Single answerDifficulty 2/5 · StandardOlympiadQuestions & methodsArgumentation
Hormones on beads
Topic: Modes of cell communication
A lab has two newly purified hormones, X and Y, that both act on cultured rat liver cells. To find where each hormone's receptor is, the team ran three tests. In one, each hormone was chemically attached to plastic beads far too large to enter a cell; checks showed that less than 0.1% of the hormone leaked off the beads. In another, radioactively labelled hormone was added, and 15 minutes later the cells were broken open and separated into fractions.
Experimental setup
- Question
- Does each hormone act from outside the cell or from inside it?
- Independent variable
- Which hormone, and whether it is free, bead-bound, or released from the beads
- Dependent variable
- The cells' response, and where the radiolabel ends up
- Kept constant
- Same liver cell line · Same hormone concentration · Temperature (37 °C) · Same measurement times
- Groups
- Free hormone: Hormone X or Y added to the medium
- Bead-bound hormone: Hormone X or Y attached to large beads
- Linker control: Hormone attached to beads, then cut free before being added
Data
| Test | Hormone X | Hormone Y |
|---|---|---|
| Free hormone | Enzyme activity rises within 1 minute | A new protein appears after about 2 hours |
| Hormone on beads | Full response | No response |
| Hormone cut free from beads | Full response | Full response |
| Radiolabel location after 15 min | Plasma membrane fraction only | Cytoplasm and nucleus |
Which conclusion do the results best support?
Answer every part to submit.