Outline of Campbell's Biology Text


As is typical of any open system, cells require outside energy sources to perform cellular work (e.g. chemical, transport and mechanical).

  • Energy flows into the living world mostly as sunlight
  • Photosynthetic organisms trap a portion of the light energy and transform it into chemical bond energy of organic molecules
  • Cells use some of the chemical bond energy in organic molecules to make ATP - the energy source for cellular work
  • Energy leaves living organisms as it dissipates as heat

How do cells harvest chemical energy?

Major Catabolic Pathways:

  • Fermentation = Anaerobic catabolism of organic nutrients which results in a partial degradation of organic molecules.
  • Cellular respiration = Aerobic catabolism of organic of organic nutrients which is the most prevalent and efficient catabolic pathway.

Chemical Recycling, the Carbon Cycle:

  • The waste products of the major catabolic pathway, respiration, are used as the raw materials for photosynthesis.
  • Photosynthesis produces glucose and oxygen, the raw materials for respiration.
  • Although chemical elements essential for life are recycled, energy is not.

To fully investigate the area of nutrient and energy cycling we will examine respiration in this module and photosynthesis in the next. The respiration module comprises the following sections. You may click on the topics of choice.

  1. How cells produce cellular energy: an Introduction
  2. Redox reactions in metabolism
  3. Glycolysis
  4. The Citric Acid Cycle (Kreb's Cycle)
  5. The Electron Transport Chain and oxidative phosphorylation
  6. Fermentation: Anaerobic mechanism
  7. Comparison of Aerobic and anaerobic catabolism
  8. Catabolism of other biomolecules
  9. Biosynthesis
  10. Control of respiration.