Ch 9Biomolecules — Class 11 Biology, concept-first.

Living organisms are extraordinarily diverse — yet a simple question sits underneath that diversity: are all living things built from the same chemical elements? Chemistry gives us a way to answer thi…

Every living organism is built from carbon compounds, and the way biologists find out exactly which compounds are present is by doing a chemical analysis of the tissue.

One of the most exciting parts of biological chemistry is taking a living organism apart chemically — isolating thousands of compounds, both small and large, working out their structures, and where po…

When the compounds of a living tissue are sorted by size, a clear pattern emerges, and it lines up neatly with the acid-soluble versus acid-insoluble split introduced earlier.

Proteins are the acid-insoluble macromolecules built from amino acids, and they are among the most important and abundant compounds in living things.

Polysaccharides are the carbohydrate macromolecules of the acid-insoluble pellet, and like proteins they are long polymeric chains — but here the building blocks are sugars.

Nucleic acids are the second great class of macromolecule found in the acid-insoluble fraction of a living tissue, sitting alongside polysaccharides and polypeptides.

Proteins are heteropolymers — long chains made from many different amino acids strung together. Because they are so large and elaborate, biologists do not describe a protein's shape with a single pict…

Almost every enzyme is a protein. There is, however, an important exception: certain nucleic acids can also act as enzymes, and these are called ribozymes.

To understand enzymes, it helps to first be clear about what a chemical reaction actually is, and how it differs from a merely physical change.

To see how enzymes achieve their remarkable speeds, we need to look a little more closely at how an enzyme handles its substrate.

An enzyme does its work by physically holding on to the molecule it acts upon and then rearranging its chemistry.

How fast an enzyme works is not fixed; it responds to the conditions around it. Anything that disturbs the delicate three-dimensional (tertiary) folding of the enzyme's protein will change how well it…

Thousands of enzymes have been found, purified and studied, and to bring order to this variety they are sorted into groups according to the kind of chemical reaction each one drives.

Some enzymes are complete and active as protein alone, but many are not. In a large number of cases an enzyme needs an extra, non-protein partner in order to become catalytically active.

Living organisms are astonishingly varied, yet at the chemical level they are strikingly alike, both in what they are built from and in the reactions they run.

Higher-order thinking problems from the NCERT Exemplar.