What are the evidences of endosymbiotic theory?

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Mitochondria and chloroplasts have their own DNA, which is similar to the DNA of

Possible Answers:

bacteria

humans

protozoa

fungi

Explanation:

Bacteria, a prokaryote, has circular DNA, as do mitochondria and chloroplasts. This provides support for the Endosymbiotic Theory, which states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote).

Reproduction of chloroplasts and mitochondria occurs via

Possible Answers:

Meiosis

Fission-like process, similar to the reproduction process of eukaryotes

Mitosis

Fission-like process, similar to the reproduction process of bacteria

Correct answer:

Fission-like process, similar to the reproduction process of bacteria

Explanation:

Chloroplasts and mitochondria reproduce through fission, the same process through which bacteria reproduce. Eukaryotes reproduce through mitosis or meiosis, depending upon the type of cell.

Supporting the Endosymbiotic Theory, mitochondria and chloroplasts have a _________ membrane.

Explanation:

The Endosymbiotic Theory states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). Mitochondria and chloroplasts have a double membrane (the inner membrane would have initially been the ingested prokaryote’s single membrane).

Mitochondria and chloroplasts have ribosomes that are ___, similar to __ cells.

Possible Answers:

80S, eukaryotic

70S, eukaryotic

80S, prokaryotic

70 S, prokaryotic

Correct answer:

70 S, prokaryotic

Explanation:

Prokaryotic cells, mitochondria, and chloroplasts have 70S ribosomes, whereas eukaryotic cells have 80S ribosomes. This provides support for the Endosymbiotic Theory, which states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote).

The Endosymbiotic Theory posits that, before being engulfed by a eukaryotic cell, they were

Possible Answers:

Viruses

Organelles

Free-living eukaryotes

Free-living prokaryotes

Correct answer:

Free-living prokaryotes

Explanation:

The Endosymbiotic Theory states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). The aerobic bacteria were initially free-living prokaryotes, before being ingested by anaerobic bacteria.

Which of the following is NOT evidence for the Endosymbiotic Theory?

Possible Answers:

Mitochondria and chloroplasts have 70S ribosomes

Mitochondria and chloroplasts have a double membrane

Mitochondria and chloroplasts have circular DNA

Mitochondria and chloroplasts have a single membrane

Correct answer:

Mitochondria and chloroplasts have a single membrane

Explanation:

The Endosymbiotic Theory states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote). This theory explains the origin of eukaryotic cells. Numerous lines of evidence exist, including that mitochondria and chloroplasts have their own circular DNA (prokaryotes also have circular DNA), mitochondria and chloroplasts have a double membrane (the inner membrane would have initially been the ingested prokaryote’s single membrane, and the outer membrane initially would have come from the cell that engulfed it), mitochondria and chloroplasts have 70S ribosomes (prokaryotes 70S have ribosomes, whereas eukaryotes have 80S ribosomes).

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Evidence of endosymbiotic theory support that mitochondria and chloroplasts originated from prokaryotic cells. In this article, 10 evidence of endosymbiotic theory is discussed that support the endosymbiotic theory and show how eukaryotic cells originated from bacteria.

Question is- how mitochondria and chloroplasts resemble with bacteria or what are the evidences that mitochondria and chloroplast evolved from bacteria.

• What is the Endosymbiotic theory?
• 10 Evidence of endosymbiotic theory:
  • i) Presence of DNA:
  • ii) Size of Ribosomes:
  • iii) Inhibition by antibiotics:
  • iv) Evolutionary relationship:
  • v) Same size:
  • vi) Plasma-Membrane:
  • vii) Enzyme secretion:
  • viii) Replication and protein synthesis:
  • ix) Bacterial binary fission:
  • x) Electron transport chain:

What is the Endosymbiotic theory?

Endosymbiotic theory stats that, the modern eukaryotic cells (mitochondria) evolved in steps through inter-cooperation into cells from a nuclear line of descendants of chemoorganotrophic and phototrophic symbionts.

It states that Mitochondria and Chloroplast were free-living bacteria that established residency in the primitive eukaryotic cells, eventually yielding the modern eukaryotic cell.

