Prokaryotic cells are distinguished from eukaryotes by their structure. While eukaryotic cells have complex structures, formed by internal membranes, cytoskeleton and a nucleus, prokaryote cells do not contain nuclei and other membrane-bound organelles.
Prokaryotic cells were the only life form on Earth for millions of years, until the most complex eukaryotic cells emerged through the process of evolution.
|What is||Prokaryotic cells are the most primitive cells. They have a less complex structure, without a nucleus, and the genetic material is dispersed within the cytoplasm.||They are believed to have evolved from prokaryotes. Eukaryotic cells are larger than prokaryotic cells, and show better structural organization and functional efficiency.|
|Core||They do not have a defined core.||Contains core.|
|Cell wall||The cell wall, if present, contains peptidoglycan.||The cell wall, when existing, contains cellulose.|
|Meaning||From the Greek, “before the nucleus” (pro = before, primitive and karyon = nucleus).||From the Greek, “true nucleus” (eu = true and karyon = nucleus).|
|DNA||DNA is generally circular, and has no association with histone proteins.||DNA is commonly linear, is within the nucleus, and is associated with histones.|
|Transcription||Transcription occurs in the cytoplasm.||Transcription occurs within the nucleus.|
|Examples||Unicellular beings, such as some bacteria, cyanophytic algae, blue algae and mycoplasmas.||Animals, plants, fungi and protists.|
|Size||1 to 5 μm in diameter.||10 to 100 μm in diameter.|
Definition of eukaryotes and prokaryotes
Prokaryotic cells, or prokaryotic cells, are organisms without a cell nucleus or any other membrane-bound organelle. Their genetic material is dispersed in the cytoplasm, and most prokaryotic beings are single-celled, although some prokaryotes are multicellular.
Eukaryotic cells, or eukaryotes, are organized into complex structures by internal membranes and a cytoskeleton. The most characteristic structure of the membrane is the nucleus.
Structure and functions of prokaryotic cells
Prokaryotic cells are less complex than eukaryotic cells. They have no true nucleus, because the DNA is not contained within a membrane or separated from the rest of the cell, but dispersed in a region of the cytoplasm called the nucleoid.
The following structures and organelles can be found in prokaryotic cells:
- Capsule: additional external cover that protects the cell, prevents dehydration and favors adhesion to surfaces;
- Cell wall: external cover that protects the bacterial cell and gives it its shape;
- Cytoplasm: it is a gel-like substance. Its role is to give structure and maintain the shape of the cell;
- Plasmid: are double DNA molecules that store genetic material;
- Cell Membrane: it is responsible for involving the cell’s cytoplasm and regulates the flow of substances inside and outside it;
- Flagellum and cilium: help in locomotion of the cell;
- Ribosome: are cellular structures responsible for the production of proteins;
- Nucleoid: area of the cytoplasm that contains the DNA molecule.
Also know the difference between DNA and RNA .
Structure and functions of eukaryotic cells
- Nucleus: it is the largest and most visible organelle in a eukaryotic cell. It contains the cell’s DNA;
- Endoplasmic Reticulum: its function is to produce and send proteins and lipids;
- Golgi complex: is responsible for modifying cellular molecules and sending materials out of the cell. It is also the only organelle that can generate lysosomes;
- Lysosomes: play an important role in cell digestion;
- Peroxisomes: are structures that have enzymes that transform hydrogen atoms into oxygen;
- Nucleoli: are located inside the nucleus, where the synthesis of ribosomes takes place;
- Mitochondria: responsible for releasing energy from glucose molecules and fatty acids;
- Vacuoles: structures that store substances related to digestion or cellular nutrition;
- Plastids: present only in eukaryotic plant cells. Responsible for photosynthesis and storage of substances. They are of three types: chloroplasts, chromoplasts and leukoplasts.