Cell biology is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and functioning of organisms. Cell biology is the study of structural and functional units of cells. Cell biology encompasses both prokaryotic and eukaryotic cells and has many subtopics which may include the study of cell metabolism, cell communication, cell cycle, biochemistry, and cell composition. The study of cells is performed using several microscopy techniques, cell culture, and cell fractionation. These have allowed for and are currently being used for discoveries and research pertaining to how cells function, ultimately giving insight into understanding larger organisms. Knowing the components of cells and how cells work is fundamental to all biological sciences while also being essential for research in biomedical fields such as cancer, and other diseases. Research in cell biology is interconnected to other fields such as genetics, molecular genetics, molecular biology, medical microbiology, immunology, and cytochemistry.
A mitochondrion is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used throughout the cell as a source of chemical energy. They were discovered by Albert von Kölliker in 1857 in the voluntary muscles of insects. The term mitochondrion was coined by Carl Benda in 1898. The mitochondrion is popularly nicknamed the "powerhouse of the cell", a phrase coined by Philip Siekevitz in a 1957 article of the same name.
FtsZ is a protein encoded by the ftsZ gene that assembles into a ring at the future site of bacterial cell division. FtsZ is a prokaryotic homologue of the eukaryotic protein tubulin. The initials FtsZ mean "Filamenting temperature-sensitive mutant Z." The hypothesis was that cell division mutants of E. coli would grow as filaments due to the inability of the daughter cells to separate from one another. FtsZ is found in almost all bacteria, many archaea, all chloroplasts and some mitochondria, where it is essential for cell division. FtsZ assembles the cytoskeletal scaffold of the Z ring that, along with additional proteins, constricts to divide the cell in two.
COPI is a coatomer, a protein complex that coats vesicles transporting proteins from the cis end of the Golgi complex back to the rough endoplasmic reticulum (ER), where they were originally synthesized, and between Golgi compartments. This type of transport is retrograde transport, in contrast to the anterograde transport associated with the COPII protein. The name "COPI" refers to the specific coat protein complex that initiates the budding process on the cis-Golgi membrane. The coat consists of large protein subcomplexes that are made of seven different protein subunits, namely α, β, β', γ, δ, ε and ζ.
Endosomes are a collection of intracellular sorting organelles in eukaryotic cells. They are parts of endocytic membrane transport pathway originating from the trans Golgi network. Molecules or ligands internalized from the plasma membrane can follow this pathway all the way to lysosomes for degradation or can be recycled back to the cell membrane in the endocytic cycle. Molecules are also transported to endosomes from the trans Golgi network and either continue to lysosomes or recycle back to the Golgi apparatus.
The exocyst is an octameric protein complex involved in vesicle trafficking, specifically the tethering and spatial targeting of post-Golgi vesicles to the plasma membrane prior to vesicle fusion. It is implicated in a number of cell processes, including exocytosis, cell migration, and growth.
In cell biology, a phagosome is a vesicle formed around a particle engulfed by a phagocyte via phagocytosis. Professional phagocytes include macrophages, neutrophils, and dendritic cells (DCs).
The coatomer is a protein complex that coats membrane-bound transport vesicles. Two types of coatomers are known:
Mitofusin-2 is a protein that in humans is encoded by the MFN2 gene. Mitofusins are GTPases embedded in the outer membrane of the mitochondria. In mammals MFN1 and MFN2 are essential for mitochondrial fusion. In addition to the mitofusins, OPA1 regulates inner mitochondrial membrane fusion, and DRP1 is responsible for mitochondrial fission.
PTEN-induced kinase 1 (PINK1) is a mitochondrial serine/threonine-protein kinase encoded by the PINK1 gene.
Dynamin-1-like protein is a GTPase that regulates mitochondrial fission. In humans, dynamin-1-like protein, which is typically referred to as dynamin-related protein 1 (Drp1), is encoded by the DNM1L gene and is part of the dynamin superfamily (DSP) family of proteins.
Mitochondrial fission 1 protein (FIS1) is a protein that in humans is encoded by the FIS1 gene on chromosome 7. This protein is a component of a mitochondrial complex, the ARCosome, that promotes mitochondrial fission. Its role in mitochondrial fission thus implicates it in the regulation of mitochondrial morphology, the cell cycle, and apoptosis. By extension, the protein is involved in associated diseases, including neurodegenerative diseases and cancers.
E3 ubiquitin-protein ligase MARCH5, also known as membrane-associated ring finger (C3HC4) 5, is an enzyme that, in humans, is encoded by the MARCH5 gene. It is localized in the mitochondrial outer membrane and has four transmembrane domains.
Membrane contact sites (MCS) are close appositions between two organelles. Ultrastructural studies typically reveal an intermembrane distance in the order of the size of a single protein, as small as 10 nm or wider, with no clear upper limit. These zones of apposition are highly conserved in evolution. These sites are thought to be important to facilitate signalling, and they promote the passage of small molecules, including ions, lipids and reactive oxygen species. MCS are important in the function of the endoplasmic reticulum (ER), since this is the major site of lipid synthesis within cells. The ER makes close contact with many organelles, including mitochondria, Golgi, endosomes, lysosomes, peroxisomes, chloroplasts and the plasma membrane. Both mitochondria and sorting endosomes undergo major rearrangements leading to fission where they contact the ER. Sites of close apposition can also form between most of these organelles most pairwise combinations. First mentions of these contact sites can be found in papers published in the late 1950s mainly visualized using electron microscopy (EM) techniques. Copeland and Dalton described them as “highly specialized tubular form of endoplasmic reticulum in association with the mitochondria and apparently in turn, with the vascular border of the cell”.
Immunity Related Guanosine Triphosphatases or IRGs are proteins activated as part of an early immune response. IRGs have been described in various mammals but are most well characterized in mice. IRG activation in most cases is induced by an immune response and leads to clearance of certain pathogens.
Mitochondrial fission factor (Mff) is a protein that in humans is encoded by the MFF gene. Its primary role is in controlling the division of mitochondria. It has also been shown to regulate peroxisome morphology.
Mitochondria are dynamic organelles with the ability to fuse and divide (fission), forming constantly changing tubular networks in most eukaryotic cells. These mitochondrial dynamics, first observed over a hundred years ago are important for the health of the cell, and defects in dynamics lead to genetic disorders. Through fusion, mitochondria can overcome the dangerous consequences of genetic malfunction. The process of mitochondrial fusion involves a variety of proteins that assist the cell throughout the series of events that form this process.
Mitochondria-associated membranes (MAM) represent a region of the endoplasmic reticulum (ER) which is reversibly tethered to mitochondria. These membranes are involved in import of certain lipids from the ER to mitochondria and in regulation of calcium homeostasis, mitochondrial function, autophagy and apoptosis. They also play a role in development of neurodegenerative diseases and glucose homeostasis.
Mitochondrial elongation factor 2 is a protein that in humans is encoded by the MIEF2 gene.
The divisome is a protein complex in bacteria that is responsible for cell division, constriction of inner and outer membranes during division, and peptidoglycan (PG) synthesis at the division site. The divisome is a membrane protein complex with proteins on both sides of the cytoplasmic membrane. In gram-negative cells it is located in the inner membrane. The divisome is nearly ubiquitous in bacteria although its composition may vary between species.
