"Why is it so slow?"
Toma was looking at the reaction solution. After an hour, there was hardly any change.
"The wall of activation energy," Rei said. "For reaction to proceed, you must climb over an energy mountain."
Kana looked at the graph. "From reactants to products, there's a mountain in the middle."
"Transition state," Rei explained. "The highest energy state of the reaction."
"Why is it high?" Toma asked.
"Bonds are breaking, new bonds aren't formed yet. Unstable state."
Kana began to understand. "So energy is needed."
"Yes. The energy to climb that mountain is the activation energy Ea."
Toma wrote in his notebook. "Higher mountain, slower reaction."
"Correct. Can be expressed by Arrhenius equation. k = A exp(-Ea/RT)."
"Looks difficult..."
"When temperature T rises, reaction rate k increases. When Ea is lower, it gets faster."
Kana asked. "So how do you lower the mountain?"
"Catalyst," Rei smiled. "Especially enzymes."
Toma added enzyme. The reaction instantly proceeded.
"Whoa! Fast."
"Enzymes lower activation energy," Rei explained. "Same reaction proceeds over a lower mountain."
Kana looked at the graph. "With and without catalyst, mountain height is different."
"Yes. But final products are the same. Thermodynamically unchanged."
"Only changes speed," Toma understood.
"Exactly. Enzymes don't change reaction equilibrium. But dramatically shorten time to reach equilibrium."
Kana thought. "How do they lower it?"
"Fix substrate in correct orientation," Rei explained. "In active site, make it reaction-ready shape."
"Fit into a mold?"
"Yes. Stabilize transition state. Lower energy."
Toma drew on the whiteboard. "Like key and lock."
"Good metaphor but slightly different," Rei corrected. "Induced fit model. Enzyme changes shape to match substrate."
"It's flexible."
"Not a rigid keyhole. Like a handshake, adjusting shapes mutually."
Kana organized in her notebook. "Substrate binding → shape change → transition state stabilization → product release."
"Perfect," Rei acknowledged.
Toma asked. "How much faster do enzymes make it?"
"10 to the 6th to 10 to the 17th power times."
"What!?" Kana was surprised.
"Catalase decomposes 4 million hydrogen peroxide molecules per second. One molecule."
"Unbelievable," Toma said.
"That's the speed of life," Rei said quietly. "Without enzymes, reactions can't keep up at body temperature."
Kana understood. "That's why enzymes are needed."
"Yes. DNA replication, protein synthesis, metabolism. Everything depends on enzymes."
Toma suddenly thought. "But what if we raise body temperature?"
"Proteins denature," Rei answered. "Above 40 degrees, structure collapses."
"So solve it with enzymes."
"Exactly. Speed up reactions without raising temperature. That's life's strategy."
Kana looked at another reaction. "Without enzyme, how many years would this take?"
Rei calculated. "At room temperature, about 78 million years."
"What..."
"With enzyme, 1 second."
Toma laughed. "The wall of activation energy is quite a wall."
"But it can be overcome," Rei said. "With the tool called enzyme."
Kana gazed at the energy diagram. The mountain peak. It looks impossibly high. But there's a path.
"Enzymes dig tunnels."
"Good expression," Rei smiled. "Don't erase the mountain. Create another path."
Toma was impressed. "Smart."
"Wisdom born from 3.5 billion years of evolution," Rei said. "Optimized catalytic system."
The three stared at the reaction solution. In the transparent liquid, an invisible battle occurs. Molecules climb over walls, transform, are reborn.
"The wall of activation energy," Kana murmured.
"But a wall that can be overcome," Toma continued.
"A wall that life continues to overcome," Rei concluded.