CHM095 · Biochemistry · Classes 9–12
Protein Folding Concept
Objective: To explore the four levels of protein structure.
🧰 Virtual materials and apparatus
- Virtual chain of amino acids that folds through four levels
- On-screen controls and live readout
📐 Formulas and SI units
peptide bonds = n − 1
mass ≈ 110 Da × n
💡 Theory
Proteins are chains of amino acids joined by peptide bonds (n amino acids, n − 1 bonds). The primary structure is the sequence; secondary structure is local folding into helices and sheets; tertiary structure is the overall 3D fold; quaternary structure is several chains together (like haemoglobin). The shape decides the function.
🪜 Guided virtual procedure
- Start at level 1: a straight chain.
- Step to level 2: a helix.
- Step to levels 3 and 4.
- Change the number of amino acids and read the peptide bonds and mass.
- Explain why shape matters.
📋 Observations Simulated values
✅ Result and conclusion
A 100-amino-acid protein has 99 peptide bonds and a mass of about 11 kDa.
🔬 Real lab vs simulation
This is not a predictive folding engine; real folding depends on the sequence and surroundings.
⚠️ Safety
Conceptual model only. Real laboratory chemicals are handled only by teachers.
❓ Quick check
1. Primary structure is…
2. Peptide bonds in a 50-residue chain?
3. Haemoglobin has … structure.
🏋️ Practice
EasyMass of a 300-residue protein?
Answer: ≈ 33 kDa
MediumWhat holds a helix together?
Answer: Hydrogen bonds
ChallengeWhy does cooking change egg white?
Answer: Heat unfolds (denatures) the proteins