Final answer:
A diffusible biochemical molecule that influences cell fate by its concentration is called a morphogen. These molecules play an important role in guiding tissue development by creating concentration gradients that cells can response to, leading to differentiation.
Step-by-step explanation:
The term used to refer to a diffusible biochemical molecule that can determine the fate of a cell by its concentration is a morphogen. Morphogens are significant during embryonic development where their gradient concentrations can affect cell differentiation and tissue development. For example, if a morphogen is present in a high concentration, it might induce the development of one type of tissue, whereas at a lower concentration it could induce a different type of tissue.
Addressing the examples provided:
- The scientist's observation of cells turning off the transcription of a gene upon the addition of a small molecule suggests that the molecule is acting as a ligand that binds to a specific cellular receptor, which may result in changes in gene expression.
- When cells are mixed with a dye that can't normally penetrate them but enters the cells after a ligand is added, this suggests that the ligand is binding to a receptor type that triggers a response allowing the dye to enter. This is indicative of a receptor-mediated cellular response, possibly through endocytosis.