Biology Chapter on Energy and Enzymes

Energy

• The capacity to do work
• Can be converted from one form to another
• Some energy is always lost during conversions

Endergonic Reactions

• Require an input of energy
• Products contain more energy than the reactants

Exergonic Reactions

• Release energy

ATP

• Adenosine triphosphate
• Composed of adenosine and three phosphate groups
• Stores small amounts of energy for short periods of time
• The unit of energy used by cells
• Phosphate groups are held on with high energy bonds
• Phosphate groups are released through hydrolysis
• The removal of a phosphate group produces ADP
• Phosphate groups can be transferred to other molecules, a process called phosphorylation

Enzymes

• Proteins
• Catalysts
• Speed up reactions without being altered themselves
• Lower the activation energy of a reaction
• Have specificity

Enzyme Action

• Enzymes have an active site with a shape that matches a specific substrate
• The substrate is the substance that the enzyme acts on
• The substrate binds to the active site of the enzyme

Enzyme Function

• Factors affecting enzyme function include:
  • Optimal temperature
  • Optimal pH
  • Concentration of salts and other chemicals
  • Cofactors and coenzymes, which help the enzyme catalyze a reaction
    • Cofactors are often metal ions
    • Coenzymes are often vitamins

Enzyme Regulation

• Several mechanisms regulate enzyme function:
  • Amount of enzyme
    • More enzyme = greater rate of reaction
  • Competitive inhibition: Two substances compete to bind to the active site (substrate and inhibitor)
    • When the inhibitor is bound, the substrate cannot bind.
  • Non-competitive inhibition: The inhibitor binds to a site that is not the active site, changing the enzyme’s shape.
  • Feedback inhibition: The final product inhibits an enzyme, shutting down a series of reactions

Oxidation & Reduction (Redox Reactions)

• Oxidation – loss of electrons from a substance
• Reduction – addition (gain) of electrons to a substance
• Hydrogen atom = 1 electron and 1 proton

This quiz covers key concepts related to energy transformations, endergonic and exergonic reactions, the role of ATP in cellular processes, and the function of enzymes as biological catalysts. Test your understanding of how energy is stored and utilized in biological systems. It's a great review for students of biology.