Bacterial cell.
Prokaryotes include the kingdoms of Monera (simple bacteria) and Archaea. At a basic level a prokaryote is an aqueous emulsion containing biomolecules and other substances surrounded by a membrane and a cell wall. Prokaryotic cells don't possess membrane bound organelles. Of course things are never that simple in biology. At least some prokaryotes do contain intracellular structures that can be seen as primitive organelles. Intracellular membranes are known in some groups of prokaryotes, such as membrane systems devoted to special metabolic properties.
For the future doctor, prokaryotes are an important subject of study given that many infectious diseases arise from bacterial infection. In addition to an awareness of the structural features of bacterial cells, you should have a good basic sense of morphological classification in bacteria, modes of reproduction and DNA transfer, and an understanding of sociality in bacteria and patterns of interacting with the environment.
WikiPremed Resources
The Prokaryotic Cell Images
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Conceptual Vocabulary for Microbiology
Microbiology
Each list begins with basic conceptual vocabulary you need to know for MCAT questions and proceeds to advanced terms that might appear in context in MCAT passages. The terms are links to Wikipedia articles.
Prokaryote
Prokaryotes are a group of organisms that lack a cell nucleus, or any other membrane-bound organelles.
Prokaryotes are a group of organisms that lack a cell nucleus, or any other membrane-bound organelles.
Nucleoid
In prokaryotes, the nucleoid (also known as the nuclear region, nuclear body or chromatin body) is an irregularly shaped region where the genetic material is localized.
In prokaryotes, the nucleoid (also known as the nuclear region, nuclear body or chromatin body) is an irregularly shaped region where the genetic material is localized.
Ribosome
A ribosome is a small, dense, functional structure found in most known cells that assembles proteins and polypeptides used in cell division.
A ribosome is a small, dense, functional structure found in most known cells that assembles proteins and polypeptides used in cell division.
Virus
A virus is a sub-microscopic particle that can infect the cells of a biological organism and which can replicate itself only by infecting a host cell.
A virus is a sub-microscopic particle that can infect the cells of a biological organism and which can replicate itself only by infecting a host cell.
Capsid
A capsid is the protein shell of a virus.
A capsid is the protein shell of a virus.
Viral envelope
Viral envelopes are present in many viruses, covering the protein capsid, typically derived from portions of the host cell membranes but including some viral glycoproteins.
Viral envelopes are present in many viruses, covering the protein capsid, typically derived from portions of the host cell membranes but including some viral glycoproteins.
Prokaryote
Prokaryotes are a group of organisms that lack a cell nucleus or any other membrane-bound organelles.
Prokaryotes are a group of organisms that lack a cell nucleus or any other membrane-bound organelles.
Microorganism
A microorganism is an organism that is too small to be seen by the human eye.
A microorganism is an organism that is too small to be seen by the human eye.
Bacteria
Bacteria are prokaryotic unicellular microorganisms ubiquitous in every habitat on Earth.
Bacteria are prokaryotic unicellular microorganisms ubiquitous in every habitat on Earth.
Archaea
The Archaea, or archaebacteria, are a major group of prokaryotic microorganisms in which many species are extremophiles.
The Archaea, or archaebacteria, are a major group of prokaryotic microorganisms in which many species are extremophiles.
Cell wall
A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane.
A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane.
Flagellum
A flagellum is a long, slender projection from the cell body, composed of microtubules and surrounded by the plasma membrane.
A flagellum is a long, slender projection from the cell body, composed of microtubules and surrounded by the plasma membrane.
Cell wall
A cell wall is a fairly rigid layer surrounding a prokaryotic cell, located external to the cell membrane, which provides the cell with structural support, protection, and acts as a filtering mechanism.
A cell wall is a fairly rigid layer surrounding a prokaryotic cell, located external to the cell membrane, which provides the cell with structural support, protection, and acts as a filtering mechanism.
Retrovirus
A retrovirus is an enveloped viruses possessing a RNA genome, which replicates via a DNA intermediate.
A retrovirus is an enveloped viruses possessing a RNA genome, which replicates via a DNA intermediate.
