A monomer is a single unit; a polymer is a chain of them. Most biological molecules are polymers.
Polymer A large molecule built from repeating monomer units.
Step 1: Something to Notice
Watch first. The explanation comes later.
Proteins perform more distinct jobs than the other three families combined — enzymes, structure, transport, signalling, defense, movement.
What about their structure allows that range?
Step 2: Find Out
Hold the chain length constant and change the family. Isolate what produces the difference in possible sequences.
Step 1 — Predict
Why can proteins do so many more jobs than polysaccharides?
Choose what you think will happen. You cannot see the experiment until you do — guessing first is what makes it worth watching.
Step 3: So Here Is Why
Now the explanation, after you have seen it happen.
Condensation builds, hydrolysis breaks
Each bond forms by removing a water molecule and breaks by adding one back. n units need n−1 bonds.
Condensation Joining two monomers by removing a water molecule.
Carbohydrates and lipids
Carbohydrates are sugar chains for energy and structure. Lipids are not true polymers and are grouped by being insoluble.
Proteins
Twenty amino acids in any order. Sequence sets folding, folding sets shape, and shape sets function.
Nucleic acids
Four nucleotides carrying information rather than doing chemistry. Enough variety to encode, not enough to catalyse widely.
Structure determines function
This is the organizing principle of the whole course, and it starts at the level of molecules.
Four families, one assembly reaction
Carbohydrates, lipids, proteins and nucleic acids. Three of the four are polymers built by removing water between monomers, and broken down by adding it back. One reaction type covers most of biochemistry.
Function follows from shape
A protein's job depends on the three-dimensional shape its amino acid sequence folds into. Change the sequence, change the shape, lose the function — which is what most harmful mutations do.
Step 4: A Common Mistake
Lots of people think
“The four macromolecule families are four unrelated topics to memorize.”
Step 5: Why Water Is the Reaction Both Ways
The same idea somewhere new.
Condensation removes a water molecule to form each bond; hydrolysis adds one to break it. That is why digestion is chemically the reverse of synthesis, and why the same enzyme families appear across very different organisms — the underlying chemistry has not changed in billions of years.
Step 6: Think It Through
Practice makes it stick.
Counting Water
Problem 1 of 2
Eight monomers are joined into one chain. How many water molecules are released?
molecules
Sequence Counts
Problem 2 of 2
How many sequences are possible for a chain of 4 amino acids drawn from 20 kinds?
sequences
Four Families, One Chemistry
1 of 5
Match each family to its monomer.
Tap a card on the left to start.
2 of 5
Which family is not a true polymer?
3 of 5
What reaction breaks a polymer apart?
4 of 5
Why are proteins so versatile?
5 of 5
How many bonds join 10 monomers into one chain?
bonds
Step 7: Quick Check
Show what you know.
Question 1 of 1
What gives proteins their functional range?
Step 8: Explain It in Writing
Claim, evidence, then reasoning.
The question
Explain why proteins perform more distinct functions than carbohydrates, using the relationship between monomer variety and possible structures.
Fill in all three boxes. The reasoning box is the one that matters most.
What You Found Out
- Monomers join into polymers by condensation, releasing one water per bond.
- Hydrolysis reverses it, which is why digestion is chemically the reverse of synthesis.
- Carbohydrates and nucleic acids have few monomer types; proteins have twenty.
- Sequence sets folding, folding sets shape, and shape sets function.