The Endosymbiotic Theory: How Eucaryotic Cells Evolved from Procaryotic Cells

Table of Content

There are many groundss that support the endosymbiotic theory to be established. Endosymbiosis intending shared internal life informs how eucaryotic characteristics evolved from the procaryotic cells. ( Reece, C. et al 2008 ) . Mitochondria being a b-proteobacteria ( aerophilic bacteriums ) and chloroplast being cynobacteria ( photosynthetic bacteriums ) started life as procaryotes populating within a larger cell ( Archibald 438-46 ) .

Harmonizing to the theory, the cell wall for the larger bacteriums disappeared and started to consume the smaller bacterium cells. In 1967, Lynn Margulis suggested a hypothesis that one million millions of old ages ago, the opportunity of beings that were geting their energy from organic substance manufactured by cells must hold ingested aerophilic bacteriums in which some of the bacteriums cells started life within the cell ( Tortora, G. et Al. Eds. 2007). Due to symbiotic relationship of different beings interacting and deriving something constructive in an environment without doing injury to each other, the bacteriums began to germinate and bring forth energy that could be used by the cell as the cell besides supplied foods ( Oliver. 2003 ) .

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There are groundss that support the endosymbiotic theory and be the likeliness of chondriosomes and chloroplast holding similarities with procaryotes in elaborate comparing and it is as followed:

Deoxyribonucleic acid

Even though chloroplast and chondriosomes are present in the eucaryotic cell, the constellations of their Deoxyribonucleic acid are different. The Deoxyribonucleic acid molecule in the eucaryotic cell is multiple additive and the chromosomes are grouped in a karyon but the chondriosome and the chloroplast have one individual cringle DNA genome and a round chromosome which is similar to a procaryotic cell. ( IUPUI Department of Biology. 2002 )


The size of the eucaryotic cell is 50- 500 micrometers but the size of both chondriosomes and chloroplast are 1- 10 micrometers which is the same as a procaryotic cell. In comparing with the procaryotic cell, the eucaryotic cell is large. These similarities indicates how both chloroplast and the chondriosomes were originates of the procaryotes. ( IUPUI Department of Biology. 2002 )


The ribosomal unit in the chondriosome and the chloroplast are the same as the procaryotes and it is 70S but the eucaryotic is 80S. ( IUPUI Department of Biology. 2002 )

Reproduction and Reproduction

Mitochondria and chloroplast replicate and reproduce by binary fission ( 1 cell splits into 2 ) which is the same as the procaryotic cell but the eucaryotic undergoes that procedure by mitosis. ( IUPUI Department of Biology. 2002 )

Electron conveyance concatenation

The negatron conveyance concatenation are found in the plasma membrane for the chondriosome and the chloroplast which is besides the same as the procaryotes but there is none found in the plasma membrane of the eucaryotes. ( IUPUI Department of Biology. 2002 )

Appearance on Earth

Harmonizing to the IUPUI Department of Biology ( 2002 ) , the first constitution of the procaryotic for anaerobiotic bacteriums was about 3.8 billion old ages ago, photosynthetic bacterium was 3.2 billion old ages ago and the aerophilic bacterium was 2.5 billion old ages but the eucaryotic, chondriosomes and chloroplast are the same. Reece, C. et Al ( 2008 ) , shows that all three were established 2.1 billion old ages ago.

All these grounds from the comparing and dodo records indicates that chondriosome and chloroplast evolved as procaryotes but have integrated and is now dependent of eucaryotic cell. For case, because of the synthesis of ATP, mitochondria depend on the eucaryotic cell for ribosome for the devising of protein that will be contributed to the chondriosome. ( Reece, C. et Al. 2008 )

Reference List

  1. Archibald, J. M. “ Secondary Endosymbiosis. ” Encyclopedia of Microbiology. Ed. Schaechter Moselio. Oxford: Academic Press, 2009. 438-46.
  2. OLIVER. 2003. , A The Student ‘s Guide To Research Ethics. [ on-line ] .A Open University Press. Available from: & lt ; hypertext transfer protocol: // ID=94751 & gt ; 2 November 2010
  3. IUPUI DEPARTMENT OF BIOLOGY ( 2002 ) : The endosymbiotic theory [ online ]available at: hypertext transfer protocol: // [ accessed 2 november 2010]
  4. Tortora, G et Al. ( 2007 ) .Microbiology: An Introduction, 9th edition, Pearson International Edition
  5. Reece, C. et Al. ( 2008 ) . Biology, Pearson International Edition

Describe the function of helicase in the Deoxyribonucleic acid reproduction

Deoxyribonucleic acid ( deoxyribonucleic Acid ) reproduction is an indispensable procedure which ensures that an accurate transcript of the original nucleotide sequence is duplicated in readying for the devisings of a girl cell ( Faning et al. 156-77 ) .

The procedure of DNA reproduction is semi-conservative because when the DNA transcripts an indistinguishable signifier of itself, one strand of the parental semidetached house is conserved under an accurate reproduction of familial information and the complimentary DNA strand is so biosynthesised utilizing each of the two parental strands as templets ( Schempp 119-45 ) .

A Deoxyribonucleic acid molecule consists of a phosphate binding to a deoxyribose sugar doing it the anchor of the Deoxyribonucleic acid. They are linked together by a strong covalent bond. The bases in the center are connected to their complimentary strand and they are categorised into two groups which are the purines ( A-T, Adenosine- Thymine ) and the pyrimidines ( G-C, Guanine- Cytosine ) . This is called the base sliver regulations ( Reece, C. et al 2008 )

When a Deoxyribonucleic acid molecule transcripts or extra, each strand becomes a templet for teaching bases into new complimentary strands. These bases are lined up alongside the templets harmonizing to their base brace.

A Deoxyribonucleic acid molecule begins reproduction at particular sites called beginnings of reproduction. The procedure at each beginning is bidirectional until the duplicate of the whole molecule. Each terminal of a reproduction bubble is known as a reproduction fork ; this part is ‘Y-shaped ‘ where the unwinding of the parental strands takes topographic point. A figure of proteins contribute in the unwinding of the parental strands.

Deoxyribonucleic acid requires different maps of different proteins such as helicase, Topoisomerase, SSB ( Single-Stranded Binding ) , DNA polymerase and DNA ligase. ( Reece, C. et al 2008 )

Helicase is an enzyme every bit good as a motor protein that begins the reproduction procedure by untwisting the dual spiral and dividing the two parental DNA strands. The procedure occurs by catalyzing the intervention of the H bonds that secures the nucleic acids together with energy obtained from ATP hydrolysis doing them into templet strands. When they separate, the two annealed nucleic acerb moves along a nucleic acid phosphordiester anchor ( Matson, Bean, and George 13-22 ) .

There are other enzymes that help helicase undergo its function and so hence after the separation, SSB ( Single- Strand Binding ) proteins connect to the odd DNA strand which stabilises them. Untwisting of the dual spiral causes a strong turn and strain in front of the reproduction fork. Topoisomerase is an enzyme which helps helicase in many ways. It prevents the strain by interrupting, revolving and rejoining. ( Reece, C. et al 2008 )

Helicase performs strand separation procedure by adhering to a part on a individual stranded nucleic acid. After this procedure it so translocate at different way 5’-3 ‘ or 3’-5 ‘ premier doing it anti-parallel. ( Biochemical Society Transaction 2005 ) .

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The Endosymbiotic Theory: How Eucaryotic Cells Evolved from Procaryotic Cells. (2017, Jul 07). Retrieved from

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