Human immunodeficiency virus
Human immunodeficiency virus (HIV) is a retrovirus that can lead to AIDS, a condition in humans in which the immune system begins to fail.
Human immunodeficiency virus (HIV) is a retrovirus that can lead to AIDS, a condition in humans in which the immune system begins to fail.
Bacteriophage
A bacteriophage is any one of a number of viruses that infect bacteria.
A bacteriophage is any one of a number of viruses that infect bacteria.
Binary fission
Binary fission is the form of asexual reproduction in prokaryotic single-celled organisms by which one cell divides into two cells of the same size.
Binary fission is the form of asexual reproduction in prokaryotic single-celled organisms by which one cell divides into two cells of the same size.
Cocci
Cocci are microorganisms whose overall shape is spherical or nearly spherical.
Cocci are microorganisms whose overall shape is spherical or nearly spherical.
Spirillum
Spirillum in microbiology refers to a bacterium with a cell body that twists like a spiral.
Spirillum in microbiology refers to a bacterium with a cell body that twists like a spiral.
Flagellum
A flagellum is a long, slender projection from the cell body, composed of microtubules and surrounded by the plasma membrane.
A flagellum is a long, slender projection from the cell body, composed of microtubules and surrounded by the plasma membrane.
Peptidoglycan
Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of eubacteria.
Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of eubacteria.
Pilus
A pilus is a hairlike appendage found on the surface of many bacteria. This term and fimbria are often used interchangeably.
A pilus is a hairlike appendage found on the surface of many bacteria. This term and fimbria are often used interchangeably.
Flagellin
Flagellin is a protein that arranges itself in a hollow cylinder to form the filament in bacterial flagellum
Flagellin is a protein that arranges itself in a hollow cylinder to form the filament in bacterial flagellum
Lytic cycle
The lytic cycle is the one of the two cycles of viral reproduction that is typically considered the main method of viral replication, since it results in the destruction of the infected cell and release of virus particles.
The lytic cycle is the one of the two cycles of viral reproduction that is typically considered the main method of viral replication, since it results in the destruction of the infected cell and release of virus particles.
Lysogenic cycle
The lysogenic cycle is the mode of viral reproduction characterized by the fusion of the nucleic acid of a bacteriophage with that of a host so that the integrated prophage can then be transmitted to daughter cells in subsequent cell divisions.
The lysogenic cycle is the mode of viral reproduction characterized by the fusion of the nucleic acid of a bacteriophage with that of a host so that the integrated prophage can then be transmitted to daughter cells in subsequent cell divisions.
Peptidoglycan
Peptidoglycan or murein is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of eubacteria.
Peptidoglycan or murein is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of eubacteria.
Nucleoid
The nucleoid in prokaryotes is an irregularly shaped region within the cell where the genetic material is localized.
The nucleoid in prokaryotes is an irregularly shaped region within the cell where the genetic material is localized.
Pilus
A pilus is a hairlike appendage found on the surface of many bacteria.
A pilus is a hairlike appendage found on the surface of many bacteria.
Autotroph
An autotroph is an organism that produces complex organic compounds from simple inorganic molecules and an external source of energy.
An autotroph is an organism that produces complex organic compounds from simple inorganic molecules and an external source of energy.
Gram-positive
Gram-positive bacteria are those that retain a crystal violet dye during the Gram stain process.
Gram-positive bacteria are those that retain a crystal violet dye during the Gram stain process.
Lipopolysaccharide
A lipopolysaccharide is a large molecule consisting of a lipid and a polysaccharide (carbohydrate) joined by a covalent bond.
A lipopolysaccharide is a large molecule consisting of a lipid and a polysaccharide (carbohydrate) joined by a covalent bond.
Cell envelope
The cell envelope is the cell membrane and cell wall plus an outer membrane, if one is present. Most bacterial cell envelopes fall into two major categories: Gram positive and Gram negative.
The cell envelope is the cell membrane and cell wall plus an outer membrane, if one is present. Most bacterial cell envelopes fall into two major categories: Gram positive and Gram negative.
Influenza
Influenza, commonly known as flu, is an infectious disease of birds and mammals caused by RNA viruses of the family Orthomyxoviridae.
