Overview
This lecture covers the types of chemical reactions, the role and forms of energy in reactions, and key factors that influence reaction rates in the human body.
Metabolism and Energy in Chemical Reactions
- Metabolism is all chemical reactions maintaining life, including anabolism (building) and catabolism (breaking down).
- Kinetic energy powers matter in motion, while potential energy is stored due to position or structure.
- Chemical energy is a form of potential energy stored in chemical bonds.
Exergonic and Endergonic Reactions
- Exergonic reactions release more energy than they absorb (e.g., catabolism of food).
- Endergonic reactions absorb more energy than they release and require input from other reactions.
- Energy is neither created nor destroyed, just converted between forms.
Forms of Energy Important in the Body
- Chemical energy is stored/released by bonds in molecules.
- Mechanical energy powers the movement of matter in the body.
- Radiant energy is transmitted as waves; UV converts skin compounds to vitamin D.
- Electrical energy from electrolytes helps transmit nerve and muscle impulses.
Types of Chemical Reactions
- Synthesis (anabolic) reactions combine smaller components (A + B → AB) and require energy.
- Decomposition (catabolic) reactions break down molecules (AB → A + B) and release energy.
- Exchange reactions involve both synthesis and decomposition (A + BC → AB + C).
- Many reactions are reversible, shown by double arrows in chemical equations.
Factors Influencing Reaction Rates
- Reactant properties: higher surface area, smaller size, and higher reactivity increase reaction rate.
- Temperature: higher temperatures increase kinetic energy and reaction rate.
- Concentration and pressure: more particles or higher pressure increases chances of collisions.
- Catalysts and enzymes: lower activation energy needed, increasing reaction speed without being changed themselves.
Key Terms & Definitions
- Metabolism — sum of all chemical reactions in an organism.
- Kinetic energy — energy of matter in motion.
- Potential energy — energy stored due to position or arrangement.
- Chemical energy — potential energy stored in chemical bonds.
- Exergonic reaction — releases more energy than it absorbs.
- Endergonic reaction — absorbs more energy than it releases.
- Synthesis reaction — chemical reaction joining components to make larger molecules.
- Decomposition reaction — reaction breaking larger molecules into smaller parts.
- Exchange reaction — reaction with both synthesis and decomposition steps.
- Catalyst — substance that speeds up chemical reactions without being changed.
- Enzyme — biological catalyst made of protein or RNA.
Action Items / Next Steps
- Review figure examples of synthesis, decomposition, and exchange reactions.
- Ensure understanding of how enzymes reduce activation energy.
- Complete any assigned readings or exercises related to chemical reactions and energy.