Difference between Action Spectrum and Absorption Spectrum of Photosynthesis || BiologyExams4u

Summary

This educational video explores the vital role of pigments in photosynthesis, focusing on chlorophyll and carotenoids. It explains the visible light spectrum's absorption by plants, particularly in the blue and red wavelengths, which peak in the action spectrum indicating optimal photosynthesis. The absorption spectrum aligns, showing how pigments absorb light, with chlorophyll being most efficient. The video clarifies why leaves appear green, as they reflect green light, not absorbing it for photosynthesis.

Takeaways

• 🌿 **Pigments in Photosynthesis**: Pigments like chlorophyll, carotenoids, and phycocyanin absorb light in the visible spectrum (400-700 nanometers), known as photosynthetically active radiation (PAR).
• 🍃 **Chloroplasts and Thylakoids**: Pigments are located in the chloroplasts' thylakoid membranes, which are the sites of light-dependent reactions in photosynthesis.
• 🔵 **Action Spectrum**: It's a graph showing the rate of photosynthesis at different light wavelengths, with peaks in the blue and red regions indicating maximum photosynthesis.
• 🟢 **Absorption Spectrum**: It's a graph showing the absorption of light by pigments, with chlorophyll a and b absorbing blue and red light, and carotenoids absorbing violet and blue-green light.
• 🌱 **Green Light Reflection**: Plants appear green because they reflect green light, which is not absorbed well by the pigments, leading to a dip in the action spectrum.
• 📊 **Coinciding Graphs**: The action and absorption spectra coincide, indicating that the pigments' light absorption patterns match their effectiveness in photosynthesis.
• 🌟 **Chlorophyll Dominance**: Chlorophyll is the most prominent pigment involved in photosynthesis, absorbing light most effectively for the process.
• 🌐 **Electromagnetic Spectrum**: The visible region of the electromagnetic spectrum, where pigments absorb light, is crucial for photosynthesis.
• 🔬 **Scientific Discovery**: The action spectrum was developed by T.W. Engelmann, providing foundational knowledge on how different wavelengths affect photosynthesis.
• 🌱 **Photosynthesis Efficiency**: The efficiency of photosynthesis is highest with blue and red light, which is why these wavelengths are crucial for plant growth and health.

Q & A

What are pigments and how do they relate to photosynthesis?

Pigments are chemicals that absorb light rays from the visible region of the electromagnetic spectrum. They play a crucial role in photosynthesis by absorbing light energy and converting it into chemical energy within the chloroplasts of plant cells.

What is the range of the visible region of the electromagnetic spectrum?

The visible region of the electromagnetic spectrum ranges from 400 nanometers to 700 nanometers.

What is Photosynthetically Active Radiation (PAR)?

Photosynthetically Active Radiation (PAR) refers to the region of the electromagnetic spectrum that is absorbed by plants for photosynthesis, which is from 400 nanometers to 700 nanometers.

Which pigments are involved in photosynthesis and where are they located?

Pigments involved in photosynthesis include chlorophyll, carotenoids, and phycocyanin. They are located in the chloroplasts of plant cells, specifically in the thylakoid membrane.

What is the significance of the thylakoid membrane in photosynthesis?

The thylakoid membrane is significant in photosynthesis because it is the site where pigments are located and where light energy is converted into chemical energy during the light-dependent reactions of photosynthesis.

Who first developed the concept of the action spectrum?

The concept of the action spectrum was first developed by T.W. Engelmann while studying photosynthesis in Alcaligenes.

What is an action spectrum and how is it represented?

An action spectrum is a graph that shows the rate of photosynthesis at different wavelengths of light. It is represented with the rate of photosynthesis on the Y-axis and the wavelength of light on the X-axis.

Why do plants appear green and what does this indicate about pigment absorption?

Plants appear green because the pigments in their leaves absorb less green light and reflect it. This indicates that green light is not absorbed efficiently by the pigments involved in photosynthesis.

What is the difference between the action spectrum and absorption spectrum?

The action spectrum shows the effectiveness of different wavelengths of light on the rate of photosynthesis, while the absorption spectrum shows the amount of light absorbed by different pigments at various wavelengths.

Which pigments absorb light most effectively for photosynthesis?

Chlorophyll a and chlorophyll b are the most prominent pigments involved in photosynthesis, as they absorb light most effectively in the blue and red regions of the spectrum.

What role do carotenoids play in the absorption spectrum?

Carotenoids play a role in the absorption spectrum by absorbing violet and blue-green light, which helps in the overall process of photosynthesis by assisting in light harvesting.