Prokaryotes are simple organisms that contain no membrane bound organelles. These simple organisms are commonly known as bacteria, viruses and bacteriophages. A few specific examples of prokaryotic cells cyanobacteria and archaebacteria. Prokaryotic cells only contain a small amount of DNA
They may also contain plasmids, which is a small ring that contains a few genes that may offer antibacterial resistance. The plasmid replicates independently of the genome and is not a vital structure. This allows prokaryotic cells such as bacteria to have a high degree of genetic variation and adaptability.
Prokaryotes also have 50s/30s subunit ribosomes and have locomotion through their flagella
Simple prokaryotic cells such as bacteria and viruses replicate asexually which means that they do not require a partner to make an offspring. Prokaryotic cells have many methods of creating genetically identical copies of themselves, and methods vary by organism. A few examples tested on the MCAT are:
- Binary Fission
Asexual vs. Sexual Replication
There are many key differences between asexual and sexual reproduction that you should know for the MCAT exam. Use the following table to learn the concepts for what is on the MCAT
|Feature||Asexual Reproduction||Sexual Reproduction|
|Parents Required||One Parent||Two Parents|
|Type of Replication||Binary Fission, Budding, Regeneration, Parthenogenesis||Meiosis|
|Occurs In||Lower Organisms||Invertebrates and Vertebrates|
|Genetic Variation||Identical (only some mutations)||Unique Genetic Material (Fundamental for Evolution)|
|Sex Cells Required or Formed?||No||Yes (Gametes)|
|Energy Required||Small Amount||More Energy Required|
|Number of Offspring Produced||2+||1+|
There are two types of bacteria, spherical (cocci) and rod shaped (bacilli). Instead of having a nucleus, prokaryotes have a nucleoid region, which is simply DNA supercoiled around histones floating together in the cytoplasm.
A common example of a bacteria is the cyanobacteria.
Bacteria can be classified into 2 main types based on their morphology. These are bacilli and cocci. Bacilli bacteria have a more oval and oblique shape while cocci bacteria have a more spherical and rounded shape.
There are many differences between bacteria and viruses. Use this table to see a side by side comparison.
Click here to move onto eukaryotic cells.