What does heat undo in a protein?
"What does heat undo in a protein?" is a free, interactive Class 12 Chemistry simulation for NEET and JEE, built on the lesson "Peptides and the four levels of protein structure" in Biomolecules. Pick a structure level to see it, then heat the protein or change the pH. Each bead is one amino acid, labelled with its one-letter code; the sequence is made up for the picture. 1° is the sequence, held by peptide bonds. 2° and 3° depend on hydrogen bonds and other weak forces, and 4° packs sub-units. Denaturation destroys 2° and 3° but leaves 1° intact. JEE Main asked 50 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Peptides and the four levels of protein structure in Biomolecules. Change the values and watch what happens.
In JEE Main
42 shifts analysed
50 questions from Biomolecules across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT §10.2.3
- A peptide bond is an amide, –CO–NH–, formed when the carboxyl group of one amino acid joins the amino group of another with loss of water. Glycine's –COOH with alanine's –NH₂ gives the dipeptide glycylalanine.
- Three amino acids joined by two peptide bonds make a tripeptide; then tetra-, penta-, hexapeptide. More than ten amino acids make a polypeptide.
- A polypeptide with over a hundred residues and molecular mass above 10,000 u is called a protein. The line is not sharp: insulin, with only 51 amino acids, counts as a protein because it has a definite protein-like shape.
- By shape. Fibrous proteins: parallel chains held by hydrogen and disulphide bonds form fibres, generally insoluble in water, e.g. keratin (hair, wool, silk) and myosin (muscles). Globular proteins: chains coil into a sphere and usually dissolve in water, e.g. insulin and albumins.
- Primary structure: the exact sequence of amino acids in each chain. Change the sequence and you have a different protein.
- Secondary structure: the shape of the backbone, held by hydrogen bonds between the C=O and –NH– groups of peptide bonds. Two kinds occur: α-helix and β-pleated sheet.
- α-Helix: the chain twists into a right-handed screw so that each residue's –NH is hydrogen-bonded to a C=O on the next turn, making the most hydrogen bonds possible.
- β-Pleated sheet: chains stretched almost fully lie side by side, held by hydrogen bonds between chains; the folds look like pleated drapery.
- Tertiary structure: the overall folding of the chain beyond the secondary structure, giving the fibrous or globular shape. Hydrogen bonds, disulphide linkages, van der Waals forces and electrostatic attraction stabilise 2° and 3° structure.
- Quaternary structure: the arrangement in space of two or more chains (sub-units) in one protein. Haemoglobin is NCERT's example.
Questions
3 answers
- What does the "What does heat undo in a protein?" simulation show?
- Pick a structure level to see it, then heat the protein or change the pH. Each bead is one amino acid, labelled with its one-letter code; the sequence is made up for the picture.
- Does JEE Main ask questions from Biomolecules?
- Yes. JEE Main asked 50 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Peptides and the four levels of protein structure" in Biomolecules (Class 12 Chemistry).
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