8.1: What Physical Principles Underlie Biological Energy Transformations?
Metabolism: sum total of all the chemical reactions occurring in a biological system
• Involve energy changes.
• Energy is the capacity to do work, or the capacity for change.
There are two basic types of energy
1. Potential Energy: energy of state/position (stored energy)
Ex: chemical bonds, concentration gradient
2. Kinetic Energy: energy of movement, does work
Ex: heat causes molecular motions, break chemical bonds
There are two basic types of metabolism
Anabolic Reactions: link simple molecules to form complex
• These types of reactions require an input of energy. Energy is captured in the chemical
bonds that are formed.
• The captured energy is stored (potential energy)
• Ex: glycosidic bond (condensation/dehydration)
Catabolic Reactions: break down complex molecules into simpler ones. Energy that is stored in
chemical bonds is released
• Ex: sucrose is hydrolyzed
Catabolic and anabolic reactions are often linked—the energy released in catabolic is used to
i.e. The energy released by the breakdown of glucose (catabolic) is used to drive anabolic
reactions such as the synthesis of triglycerides
The first law of thermodynamics: Energy is neither created nor destroyed
Total energy before and after is the same. The potential energy present in the chemical
carbohydrates and lipids can be converted to potential energy in the form ofATP. This can then
be converted into kinetic energy to do mechanical work.
The second law of thermodynamics: Disorder tends to increase