Introduction to Macromolecules
Introduced| English | Meaning |
|---|---|
| monomer/ˈmɒnəʊmə/ | A molecule that can join with other molecules to form a polymer. |
| polymer/ˈpɒlɪmə/ | A large molecule made from many linked repeating units derived from smaller molecules. |
| condensation reaction/kɒndenˈseɪʃn rɪˈækʃn/ | condensation reaction |
| hydrolysis/haɪˈdrɒləsɪs/ | Breaking chemical bonds by reaction with water. |
Big molecules from small parts
- The largest molecules in a cell are built like a train — many identical carriages linked in a row.
- Cells make these giants from small, repeating building blocks.
- The same trick — join small parts into a chain — builds most of what a cell is made of.
- Four families of these giant molecules run all of life.
Monomers and polymers
- A monomer 单体 is a single small building-block molecule.
- A polymer 聚合物 is a long chain of many monomers linked together.
- Think beads (monomers) threaded into a necklace (polymer).
- Different monomers give polymers with completely different jobs.
A polymer is best described as…
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A polymer is a large molecule made by linking many small monomer subunits into a chain.
Condensation joins them
- To link two monomers, the cell runs a condensation reaction 缩合反应.
- Each new bond releases one molecule of water.
- Do this many times and a short monomer becomes a long polymer.
- This is how the cell builds starch, proteins, and DNA.
A condensation reaction uses up a molecule of water each time it joins two monomers.
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False. Condensation joins monomers and releases one water molecule per bond formed. Hydrolysis is the reaction that uses water to split a polymer.
Hydrolysis breaks them
- The reverse reaction is hydrolysis 水解 — "splitting with water".
- Adding a water molecule breaks the bond between two monomers.
- This is how digestion breaks big food molecules into small ones.
- Condensation builds up; hydrolysis breaks down.
Breaking a polymer by adding water is called ____.
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Hydrolysis ("water-splitting") adds water to break the bond — the reverse of condensation.
The four families
- Carbohydrates: sugar monomers, for quick energy and structure.
- Proteins: amino-acid monomers, doing thousands of different jobs.
- Nucleic acids: nucleotide monomers, storing genetic information.
- Lipids: fats and oils — the odd one out, not built as a true polymer.
Which macromolecule?
Sort each example into its macromolecule family by its building block and job.
Which of these is not one of the four biological macromolecule families?
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The four families are carbohydrates, lipids, proteins, and nucleic acids — metals are not macromolecules.
Select all true statements about macromolecules.
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Macromolecules are carbon-based, not metallic. The other three statements are correct.
Lipids are usually grouped with the macromolecules, but they are not true polymers — they are not long chains of one repeating monomer. Do not describe a fat as a "polymer of fatty acids" the way starch is a polymer of glucose.
Starch, step by step:
- One glucose monomer joins another by condensation, releasing water.
- Repeat hundreds of times to build a long starch polymer.
- To use it, the cell runs hydrolysis, adding water to release glucose again.
Big biological molecules are polymers — chains of small monomers. A condensation reaction joins monomers and releases water; hydrolysis adds water to break them apart. The four families are carbohydrates, proteins, nucleic acids, and lipids (the odd one, not a true polymer).
Write from 4 water molecules released
- Five monomers join into one chain by dehydration synthesis.
- No monomer is left over.
How many water molecules are released?
Links in a linear chain are one fewer than the monomers.
How many waters does joining five monomers release?
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Five monomers need four dehydration links.