Chapter 3.1: Energy, Catalysis, and Biosynthesis - BMEN 240

Metabolic Pathway

A series of enzyme-catalyzed chemical reactions that convert precursor molecules into final products.

Enzyme

A biological catalyst that accelerates specific chemical reactions without being permanently altered itself.

Catabolism

Metabolic pathways that break down food molecules into smaller units, releasing energy and heat.

Anabolism

Metabolic pathways that use energy to synthesize complex molecules needed by the cell.

Second Law of Thermodynamics

The law stating that the entropy (disorder) of an isolated system or the universe always increases.

How Cells Maintain Internal Order

They take in energy and release heat, increasing disorder in the environment to balance internal order.

Biological Energy Coupling

Tightly linking heat-generating reactions to processes that build order, preventing wasteful heat loss.

Photosynthesis

The process by which plants and bacteria convert light energy, CO₂, and water into sugars and oxygen.

Photosynthesis and Respiration Relationship

They are complementary processes; photosynthesis produces organic molecules and O₂ used in cell respiration.

Carbon Cycle

The continuous movement of carbon atoms between atmospheric CO₂, organic compounds in organisms, and ecosystems.

Oxidation

The chemical process involving the removal or loss of electrons from an atom or molecule.

Reduction

The chemical process involving the addition or gain of electrons by an atom or molecule.

Redox Reaction Coupling

Oxidation and reduction always occur simultaneously because electron count is conserved in reactions.

Activation Energy

The minimum energy barrier substrate molecules must overcome to initiate a chemical reaction.

Enzymatic Catalysis Mechanism

Enzymes lower the activation energy barrier, greatly increasing the probability that a reaction will occur.

Active Site

The specific region of an enzyme where substrate molecules bind to undergo a chemical reaction.

Free Energy Change (ΔG)

The amount of useful energy released or absorbed during a chemical reaction.

Energetically Favorable Reaction

A reaction with a negative ΔG (decreases free energy), increasing universal disorder.

Energetically Unfavorable Reaction

A reaction with a positive ΔG that requires energy input to proceed.

Reaction Coupling

Driving an unfavorable reaction (+ΔG) by pairing it directly with a favorable reaction (-ΔG).

Chemical Siphon

A process where a rapid downstream favorable reaction consumes products, driving an upstream reaction forward.

Chemical Equilibrium

The state in a reversible reaction where forward and reverse reaction rates are equal (net ΔG = 0).

Rapid Diffusion in Cells

Random thermal collisions that allow small substrate molecules to quickly move and collide with enzymes.