3.3 Cellular Energy

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.

Explain how shared, conserved, and fundamental processes and features support the concept of common ancestry for all organisms.

• Core metabolic pathways (e.g., glycolysis, oxidative phosphorylation) are conserved across all currently recognized domains (Archaea, Bacteria, and Eukarya). 72 Cellular Energetics UNIT 3 c