High school biology
|Endosymbiotic theory||Theory proposing that eukaryotic cells formed from a symbiotic relationship among prokaryotic cells|
How do prokaryotic and eukaryotic cells differ?
|Genetic information||DNA is circular, usually free-floating in cytoplasm||DNA is linear, found in nucleus|
|Organelles||No nucleus or membrane-bound organelles||Has nucleus and membrane-bound organelles (ie: mitochondria, chloroplasts, Golgi body, ER)|
|Size||Small (1-5 micrometers)||Larger (10-100 micrometers)|
|Organisms||Bacteria/archaea||Animals, plants, fungi, protists|
|Cell structure||Always unicellular||Can be unicellular or multicellular|
What is the endosymbiotic theory?
One theory that may explain how eukaryotes became so complex is the endosymbiotic theory.
This theory proposes that organelles like mitochondria and chloroplasts were once free-living prokaryotic cells that began to live within a larger host cell. Over a long time, the prokaryotes and their hosts evolved together until one could not function without the other.
Common mistakes and misconceptions
- Eukaryotes can be unicellular. Many people think that eukaryotes are all multicellular, but this is not the case. While prokaryotes are always unicellular organisms, eukaryotes can be either unicellular or multicellular. For example, most protists are single-celled eukaryotes!
- Even though prokaryotes do not have a nucleus, they DO contain genetic information. Prokaryotes generally have single circular chromosomes where they store their genetic information.
Want to join the conversation?
- I thought some prokaryotic organisms could be multicellular;such as blue green algae, isn't that a multicellular prokaryotic?(16 votes)
- There are some cyanobacteria that form filaments with a differentiated cell type that fixes nitrogen and 'normal' photosynthesising cells. It's a form of symbiosis that could be classified as multicellular.(11 votes)
- How can eukaryotes be multicellular? Aren't they cells on their own?(9 votes)
- A eukaryote is an organism with complex cells, or a single cell with a complex structures. In these cells the genetic material is organized into chromosomes in the cell nucleus. Animals, plants, algae and fungi are all eukaryotes. There are also eukaryotes amongst single-celled protists. Unlike unicellular archaea and bacteria, eukaryotes may also be multicellular and include organisms consisting of many cell types forming different kinds of tissue. Prokaryotes are singled cell organisms.(10 votes)
- So chromosomes/chromatin can be floating around anywhere with DNA inside the cell and that it doesn't need to be around a nucleus?
I'm sorry if I seem dumb I'm new to this.(9 votes)
- No worries! We were all new to this at one time or another! To answer your question, yes, it doesn't need to be inside a membrane-bound nucleus in the case of prokaryotes
Hope this helps!(9 votes)
- I read on another article here on Khan Academy that prokaryotic cells can organize to form something that resembles a multicellular organism, and that it can be discussed if that's multicellular or not. So how can prokaryotes "always" be unicellular?
"In general, prokaryotes are single-celled organisms. However, there's increasing evidence that some groups of prokaryotic cells can organize to form structures that resemble multicellular organisms. Whether this counts as "real" multicellularity is a question hotly debated by researchers today."(9 votes)
- I believe that the debate is continued, so we should still agree to the previous answer that prokaryotes CANNOT be multicellular. Bacteria might be an interesting exception, but further research shows that the cells might work together, but they lack the organization that other multicellular beings have.
Hope this helps!(3 votes)
- How Can a cell be multicellular?(2 votes)
- It is not saying that a cell is multicellular. When it says eukaryotes can be multicellular it is referring to an organism made of eukaryotic cells.(9 votes)
- are biofilms made with prokaryotes or Eukaryotes cells?(4 votes)
- Biofilm Structure A microbial biofilm is made up of many prokaryotic organisms that combine to form a colony. The colony is adhered to a surface and coated with a polysaccharide layer (or slime layer).(2 votes)
- do eukaryotes cells live longer than prokaryotes(3 votes)
- The answer really lies in whether or not the cells combine to form a multicellular mass or if they prefer living by themselves. Ones that form together tend to live longer.
Hope this helps!(3 votes)
- How does the cell wall protect the nucleus(2 votes)
- The cell wall is a sturdy structure that forms a protective envelope around the cell, and prevents physical damage.(3 votes)
- How come eukaryotes and prokaryotes are similar in use but for different cells.(3 votes)
- The endosymbiotic theory states that prokaryotes may have started living inside other cells a long time ago. This means that eukaryotic organisms have different properties, such as being (sometimes) multicellular.(1 vote)