Biomolecules: Carbohydrates, Proteins, Lipids, Enzymes and the Food Tests

The Four Molecules Inside Every Cell

Every cell, from a bacterium to a human liver, is built and run by the same four families of large molecules: carbohydrates, proteins, lipids and nucleic acids. Each is a polymer, a long chain made by joining small repeating units called monomers. Carbohydrates are chains of sugars, proteins are chains of amino acids, lipids are built from glycerol and fatty acids, and nucleic acids are chains of nucleotides. This one idea, big molecule equals small unit repeated, answers many exam questions without memorising anything extra. Enzymes are a special group of proteins that speed up reactions in the body. Questions on this topic usually ask three things: what is the monomer, where is it stored, and which test detects it. This short builds all three, so the answers become automatic.

1. Which enzyme digests protein in the acidic medium of the stomach?

2. Milk sugar is chemically known as:

3. The peptide bond joins which units?

4. How much energy does one gram of fat provide?

5. Cellulose, the main component of plant cell walls, is a polymer of:

6. Which test turns a protein solution violet?

7. In which form do animals, including humans, store carbohydrate in the liver and muscles?

8. Why does an enzyme stop working when heated far above its optimum temperature?