Cell Types: Eukaryotic versus Prokaryotic

Organisms can be mostly classified into 2 groups, prokaryotes and eukaryotes, which have fundamental differences at the cellular level. Prokaryotes are unicellular organisms that include 2 of the 3 domains of life: bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology: Overview and archaea. Eukaryotes can be single-celled or multicellular organisms and include plants, animals, fungi Fungi Fungi belong to the eukaryote domain and, like plants, have cell walls and vacuoles, exhibit cytoplasmic streaming, and are immobile. Almost all fungi, however, have cell walls composed of chitin and not cellulose. Fungi do not carry out photosynthesis but obtain their substrates for metabolism as saprophytes (obtain their food from dead matter). Mycosis is an infection caused by fungi. Mycology: Overview, and protozoa. Prokaryotic cells consist of a single cytoplasm-filled compartment enclosed by a cell membrane Cell Membrane A cell membrane (also known as the plasma membrane or plasmalemma) is a biological membrane that separates the cell contents from the outside environment. A cell membrane is composed of a phospholipid bilayer and proteins that function to protect cellular DNA and mediate the exchange of ions and molecules. The Cell: Cell Membrane and cell wall, while eukaryotic cells contain a well-organized nucleus contained by a membrane, along with other membrane-bound organelles Organelles A cell is a complex unit that performs several complex functions. An organelle is a specialized subunit within a cell that fulfills a specific role or function. Organelles are enclosed within their own lipid bilayers or are unbound by membranes. The Cell: Organelles.

Last update:

Table of Contents

Share this concept:

Share on facebook
Share on twitter
Share on linkedin
Share on reddit
Share on email
Share on whatsapp

Eukaryotic Organisms

Eukaryotic organisms include:

  • Protozoans
  • Algae
  • Fungi
  • Plants
  • Animals

Cellular organization

  • Unicellular
  • Multicellular

Cellular characteristics

  • Size:
    • Large
    • 0.5–100 μm in diameter
  • Organization:
    • Compartmentalized in membrane-bound organelles Organelles A cell is a complex unit that performs several complex functions. An organelle is a specialized subunit within a cell that fulfills a specific role or function. Organelles are enclosed within their own lipid bilayers or are unbound by membranes. The Cell: Organelles
    • Shape determined by cytoskeleton Cytoskeleton A cell's cytosol is the liquid inside the cell membrane that surrounds the organelles and cytoskeleton. The cytosol is a complex solution where many biochemical processes take place. The Cell: Cytosol and Cytoskeleton
    • Endomembrane system (endoplasmic reticulum, Golgi, lysosomes) containing large ribosomes for protein synthesis
  • DNA DNA The molecule DNA is the repository of heritable genetic information. In humans, DNA is contained in 23 chromosome pairs within the nucleus. The molecule provides the basic template for replication of genetic information, RNA transcription, and protein biosynthesis to promote cellular function and survival. DNA Types and Structure:
    • Linear
    • Structured in multiple rod-shaped chromosomes
    • Organized and packaged with histones
    • Chromosomes can be haploid (unpaired) or diploid (paired).
    • Stored in membrane-bound nucleus
    • Transcription Transcription Transcription of genetic information is the first step in gene expression. Transcription is the process by which DNA is used as a template to make mRNA. This process is divided into 3 stages: initiation, elongation, and termination. Stages of Transcription occurs inside the nucleus; translation Translation Translation is the process of synthesizing a protein from a messenger RNA (mRNA) transcript. This process is divided into three primary stages: initiation, elongation, and termination. Translation is catalyzed by structures known as ribosomes, which are large complexes of proteins and ribosomal RNA (rRNA). Stages and Regulation of Translation occurs in the cytosol.
  • Cell membrane: lipid bilayer 
  • Cell wall:
    • Only present in some cells
    • Composed of cellulose (plants and algae) or chitin (mollusks, insects, crustaceans, fungi Fungi Fungi belong to the eukaryote domain and, like plants, have cell walls and vacuoles, exhibit cytoplasmic streaming, and are immobile. Almost all fungi, however, have cell walls composed of chitin and not cellulose. Fungi do not carry out photosynthesis but obtain their substrates for metabolism as saprophytes (obtain their food from dead matter). Mycosis is an infection caused by fungi. Mycology: Overview)
  • Motility:
    • Flagella
    • Flexible projections made of microtubules
  • Cell division:
    • Meiosis Meiosis The creation of eukaryotic gametes involves a DNA replication phase followed by 2 cellular division stages: meiosis I and meiosis II. Meiosis I separates homologous chromosomes into separate cells (1n, 2c), while meiosis II separates sister chromatids into gametes (1n, 1c). Meiosis 
    • Mitosis
  • Transport of matter across cell membrane Cell Membrane A cell membrane (also known as the plasma membrane or plasmalemma) is a biological membrane that separates the cell contents from the outside environment. A cell membrane is composed of a phospholipid bilayer and proteins that function to protect cellular DNA and mediate the exchange of ions and molecules. The Cell: Cell Membrane:
    • Simple and facilitated diffusion
    • Phagocytosis
Eukaryotic cell

An eukaryotic cell and its components

Image: “Animal cell structure” by Mariana Ruiz. License: Public Domain

Prokaryotic Organisms

Prokaryotic organisms include bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology: Overview and archea.

