Main Difference – Chlorophyll vs Chloroplast
Chlorophyll and chloroplast are both involved in the photosynthesis of eukaryotes. Chlorophylls are found in both eukaryotes and prokaryotes. But, chloroplasts are only found in eukaryotic plants and algae. The main difference between chlorophyll and chloroplast is that chlorophyll is the pigment, involved in photosynthesis whereas chloroplast is the organelle involved in photosynthesis.
This article explains,
1. What is Chlorophyll
– Definition, Characteristics, Function
2. What is Chloroplast
– Definition, Characteristics, Function
3. What is the difference between Chlorophyll and Chloroplast
What is Chlorophyll
Chlorophyll is the green pigment which is responsible for the absorption of light, providing energy for oxygenic photosynthesis. Several types of chlorophylls are found among photosynthetic organisms. The major types of chlorophylls are chlorophyll A and B. chlorophyll A is found in all plants, algae and cyanobacteria. Chlorophyll B is found mostly in plants. In addition, chlorophyll C1, C2, D and F are found in algae and cyanobacteria. The strongest absorption of light by chlorophylls is found in the blue portion of the spectrum. In chlorophyll A, the most effectively absorbing wavelengths of the spectrum are 429 nm and 659 nm, which are responsible for violet-blue and orange-red colors respectively. In contrast, chlorophyll A reflects blue-green color, which is responsible for the green color of most land plants. In chlorophyll B, the most effectively absorbing wavelengths of the spectrum are 455 nm and 642 nm, which are responsible for violet and red colors, respectively. Chlorophyll B reflects a yellow-green color.
Chlorophyll A is the most important pigment in photosynthesis, which serves as the primary electron donor in the electron transport chain of photosynthesis. On the other hand, it transfers the light energy trapped in the antenna complex into the photosystems P680 and P700, where the specific chlorophylls are present in the thylakoid membrane of the chloroplast. In land plants, most of the chlorophyll B is found in light trapping antenna in photosystem P680. Chlorophyll B serves as the secondary pigment in photosynthesis, trapping light energy and passing the high energy electrons to chlorophyll A. Both chlorophyll A and B are similar in structure. They consist of a chlorin ring, where the four nitrogen atoms surrounds a magnesium ion. Several side chains and hydrocarbon tails are also attached to the chlorin ring. The C-7 position of the chlorin ring is attached to a methyl group in chlorophyll A. But in chlorophyll B, the C-7 methyl group is replaced by an aldehyde group. Chlorophyll C1 and C2, which are found in algae, consist of double porphyrin rings. Chlorophylls concentrated into structures called chloroplasts in Plagiomnium affine as shown in figure 1.
Figure 1: Chlorophylls on chloroplasts of Plagiomnium affine
What is Chloroplast
Chloroplasts are a type of organelles found in algal and plant cells, involved in the photosynthesis. They contain chlorophyll pigments in order to capture the light energy, which drives the light reaction of photosynthesis. Chloroplasts provide the space and required enzymes in order to carry out both light and dark reaction of photosynthesis. During photosynthesis, the organic molecule glucose is produced from CO2 and H2O with the aid of sunlight.
Algal cells consist of a single chloroplast per cell, which is a net, cup, or ribbon-like spiral in shape. In plants, chloroplasts are lens-shaped organelles. They are 3-10 µm in diameter and their thickness is around 1-3 µm. Plant cells process 10-100 chloroplasts per cell. Three membrane systems can be identified in a chloroplast. They are outer membrane, inner membrane and the thylakoid membrane. Outer and inner membranes allow molecules to pass in order to maintain a constant environment inside the chloroplast. Thylakoids are membranous sacks which contain chlorophylls like photosynthetic pigments on the membrane. Thylakoids are arranged into grana. Two grana are connected with each other by the stromal thylakoids. The matrix of the chloroplast is called chloroplast stroma. It contains chloroplast DNA, 70S ribosomes, as well as starch granules. Light reaction occurs in the thylakoid membrane and the dark reaction occurs in the stroma of the chloroplast. Chloroplast ultrastructure is shown in figure 2.
Figure 2: Chloroplast ultrastructure
1.Outer membrane, 2. Intermediate membrane, 3. Inner membrane, 4. Stroma, 5. Thylakoid lumen, 6. Thylakoid membrane, 7. Granum, 8. Thylakoid, 9. Starch, 10. Ribosome, 11. Chloroplast DNA, 12. Plastoglobule
Difference Between Chlorophyll and Chloroplast
Correspondence
Chlorophyll: Chlorophyll is the pigment involved in the photosynthesis.
Chloroplast: Chloroplast is the organelle involved in photosynthesis.
Function
Chlorophyll: Chlorophyll traps light and passes high energy electrons into photosystems.
Chloroplast: Chlorophylls are organized into chloroplasts, which provide space for both light and dark reactions of photosynthesis.
Types
Chlorophyll: Several types of chlorophylls exist. Major types are chlorophyll A and B.
Chloroplast: Two types of chloroplast are found in algae and plants respectively.
Color
Chlorophyll: Chlorophylls give a green color to chloroplasts.
Chloroplast: Chloroplasts give a green color to plants.
Presence
Chlorophyll: Chlorophylls are found in all plants, algae and cyanobacteria.
Chloroplast: Chloroplast is found in all plants and algae.
DNA
Chlorophyll: Chlorophylls are pigments. Thereby, they lack DNA.
Chloroplast: Chloroplasts consist of their own organelle DNA called cpDNA.
Location
Chlorophyll: Chlorophylls is found in the thylakoid membrane of chloroplasts.
Chloroplast: Chloroplasts is mostly found in leaves of plants.
Conclusion
Chlorophyll and chloroplast are two requirements of photosynthesis in plants and algae. Chlorophylls are found in all photosynthetic organisms, both prokaryotes and eukaryotes. But, since chloroplasts are membrane-bound organelles, they are only found in eukaryotes, plants and algae. Cyanobacteria are photosynthetic prokaryotes, containing only chlorophylls. Other than chlorophylls, plants also contain carotenoids, which absorb light in the spectrum that is not efficiently absorbed by chlorophylls. Chlorophylls are found in the thylakoid membrane of the chloroplasts. They trap light in violet-blue and orange-red regions in the spectrum more efficiently. The reflecting color is green. Hence, photosynthetic organisms can be seen in green color. Light reaction of photosynthesis occurs in the thylakoid membrane of chloroplasts, where chlorophylls are present. The dark reaction occurs in the stroma of the chloroplast. Hence, chloroplast provides the space and requirements for the occurrence of photosynthesis in cells. Therefore, the main difference between chlorophyll and chloroplast is their role in photosynthesis in eukaryotes.
Reference:
1. Light reactions.” Light reactions. N.p., n.d. Web. 09 Apr. 2017. <http://www2.mcdaniel.edu/Biology/botf99/photo/l4ightrx.html>.
2. Johnson, George B., and Raven, Peter H., Photosynthesis. Part. III. Energetics. New York: McGraw-Hill Global Education Holdings, LLC, 2017. Web. 09 Apr. 2017. <http://mhhe.com/biosci/genbio/raven6b/graphics/raven06b/other/raven06b_10.pdf>.
Image Courtesy:
1. “Plagiomnium affine laminazellen” By Kristian Peters — Fabelfroh (CC BY-SA 3.0) via Commons Wikimedia
2. “Chloroplast” By SuperManu – own work based on Chloroplaste-schema.gif 9 (CC BY-SA 3.0) via Commons Wikimedia
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