Do Mitochondria Have Ribosomes? 7 Facts You Should Know

Mitochondria is found in all eukaryotic cell attached with external membranes and is known to be a part of endomembrane system. Let us see if mitochondria have ribosomes.

Ribosomes are found in the mitochondria. Mitochondria have their own ribosomes, which are named as mitoribosomes present within eukaryotic cells. Mitoribosomes are the protein complexes which are found active in the mitochondria and functions in translating riboproteins.

Mitochondria Image from Wikipedia

Ribosomes are found lying freely in the cytoplasm of the cells and also in the inner membrane of mitochondria. These are made up of RNA and proteins and participate in the production of proteins inside the cells. The ribosomes read the genetic code and translate it into amino acid residues.

Functions of ribosome in mitochondria

Mitochondria plays multiple functions inside the cells. Let us now discuss the functions of ribosome in mitochondria.

List of functions performed by ribosomes in mitochondria:

  • Mitochondria is a site for aerobic respiration which involves, glycolysis, TCA cycle and electron transport.
  • Mitochondria is the site for heat generation in living organisms, a process called thermogenesis.
  • Mitochondria possess their own circular double stranded DNA which is of maternal inheritance.
  • Mitochondria plays a part in facilitating apoptosis which is known as programmed cell death necessary for cell survival.
  • Mitochondria is a hub of calcium ions which are important in various processes such as, signal pathways, neurotransmitter release, muscle contraction, fertilization, etc.
  • Mitochondria is a place of various important cellular processes such as, synthesizing of certain hormones such as estrogen and testosterone, break-down processes and recycling of biochemicals.
  • They play a part in regulating cholesterol metabolism, neurotransmitter metabolism and detoxification of ammonia.

There can be one to 10,000 mitochondria present in a single cell. The number of mitochondria and their functions varies from cell to cell.

How many ribosomes do mitochondria have?

Ribosomes are made up of RNA and proteins inside the cells. Let us find out the number of ribosomes a mitochondria possess.

Mitochondria have around 10 million ribosomes in mammalian cells. The subunits of ribosomes vary in organisms, for example the ribosomes found in mammals are of 55S with small 28S subunit and 39S large subunit and plants contain 78S ribosomes with 33S small and 50S large subunit.

Subunits of Ribosomes Image from Wikipedia

70S type of ribosomes are found in prokaryotes as well as in mitochondria.

Do mitochondria produce ribosomes?

Nucleus gives rise to the proteins and other molecules that are involved in the synthesis of mitochondria. Let us explore if it helps mitochondria in producing the ribosomes.

The ribosomes are not directly produced by the mitochondria. The sequence of proteins that are involved in mitoribosomes synthesis is encoded by the nucleus and are assembled by cytoplasmic ribosomes prior to implantation into mitochondria.

The ribosomes in eukaryotes are synthesized and lined up in nucleolus. Ribosomes are made up of ribosomal RNAs and several proteins. There are two types of ribosomes found in the cells; some are freely floating in the cytoplasm while some are found bound to the endoplasmic reticulum (ER) making it rough endoplasmic reticulum.

Do plant cells have mitochondria and ribosomes?

Eukaryotic cells including, plant cells and animal cells contains variety of same types of membrane bound organelles. Let us discuss if they have mitochondria and ribosomes.

Plant cells contain mitochondria and ribosomes. In plant cells, ribosomes are present in cytoplasm, mitochondria and chloroplasts. Ribosomes are named based on the organelle in which they are found, for example mitochondrial ribosomes are called mitoribosomes.

Both mitochondria and ribosomes play an active role inside the plant cells. Mitochondria is a power generating machinery and ribosomes help in protein formation. Ribosomes attach themselves to the t-RNA and mRNA for the synthesis of proteins and polypeptides.

Do mitochondria lack ribosomes?

Ribosomes are small units present inside the cells that participate in protein synthesis machinery. Let us now discuss if mitochondria lack ribosomes or not.

Mitochondria do not lack ribosomes instead they have their own ribosomes which participate in the synthesis of proteins. Ribosomes functions in translating the information from mRNA into the polypeptide sequence.

The functions of ribosomes are present in its subunits called ribonucleoprotein particles. The subunits of ribosomes are formed of ribosomal RNA (rRNA) and several proteins. Ribosomes help in damage repair processes and other chemical processes.

Conclusion

To conclude the article, we can say that mitochondria consist of ribosomes and play an important role in electron transport chain, generating cellular energy and in protein synthesis. They are found in all eukaryotes, including plants, animals, humans and yeast.

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