"Why won't it react?"
Toma shook the test tube with dissatisfaction.
Kana peeked in. "All reagents added?"
"Added. But nothing's happening."
Rei approached. "Not enough energy."
"Energy?" Toma asked back.
"Activation energy. Minimum energy to start reaction."
Kana opened her notebook. "Why is energy needed?"
Rei drew a graph on the whiteboard. "Like crossing a mountain."
"Mountain?"
"To go from reactants to products, must cross energy mountain."
Toma pointed. "What's the mountain peak?"
"Transition state. Highest energy state."
Kana took notes. "Transition state?"
"Unstable state in middle of reaction. Immediately collapses."
Milia arrived. "Like climbing a hill."
"Climbing a hill?" Kana asked.
"Can't descend other side without reaching summit."
Rei continued explaining. "Most molecules don't have enough energy to cross mountain."
"Then how do they react?" Toma asked.
"Through thermal motion, molecules that happen to have energy react."
Kana understood. "So raising temperature makes reaction faster?"
"Correct. Proportion of high-energy molecules increases."
Rei wrote an equation. "Arrhenius equation. k = A・exp(-Ea/RT)."
"What's this?" Toma tilted his head.
"Reaction rate constant k. Ea is activation energy, T is temperature."
Milia supplemented. "When temperature rises, becomes exponentially faster."
Kana calculated. "About double when 10 degrees rise?"
"For many reactions. But depends on Ea."
Toma tried to heat. "Then let's warm it."
"Wait," Rei stopped. "Side reactions or decomposition might occur."
"Then what should I do?"
"Catalyst," Milia answered.
"Catalyst?" Kana asked.
Rei drew new diagram. "Lowers activation energy."
"Lowers the mountain?"
"Yes. Provides alternate route through lower mountain."
Toma became interested. "How?"
"Stabilizes transition state. Or divides into multiple small steps."
Milia showed example. "Enzymes are perfect catalysts."
"What do enzymes do?" Kana asked.
"Bind substrate and create environment where reaction occurs easily."
Rei explained in detail. "At active site, arrange substrate in appropriate configuration."
"Configuration?"
"Orientation and distance where reaction occurs easily. Shape close to transition state."
Toma tried to understand. "So helps prepare for reaction?"
"Yes. Stabilizing transition state is key."
Kana had a doubt. "But can't completely make activation energy zero?"
"Can't. Then reverse reaction would be equally fast."
Milia supplemented. "Catalyst doesn't change equilibrium. Only changes rate."
"Equilibrium?"
Rei explained. "Final ratio of reactants and products. This is determined by thermodynamics."
"Activation energy is?"
"Kinetics. How fast equilibrium is reached."
Toma organized. "Catalyst makes path easier without changing goal."
"Good expression," Rei acknowledged.
Kana had another doubt. "Do all reactions in body have catalysts?"
"Most are catalyzed by enzymes. But some spontaneous reactions exist."
Milia gave example. "ATP hydrolysis. Occurs even without enzyme."
"But slow?"
"Very slow. Cells control with enzymes."
Rei continued. "Control is important. Trouble if reactions happen randomly."
Toma understood. "So high activation energy is necessary."
"Yes. Only when needed, accelerate with catalyst."
Kana admired. "Activation energy is both barrier and control means."
"Exactly," Rei nodded.
Milia proposed experiment. "Let's use platinum catalyst."
Toma prepared reagents. When platinum was added, reaction proceeded rapidly.
"Amazing!" Kana was surprised.
Rei explained. "On platinum surface, hydrogen is activated. Activation energy greatly decreased."
"Surface?"
"Catalysts often work on surface. Adsorption, reaction, desorption."
Toma was moved. "Crossed the mountain."
"Power of catalyst," Milia smiled.
Kana looked out window. "In the body too, countless enzymes are lowering mountains."
"And life moves," Rei said.
Toma resolved. "I want to overcome activation energy too."
"Of what?" Kana laughed.
"Of life."
The three laughed. With a catalyst, any mountain can be crossed.