Difference Between Mitochondria and Plastids - A Detailed Summary

Two organelles found in cells are chloroplasts and mitochondria. Only algae and plant cells have the membrane-bound organelle known as the chloroplast. Eukaryotic cells in animals, plants, and fungi all have mitochondria. The primary distinction between chloroplasts and mitochondria is how they work. While mitochondria are the powerhouses of the cell, breaking down sugar to release energy through cellular respiration, chloroplasts are responsible for producing carbohydrates with the help of sunlight.

What are Mitochondria? 

All eukaryotic cells have a membrane-bound organelle called a mitochondrion. The mitochondria produce ATP, which serves as the cell's chemical energy source. Inside the organelle of the mitochondria is their own DNA.

Structure of Mitochondria

A mitochondrion is a bean-shaped structure with a diameter of 0.75m to 3m. Depending on the cell type, tissue, and organism, a given cell may have one or several mitochondria. While the inner membrane is deeply folded, the outer membrane is porous. However, these folds enhance the surface area for chemical processes that produce ATP. The mitochondria release these energies, which are needed for a variety of chemical reactions, in the form of ATP (Adenosine triphosphate) molecules.

Porins are numerous integral membrane proteins found throughout the outer mitochondrial membrane. An outer membrane protein is a translocase. The N-terminal signal sequence of big proteins that are translocase-bound permits the protein to reach mitochondria. MAM is a structure created by the union of the mitochondrial outer membrane and endoplasmic reticulum (mitochondria-associated ER-membrane). Through calcium signalling, MAM enables the transfer of lipids between mitochondria and the ER.

There are more than 151 protein types in the inner mitochondrial membrane, and they all play various roles in the body. It lacks porins; the inner membrane's translocase is of the TIC complex type. Between the inner and outer mitochondrial membranes is the intermembrane gap. 

The matrix is the area where the two mitochondrial membranes encompass. In the matrix are ribosomes with a variety of enzymes and mitochondrial DNA. DNA found in mitochondria is a circular molecule. The DNA is about 16 kb in size and contains 37 genes. The DNA of mitochondria may be present in the organelle in 2–10 copies. Cristae, or folds of the inner mitochondrial membrane, are formed in the matrix. Cristae expand the surface area of the inner membrane.

Function of Mitochondria

Respiration is the mechanism by which mitochondria convert chemical energy into ATP for use in cellular processes. Other mitochondrial functions include control of cellular metabolism, steroid synthesis, calcium storage in the cell for signal transduction, cell membrane potential control, utilizing reactive oxygen species for signalling, the heme synthesis pathway's production of porphyrin, hormonal communication and control over apoptosis.

What are Plastids?

Algal and plant cells include plastids known as chloroplasts. To perform photosynthesis, they have chlorophyll pigments. Their own DNA is found in the chloroplast. The creation of organic molecules, specifically glucose from CO2 and water with the help of sunshine, is the primary activity of the chloroplast.

Types of Plastids

Chromoplasts and leucoplasts are two different forms of plastids. Chloroplasts are pigments that include chlorophyll. Chloroplasts play a crucial role in photosynthesis in plants, though. However, in addition to chlorophyll, the chloroplasts also contain yellow or orange pigments. Oils, carbohydrates, and protein granules are generally stored in leucoplasts, which are organelles.

Function of Plastids

Plant stems, cactus, and leaves all contain chloroplasts. Chlorenchyma is the name of a chlorophyll-rich plant cell. Depending on the amount of sunlight present, chloroplasts can change their orientation. In a process known as photosynthesis, chloroplasts can convert carbon dioxide and water into glucose with the help of light energy. The two steps of photosynthesis are the light reaction and the dark reaction.

Difference Between Mitochondria and Plastids

Occurrence: Mitochondria are found in eukaryotic cells, while plastids are found in plant cells.

Function: Cell respiration is mitochondria's primary function, while the main photosynthesis organelle in plants are plastids 

Pigments: Mitochondria is devoid of pigments, while pigments are present in plastids.

Size: Mitochondria are small in size,  while plastids are huge in size.

ATP: Mitochondria aid in ATP production, while plastids aid in the synthesis of glucose.

Interesting Facts

• The inner membrane and the outer membrane are the two membranes that cover the mitochondria.

• The primary distinction between mitochondria and chloroplasts relates to how they function.

• The primary distinction between plastids and mitochondria is that plastids are found solely in plants, whereas mitochondria are found in all eukaryotic cells. Plastid, on the other hand, has a disc-like form, whereas mitochondria are shaped like beans.

Important Questions

1. What is ATP?

Ans: At the cellular level, energy is used and stored as adenosine triphosphate (ATP).

2. What is the function of leucoplasts?

Ans: Leucoplasts’ primary purpose is to store vital substances such as proteins, lipids, and starches.

Key Features

• Both mitochondria and chloroplasts are membrane-bound organelles involved in energy conversion.

• During photosynthesis, light energy is stored in chloroplasts in the chemical bonds of glucose. In order for ATP to be utilised in cellular functions, mitochondria transform the light energy held in glucose into chemical energy called cellular respiration. Carbon dioxide and oxygen are used in the operations of both organelles. 

• Endosymbiotic relationships are thought to have given rise to both organelles. Their DNA is unique to them.