Chlorophyll a appears __________ in color and chlorophyll b appears __________ in color in the chromatogram

Answer: Chlorophyll is a green pigment found in the leaves of plants that helps in photosynthesis. Among its types, chlorophyll a is the primary pigment present in all photosynthetic organisms and appears bluish-green on a chromatogram due to its unique structure, which includes a methyl group. On the other hand, chlorophyll b is a secondary pigment found in green algae and higher plants, and it appears yellowish-green due to the presence of an aldehyde group instead of the methyl group. This difference in structure causes them to absorb and reflect different wavelengths of light, resulting in different colors during chromatography.

Complete Answer:

Chlorophyll is a green pigment found in the leaves of plants that helps them prepare food through photosynthesis. It is mainly present in the grana lamellae of the chloroplast. Chlorophyll is a fat-soluble pigment and is essential for capturing sunlight. There are five types of chlorophyll: chlorophyll a, b, c, d, and e, but the most important among them are chlorophyll a and chlorophyll b.

Chlorophyll a is the main or primary pigment that is found in all photosynthetic organisms including green plants, algae, and cyanobacteria. It plays a direct role in the light reactions of photosynthesis. It is called the universal pigment because it is present in all photosynthetic organisms. Chlorophyll a appears bluish-green in color when separated in a chromatogram. The reason for this color is due to its chemical structure. The molecular formula of chlorophyll a is C₅₅H₇₂MgN₄O₅. It contains a methyl group (–CH₃), which reflects light in the bluish-green region of the visible spectrum. This is why it shows this specific color during chromatography.

Chlorophyll b is a secondary or accessory pigment. It is found in green algae, euglenoids, and higher plants, but not in all photosynthetic organisms. It does not directly take part in the light reaction but helps chlorophyll a by absorbing light of different wavelengths, increasing the range of light the plant can use. Chlorophyll b appears yellowish-green in the chromatogram. This is because it contains an aldehyde group (–CHO) instead of a methyl group, which changes the light it reflects. Its molecular formula is C₅₅H₇₀MgN₄O₆. The presence of the extra oxygen atom changes its absorption properties, giving it a lighter, yellowish-green appearance.

Let’s understand why other options are incorrect:

• A) Yellowish green, bluish-green: This is the reverse of the correct answer. Chlorophyll a is not yellowish-green—it is bluish-green, while chlorophyll b is yellowish-green, not the other way around.
• C) Green, green: This option is too vague. Though both pigments may appear green to the naked eye, chromatography helps us see the distinct shades: bluish-green for a and yellowish-green for b. Saying just “green” doesn’t show the actual difference between the two.
• D) Blue, blue: This is scientifically wrong. Neither chlorophyll a nor b appears completely blue. Both reflect greenish light—chlorophyll a reflects bluish-green and chlorophyll b reflects yellowish-green.

So, option B is the best answer because it correctly identifies the visible colors based on how these pigments reflect light after separation in a chromatogram.

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