A Level Biology Practice Exam

What is the purpose of stains in microscopy?

1. To determine pH levels

2. To increase contrast or identify specific components

3. To preserve sample integrity

4. To assist in cell division studies

The correct answer is: To increase contrast or identify specific components

Stains play a crucial role in microscopy primarily by increasing contrast and helping to identify specific components within a sample. Biological samples are often transparent or have low contrast, making it difficult to see fine details under a microscope. By applying stains, which are colored chemical compounds, different cellular structures and components can become more visible. For instance, certain stains bind specifically to DNA or proteins, allowing researchers to visualize nuclei or certain organelles distinctly. This increased contrast makes it easier to differentiate between different types of cells, tissues, or other structures, enhancing the overall clarity and detail of microscopic images. The ability to target specific components with particular stains is vital for various applications, from identifying pathogens in a laboratory setting to conducting detailed studies of cellular structures and functions.