Symbiosis is a specific type of relationship in which organisms from two different species live in a close, dependent relationship take advantage of each other.

Endosymbiosis is a relationship where one organism lives inside the other and both are benefited. It is thought that ancestral eukaryotic cells consumed aerobic bacteria and photosynthetic bacteria leading them to evolve into mitochondria and chloroplast respectively.

On the basis of their relative autonomy and morphological resemblance to bacteria, it was suggested long ago that mitochondria and chloroplast were descendants of ancient prokaryotic organisms.

The theory postulate that an aerobic bacteria established residency within the cytoplasm of a primitive eukaryotic cell. This bacterium would represent the precursor of the present mitochondrion.

In a similar fashion, the endosymbiotic uptake of an oxygenic phototrophic prokaryote would have made the primitive eukaryotic photosynthesis. This phototrophic bacterium would then be considered the precursor of the present chloroplast.

i) Presence of DNA:

Mitochondria and Chloroplast DNA exists in closed circular form as it does in a prokaryotic cell. This DNA of the chloroplast is very similar to photosynthetic blue-green bacteria, while the mitochondrion DNA is very similar to the aerobic bacteria. Both organelles lack histones and introns like bacteria.

ii) Size of Ribosomes:

Ribosome exists either in a larger form (the 80s), typical of the cytoplasm of eukaryotic cells or smaller form (70s), unique to prokaryotes. Mitochondria and Chloroplast’s ribosome are the 70s in size, the same as those of prokaryotes.

iii) Inhibition by antibiotics:

Several antibiotics kill or inhibit bacteria by disrupting their 70s ribosomal function. The same antibiotics also inhibit ribosomal function in mitochondria and chloroplast. Like bacteria, mitochondria and chloroplast are sensitive to chloramphenicol, streptomycin, etc.

iv) Evolutionary relationship:

Phylogenetic analyses using the ribosomal RNA sequencing method, convincingly suggested that mitochondria and chloroplast are evolutionarily related to bacteria. The sequence comparison of mitochondria and chloroplast show that mitochondria came from bacterial lines related to alpha-proteobacteria and chloroplast originated from cyanobacteria.

v) Same size:

Mitochondria and chloroplast are the same in size as bacteria. The size of bacteria is commonly 0.1-10 micrometers, while the size of mitochondria and chloroplast is 0.5-10 micrometers and 1- 10 micrometers respectively.

vi) Plasma-Membrane:

Mitochondria and chloroplasts are surrounded by two or more membranes like bacteria. Mitochondria have a double membrane that is a phospholipid bilayer. Chloroplast has three membranes outer membrane inner membrane, and thylakoid membrane. Gram-positive bacteria have a plasma membrane and a cell wall although gram-negative bacteria have an additional outer membrane.

vii) Enzyme secretion:

Mitochondria and chloroplast secrete several enzymes like bacteria. For example, mitochondria secrete monoamine oxidase, kynurenine hydroxylase, c-reductase fatty acid Co-A ligase, ATP synthase, etc. Chloroplast enzymes include ATP synthase, NADP-malate dehydrogenase fructose-1, 6-bisphosphatase, phosphoribulokinase, glucose-6-phosphate dehydrogenase, etc.

SEE MORE:

Chloroplast | Function, Location, & Diagram

viii) Replication and protein synthesis:

Like bacteria, mitochondria and chloroplasts can replicate their genome and translate it to protein. Protein synthesis in mitochondria and chloroplast takes place by N-formyl methionyl tRNA that resembles bacterial protein synthesis.

ix) Bacterial binary fission:

Mitochondria and chloroplast are divided by binary fission like bacteria. Like bacterial binary fission, mitochondria and chloroplast also replicate their genome and divide into two new organelles.

x) Electron transport chain:

The electron transport chain is one of the most important evidence of endosymbiotic theory.

Like bacterial electron transport chains that occurred in the bacterial plasma membrane, mitochondria and chloroplast have also an electron transport chain occurring in the inner mitochondrial membrane and thylakoid membrane of chloroplast respectively.

See more:

10 Importance of Microbiology in Everyday Life

Molecular Expressions Cell Biology: Mitochondria

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