Cellular Energy

Basic Principles of Cellular Energy

  • All cells need energy to perform various functions, and this energy is usually in the form of ATP (adenosine triphosphate).
  • ATP is synthesized during the process of cellular respiration which occurs in the mitochondria.
  • Glucose is the primary fuel for cellular respiration, which is broken down into ATP.

Photosynthesis

  • Photosynthesis is the process by which plants, algae, and some bacteria convert sunlight into chemical energy.
  • The process occurs in the chloroplasts and involves two stages: light-dependent reactions and light-independent reactions.
  • Light-dependent reactions convert sunlight into ATP and NADPH, light-independent reactions use ATP and NADPH to turn carbon dioxide into glucose.

Cellular Respiration

  • Cellular respiration is the process by which cells convert glucose and oxygen into ATP, carbon dioxide, and water.
  • This process has three stages: glycolysis, the Krebs cycle, and the electron transport chain.
  • Glycolysis takes place in the cytoplasm and doesn’t require oxygen, while the Krebs cycle and electron transport chain occur in mitochondria and do require oxygen.

Fermentation

  • When oxygen is scarce, cells can switch to a process called fermentation to produce ATP.
  • There are two types of fermentation: lactic acid fermentation (performed by animals and some bacteria) and alcohol fermentation (performed by yeast and some bacteria).
  • Unlike cellular respiration, fermentation doesn’t fully break down glucose, making it less efficient in producing ATP.

Energy and Life Processes

  • Cellular energy is used to fuel all of life’s processes, from growth and reproduction to movement and response to the environment.
  • Homeostasis in the body is maintained through the use of energy, including maintaining body temperature and regulating blood sugar levels.

Understanding ATP

  • ATP is considered the cell’s energy currency, it’s used to perform work in the cell.
  • Energy from ATP is released when a phosphate group is detached, converting ATP into ADP and a free phosphate ion.
  • The process of phosphorylation, attaching a free phosphate ion to ADP, generates new ATP. This cycle of energy release and storage is ongoing in active cells.

Energy Efficiency of Cellular Processes

  • Each stage of cellular respiration and photosynthesis has a different energy efficiency, presenting numerous opportunities for regulation and adaptation.
  • While cellular respiration is more energy-efficient than fermentation, it requires oxygen, which may not always be readily available to cells.