Molecule builder sim
Drag glucose units into starch, glycogen or cellulose, amino acids into a polypeptide, or glycerol and fatty acids into a fat, count the water each join releases, and split the bonds again by hydrolysis.
Biological molecules: building and breaking large molecules · covers the O-Level, IGCSE, GCSE topic
What the sim shows
Large food molecules are built from small units. Each join is a condensation reaction: two units bond and one molecule of water is released. Hydrolysis is the reverse: a molecule of water is used to split a bond, and that is what every digestive enzyme does. Starch, glycogen and cellulose are all made of glucose joined in different ways: starch is long chains (which coil) stored by plants: it is insoluble, so it stores well without affecting osmosis; glycogen is highly branched and stored by animals in the liver and muscles; cellulose has straight chains with every other glucose turned over, joined by different bonds that humans have no enzyme to break, so it is dietary fibre. A protein is a chain of amino acids (about 20 kinds) joined by peptide bonds, which then folds into a shape. A fat is one glycerol joined to three fatty acids. The model kit counts the units, the bonds and the water released, and works out the formula and the relative molecular mass (Mr) using C = 12, H = 1, N = 14, O = 16, S = 32: for example maltose (2 glucose) is 2 × 180 − 18 = 342. Model limits: the board holds up to 8 glucose units in a chain (10 in branched glycogen), while real starch and glycogen have thousands; the pieces are flat shapes, not the molecules' real 3D shapes; the fatty acid shown is stearic acid; the bonds are not named by type except the peptide bond; the kit's hydrolysis always splits the last bond made, while real enzymes cut along the molecule (amylase gives maltose).
- Build board: units joined into one large molecule
- Glass dish: one bead of water for every bond made
- Hydrolysis: drag a bead back onto the molecule to split a bond
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 biology sims
- Inspired and expired air simBreathe in through one tube of limewater and out through the other, watch the cross behind each tube, and find out why only the air you breathe out turns limewater milky.
- Liver and hepatic portal vein simPlay a meal or a fast half an hour at a time, sample the hepatic portal vein and the hepatic vein, and see the liver store glucose as glycogen, release it again, and turn excess amino acids into urea.
- Mystery food bench simRun the iodine, Benedict's, biuret and ethanol emulsion tests on an unknown food, heating the Benedict's tube in a water bath, record each colour in a results table and work out which food it was.
- Peristalsis simContract the circular muscles behind a bolus and the longitudinal muscles in front of it, segment by segment, then turn the oesophagus upright, lying down or upside down and switch gravity off: the food still arrives at the same speed.
- Smoking and the airways simSet how many cigarettes a day, watch tar stop the cilia and mucus build up in the airway, and measure how much haemoglobin carbon monoxide takes away from oxygen.
- Villus absorption simZoom from the gut wall into one villus and two of its cells, turn knobs for the microvilli, the wall's thickness and the blood flow, and run a minute at a time to see glucose and amino acids go into the blood and fats into the lacteal.