Natural polymers: hydrolyse, then find the monomers sim
Heat a protein with acid, take samples over time and run them beside known amino acids. Spray the dried paper, measure the Rf values of the spots that appear, and see why early samples show fewer. Then join amino acids into a chain and count the water given off.
Natural polymers: hydrolysing proteins and starch, and identifying the monomers by chromatography · covers the GCSE (Higher), IGCSE (Supplement), O-Level (Rf and locating agents only) topic
What the sim shows
Proteins and starch are natural polymers. A protein is a polyamide: amino acids joined by peptide (amide) links, -CONH-, each made by condensation, with one water given off per link. Heating the protein under reflux with hydrochloric acid hydrolyses those links (water is added back) and sets the amino acids free; starch is hydrolysed by acid right down to glucose (maltose on the way) or by the enzyme amylase (which stops mostly at maltose). Amino acids and sugars are colourless, so the dried chromatogram is sprayed with a locating agent that makes the spots show. Rf = distance moved by the spot / distance moved by the solvent front, both from the pencil line; a spot at the same Rf as a known amino acid in the same solvent is that amino acid. A sample taken before heating shows nothing; for the protein, early samples show fewer spots than later ones, because the hydrolysis is not finished. The paper and solvent follow the library's chromatography figure: the paper is wet √(0.09 × time) up from the solvent, which sits 0.5 cm below the pencil line. Model limits: the Rf values are examples for one solvent; how fast each amino acid is set free, and the least that shows as a spot, are illustrative; gelatin holds many more amino acids than the four shown; you do not need to know the name of any locating agent.
- Reflux: the flask on a heating mantle, condenser on top
- Standards, paper on a tile, tank with solvent
- Spray: a locating agent shows colourless spots
Use it in your lessons
- Try it here: anyone can unlock 2 figures free, and a free account unlocks up to 5. Runs on a laptop, a Chromebook or a phone; nothing to install.
- Present it and share student links with the teacher plan, from US$5 a month, billed yearly.
- Put it on your own website or LMS for US$9, paid once, or every sim from US$29 a month.
Free guide: 12 practicals as sims, and how to run one in a lesson →
Need a version for your exact set-up? Have one made: US$49 a figure in an order of 5.
More chemistry sims
- Filtration, evaporation and crystallisation simStir, filter and then evaporate or crystallise to get salt or copper(II) sulfate back out of a mixture with sand, and see how much you recover.
- Flame tests and the spectroscope simClean a nichrome loop in acid, dip it in a solid, hold it in a roaring blue flame, record the colour, name the metal ion and match its line spectrum.
- The greenhouse effect simChange the carbon dioxide and methane in the air (or pick a year from the record), watch infrared being absorbed and sent back down, and read the extra heating and settled temperature; then sort out the ozone-hole mix-up.
- Group 1 metals in water simDrop the same size piece of lithium, sodium or potassium into water with universal indicator: floating, melting, fizzing, the lilac flame, the hydrogen and the pH, with the trend explained. Rubidium and caesium as a clearly marked prediction only.
- The hydrogen–oxygen fuel cell simOpen the hydrogen and oxygen valves of a fuel cell, watch electrons drive a motor and water drip out, read the voltage and current, and compare the fuel cell with a battery and a petrol engine.
- Iron and sulfur: mixture or compound? simPull iron out of an iron and sulfur mixture with a magnet, then heat a fresh mixture until it glows and forms black iron(II) sulfide, which the magnet no longer attracts, and find the fixed proportion from your own masses.