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Type
science_lab
Pre Lab
Background: All living things are made of large molecules called **macromolecules**. There are four major types of macromolecules found in food: **carbohydrates** (including **starch** and **reducing sugars** like glucose), **proteins**, **lipids** (fats), and nucleic acids. Each macromolecule has a specific job in the body. Starch is a long-chain carbohydrate used for energy storage in plants. Reducing sugars are simple carbohydrates that provide quick energy. Proteins are made of amino acids and are used to build and repair body structures. Fats (lipids) store energy and help build cell membranes.
Scientists use chemical indicators as **models** to detect the presence of specific macromolecules. Each indicator causes a visible color change ONLY when its target macromolecule is present. The **iodine test** detects starch — a positive result turns the solution from orange-brown to blue-black. **Benedict's test** detects reducing sugars — a positive result turns the solution from blue to orange or brick-red when heated. The **Biuret test** detects proteins — a positive result turns the solution from light blue to purple or violet. **Sudan IV** detects fats (lipids) — a positive result produces a bright red or pink color in the fat layer.
In today's lab, you are a forensic food scientist called to a crime scene. A mysterious dinner party ended badly, and you must analyze the food samples left behind to identify what was served. By running a series of macromolecule indicator tests on known food samples and then on mystery samples, you will construct an explanation — just like a real scientist — to solve the case. Remember: a **negative result** (no color change) is just as important as a positive one. Every piece of evidence matters!
Vocabulary
Term: macromolecule
Definition: A very large molecule made of smaller repeating units; the four main types in living things are carbohydrates, proteins, lipids, and nucleic acids.
Term: starch
Lab Type
Post Lab
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