3.3.A—Describe the role of energy in living organisms

Describe the role of energy in living organisms.

• All living systems require an input of energy.
• Life requires a highly ordered system and does not violate the first and second laws of thermodynamics.
  • i. Energy input must exceed energy loss to maintain order and to power cellular processes.
  • ii. Cellular processes that release energy may be coupled with cellular processes that require energy.
  • iii. Significant loss of order or energy flow results in death.
  • Exclusion: Students will need to understand the concept of energy, but the equation for Gibbs free energy is beyond the scope of the AP Exam.
• Energy-related pathways in biological systems are sequential to allow for a more controlled transfer of energy. A product of a reaction in a metabolic pathway is typically the reactant for the subsequent step in the pathway.