Choose the right matches:
(1) Carotenoid - C55H70O6N4Mg
(2) Chlorophyll 'a' - C55H72O5N4Mg
(3) Chlorophyll 'b' - C55H70O6N4Mg
(4) Xanthophyll - C50H70O5Mg
Understanding Photosynthetic Pigment Chemical Formulae
Photosynthetic pigments are molecules found in plants, algae, and bacteria that absorb light energy for photosynthesis. Different pigments absorb light at different wavelengths. Some of the primary pigments include chlorophylls, carotenoids, and xanthophylls. Each pigment has a specific chemical structure and formula.
Analyzing the Chemical Formulae of Photosynthetic Pigments
Let's examine the common chemical formulae for the pigments mentioned in the statements:
- Chlorophyll a: This is the primary photosynthetic pigment and has the chemical formula \(\text{C}_{55}\text{H}_{72}\text{O}_5\text{N}_4\text{Mg}\).
- Chlorophyll b: An accessory pigment, chlorophyll b, has a slightly different formula compared to chlorophyll a, which is \(\text{C}_{55}\text{H}_{70}\text{O}_6\text{N}_4\text{Mg}\). Note the difference in hydrogen and oxygen atoms.
- Carotenoids: These are a group of accessory pigments. They are typically hydrocarbons (composed only of carbon and hydrogen). A common example is \(\beta\)-carotene, with the formula \(\text{C}_{40}\text{H}_{56}\).
- Xanthophylls: These are oxygenated carotenoids, meaning they have oxygen atoms in addition to carbon and hydrogen. A common example is Lutein, with the formula \(\text{C}_{40}\text{H}_{56}\text{O}_2\).
Evaluating Each Statement
Now let's compare the provided statements with the correct chemical formulae:
- Statement (1) Carotenoid - \(\text{C}_{55}\text{H}_{70}\text{O}_6\text{N}_4\text{Mg}\): This statement gives a formula that includes Oxygen, Nitrogen, and Magnesium. Carotenoids, like \(\beta\)-carotene (\(\text{C}_{40}\text{H}_{56}\)), are hydrocarbons or oxygenated hydrocarbons (xanthophylls) and do not contain Nitrogen or Magnesium. The given formula is actually that of Chlorophyll b. Therefore, statement (1) is incorrect.
- Statement (2) Chlorophyll 'a' - \(\text{C}_{55}\text{H}_{72}\text{O}_5\text{N}_4\text{Mg}\): This formula correctly matches the known chemical formula for Chlorophyll 'a'. Therefore, statement (2) is correct.
- Statement (3) Chlorophyll 'b' - \(\text{C}_{55}\text{H}_{70}\text{O}_6\text{N}_4\text{Mg}\): This formula correctly matches the known chemical formula for Chlorophyll 'b'. Therefore, statement (3) is correct.
- Statement (4) Xanthophyll - \(\text{C}_{50}\text{H}_{70}\text{O}_5\text{Mg}\): This statement provides a formula containing Magnesium, which is not present in xanthophylls. Typical xanthophylls, like Lutein (\(\text{C}_{40}\text{H}_{56}\text{O}_2\)), have a different structure and composition. Therefore, statement (4) is incorrect.
Identifying the Correct Matches
Based on our analysis:
- Statement (1) is incorrect.
- Statement (2) is correct.
- Statement (3) is correct.
- Statement (4) is incorrect.
The statements that are correct are (2) and (3).
Conclusion
The option that lists (2) and (3) as correct statements is the right answer.
Revision Table: Photosynthetic Pigment Formulae
| Pigment Name | Correct Chemical Formula |
|---|---|
| Chlorophyll 'a' | \(\text{C}_{55}\text{H}_{72}\text{O}_5\text{N}_4\text{Mg}\) |
| Chlorophyll 'b' | \(\text{C}_{55}\text{H}_{70}\text{O}_6\text{N}_4\text{Mg}\) |
| Carotenoids (e.g., \(\beta\)-carotene) | \(\text{C}_{40}\text{H}_{56}\) |
| Xanthophylls (e.g., Lutein) | \(\text{C}_{40}\text{H}_{56}\text{O}_2\) |
Additional Information on Photosynthetic Pigments
Photosynthetic pigments play a vital role in capturing light energy. They are located in the chloroplasts of plant cells, specifically within the thylakoid membranes.
- Chlorophylls: These are the most abundant pigments and absorb strongly in the blue and red parts of the spectrum, reflecting green light (hence plants appear green). Their structure includes a porphyrin ring with a magnesium ion at the center and a long phytol tail. Chlorophyll a is found in all photosynthetic eukaryotes and cyanobacteria, while chlorophyll b is found in plants, green algae, and euglenoids.
- Carotenoids: These pigments absorb light mainly in the blue-green region of the spectrum. They serve several functions, including transferring absorbed energy to chlorophyll, protecting chlorophyll from photodamage (acting as antioxidants), and contributing to the yellow, orange, or red colors in fruits, flowers, and autumn leaves. Carotenoids are generally made of isoprene units and can be linear or cyclic. They are divided into two main groups: carotenes (hydrocarbons) and xanthophylls (oxygen-containing derivatives of carotenes).
- Absorption Spectra: Different pigments have different absorption spectra, meaning they absorb light most effectively at different wavelengths. This broadens the range of light energy that can be harvested for photosynthesis. For example, carotenoids can absorb light that chlorophylls do not, and this energy is then transferred to chlorophyll a for use in photosynthesis.
Important Questions from Miscellaneous
A stone is thrown horizontally from the top of a 20 m high building with a speed of 12 m/s. It hits the ground at a distance R from the building. Taking g = 10 m/s2 and neglecting air resistance will give :
A sphere of volume V is made of a material with lower density than water. While on Earth, it floats on water with its volume f1V (f1 < 1) submerged. On the other hand, on a spaceship accelerating with acceleration a < g (g is the acceleration due to gravity on Earth) in outer space, its submerged volume in water is f2V. Then:
A railway wagon (open at the top) of mass M1 is moving with speed v1 along a straight track. As a result of rain, after some time it gets partially filled with water so that the mass of the wagon becomes M2 and speed becomes v2. Taking the rain to be falling vertically and the water stationery inside the wagon, the relation between the two speeds v1 and v2 is :
Consider the following statements:
1. Distance between the longitudes becomes zero on North Pole and South Pole.
2. Distance between the longitudes is maximum on the Equator.
3. Number of longitudes is more than number of latitudes.
Which of the statements given above is/are correct?
One block of 2⋅0 kg mass is placed on top of another block of 3⋅0 kg mass. The coefficient of static friction between the two blocks is 0⋅2. The bottom block is pulled with a horizontal force F such that both the blocks move together without slipping. Taking acceleration due to gravity as 10 m/s2, the maximum value of the frictional force is :