Influenza, commonly known as flu, is an infectious disease of birds and mammals caused by RNA viruses of the family Orthomyxoviridae.
Positive-sense
Positive-sense viral RNA is viral RNA which may be directly translated into the desired viral proteins.
Positive-sense viral RNA is viral RNA which may be directly translated into the desired viral proteins.
Negative-sense
Negative-sense viral RNA is complementary to the viral mRNA and thus must be converted to positive-sense RNA by an RNA polymerase prior to translation.
Negative-sense viral RNA is complementary to the viral mRNA and thus must be converted to positive-sense RNA by an RNA polymerase prior to translation.
Gram-positive
Gram-positive bacteria are those that retain a crystal violet dye during the Gram stain process.
Gram-positive bacteria are those that retain a crystal violet dye during the Gram stain process.
Petri dish
A Petri dish is a shallow glass or plastic cylindrical dish that biologists use to culture cells.
A Petri dish is a shallow glass or plastic cylindrical dish that biologists use to culture cells.
Cell envelope
The cell envelope of a bacterium is the cell membrane and cell wall plus an outer membrane.
The cell envelope of a bacterium is the cell membrane and cell wall plus an outer membrane.
Flagellin
Flagellin is a protein that arranges itself in a hollow cylinder to form the filament in bacterial flagellum
Flagellin is a protein that arranges itself in a hollow cylinder to form the filament in bacterial flagellum
Carboxysome
The carboxysome is a bacterial microcompartment made up of a protein shell, that contains enzymes involved in carbon fixation reactions.
The carboxysome is a bacterial microcompartment made up of a protein shell, that contains enzymes involved in carbon fixation reactions.
Outer membrane
The outer membrane refers to the outside membranes of Gram-negative bacteria.
The outer membrane refers to the outside membranes of Gram-negative bacteria.
Periplasmic space
The periplasmic space is the space seen between the plasma membrane and the outer membrane in the gram-negative bacteria.
The periplasmic space is the space seen between the plasma membrane and the outer membrane in the gram-negative bacteria.
Glycocalyx
Glycocalyx is a general term referring to extracellular polymeric material produced by some bacteria, epithelia and other cells.
Glycocalyx is a general term referring to extracellular polymeric material produced by some bacteria, epithelia and other cells.
Reverse transcriptase
A reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase enzyme that transcribes single-stranded RNA into single-stranded DNA.
A reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase enzyme that transcribes single-stranded RNA into single-stranded DNA.
Provirus
A provirus is a virus genome that has integrated itself into the DNA of a host cell.
A provirus is a virus genome that has integrated itself into the DNA of a host cell.
Tobacco mosaic virus
Tobacco mosaic virus is an RNA virus that infects plants. It was the first virus to be discovered.
Tobacco mosaic virus is an RNA virus that infects plants. It was the first virus to be discovered.
Endospore
An endospore is a dormant, tough, non-reproductive structure produced by a small number of bacteria the purpose of which is to ensure the survival of the bacterium through periods of environmental stress.
An endospore is a dormant, tough, non-reproductive structure produced by a small number of bacteria the purpose of which is to ensure the survival of the bacterium through periods of environmental stress.
Cyanobacteria
Cyanobacteria is a phylum of bacteria which obtain their energy through photosynthesis, often referred to as blue-green algae.
Cyanobacteria is a phylum of bacteria which obtain their energy through photosynthesis, often referred to as blue-green algae.
Extremophile
An extremophile is an organism that thrives in and may even require physically or geochemically extreme conditions that are detrimental to the majority of life on Earth.
An extremophile is an organism that thrives in and may even require physically or geochemically extreme conditions that are detrimental to the majority of life on Earth.
Fimbria
A fimbria is a proteinaceous appendage in many gram-negative bacteria that is thinner and shorter than a flagellum.
A fimbria is a proteinaceous appendage in many gram-negative bacteria that is thinner and shorter than a flagellum.
Carboxysome
The carboxysome is a bacterial microcompartment, roughly 90-500 nm in diameter, made up of a protein shell, that contains enzymes involved in carbon fixation reactions.
