"Are sugars just energy sources?"
Kana stared at the sugar molecule model.
Milia smiled. "That's one aspect. There are deeper roles."
"Deeper?"
Rei explained. "Glycans. Structures where multiple sugars link in chains."
Kana asked. "Like proteins and nucleic acids, do they carry information?"
"Yes. But more complex information."
Milia drew a diagram. "Nucleic acids are linear. Four-letter alphabet."
"DNA's A, T, G, C?"
"Yes. But glycans branch."
Rei continued. "Many types of monosaccharides. Glucose, galactose, mannose..."
"There are many."
"Moreover, linkage methods are complex. Alpha or beta, which carbon to link."
Milia showed an animation. "Same monosaccharides, completely different structures by combination."
Kana was surprised. "Combinatorial explosion?"
"Exactly. Glycan diversity exceeds nucleic acids and proteins."
Rei gave a concrete example. "Blood types. A, B, O types are glycan differences."
"Sugar differences?" Kana was surprised.
"Glycans on red blood cell surface. Just one terminal sugar difference."
Milia explained. "A type has N-acetylgalactosamine, B type has galactose."
"Just that?"
"The immune system recognizes that subtle difference. Distinguishes self from non-self."
Kana thought. "So glycans are identification codes?"
"Correct," Rei acknowledged. "Cell surfaces are covered with glycans."
Milia continued. "Called glycocalyx. Sugar coat."
"For what?"
"Cell-to-cell recognition. Which cell, which tissue, healthy or diseased."
Rei added. "Proteins called lectins read glycans."
"Read?"
"Bind to specific glycan structures. Like lock and key."
Kana asked. "Related to disease?"
"Cancer cells have altered glycan patterns," Milia answered.
"How altered?"
"Express abnormal glycans. Evade immune system, promote metastasis."
Rei explained. "So glycans become biomarkers. Used for disease diagnosis."
Kana was impressed. "Glycans are language."
"Glycan code," Milia used the technical term. "The sugar language cells speak."
Rei continued. "But that language is complex. Not fully decoded yet."
"Decoded?"
"What each glycan means. Understanding vast patterns."
Kana wrote in her notebook. "Glycomics?"
"Yes. Comprehensive glycan analysis. Field following genomics, proteomics."
Milia said quietly. "Glycans weave stories. Cell history, state, fate."
Rei nodded. "Protein glycosylation. Functions change when glycans are added."
"How change?"
"Stability, localization, interactions. Glycans are a type of post-translational modification."
Kana asked. "Where are glycans attached?"
"Endoplasmic reticulum and Golgi apparatus," Milia answered. "Sugars added stepwise."
Rei drew a diagram. "N-type and O-type. Different attachment sites."
"Too complex..."
"But that complexity creates life's diversity," Milia said.
Kana stared at the model. "Glycans are invisible stories."
Rei said quietly. "Sweet codes cells weave."
Milia smiled. "And we're trying to decipher those stories."
The three fell silent. Sugar chains write life's stories.