Prokaryotes Vs Eukaryotes: (Similarities and Differences Between Prokaryotes & Eukaryotes)


Difference between Prokaryotes and Eukaryotes

.Prokaryotes and Eukaryotes are the two fundamental or basic classes of cells. They are mainly distinguished by their size and internal structures. The existence of two classes of cells without any intermediate type represents one of the most fundamental evolutionary separations in the living world. Prokaryotes are structurally and evolutionarily more primitive to eukaryotes. Even though they are two separate classes of living organisms, they share many common characteristics. The shared properties reflect the fact that eukaryotic cells most certainly evolved from prokaryotic ancestors.

Shared common characters of prokaryotes and eukaryotes are as follows:

(1).   Cellular contents in both prokaryotes and eukaryotes are limited by plasma membrane

(2).   In both groups, plasma membrane composed of lipid bilayer with intermittent protein molecules

(3).   DNA is the genetic information carrier in both the groups

(4).   Chemical composition of nucleic acids (DNA and RNA), their structure and their organization are similar in both groups

(5).  Even though the mechanism slightly varies, the process of transcription, translation and DNA replication occurs in both prokaryotes and eukaryotes

(6).   Both groups processes regulation of expression of genetic information

(7).    mRNA acts as the intermediate molecule between genetic information and their expression (as proteins) in both groups

(8).    Proteins are the expression of genetic information in both groups

(9).    All the 20 protein coding amino acids are similar in prokaryotes and eukaryotes

(10).  All the 61 codons are similar in both groups

(11).   All the tree stop codons (UAA, UAG, UGA) are similar in both groups

(12).   Structure of tRNA is similar in both groups

(13).   Metabolic pathways such as glycolysis and TCA cycle are similar in both prokaryotes and eukaryotes

(14).   In both groups, the metabolic pathways are multi-step processes each step catalyzed by specialized proteins called enzymes

(15).    ATP is the energy currency in both prokaryotes and eukaryotes

(16).    ATP is produced by the use of proton (H+) gradient, which is similar in both groups

(17).    Photosynthesis is similar in both prokaryotes (blue green algae) and eukaryotes (plants)

(18).    In both forms, photosynthesis consists of two process, light dependent ‘light reaction’ and light independent and ‘dark reaction’

(19).    Proteasomes are with similar structure and working in both groups

Thus the overall biological process, events and organization are similar in both prokaryotes and eukaryotes. However each component and their interactions to each other vary in both groups.

The major differences between Prokaryotes and Eukaryotes are summarized in the following table:

.

Sl. No.ProkaryotesEukaryotes
1‘pro’ = pre, ‘karyon’= nucleus‘eu’ = true, ‘karyo’ = nucleus
2Originated about 3.5 billion years agoOriginated about 1.2 billion years ago
3Primitive formsAdvanced forms
4Usually unicellular organizationUsually multicellular organization
5Incipient nucleus, true nucleus absentTrue nucleus present
6Small cell size, usually 1 – 10 µmLarger cell size, usually 5 – 100 µm, sometimes very large and macroscopic
7Membrane bounded organelles such as nucleus, mitochondria, Golgi bodies, chloroplasts, lysosome, peroxisomes, ER etc. are absentMembrane bounded organelles present. Majority of organelles have single or double membrane system
8Genetic material consists of single chromosomeGenetic materials usually consists of more than one chromosomes
9Genetic material is freely distributed in the central portion of the cell (nucleoplasm)Genetic material is located in the nucleus
10Chromosome with covalently closed circular DNA (ccc DNA)Chromosome with linear DNA
11Cell division by fission or budding, Mitosis and Meiosis completely absentCell division by mitosis and meiosis
12Nucleolus absentA well-developed nucleolus present
13Ribosome 70S typeRibosome 80S type
14Two subunits of ribosomes are 50S large subunit and 30S small subunitTwo subunits of ribosome are 60S larger subunit and 40S smaller subunit
15DNA is naked, not associated with histone proteinsDNA is wrapped around histone proteins
16Endoplasmic reticulum absent and hence protein synthesizing ribosome freely distributed in the cytoplasmEndoplasmic reticulum present, protein synthesizing ribosome usually attached to endoplasmic reticulum
17Internal membrane system scarce. If present, associated with respiration and photosynthesisInternal membrane system well developed. Cell organelles are surrounded by single or double membranes
18Flagella with simple organizationFlagella (if present) is very complex with 9 + 2 arrangement of microtubules
19Microtubules absent in flagellaMicrotubules present in flagella
20Flagella extracellular and not enclosed by cell surface membraneFlagella intracellular and surrounded by cell surface membrane
21Cell wall is composed of muco-polysaccharidesCell wall (if present) composed of cellulose (in plants) and chitin (in fungi). Cell wall absent in animal cells
22Organisms haploid, contain only a single copy of genomeOrganisms usually diploid very rarely polyploids, contains two copies of genome, one from each parent
23Plasmid (extra-chromosomal genetic materials) usually presentPlasmids absent, however mitochondria and chloroplasts are autonomous with its own genetic materials
24Cytoskeleton system absentCytoskeleton system well developed
25Sexual reproduction absentSexual reproduction present
26Processes like transformation conjugation and, transduction present for genetic material exchangeAll such processes completely absent, and genetic exchange occurs through sexual reproduction
27Respiration is by mesosomesRespiration is by mitochondria
28Chloroplasts and mitochondria absentChloroplasts and mitochondria present, both are double membrane bounded and autonomous with its own genetic materials
29Photosynthesis takes place in the membrane system of cytoplasmPhotosynthesis takes place in chloroplast. Chloroplasts contains membrane stacks into lamella or stroma
30Nitrogen fixing capacity is present in some formsNitrogen fixing capacity is completely absent. None of the eukaryotic cells is known to processes nitrogen fixing ability both in plants and animals
31Endocytosis and phagocytosis completely absentEndocytosis and phagocytosis is present in some animals cells
32Cytoplasmic movement (cyclosis) absentCyclosis present
33Well-developed intracellular and extracellular communication system absentCommunication system is well developed and advanced
34Cell cycle duration about 20 – 60 minutesHighly varies, rapidly dividing cells the cell cycle is ~ 24 hours
35Regulatory mechanisms of DNA relatively simpleRegulatory mechanism highly complex
36Transcription and translation are continuous process and occurs simultaneously in the cytoplasmThey are separate processes, transcription occurs in the nucleus whereas translation occurs in the cytoplasm


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