Difference Between Mitochondria and Chloroplast

The key difference between mitochondria and chloroplast is that mitochondria are the membrane-bound cell organelles that generate energy in the eukaryotic cells, while chloroplast is a type of eukaryotic cell organelle that carries out photosynthesis in plants and algae.

Both mitochondria and chloroplast are two large organelles found in eukaryotic cells. In fact, they are the cellular generators of eukaryotic cells. These two organelles and symbiotic bacterial cells share some structural features such as the ability to self-replicate, presence of circular DNA and similar ribosomes, etc. Because of such similarities, scientists believe that mitochondria and chloroplast have evolved from small symbiotic bacteria. Endosymbiosis is the theory that explains this phenomenon. Additionally, they show some structural and functional similarities since both these organelles actively participate in energy metabolisms in eukaryotic cells. However, there is a significant difference between mitochondria and chloroplast-based on their physiologies.

CONTENTS

1. Overview and Key Difference
2. What are Mitochondria
3. What is Chloroplast
4. Similarities Between Mitochondria and Chloroplast
5. Side by Side Comparison – Mitochondria vs Chloroplast in Tabular Form
6. Summary

What are Mitochondria?

Mitochondria are large, membrane-bound, tube-shaped organelles found in all types of eukaryotic cells. The size of mitochondria is similar to that of a bacterial cell. Mitochondria have two membranes: a smooth outer membrane, and an inner folded membrane. The inner membrane has numerous layers called cristae, which separate the mitochondrion into two sections – a matrix, and an intermembrane space. The matrix is the section that lies inside the inner membrane, and it contains mitochondrial DNA and enzymes, whereas the intermembrane space is the section that lies between the inner and outer membrane. The proteins responsible for carrying out oxidative metabolism are present mainly on or embedded within the inner membrane.

The main function of mitochondria is to metabolize sugar to generate ATP. Hence, mitochondrial DNA contains certain genes that code for essential proteins used in oxidative metabolism. Thus, mitochondria have the ability to produce proteins for their unique function, unlike most of the other organelles in the cells. However, mitochondria cannot replicate by themselves without nuclear participation. It is because some nuclear genes are essential in order to produce components needed to complete mitochondrial replication. Thus, it is impossible to grow mitochondria in cell-free culture.

What is Chloroplast?

Chloroplasts are membrane-bound large organelles found only in eukaryotic cells that carry out photosynthesis, such as plant cells and green algae. As its name implies, chloroplast contains a photosynthetic pigment called chlorophyll. Because of the presence of this pigment, chloroplasts can utilize light to synthesize ATP and sugars. Thus, organisms with chloroplasts can produce their own food.

Chloroplasts have two membranes, similar to mitochondria. In addition to these membranes, they have closed compartments called grana. Grana are present inside the inner membrane, and each granum consists of few to several dish-shaped structures called thylakoids. Thylakoids contain chlorophylls.  Stroma is the fluid matrix that surrounds the thylakoids and contains enzymes used in photosynthesis.

What are the Similarities Between Mitochondria and Chloroplast?

• Mitochondria and chloroplasts are two important organelles of a eukaryotic cell.
• It is believed that both these organelles originate in eukaryotic cells from photosynthetic bacteria.
• Moreover, both have two membranes enclosing the organelle.
• And, both organelles are involved in the generation of energy in eukaryotic cells.
• Most importantly, both these organelles contain their own DNA.

What is the Difference Between Mitochondria and Chloroplast?

Mitochondria are the cell organelles that generate ATP (energy) in eukaryotic cells while chloroplasts are the cell organelles that carry out photosynthesis in plants and algae. So, this is the key difference between mitochondria and chloroplast. Furthermore, chloroplast is a larger and more complex organelle than mitochondrion. Also, a further difference between mitochondria and chloroplasts is that while mitochondria use sugars to produce ATP, chloroplasts use light to produce ATP and sugars.

Moreover, another significant difference between mitochondria and chlorplast is the organisms that possess these organelles. Mitochondria are found in every eukaryotic organism, but chloroplasts are present only in photosynthetic eukaryotic organisms, such as plants and green algae. Besides, unlike the inner membrane of the chloroplasts, the inner membrane of the mitochondria is folded to form cristae; however, chloroplasts do not have cristae.

Below infographic on the difference between mitochondria and chlorplast provides more detailed comparison.

Summary – Mitochondria vs Chloroplast

Mitochondria and chloroplasts are two types of important organelles in eukaryotic cells. However, all eukaryotic cells have mitochondria, but only plants and algae have chloroplasts. Also, mitochondria are the powerhouses of eukaryotic cells. They play a major role in ATP production. Whereas, chloroplasts are the organelles that perform photosynthesis and produce foods from the energy obtained from sunlight. Nevertheless, both organelles have two membranes. And, both contain their own DNA. Thus, this summarizes the difference between mitochondria and chloroplast.

Reference:

1. Cooper, Geoffrey M. “Mitochondria.” The Cell: A Molecular Approach. 2nd Edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.
2. “Mitochondria and Chloroplasts.” Khan Academy,  Available here.

Image Courtesy:

1. “Animal mitochondrion diagram en” By Mariana Ruiz Villarreal LadyofHats – (Public Domain) via Commons Wikimedia
2. “Chloroplast diagram” By Chloroplast-new.jpg: User:Ollinderivative work: Smartse (talk) – Chloroplast-new.jpg (Public Domain) via Commons Wikimedia