The cellular organization is unicellular.

Cellular characteristics

  • Size:
    • Small
    • 0.5–100 μm in diameter
  • Organization:
    • No true compartmentalization
    • Metabolic reactions occur freely in cytosol.
    • Ribosomes found free in cytosol
    • Lack cytoskeleton Cytoskeleton A cell's cytosol is the liquid inside the cell membrane that surrounds the organelles and cytoskeleton. The cytosol is a complex solution where many biochemical processes take place. The Cell: Cytosol and Cytoskeleton
    • Can have “inclusion bodies”: dense polymerized aggregates of proteins or nutrients
  • DNA DNA The molecule DNA is the repository of heritable genetic information. In humans, DNA is contained in 23 chromosome pairs within the nucleus. The molecule provides the basic template for replication of genetic information, RNA transcription, and protein biosynthesis to promote cellular function and survival. DNA Types and Structure:
    • Circular 
    • Organized and packaged with nucleoid-associated proteins (NAPs)                                         
    • Chromosomes are exclusively haploid (unpaired).
    • Single chromosome
    • May have additional extrachromosomal segments of DNA DNA The molecule DNA is the repository of heritable genetic information. In humans, DNA is contained in 23 chromosome pairs within the nucleus. The molecule provides the basic template for replication of genetic information, RNA transcription, and protein biosynthesis to promote cellular function and survival. DNA Types and Structure called plasmids
    • Found in the nucleoid (nonmembrane-bound area)
    • Transcription Transcription Transcription of genetic information is the first step in gene expression. Transcription is the process by which DNA is used as a template to make mRNA. This process is divided into 3 stages: initiation, elongation, and termination. Stages of Transcription and translation Translation Translation is the process of synthesizing a protein from a messenger RNA (mRNA) transcript. This process is divided into three primary stages: initiation, elongation, and termination. Translation is catalyzed by structures known as ribosomes, which are large complexes of proteins and ribosomal RNA (rRNA). Stages and Regulation of Translation both occur in the cytosol.
  • Cell membrane: lipid bilayer 
  • Cell wall:
    • Found in almost all cells
    • Often composed of peptidoglycan
  • Motility: rigid spiral flagella
  • Cell division: binary fission
  • Transport of matter across cell membrane Cell Membrane A cell membrane (also known as the plasma membrane or plasmalemma) is a biological membrane that separates the cell contents from the outside environment. A cell membrane is composed of a phospholipid bilayer and proteins that function to protect cellular DNA and mediate the exchange of ions and molecules. The Cell: Cell Membrane: simple and facilitated diffusion
Structure of bacteria

Structure of a prokaryotic cell

Image: “Average prokaryote cell” by Mariana Ruiz Villarreal. License: Public Domain
Eukaryotes vs prokaryotes

Eukaryote and prokaryote cell comparison

Image: “The cells of eukaryotes (left) and prokaryotes (right)” by Science Primer. License: Public Domain

Clinical Relevance

  • Bacteria: prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Management of bacterial disease generally involves antibiotics; however, antibiotic choice may vary depending on the bacterial structure and metabolism.
  • Fungi: these organisms belong to the eukaryote domain and, like plants, have cell walls and vacuoles, exhibit cytoplasmic streaming, and are immobile. Almost all fungi Fungi Fungi belong to the eukaryote domain and, like plants, have cell walls and vacuoles, exhibit cytoplasmic streaming, and are immobile. Almost all fungi, however, have cell walls composed of chitin and not cellulose. Fungi do not carry out photosynthesis but obtain their substrates for metabolism as saprophytes (obtain their food from dead matter). Mycosis is an infection caused by fungi. Mycology: Overview, however, have cell walls composed of chitin, not cellulose. Fungi do not carry out photosynthesis but obtain their substrates for metabolism as saprophytes (i.e., they obtain their food from dead matter). An infection caused by a fungus is called a mycosis Mycosis Fungi belong to the eukaryote domain and, like plants, have cell walls and vacuoles, exhibit cytoplasmic streaming, and are immobile. Mycosis is an infection caused by fungi. Mycology: Overview.

References

  1. Lodish H, Berk A, Zipursky SL, et al. (2000). Molecular Cell Biology. 4th edition. New York: W. H. Freeman. Section 1.3, The Architecture of Cells. https://www.ncbi.nlm.nih.gov/books/NBK21665/
  2. Vellai T, Vida G. (1999). The origin of eukaryotes: the difference between prokaryotic and eukaryotic cells. Proc Biol Sci. 266(1428):1571-7. doi: 10.1098/rspb.1999.0817

Learn even more with Lecturio:

Complement your med school studies with Lecturio’s all-in-one study companion, delivered with evidence-based learning strategies.

Study on the Go

Lecturio Medical complements your studies with evidence-based learning strategies, video lectures, quiz questions, and more – all combined in one easy-to-use resource.

¡Hola!

Esta página está disponible en Español.

🍪 Lecturio is using cookies to improve your user experience. By continuing use of our service you agree upon our Data Privacy Statement.

Details