The carboxysome is a bacterial microcompartment, roughly 90-500 nm in diameter, made up of a protein shell, that contains enzymes involved in carbon fixation reactions.
Fimbria
A fimbria is a proteinaceous appendage in many gram-negative bacteria that is thinner and shorter than a flagellum.
A fimbria is a proteinaceous appendage in many gram-negative bacteria that is thinner and shorter than a flagellum.
Hepatitis B
Hepatitus B virus is a DNA virus, which causes an inflammatory disease of the liver, that consists of an outer lipid envelope and an icosahedral nucleocapsid core composed of protein.
Hepatitus B virus is a DNA virus, which causes an inflammatory disease of the liver, that consists of an outer lipid envelope and an icosahedral nucleocapsid core composed of protein.
RNA virus
An RNA virus is one belonging to either Group III, Group IV or Group V of the Baltimore classification system, so it possesses ribonucleic acid as its genetic material and does not replicate using a DNA intermediate.
An RNA virus is one belonging to either Group III, Group IV or Group V of the Baltimore classification system, so it possesses ribonucleic acid as its genetic material and does not replicate using a DNA intermediate.
Hepatitis C
The Hepatitis C virus, which causes an inflammatory disease of the liver, is a small enveloped, single-stranded, positive sense RNA virus.
The Hepatitis C virus, which causes an inflammatory disease of the liver, is a small enveloped, single-stranded, positive sense RNA virus.
Chemotaxis
Chemotaxis is the phenomenon in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment.
Chemotaxis is the phenomenon in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment.
Pseudopeptidoglycan
Pseudopeptidoglycan or pseudomurein is a major cell wall component of some archaebacteria that chemically differs from but resembles eubacterial peptidoglycan.
Pseudopeptidoglycan or pseudomurein is a major cell wall component of some archaebacteria that chemically differs from but resembles eubacterial peptidoglycan.
S-layer
An S-layer is a part of the cell envelope commonly found in bacteria, as well as among archaea, consisting of a monomolecular layer composed of identical proteins or glycoproteins.
An S-layer is a part of the cell envelope commonly found in bacteria, as well as among archaea, consisting of a monomolecular layer composed of identical proteins or glycoproteins.
Nitrifying bacteria
Nitrifying bacteria are chemoautotrophic bacteria that grow at the expense of inorganic nitrogen compounds.
Nitrifying bacteria are chemoautotrophic bacteria that grow at the expense of inorganic nitrogen compounds.
Genophore
A genophore is the DNA of a prokaryote.
A genophore is the DNA of a prokaryote.
S-layer
A S-layer (surface layer) is a part of the cell envelope commonly found in bacteria, as well as among archaea. It consists of a monomolecular layer composed of identical proteins or glycoproteins.
A S-layer (surface layer) is a part of the cell envelope commonly found in bacteria, as well as among archaea. It consists of a monomolecular layer composed of identical proteins or glycoproteins.
Endotoxin
Endotoxins are potentially toxic, natural compounds found inside pathogens such as bacteria, released mainly when bacteria are lysed.
Endotoxins are potentially toxic, natural compounds found inside pathogens such as bacteria, released mainly when bacteria are lysed.
Integrase
Integrase is an enzyme produced by a retrovirus that enables its genetic material to be integrated into the DNA of the infected cell.
Integrase is an enzyme produced by a retrovirus that enables its genetic material to be integrated into the DNA of the infected cell.
Prion
A prion is an infectious agent composed only of protein.
A prion is an infectious agent composed only of protein.
Severe acute respiratory syndrome
Severe acute respiratory syndrome is a disease in humans which is caused by the SARS coronavirus.
Severe acute respiratory syndrome is a disease in humans which is caused by the SARS coronavirus.
Periplasmic space
The periplasmic space is the space seen between the plasma membrane and the outer membrane in the Gram-negative bacteria.
The periplasmic space is the space seen between the plasma membrane and the outer membrane in the Gram-negative bacteria.
Magnetosome
Magnetosome chains are membranous prokaryotic organelles present in magnetotactic bacteria containing 15 to 20 magnetite crystals that together orient magnetotactic bacteria in geomagnetic fields.
