Final answer:
Cell-surface receptors bind to ligands to induce changes in cellular functions, leading to alterations in gene transcription and protein production. Early induced proteins such as interferons are synthesized in response to stimuli to protect cells during immune responses.
Step-by-step explanation:
Proteins that induce change in a cell upon contact with specific molecules in the environment or on the surfaces of neighboring cells are known as cell-surface receptors. They are membrane-anchored integral proteins that participate in signal transduction by binding to external ligand molecules. Upon ligand binding, these receptors undergo a structural change, which then triggers chemical signals that can lead to alterations in the cell such as turning transcription of DNA "on" or "off", impacting protein production and ultimately modifying cellular activities.
Early induced proteins, such as interferons and C-reactive protein, are not constantly present but are synthesized in response to specific stimuli, particularly during the immune response. For example, interferons released by virus-infected cells protect surrounding cells by inducing them to make antiviral proteins. Hence, even though the first cell may be compromised, its neighbors are guarded against the viral threat.