Bioactivity screen lab
Fri, Dec 18, 2026 · Week 17 · Principles of Biomedical Technology (Principles of Biomedical Science)
Today's goal: Run the qualitative screen on five samples and record a positive or negative result for each.
This is a model of the work you should turn in today. Use it to check your own: match the structure and the level of detail, do not copy it. Your data and wording should be your own.
Labeling scheme, written before any liquid moved:
- Tubes M1 to M5 for the five marine samples, plus C+ for the positive control and C- for the negative control. Initials and period on every cap.
- I labeled the sides and the caps, because a cap can get swapped between tubes while the rack sits open.
Technique for this run: fresh tip for every sample, bench wiped before and after, tubes kept closed except while I was pipetting into them, beaker covered on the hot plate.
Module I results, scored by color after the stated development time:
- C+ positive control: strong color. The chemistry worked, so a negative on a sample means something.
- C- negative control: no color. Nothing in the reagents is producing color on its own.
- M1: color. Positive.
- M2: no color. Negative.
- M3: color, fainter than M1. Positive.
- M4: no color. Negative.
- M5: color, the deepest in the rack. Positive.
Three of the five samples screened positive: M1, M3, and M5.
What this result cannot tell me: none of it is a quantity. A color says the compound is there or it is not. M5 looked deepest and M3 looked faintest, and I am not entitled to conclude from that alone that M5 holds more of the compound than M3, because color depth in a screen like this also moves with how much extract went in, how long it developed, and whatever else in the extract absorbs light. Ranking M1, M3, and M5 by amount takes Module II: known standards, a curve, and a measured concentration for each.
Why both controls matter: without C+, a negative sample could mean the compound is absent or the reagents were dead, and I would have no way to tell those two apart.
This model shows the level of evidence and organization needed to complete: Completes the Module I screen: the labeling scheme recorded, all five samples scored positive or negative by color, and one sentence stating what a qualitative result cannot tell you.
- Identify the purpose, hazards, and required controls.
- Write the procedure in a usable order.
- Confirm materials, measurements, and waste handling before starting.
Keep the structure. Replace the question, facts, measurements, and evidence. Then recheck units, vocabulary, and whether the conclusion goes beyond the evidence.
Also due today: Submit your Module I results table on the class site, or hand it to Mr. Mendoza in class before leaving.
Claim ceiling: Today's evidence supports a classroom claim about bioactivity screen lab. It cannot prove causation, diagnose a real patient, or justify action outside this room.
One exam-style question that uses exactly what you practiced today. Try it before you reveal the answer, then read why each choice is right or wrong.
Tap an answer to see the full explanation. Nothing is recorded or graded.
It builds this reusable test skill: Separating what a qualitative screen reports from what a quantitative assay reports.
- Name the concept or data pattern being tested.
- Cross out choices that violate that rule or the evidence.
- Justify the best remaining choice before checking the answer.