1961?


  1. Oxidoreductases
  2. Transferases
  3. Hydrolases
  4. Lyases
  5. Isomerases
  6. Ligases (Synthetases)
• What do oxidoreductases catalyze?


  Redox reactions, transferring electrons from donor to acceptor
• What is an example of an oxidoreductase?


  Alcohol dehydrogenase
• What do transferases do?


  They transfer groups from donor to acceptor
• What do hydrolases catalyze?


  They catalyze hydrolysis of C-O and C-N bonds