Made of Chains

What this book is about

Cell chemistry is the chapter where biology suddenly turns into a vocabulary test. Monosaccharide, glycosidic, phospholipid, tertiary structure, competitive inhibitor, phosphodiester, semi-conservative. Most students meet forty new words in a fortnight, memorise them in a panic, and never find out that almost all of them describe the same three or four ideas.

This book takes the chapter apart and puts it back in the order the ideas actually depend on one another. It follows the Higher Secondary syllabus, but it does not follow the syllabus's order, because that order is a list and this is an argument.

One thing to say at the outset: cell chemistry is printed in the botany paper, and there is nothing botanical about it. Every molecule here is found in exactly the same form in an animal, a fungus and a bacterium. The examples come from plants because that is the paper it appears in; the chemistry is universal.

The one idea to carry through: all four families of molecule in a cell are built by joining smaller pieces together, and every single one of those joins is made by taking a water molecule out. Four different bond names — one reaction.

What is inside

• Water, and the one reaction that builds everything; acids, bases and the pH a cell holds
• Carbohydrates — isomers, the glycosidic bond, starch and glycogen, and why you cannot eat

grass

• Lipids — the family that is not a polymer, and a membrane that builds itself
• Proteins — twenty molecules and one shape, four levels of structure, and why an egg will

not un-boil

• Enzymes — why sugar does not burn on the table, rate and saturation, Km, inhibitors and

vitamins

• Nucleic acids — Chargaff's puzzle, Photograph 51, why it has to be A–T and G–C,

replication, RNA, and ATP

• Two kitchen experiments, everything on one sheet, eighteen exercises with answers, a

Bangla–English glossary and a quiz