Magnetosome chains are membranous prokaryotic organelles present in magnetotactic bacteria containing 15 to 20 magnetite crystals that together orient magnetotactic bacteria in geomagnetic fields.
Glycocalyx
Glycocalyx is a general term referring to extracellular polymeric material produced by some bacteria, epithelia and other cells.
Glycocalyx is a general term referring to extracellular polymeric material produced by some bacteria, epithelia and other cells.
Teichoic acid
Teichoic acids are polymers of glycerol or ribitol found in the cell wall of gram-positive bacteria appearing to extend to the surface of the peptidoglycan layer.
Teichoic acids are polymers of glycerol or ribitol found in the cell wall of gram-positive bacteria appearing to extend to the surface of the peptidoglycan layer.
Teichoic acid
Teichoic acids are polymers of glycerol or ribitol linked via phosphodiester bonds. These acids can be found in the cell wall of gram-positive bacteria and appear to extend to the surface of the peptidoglycan layer.
Teichoic acids are polymers of glycerol or ribitol linked via phosphodiester bonds. These acids can be found in the cell wall of gram-positive bacteria and appear to extend to the surface of the peptidoglycan layer.
Lipoteichoic acid
Lipoteichoic acid is a surface-associated adhesion amphiphile from Gram-positive bacteria and regulator of autolytic wall enzymes (muramidases).
Lipoteichoic acid is a surface-associated adhesion amphiphile from Gram-positive bacteria and regulator of autolytic wall enzymes (muramidases).
Endogenous retrovirus
Endogenous retroviruses are derived from ancient infections of germ cells in humans and other vertebrates with their proviruses now being passed on generation after generation.
Endogenous retroviruses are derived from ancient infections of germ cells in humans and other vertebrates with their proviruses now being passed on generation after generation.
Viroid
Viroids are plant pathogens that consist of a short stretch of highly complementary, circular, single-stranded RNA without the protein coat that is typical for viruses.
Viroids are plant pathogens that consist of a short stretch of highly complementary, circular, single-stranded RNA without the protein coat that is typical for viruses.
Satellite
Satellites are subviral agents composed of nucleic acids that depend for their multiplication on coinfection of a host cell with a helper virus.
Satellites are subviral agents composed of nucleic acids that depend for their multiplication on coinfection of a host cell with a helper virus.
FtsZ
FtsZ is a protein that assembles into a ring at the future site of the septum of bacterial cell division. Named after filamenting temperature-sensitive mutant Z, is a prokaryotic homologue to the eukaryotic protein tubulin.
FtsZ is a protein that assembles into a ring at the future site of the septum of bacterial cell division. Named after filamenting temperature-sensitive mutant Z, is a prokaryotic homologue to the eukaryotic protein tubulin.
MreB
MreB is a protein found in bacteria that has been identified as a homologue of actin, as indicated by similarities in tertiary structure and conservation of active site peptide sequence.
MreB is a protein found in bacteria that has been identified as a homologue of actin, as indicated by similarities in tertiary structure and conservation of active site peptide sequence.
Chlorosome
A chlorosome is a photosynthetic antenna complex found in green sulfur bacteria and some green filamentous anoxygenic phototrophs.
A chlorosome is a photosynthetic antenna complex found in green sulfur bacteria and some green filamentous anoxygenic phototrophs.
Oncolytic virus
An oncolytic virus is a virus used to treat cancer due to their ability to specifically infect cancer cells, while leaving normal cells unharmed.
An oncolytic virus is a virus used to treat cancer due to their ability to specifically infect cancer cells, while leaving normal cells unharmed.
Human T-lymphotropic virus
Human T-lymphotropic virus is a human, single-stranded RNA retrovirus that causes T-cell leukemia and T-cell lymphoma in adults.
Human T-lymphotropic virus is a human, single-stranded RNA retrovirus that causes T-cell leukemia and T-cell lymphoma in adults.
Reoviridae
Reoviridae is a family of viruses such as Rotavirus that can affect the gastrointestinal system and respiratory tract.
Reoviridae is a family of viruses such as Rotavirus that can affect the gastrointestinal system and respiratory tract.