Identify Biomolecules From Indicator Data
Use indicator color changes to identify carbohydrates, proteins, and lipids in evidence samples.
- Use a reference chart: Indicators and microscope features must be compared to a known guide.
- Structure and function: Students connect visible features to what tissues or molecules do.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
Use indicator color changes to identify carbohydrates, proteins, and lipids in evidence samples.
| Indicator | Positive result | Biomolecule |
|---|---|---|
| Benedict after heat | orange | reducing sugar |
| Iodine | blue-black | starch |
| Biuret | purple | protein |
| Brown paper | translucent spot | lipid |
Use the biomolecule chart. Which positive result identifies protein?
Reviewed| Indicator | Positive result | Biomolecule |
|---|---|---|
| Benedict after heat | orange | reducing sugar |
| Iodine | blue-black | starch |
| Biuret | purple | protein |
| Brown paper | translucent spot | lipid |
- A.Benedict turns orange
- B.Iodine turns blue-black
- C.Biuret turns purple
- D.Brown paper turns translucent
Show the worked solution ▾
Answer: C. Biuret turns purple
- Step 1: Find protein row: The chart links protein to Biuret.
- Step 2: Read result: Biuret positive is purple.
Why it's right: Purple Biuret indicates protein.
- A: Orange Benedict indicates reducing sugar.
- B: Blue-black iodine indicates starch.
- D: Translucent spot indicates lipid.
Aligned to Biotechnology Research and Experiments · reading level ~grade 9
A drop of an unknown liquid is placed on brown paper and left to dry. Twenty minutes later the spot is still see-through and lets light pass. Which biomolecule does that point to?
Reviewed- A.Starch, which would need iodine to show blue-black
- B.Protein, which would need Biuret to show purple
- C.Lipid, because oils leave a lasting see-through spot
- D.Reducing sugar, which would need Benedict and heat
Show the worked solution ▾
Answer: C. Lipid, because oils leave a lasting see-through spot
- Step 1: Ask which test was run: Brown paper is the test used for fats and oils.
- Step 2: Read the result: Water evaporates and the paper dries clear, but a lipid leaves a spot that keeps letting light through.
Why it's right: The brown paper test is positive for lipid when the spot stays see-through after the liquid has had time to dry.
- A: Starch is read with iodine, and no iodine was used here.
- B: Protein is read with Biuret reagent, and no Biuret was used here.
- D: Reducing sugar is read with Benedict solution and heating, neither of which happened.
Aligned to Biotechnology Research and Experiments · reading level ~grade 9
- In Unit 1.1 to 1.2 Evidence & Biomolecules, this skill turns class evidence into a result another person can check.
Fill these in as you work through the lesson.
- Indicator (chemical test that changes if target is present):
- Starch (large carbohydrate):
- Protein (macromolecule made of amino acids):
- Lipid (fat or oil molecule):
Match the indicator to the chart before naming the biomolecule present in the .
- Which indicator was used?
- What color did the sample turn?
- Which biomolecule matches that color?
Iodine turns an unknown blue-black. Use the chart to identify the biomolecule.