1.3.2. Differences between Prokaryotes and Eukaryotes

1.3.2. Differences between Prokaryotes and Eukaryotes

Characters

Prokaryotes

Eukaryotes

Groups where found

Bacteria, Cyanobacteria, Archaea

Algae, Fungi, Protoza, Plants and Animals

Size

1-2 by 1-4 m m or less

Greater than 5 m m

Cell wall

Made up of peptidoglycan

Made of cellulose in algae and plants, of fungal cellulose or chitin in fungi, absent in protozoan and animals

Osmotic control

Wall possesses mechanical strength necessary to counter balance turgor pressure of cytoplasm

Maintained by contractile vacuole

Plasma membrane

Does not contain sterols except in Mycoplasma

Sterol present


Fatty acids, exclusively saturated or monounsaturated, except in cyanobacteria which are able to synthesize polyunsaturated fatty acids

All lipids polyunsaturated


No inter membrane structure is connected to plasma membrane

Complex network of intermembrane connected with plasma membrane


Plasma membrane is the only membrane

Several cell organelles also covered by membrane (Unit mem-brane)


Plasma membrane folded to form mesosomes.

Mesosomes are absent, but in animal cells, it is folded to form finger like microvilli.


Contains the respiratory machinery i.e. E.T.S., enzymes etc. and carries out respiration.

E.T.S. is present on mitochondrial membrane.


Photosynthetic machinery present on bacterial membrane. In cyanobacteria membrane forms vesicles which carry pigments.

Photosynthetic pigments and ETS present in the chloroplast membrane.

Cytoplasm

Granular due to presence of ribosomes, fibrous cytoskeleton absent

Fibrillar made up of fibrous proteins which form fibrous cytoskeleton

Pinocytosis, Exocytosis, Endocytosis, Phagocytosis

Absent, intracellular digestion.

Present.

Gas vacuoles

Present

Absent

Ribosomes

70S, freely distributed in cytoplasm

80S free as well bounded to ER. 70S in mitochondria and chloroplast.

Mitochondria

Absent

Present

Chloroplast

Absent, in cyanobacteria thylakoid vesicles present.

Present in plant cells and absent in fungi, protozoa and animal cell.

Golgi apparatus

Absent

Present

Lysosomes

Absent

Present

Endoplasmic Reticulum

Absent

Present

Peroxisomes

Absent

Present

Centrioles

Absent

Present

Nucleolus

Absent

Present

True vacuoles

Absent

Present

Gas vesicles and carboxysomes

Present

Absent

Flagella

Made up of flagellin fibrils. Flagellin sub-units arranged in a ring helically around a central core.

Made up of tubulin microtubules arranged in 9+2 formation

Pili

Present

Absent

Cilia

Absent

Present in protozoans

Replication of DNA

Through out cell cycle

Only during ‘S’ phase

Synthesis of histone proteins

Absent

Only during ‘S’ phase

Cell growth, synthesis of RNA, membrane, macromolecules

Through out cell cycle

During Interphase

Cell division

Immediately after replication or simultaneously

During mitosis (M) phase

Meosis or reduction division

Absent

Present

Chromosome number

Usually 1

Variable, 2 to many

DNA

Circular, single chromosome, single or double stranded, helically coiled, usually haploid chromosome.

Single, linear, double stranded, helically coiled, chromosome diploid.

Extranuclear DNA

Present in bacteria (plasmid 0.1-5% of bacterial chromosome)

Absent except in yeasts

Histone proteins

Absent

Present

DNA position, nuclear membrane

Usually central, not surrounded by nuclear membrane

Surrounded by nuclear membrane

Chromosomal movement

Unidirectional from donor to recipient at times only exchange of plasmids.

Exchange of chromosome between two cells (gam etes)

Structure of mRNA

Polycistronic

Monocistronic

Photosynthesis

Absent in most except cyanobacteria and autotrophic bacteria

Present in plants. Absent in fungi, protozoa and animal cells.

N2 fixation

Present in some bacteria and cyanobacteria

Absent

Respiration (generation of energy)

Performed by plasma membrane

Performed by mitochondria

Anerobic respiration

Present in many bacteria

Shown by some e.g. yeasts, few protozoans, muscle cells etc

Aerobic respiration

Present

Present

Locomotion

Present in some bacteria, by flagella.

Absent in plants, algae, fungi, except in zoospores and few unicellular algae and fungi, present in animals and protozoans. (flagellated, ciliary, amieboid, gliding)

Reproduction

Simple fragmentation or binary fission, no meosis, asexual spores produced in some.

Complex, meosis present, also by fragmentation, binary fission and asexual spores in some plants. Algae and fungi and few protozoans.

Genetic recombination

Present in some but chromosomal cross over absent.

By chromosomal cross over during meiosis.

Last modified: Monday, 26 December 2011, 10:26 AM