Question

Which light is absorbed more by Chlorophyll 'a'? (a) Yellow and green (b) Red and blue (c) Yellow and orange (d) Yellow and red

Short answer

(b) Red and blue

Step-by-step solution

Identify the Knowledge Base

The key knowledge for this problem is understanding which lights are most efficiently absorbed by Chlorophyll 'a'. Chlorophyll 'a' absorbs light most efficiently in the blue (430–450 nm) and red (640–680 nm) parts of the spectrum.

Match the Knowledge with Options

Look at each option presented and identify the ones that include the colors blue and red. In the given options, only the option (b) red and blue matches with the colors most efficiently absorbed by Chlorophyll 'a'.

Select the Correct Option

Based on the facts, and matching them with the options, option (b) red and blue is the correct answer.

Key concepts

Blue Light Absorption

Chlorophyll 'a' is a key photosynthetic pigment found in the chloroplasts of plants. It plays a crucial role in absorbing light energy, which is then converted into chemical energy during photosynthesis. One of the most important aspects of this pigment is its ability to effectively absorb blue light, specifically in the wavelength range of 430–450 nm. Blue light is very energetic because of its short wavelength. This makes it highly effective for driving the processes of photosynthesis, as more energy can be captured by chlorophyll 'a' molecules in this part of the spectrum. In the light spectrum, blue light is located at the higher energy end. This energy helps to excite the electrons within the chlorophyll 'a' molecule, facilitating the energy transfer required for photosynthesis to occur. Unlike some other pigments, chlorophyll 'a' has a peak absorption in this range, making it indispensable for efficient energy capture in plants.

Red Light Absorption

Apart from blue light, chlorophyll 'a' also absorbs light efficiently in the red part of the spectrum, particularly in the range of 640–680 nm. Red light is less energetic than blue light because it has a longer wavelength, yet it is still critical for photosynthesis. Red light absorption complements the energy captured by blue light and contributes significantly to the chlorophyll 'a' absorption spectrum. By absorbing red light, chlorophyll 'a' ensures that plants can harness solar energy efficiently even when blue light is less available, such as under different environmental conditions or times of day. Thus, the absorption of red light is a vital aspect of photosynthetic efficiency, facilitating a broader range of light utilization. This ensures that plants remain productive and maintain growth and development under varying lighting conditions.

Photosynthesis Pigments

Photosynthesis pigments include a variety of molecules that plants, algae, and cyanobacteria use to absorb light. Chlorophyll 'a' is one of the most prominent photosynthesis pigments, playing a direct role in converting light energy into chemical energy. These pigments work together to capture light across different parts of the light spectrum. While chlorophyll 'a' primarily absorbs blue and red light, other pigments, such as chlorophyll 'b' and carotenoids, extend the range of light absorption.

• Chlorophyll 'b': Absorbs light in the blue and red-orange part of the spectrum, complementing chlorophyll 'a'.
• Carotenoids: Absorbs light in the blue-green spectrum, providing protection against photo-damage while aiding in photosynthesis.

By having a variety of photosynthesis pigments, plants can optimize the harvesting of light energy, making the photosynthesis process more efficient and productive under diverse lighting conditions.