absorption and action spectra
Absorption spectrum refers to the range of wavelengths of light that a substance can absorb. It is determined by the specific molecules present in the substance and their electronic structure. Different molecules have different absorption spectra, as they absorb light at different wavelengths.
Action spectrum, on the other hand, refers to the effectiveness of different wavelengths of light in driving a specific biological process or reaction. It represents the relative response or activity of a system to different wavelengths of light. The action spectrum is often measured by the rate of a specific biological process under different wavelengths of light.
Absorption and action spectra are related because the absorption spectrum of a substance determines its action spectrum. If a substance absorbs light at a certain wavelength, it is more likely to be active or effective in driving a biological process at that wavelength. The overlap between the absorption and action spectra of a substance determines the overall effectiveness of light in driving a specific biological process.
Absorption and action spectra are two important concepts in the study of light and its interaction with biological systems. Let's break down these terms step-by-step:
1. Absorption Spectrum:
- An absorption spectrum is a graphical representation or a plot that shows how strongly a substance absorbs different wavelengths of light.
- It provides information about the specific wavelengths of light that a substance can absorb and the amount of light absorbed at each wavelength.
- The absorption spectrum is obtained by passing white light through a sample and measuring the transmitted light intensity at different wavelengths using a spectrophotometer.
- The graph usually shows a peak or peaks at specific wavelengths where the absorption is highest. These peaks are known as absorption bands.
2. Action Spectrum:
- An action spectrum is a graphical representation or a plot that shows the effectiveness or response of a biological system to different wavelengths of light.
- It provides information about the wavelengths of light that are most efficiently utilized by a biological system for a specific physiological process or response.
- To obtain an action spectrum, the biological system's response to light at different wavelengths is measured, usually by monitoring a specific biological process or function.
- The graph usually shows the level of response or effectiveness of the biological system as a function of different wavelengths of light.
- The action spectrum may or may not have a direct correlation with the absorption spectrum of the chromophores (light-absorbing molecules) present in the biological system.
In summary, absorption spectrum describes how much light a substance absorbs at different wavelengths, while action spectrum represents the effectiveness or response to light of a biological system at different wavelengths.
Absorption and action spectra are concepts commonly used in the field of photobiology to understand the interaction between light and living organisms. Let's dive into each concept separately:
1. Absorption Spectrum:
An absorption spectrum refers to the range of wavelengths of electromagnetic radiation (usually in the form of light) that a particular substance can absorb. When light strikes a substance (e.g., a pigment or chromophore) present in a living organism, some of the incident light energy is absorbed by the substance, while the rest is transmitted or reflected. The absorbed energy can initiate various biological processes.
To determine the absorption spectrum of a substance, you would typically perform the following steps:
1. Obtain the substance: Extract or isolate the substance from the organism of interest, such as a pigment or protein.
2. Prepare a sample: Create a solution or thin film containing the substance.
3. Use a spectrophotometer: A spectrophotometer is an instrument that measures the amount of light absorbed by a sample at different wavelengths. Set up the spectrophotometer and configure it to scan the desired range of wavelengths.
4. Record the absorbance: Place the sample in the spectrophotometer and record the absorbance readings for each wavelength. The absorbance values indicate the amount of light absorbed by the substance at each specific wavelength.
5. Plot the absorption spectrum: Using the recorded absorbance data, create a graph that represents the absorption spectrum. The x-axis will display the range of wavelengths, while the y-axis will show the absorbance values.
2. Action Spectrum:
An action spectrum describes the effectiveness of different wavelengths of light in driving a specific biological process. It provides insights into which wavelengths of light are most efficient for driving a particular physiological response or activity in a living organism.
To determine an action spectrum, you would typically follow these steps:
1. Identify the biological process: Determine the specific physiological activity or response you want to study, such as photosynthesis or enzyme activation.
2. Select an organism: Choose a relevant organism that exhibits the desired biological process and can be easily manipulated in the laboratory.
3. Expose the organism to different wavelengths: Use a light source or filters to expose the organism to light of various wavelengths over a specified range.
4. Measure the response: Quantify the biological response or activity of interest. This could involve measuring parameters like oxygen production, chlorophyll fluorescence, or enzyme activity.
5. Plot the action spectrum: Create a graph that represents the relationship between the measured biological response and the corresponding wavelengths of light used. The resulting curve represents the action spectrum.
By understanding both the absorption spectrum and action spectrum of a particular substance or organism, researchers can gain insights into how light and different wavelengths affect various biological processes.