18.1 METABOLISM AND ATP ENERGY

18.1 METABOLISM AND ATP ENERGY:

• ATP:

  • the energy-storage molecule

  • Links energy-producing reactions with energy-requiring reactions in the cells 

• METABOLISM: 

  • All chemical reactions that provide energy and substances needed for growth 

  • CATABOLIC REACTIONS: break down large, complex molecules to provide energy and smaller molecules

  • ANABOLIC REACTIONS: use ATP energy to build larger molecules

• STAGES OF METABOLISM:

  • catabolic reactions are organized in stages:

    • Stage 1: digestion and hydrolysis break down large molecules to smaller ones that enter the bloodstream

    • Stage 2: degration breaks down molecules two- and thee-carbon compounds

    • Stage 3: Oxidation of small molecules in the citric acid cycle and electron transport provides ATP energy

  • In the three stages of catabolism, large molecules from foods are digested and degraded to give smaller molecules that can be oxidized to produce energy

• ATP AND ENERGY:

  • In the body, energy is stored as adenosine triphosphate (ATP)

• HYDROLYSIS OF ATP

  • when we contract our muscles, move substances across cellular membranes, send nerve signals, or synthesize an enzyme, we use energy from ATP hydrolysis

  • hydrolysis of ATP to ADP (adenosine diphosphate) releases 7.3 kcal per mole of ATP

    • ATP to ADP + Pi + 7.3 kcal/mole

      • ADP can also hydrolyze to form adenosine monophosphate (AMP) and an inorganic phosphate (Pi)