Metabolic Pathways and Thermodynamics
Life runs on chemical highways called metabolic pathways. These are organized sequences of enzyme-regulated biochemical reactions that either build molecules (anabolic) or break them down (catabolic). Examples include glycolysis, the Krebs cycle, and the Calvin Cycle.
Each pathway works like an assembly line, with each step catalyzed by a specific enzyme. The product of one reaction becomes the starting material for the next. Amazingly, many of these pathways are nearly identical across different species, suggesting they evolved in a common ancestor.
The laws of thermodynamics govern energy flow in living systems. The First Law states that energy cannot be created or destroyed, only transformed or transferred. The Second Law explains that every energy transfer increases entropy (disorder) in the universe, with some energy always lost as heat.
Important Insight: Living organisms don't violate the Second Law of Thermodynamics. They maintain their highly ordered state by constantly inputting more energy than they lose. When energy flow stops, disorder increases, and death occurs. You're fighting entropy every time you eat!