🔥 Chapter 8: Introduction to Energy and Metabolism
1. Energy Fundamentals & Thermodynamics
Energy is the capacity to cause change. It exists as Kinetic Energy (motion, like heat and light) and
Potential Energy (stored energy due to structure or location, like Chemical Energy in food).
Law of Principle Implications for Living Systems
Thermody
namics
First Law Conservation of Energy: Energy can be transferred or Plants convert light energy into
transformed, but it cannot be created or destroyed. chemical energy (food).
Second Entropy (S) Increase: Every energy transfer increases Cells must constantly acquire energy to
Law the entropy (disorder) of the universe. Some energy is combat increasing internal disorder and
always lost as unusable heat (Q). maintain organization.
Free Energy (G)
Free Energy is the portion of a system's energy that can perform work. It dictates whether a
reaction is spontaneous.
Reaction ΔG (Change in Free Spontaneity Energy Profile
Type Energy)
Exergonic Negative (ΔG < 0) Spontaneous Releases energy; Products have less energy than
reactants.
Endergoni Positive (ΔG > 0) Non- Requires energy input; Products have more energy
c spontaneous than reactants.
2. ATP: The Cell's Energy Currency
Adenosine Triphosphate (ATP) is the primary energy shuttle in the cell.
Structure: Adenosine (Adenine + Ribose) plus a chain of three phosphate groups (Pi ).
Energy Source: The energy is stored in the bonds between the phosphate groups (specifically
the third phosphate).
Hydrolysis: ATP → ADP + Pi (Exergonic reaction, releases ∼ 7.3kcal/mol).
Energy Coupling: The cell uses ATP hydrolysis (Exergonic) to power Endergonic
reactions. This is how the cell performs work (e.g., transport, mechanical, chemical).
3. Enzymes: Catalysts of Life
Enzymes are proteins that act as biological catalysts—they speed up reactions without being
consumed in the process.
Activation Energy (Ea ): The initial energy barrier that must be overcome to start a chemical
reaction.
1. Energy Fundamentals & Thermodynamics
Energy is the capacity to cause change. It exists as Kinetic Energy (motion, like heat and light) and
Potential Energy (stored energy due to structure or location, like Chemical Energy in food).
Law of Principle Implications for Living Systems
Thermody
namics
First Law Conservation of Energy: Energy can be transferred or Plants convert light energy into
transformed, but it cannot be created or destroyed. chemical energy (food).
Second Entropy (S) Increase: Every energy transfer increases Cells must constantly acquire energy to
Law the entropy (disorder) of the universe. Some energy is combat increasing internal disorder and
always lost as unusable heat (Q). maintain organization.
Free Energy (G)
Free Energy is the portion of a system's energy that can perform work. It dictates whether a
reaction is spontaneous.
Reaction ΔG (Change in Free Spontaneity Energy Profile
Type Energy)
Exergonic Negative (ΔG < 0) Spontaneous Releases energy; Products have less energy than
reactants.
Endergoni Positive (ΔG > 0) Non- Requires energy input; Products have more energy
c spontaneous than reactants.
2. ATP: The Cell's Energy Currency
Adenosine Triphosphate (ATP) is the primary energy shuttle in the cell.
Structure: Adenosine (Adenine + Ribose) plus a chain of three phosphate groups (Pi ).
Energy Source: The energy is stored in the bonds between the phosphate groups (specifically
the third phosphate).
Hydrolysis: ATP → ADP + Pi (Exergonic reaction, releases ∼ 7.3kcal/mol).
Energy Coupling: The cell uses ATP hydrolysis (Exergonic) to power Endergonic
reactions. This is how the cell performs work (e.g., transport, mechanical, chemical).
3. Enzymes: Catalysts of Life
Enzymes are proteins that act as biological catalysts—they speed up reactions without being
consumed in the process.
Activation Energy (Ea ): The initial energy barrier that must be overcome to start a chemical
reaction.
