CHAPTER 5

• What does metabolism refer to in living organisms?


  The sum of all chemical reactions within a living organism.
• How can metabolism be classified?


  Into reactions that release energy and those that require energy.
• What are the two main classes of metabolic reactions?

  • Reactions that release energy (catabolism)
  • Reactions that require energy (anabolism)
• What is catabolism?


  The breakdown of complex organic compounds into simpler products.
• What type of reactions are catabolic reactions?


  Enzyme-regulated chemical reactions that release energy.
• What type of reactions are generally involved in catabolism?


  Hydrolytic reactions.
• What are the characteristics of catabolic reactions?


  They are exergonic and oxidative.
• What does anabolism refer to?


  The sum total of all biosynthetic reactions in the cell.
• What is the main function of anabolic processes?


  To build complex organic molecules from simpler ones.
• What type of reactions are often involved in anabolism?


  Dehydration synthesis reactions.
• What are the characteristics of anabolic reactions?


  They are endergonic and reductive.
• What are some examples of anabolic processes?


  Formation of proteins from amino acids, nucleic acids from nucleotides, and polysaccharides from simple sugars.
• What is fermentation?


  A metabolic process that converts organic compounds into simpler ones by the action of enzymes produced by microorganisms.
• What type of process is fermentation?


  An anaerobic process.
• Which microorganisms commonly use fermentation?


  Bacteria, yeast, and fungi.
• What are the features of fermentation pathways?


  • Pyruvic acid is reduced to form organic acids or alcohols.
  • The final electron acceptor is a reduced derivative of pyruvic acid.
  • NADH is oxidized to form NAD.
  • O2 is not required.
  • No additional ATP are made.
  • Gases (CO2 and/or H2) may be released.
  • Useful in biochemical identification and industry.

  
• What is produced from pyruvic acid during fermentation?


  Reduced organic acids or alcohols.
• What is the role of NADH in fermentation?


  It is oxidized to form NAD, essential for glycolytic pathways.
• Is oxygen required for fermentation?


  No, oxygen is not required.
• Are additional ATP produced during fermentation?


  No additional ATP are made.
• What gases may be released during fermentation?

  CO2 and/or H2.
• How are fermentation pathways useful in industry?


  They are used for the synthesis of certain organic compounds.
• What is lactic acid fermentation?


  A type of fermentation found in many bacteria like Streptococcus cremoris and Lactobacillus acidophilus.
• What is mixed acid fermentation?


  A type of fermentation found in Escherichia coli.
• What is 2,3-butanediol fermentation?


  A type of fermentation found in Enterobacter aerogenes.
• How can organisms be classified metabolically based on their nutritional patterns?


  • Source of energy: phototrophs (light) or chemotrophs (oxidation-reduction reactions).
  • Source of carbon: autotrophs (CO2) or heterotrophs (organic carbon).
• What are phototrophs?


  Organisms that use light as their primary energy source.
• What are chemotrophs?


  Organisms that depend on oxidation-reduction reactions of inorganic or organic compounds for energy.
• What are autotrophs?


  Organisms that use carbon dioxide to synthesize organic molecules.
• What are heterotrophs?


  Organisms that require an organic carbon source.
• How are heterotrophs further classified?


  According to their source of organic molecules: saprophytes and parasites.
• What are saprophytes?


  Organisms that live on dead organic matter.
• What are parasites?


  Organisms that derive nutrients from a living host.
• What are the nutritional classifications of organisms based on energy and carbon sources?

  • Photoautotrophs: light energy, CO2 as carbon source.
  • Photoheterotrophs: light energy, organic compounds as carbon source.
  • Chemoautotrophs: inorganic chemicals as energy source, CO2 as carbon source.
  • Chemoheterotrophs: organic compounds as both energy and carbon source.
• What are photoautotrophs?


  Organisms that use light as a source of energy and carbon dioxide as their chief source of carbon.
• What are photoheterotrophs?


  Organisms that use light as a source of energy but cannot convert carbon dioxide to sugar.
• What are chemoautotrophs?


  Organisms that use electrons from reduced inorganic compounds as a source of energy and CO2 as their principal source of carbon.
• What are chemoheterotrophs?


  Organisms that use electrons from hydrogen atoms in organic compounds as their energy source.
• What are the products of lactose breakdown?


  • Lactose is broken down into glucose and galactose.
  • Enzyme involved: beta-galactosidase.
• What is the end product of glycolysis?


  Pyruvic acid.