Essay On Domain Eukaryotes

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All living things on earth come from three domains: bacteria, archaea, and eukaryota. The domain archaea consists of single celled microorganisms that lack a nucleus and other organelles while the domain eukaryotes consist of organisms that are either unicellular or multicellular. The most prominent form of life today is an animal, which is part of the domain eukaryotes. Animals are multicellular organisms that perform life functions, which include nutrition, transport, respiration, excretion, synthesis, reproduction, regulation, and growth (September 9, 2015 Class Notes). Animals are composed of several forms that allow them to perform these life functions. The animals’ forms and function are observable in the levels of the molecule, the cell, …show more content…
They are shaped in complex three-dimensional forms that allow for variety in functions. Proteins can function as catalysts to speed up reactions and can also function as defense, storage, transport, cellular communication, movement, and structural support (Reece 75). Proteins such as antibodies help to protect the body against diseases by destroying viruses and bacteria. Transport proteins on the cell membrane help transport molecules across the membrane. Receptor proteins are located on attached to the cell membrane but with the receptor face pointing outwards in order to receive a signal from a ligand. This allows for cell communication. Structural proteins provide the cell support and an example of this protein is keratin which is the protein used to structure hair (Reece 76). Thus, the variety of functions of proteins is due to the way in which they are …show more content…
Cells are very complex as they have many organelles but they are exceptionally organized because each organelle has a specific function to perform. All cells are membrane bound which means that there is a cell membrane that separates the internal organelles from the external environment. The membrane is composed of a phospholipid bilayer with embedded proteins. The function of the cell membrane is to protect the cell from its environment and only allows some things to enter the cell. The membrane also has receptor proteins that allow for cell signaling. A signaling molecule activates the receptor protein when it binds to the active site and triggers a series of reactions to produce a cellular response. The events leading to the response is called signal transduction: first reception, then transduction where there is a chain of phosphorylation events with the enzyme kinase and finally a response is produced (January 4, 2016 Class
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