The main difference between chloroplast and chromoplast is that chloroplast is the green color pigment in plants whereas chromoplast is a colorful pigment whose color can be yellow to red. Furthermore, chloroplast contains chlorophylls and other carotenoids while chromoplast generally contains carotenoids.
Chloroplast and chromoplast are two types of colorful plastids in plants. Chloroplasts are responsible for undergoing photosynthesis while chromoplasts synthesize and store pigments.
Key Areas Covered
1. What is a Chloroplast
– Definition, Structure, Function
2. What is a Chromoplast
– Definition, Structure, Function
3. What are the Similarities Between Chloroplast and Chromoplast
– Outline of Common Features
4. What is the Difference Between Chloroplast and Chromoplast
– Comparison of Key Differences
Key Terms
Carotenoids, Chlorophyll, Chloroplast, Chromoplast, Photosynthesis, Pigments, Plastids
What is a Chloroplast
Chloroplast is an organelle found in plants and some photosynthetic algae. It is enclosed by double membranes. Stroma refers to the fluid inside this compartment. Also, thylakoids refer to the free-floating, flattened, tiny, membranous vesicles which occur in the stroma. They form units known as grana. The main type of photosynthetic pigment present in chloroplasts is chlorophylls, which give a green color to the plastid.
Figure 1: Chloroplasts in a Moss
Furthermore, chlorophylls form photosystems on the thylakoid membrane in order to capture the energy from the sunlight. And, this energy is stored in the energy molecules including ATP and NADPH during the light reaction of photosynthesis. Moreover, these molecules are used to synthesize glucose by combining carbon dioxide and water during the dark reaction of photosynthesis.
Figure 2: Chloroplast Structure
Although the main function of chloroplasts is to carry out photosynthesis, they also perform other functions including fatty acid synthesis, amino acid synthesis, and immune function in plants.
What is a Chromoplast
Chromoplast is the other type of colorful pigment present in plants. It is a heterogeneous organelle mainly responsible for the synthesis and storage of pigments other than chlorophylls. Here, carotenoids are the type of pigments produced by chromoplasts. The two main types of carotenoids are carotene and xanthophyll. Carotene is responsible for giving an orange color while xanthophyll is responsible for giving a yellow color.
Figure 3: Tomato – A Colorful Fruit
Moreover, chromoplasts occur in the colorful parts of the plant such as flower, fruit, and aging leaves. Also, chromoplasts occur in the roots of carrots and sweet potatoes. In addition, chloroplasts in ripening, aging or stressed parts of plants transform into chromoplasts through a massive increase in the accumulation of carotenoid pigments. The main function in chromoplasts in the flower and the fruit is to attract animals by giving a color. This facilitates pollination, fertilization, as well as the dispersal of fruit.
Similarities Between Chloroplast and Chromoplast
- Chloroplast and chromoplast are two types of colorful plastids present in plants.
- The pigments present inside each plastid are responsible for the color.
- Furthermore, both types of plastids perform unique functions in plants.
- Both of them involve in the biosynthesis of various compounds as well.
- Also, both contain identical DNA.
- They are heterogeneous organelles surrounded by two membranes.
- Moreover, they contain carotene and xanthophyll.
- Generally, they divide by binary fission.
- Besides, both types of plastids occur in the exposed parts of the plant.
Difference Between Chloroplast and Chromoplast
Definition
A chloroplast refers to a plastid in green plant cells which contains chlorophyll and in which photosynthesis takes place while chromoplast refers to a colored plastid other than a chloroplast, typically containing a yellow or orange pigment. Thus, this is the fundamental difference between chloroplast and chromoplast.
Type of Pigments Present
Also, another difference between chloroplast and chromoplast is that chloroplasts contain both chlorophyll and carotenoids while chromoplasts only contain carotenoids.
Occurrence
Chloroplasts mainly occur in the mesophyll of leaves while chromoplasts occur in the petals of flowers, ripening fruits, and aging or stressed leaves. Hence, this is one other difference between chloroplast and chromoplast.
Lamellar System
Moreover, chloroplasts contain a lamellar system, but chromoplasts generally do not contain a lamellar system.
Ribosomes
Furthermore, the presence of ribosomes is another difference between chloroplast and chromoplast. Chloroplasts contain 70S ribosomes while chromoplasts do not contain ribosomes.
Cytosine Methylation in DNA
Besides, cytosine methylation in chloroplast DNA is low while the cytosine methylation in chromoplasts is high.
Function
Chloroplasts are responsible for undergoing photosynthesis while chromoplasts biosynthesize and store pigments. Hence, functionally, this is a difference between chloroplast and chromoplast.
Conclusion
Chloroplast is the plastid containing chlorophyll responsible for photosynthesis. Therefore, chloroplasts are green in color. Also, chloroplasts contain carotenoids. In comparison, chromoplast is a plastid which synthesizes and stores pigments of carotenoids. They are responsible for attracting animals to the plant, facilitating pollination, fertilization, as well as the dispersal of fruit. Both chloroplast and chromoplast are membrane-bound organelles that contain DNA. However, the main difference between chloroplast and chromoplast is the type of pigments present, structure, and function.
References:
1. Kochunni, Deena T, and Jazir Haneef. “Plastids – Leucoplasts, Chromoplasts and Chloroplasts.” Biology Exams 4 U, Available Here.
Image Courtesy:
1. “Moss chloroplasts 100× objective” By Kelvinsong – Own work (CC BY 3.0) via Commons Wikimedia
2. “Scheme Chloroplast-en” By User:Miguelsierra, adapted by User:Vossman – Own work (CC BY-SA 4.0) via Commons Wikimedia
3. “Tomato” By photon_de (CC BY 2.0) via Flickr
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