What are the differences between prokaryotic and eukaryotic cells?

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Accepted Answer

There are several significant differences between prokaryotic and eukaryotic cells, from structural variations to molecular variations. The most important difference between the two is the presence of a membrane-bound nucleus in eukaryotic cells, whereas prokaryotic cells have a nucleoid region instead of a true nucleus.

Basis of differentiation
Prokaryotic cells 
Eukaryotic cells

Definition
Unicellular organisms that lack a true membrane-bound nucleus 
Cells that contain a true nucleus enclosed within the nuclear membrane

True membrane bound nucleus
Absent - DNA is bundled together in the nucleoid region instead of within a membrane-bound nucleus
Present – all genetic information is stored in this structure

Cell structure
Unicellular (some cyanobacteria may be multicellular)
Mostly multicellular – very few unicellular

Size
Small, measuring around 0.1-5 μm in diameter.    
Large, measuring around 10-100 μm

Complexity of cells
Simple cells
More complex cells

Cytoskeleton
May be absent 
Present

Membrane bound organelles
Absent
 Present

Mitochondria
Absent
 Present

Endoplasmic reticulum
Absent
 Present

Ribosomes
Present – smaller in size
 Present - larger in size

Golgi complex
Absent 
 Present

Vesicles
Present
 Present

Microtubules
Absent or rare
 Present

Lysosomes and peroxisomes
Absent
 Present

Flagella
Smaller, narrower, and single-stranded – perform rotary motions
Larger, thicker, and eleven-stranded – perform lashing or undulating movements

Number of chromosomes
A single circular chromosome
Multiple linear chromosomes

DNA structure and location
Single loop of stable chromosomal DNA located in an area named the nucleoid
Multiple molecules of double-stranded linear DNA found on tightly bound and organized chromosomes – located in a true nucleus

DNA replication
Occurs through a single origin of replication – the prokaryotic organism duplicates its entire genome and the second copy is passed on to a daughter cell
Occurs through multiple replication origins – genome typically duplicates prior to cell division

Coupling of transcription and translation

Transcription and translation are coupled – both processes can occur simultaneously because prokaryotic DNA can interact with the cytoplasm

Transcription and translation are not coupled - transcription occurs in the nucleus and translation occurs in the cytoplasm

Number of gene copies
Most are haploid - contain only one copy of each gene 
Most are diploid - contain two copies of each gene

Chloroplasts 
Present (in plants)
Absent - chlorophyll scattered in the cytoplasm

Genetic recombination
Occurs through the unilateral transfer of DNA
 Occurs during the crossing over event of meiosis, when genetic material is exchanged by homologous chromosomes

Mitochondria
Absent
Present

Examples
Bacteria and archaea
Animals, plants, fungi, algae and protozoans

Basis of differentiation	Prokaryotic cells	Eukaryotic cells
Definition	Unicellular organisms that lack a true membrane-bound nucleus	Cells that contain a true nucleus enclosed within the nuclear membrane
True membrane bound nucleus	Absent - DNA is bundled together in the nucleoid region instead of within a membrane-bound nucleus	Present – all genetic information is stored in this structure
Cell structure	Unicellular (some cyanobacteria may be multicellular)	Mostly multicellular – very few unicellular
Size	Small, measuring around 0.1-5 μm in diameter.	Large, measuring around 10-100 μm
Complexity of cells	Simple cells	More complex cells
Cytoskeleton	May be absent	Present
Membrane bound organelles	Absent	Present
Mitochondria	Absent	Present
Endoplasmic reticulum	Absent	Present
Ribosomes	Present – smaller in size	Present - larger in size
Golgi complex	Absent	Present
Vesicles	Present	Present
Microtubules	Absent or rare	Present
Lysosomes and peroxisomes	Absent	Present
Flagella	Smaller, narrower, and single-stranded – perform rotary motions	Larger, thicker, and eleven-stranded – perform lashing or undulating movements
Number of chromosomes	A single circular chromosome	Multiple linear chromosomes
DNA structure and location	Single loop of stable chromosomal DNA located in an area named the nucleoid	Multiple molecules of double-stranded linear DNA found on tightly bound and organized chromosomes – located in a true nucleus
DNA replication	Occurs through a single origin of replication – the prokaryotic organism duplicates its entire genome and the second copy is passed on to a daughter cell	Occurs through multiple replication origins – genome typically duplicates prior to cell division
Coupling of transcription and translation	Transcription and translation are coupled – both processes can occur simultaneously because prokaryotic DNA can interact with the cytoplasm	Transcription and translation are not coupled - transcription occurs in the nucleus and translation occurs in the cytoplasm
Number of gene copies	Most are haploid - contain only one copy of each gene	Most are diploid - contain two copies of each gene
Chloroplasts	Present (in plants)	Absent - chlorophyll scattered in the cytoplasm
Genetic recombination	Occurs through the unilateral transfer of DNA	Occurs during the crossing over event of meiosis, when genetic material is exchanged by homologous chromosomes
Mitochondria	Absent	Present
Examples	Bacteria and archaea	Animals, plants, fungi, algae and protozoans

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