What is the difference between absorption and action spectra?

Absorption spectra show the wavelengths of light absorbed by a pigment, while action spectra show the effectiveness of different wavelengths in a biological process.

Absorption spectra are used to determine the wavelengths of light that are absorbed by a particular pigment. This is done by shining a beam of white light through a sample containing the pigment and measuring the amount of light that is transmitted through the sample. The resulting graph shows the wavelengths of light that are absorbed by the pigment, which can be used to identify the pigment and its function. To understand this in the context of photosynthesis, see the light-dependent reactions in photosynthesis.

Action spectra, on the other hand, show the effectiveness of different wavelengths of light in a biological process. For example, the action spectrum for photosynthesis shows the wavelengths of light that are most effective in driving the process of photosynthesis. This is determined by measuring the rate of photosynthesis at different wavelengths of light and plotting the results on a graph. Further details can be found in the fundamentals of photosynthesis.

While absorption spectra are useful for identifying pigments and their functions, action spectra provide more information about the biological processes that are driven by light. By comparing the absorption and action spectra of a pigment, scientists can gain a better understanding of how the pigment is involved in biological processes such as photosynthesis or vision. For more insights on how these processes occur within plant cells, explore the chloroplast structure and function.

A-Level Biology Tutor Summary: Absorption spectra show which wavelengths of light a pigment absorbs, while action spectra indicate which wavelengths are most effective in a biological process. Absorption spectra help identify pigments, whereas action spectra reveal how light drives processes like photosynthesis. By comparing both spectra, scientists better understand the pigment's role in biological functions. Detailed mechanisms can be examined through the light-dependent reactions.