IP Biology Notes: Biological Molecules (Upper Sec 03)

For Integrated Programme students: Your current school materials, teacher instructions, and assessment scope take precedence because IP topic sequence and depth vary by school. This is an Eclat IP guide, not the O-Level / SEC G3 exam-track guide.

How this chapter applies

• Eclat core: carbohydrates, fats, proteins, food tests, synthesis from smaller units, enzyme specificity, activation energy, temperature, and pH form the main route.
• School-sensitive extension: DCPIP and vitamin C work, molecular structures, induced-fit comparisons, and quantitative enzyme modelling should be used only where the current school teaches them.
• 2027 national comparison: K325 Topic B3 covers elements, biological roles, four food tests, synthesis of large molecules, lock-and-key enzyme action, activation energy, temperature, and pH.
• Check your school: reagent concentrations, heating methods, observation wording, and the molecular depth expected in enzyme explanations can differ.
• Exam-track route: use the separate O-Level and SEC G3 Biology notes for K325 topic ownership.

The core idea is simple: Biological molecules are tested through roles, enzymes, and food tests.

Use it as a working check: Learn what carbohydrates, fats, and proteins do, then link each food test to its reagent, condition, and positive result.

Then go one layer deeper: Example: Benedict's test needs heating in a water bath. A brick-red precipitate means reducing sugar is present, not simply that the sample turned red.

What you must know

• Carbohydrates (C, H, O): glucose, sucrose, starch, glycogen; energy source/storage. Fats (C, H, O): energy storage, insulation; formed from glycerol + fatty acids. Proteins (C, H, O, N sometimes S): structure and enzymes.
• Food tests: iodine for starch (blue-black), Benedict for reducing sugars (brick-red ppt on heating), biuret for protein (violet), ethanol emulsion for fats (white emulsion).
• Enzymes: specific active site; lock-and-key/induced fit; lower activation energy; affected by temperature (optimum then denaturation) and pH (active site charges disrupted).

Decision map - identifying an unknown food sample