Commensal mites travelling phoresy on a fly Pseudolynchia canariensis Commensalism describes a relationship between two living organisms where one benefits and the other is not significantly harmed or helped. It is derived from the English word commensalused of human social interaction.
Intermediate filaments Intermediate filaments are so Endosymbiont theory because they are thicker than actin filaments and thinner than microtubules or muscle myosin filaments. The subunits of intermediate filaments are elongated, not globular, and are associated in an antipolar manner.
As a result, the overall filament has no polarity, and therefore no motor proteins move along intermediate filaments. Intermediate filaments are found only in complex multicellular organisms. They are encoded by a large number of different genes and can be grouped into families based on their amino acid sequences.
Cells in different tissues of the body express one or another Endosymbiont theory these genes at different times. One cell can even change which type of intermediate filament protein is expressed over its lifetime.
Most likely, the different forms of intermediate filaments have subtle but critical differences in their functional characteristics, helping to define the function of the cell. In general, intermediate filaments serve as structural elements, helping cells maintain their shape and integrity.
For example, keratin filaments, the intermediate filaments of epithelial cells, which line surfaces of the body, give strength to the cell sheet that covers the surface. Mutations in keratin genes can result in blisters when the epithelial cell sheet is weak and prone to rupture.
Keratin mutations can also cause deformations in the hair, nails, and corneas. Another example of a family of intermediate filaments is the lamin family, which comprises the nuclear lamina, a fibrous shell that underlies and supports the nuclear membrane.
Cooper The cell matrix and cell-to-cell communication The development of single cells into multicellular organisms involves a number of adaptations.
The cells become specialized, acquiring distinct functions that contribute to the survival of the organism. The behaviour of individual cells is also integrated with that of similar cells, so that they act together in a regulated fashion. To achieve this integrationcells assemble into specialized tissues, each tissue being composed of cells and the spaces outside of the cells.
The surface of cells is important in coordinating their activities within tissues. Embedded in the plasma membrane of each cell are a number of proteins that interact with the surface or secretions of other cells.
These interactions are key to the organizational behaviour of cell populations and contribute to the formation of embryonic tissues and the function of normal tissue in the adult organism. The extracellular matrix A substantial part of tissues is the space outside of the cells, called the extracellular space.
This is filled with a composite materialknown as the extracellular matrix, composed of a gel in which a number of fibrous proteins are suspended.
The gel consists of large polysaccharide complex sugar molecules in a water solution of inorganic salts, nutrients, and waste products known as the interstitial fluid.
The major types of protein in the matrix are structural proteins and adhesive proteins. Electron micrograph of a small area of dense fibrous connective tissue, illustrating the intimate association of cells and fibres.
In the centre is a portion of a fibrocyte, and on either side are two collagen fibres. The collagen fibre on the left is cut transversely, showing round cross sections of the unit fibrils. The collagen fibre on the right has been cut nearly parallel to its long axis and shows extensive segments of the cross-striated fibrils.
There are two general types of tissues distinct not only in their cellular organization but also in the composition of their extracellular matrix.Multiple lines of evidence support the endosymbiotic theory.
Endosymbiosis is observed elsewhere in biology. Mitochondria and chloroplasts have intriguing similarities in structure, reproduction, biochemistry, and genetic makeup to certain prokaryotes.
The endosymbiotic theory is the accepted mechanism for how eukaryotic cells evolved from prokaryotic cells. First published by Lynn Margulis in the late s, the Endosymbiont Theory proposed that the main organelles of the eukaryotic cell were actually primitive prokaryotic cells that had been engulfed by a different, bigger .
The theory that explains how this could have happened is called endosymbiotic theory.
An endosymbiont is one organism that lives inside of another one. All eukaryotic cells, like your own, are creatures that are made up of the parts of other creatures. TITLE: The Evolution of Organelles SOURCE: Singh-Cundy and Cain, Discover Biology, Fifth Edition, W. W.
Norton & Co. © W. W.
Norton & Co. and Sumanas, Inc. Feb 19, · Biology Professor (Twitter: @DrWhitneyHolden) describes the endosymbiotic theory, which is the scientific theory describing how eukaryotic cells acquired the organelles mitochondria and.
A look at some of the literature presenting interesting or unique lines of evidence for evolution. Cichlid fish, sexual selection, sperm competition, and endosymbiosis are but a few of the topics discussed.