Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined together to form macromolecules; this process consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is synonymous with anabolism; the prerequisite elements for biosynthesis include: precursor compounds, chemical energy, catalytic enzymes which may require coenzymes. These elements create the building blocks for macromolecules; some important biological macromolecules include: proteins, which are composed of amino acid monomers joined via peptide bonds, DNA molecules, which are composed of nucleotides joined via phosphodiester bonds.
Biosynthesis occurs due to a series of chemical reactions. For these reactions to take place, the following elements are necessary: Precursor compounds: these compounds are the starting molecules or substrates in a reaction; these may be viewed as the reactants in a given chemical process. Chemical energy: chemical energy can be found in the form of high energy molecules; these molecules are required for energetically unfavorable reactions. Furthermore, the hydrolysis of these compounds drives a reaction forward. High energy molecules, such as ATP, have three phosphates; the terminal phosphate is split off during hydrolysis and transferred to another molecule. Catalytic enzymes: these molecules are special proteins that catalyze a reaction by increasing the rate of the reaction and lowering the activation energy. Coenzymes or cofactors: cofactors are molecules that assist in chemical reactions; these may be metal ions, vitamin derivatives such as NADH and acetyl CoA, or non-vitamin derivatives such as ATP.
In the case of NADH, the molecule transfers a hydrogen, whereas acetyl CoA transfers an acetyl group, ATP transfers a phosphate. In the simplest sense, the reactions that occur in biosynthesis have the following format: Reactant → e n z y m e Product Some variations of this basic equation which will be discussed in more detail are: Simple compounds which are converted into other compounds as part of a multiple step reaction pathway. Two examples of this type of reaction occur during the formation of nucleic acids and the charging of tRNA prior to translation. For some of these steps, chemical energy is required: Precursor molecule + ATP ↽ − − ⇀ product AMP + PP i Simple compounds that are converted into other compounds with the assistance of cofactors. For example, the synthesis of phospholipids requires acetyl CoA, while the synthesis of another membrane component, requires NADH and FADH for the formation the sphingosine backbone; the general equation for these examples is: Precursor molecule + Cofactor → e n z y m e macromolecule Simple compounds that join together to create a macromolecule.
For example, fatty acids join together to form phospholipids. In turn and cholesterol interact noncovalently in order to form the lipid bilayer; this reaction may be depicted as follows: Molecule 1 + Molecule 2 ⟶ macromolecule Many intricate macromolecules are synthesized in a pattern of simple, repeated structures. For example, the simplest structures of lipids are fatty acids. Fatty acids are hydrocarbon derivatives; these fatty acids create larger components, which in turn incorporate noncovalent interactions to form the lipid bilayer. Fatty acid chains are found in two major components of membrane lipids: phospholipids and sphingolipids. A third major membrane component, does not contain these fatty acid units; the foundation of all biomembranes consists of a bilayer structure of phospholipids. The phospholipid molecule is amphipathic; the phospholipid heads interact with each other and aqueous media, while the hydrocarbon tails orient themselves in the center, away from water. These latter interactions drive the bilayer structure that acts as a barrier for molecules.
There are various types of phospholipids. However, the first step in phospholipid synthesis involves the formation of phosphatidate or diacylglycerol 3-phosphate at the endoplasmic reticulum and outer mitochondrial membrane; the synthesis pathway is found below: The pathway starts with glycerol 3-phosphate, which gets converted to lysophosphatidate via the addition of a fatty acid chain provided by acyl coenzyme A. Then, lysophosphatidate is converted to phosphatidate via the addition of another fatty acid chain contributed by a second acyl CoA.
Trinodes is a genus of beetles in the family Dermestidae, the skin beetles. The genus is distributed in the Palearctic and Afrotropic ecozones. There are about 16 species. Species include: Trinodes albohirsutus Kalík, 1965 Trinodes amamiensis Ohbayashi, 1977 Trinodes carinatus Pic, 1916 Trinodes cinereohirtus Motschulsky, 1863 Trinodes emarginatus Arrow, 1915 Trinodes hirtus Fabricius, 1781 Trinodes insulanus Zhantiev, 1988 Trinodes minutus Pic, 1915 Trinodes niger Matsumura & Yokoyama, 1928 Trinodes puetzi Háva & Prokop, 2006 Trinodes rufescens Reitter, 1877 Trinodes rufithorax Pic, 1926 Trinodes senegalensis Pic, 1915 Trinodes sinensis Fairmaire, 1886 Trinodes tonkineus Pic, 1922 Trinodes villosulus Dahl, 1823
The Boston Landmarks Commission is the historic preservation agency for the City of Boston. The commission was created by state legislation in 1975. Urban renewal in the United States started with the Housing Act of 1949, part of President Harry Truman's Fair Deal. In Boston a third of the old city was demolished, including the historic West End, to make way for a new highway, low- and moderate-income high-rises, new government and commercial buildings; the Boston Landmarks Commission was created by legislation in 1975 as a response to the mass demolitions the demolition of the Jordan Marsh Building on Washington Street. Built in the 1860s, the ornate building featured a well-known corner clock tower designed by Nathaniel J. Bradlee. Along with an entire row of annex buildings, the building was torn down in 1975 and replaced by a new building. Public outrage and grass roots protests influenced preservation legislation and sparked preservation action. There are now over 8000 landmarked properties in Boston.
The chief responsibilities of the Landmark Commission include identifying historic resources through preservation surveys and recognizing historic properties through designation, preserving designated Landmarks through the design review process. The BLC administers Article 85 Demolition Delay for the entire city of Boston. Whenever a building proposed to be demolished is determined by BLC staff to be significant, the public is invited to testify at a public hearing. If the BLC invokes a 90-day Demolition Delay as a result, there is an opportunity for the community to participate in discussions with the developer and explore alternatives to demolition; the Commission meets twice a month on second and fourth Tuesdays - Design Review starts a few hours prior to the business portion at every fourth Tuesday hearing. Applicants propose changes to a Landmark by presenting at the hearing, the public is invited to comment. Commissioners are nominated by professional and neighborhood organizations, appointed by the Mayor.
Most are confirmed by City Council. All commissioner positions are voluntary. There are 85 commissioner slots among the Boston Landmarks Commission and the 9 local historic commissions, although BLC commissioners hold slots on local commissions. There are 7 historic designated districts and 2 architectural districts; each district has its own commission staffed by a preservation planner within the Boston Landmarks Commission. The commissioners assure that the architectural and historical integrity of the district is not compromised; the districts include: Historic Beacon Hill District Back Bay Architectural District Bay State Road/ Back Bay West Architectural Conservation District St. Botolph Architectural Conservation District Bay Village Historic District South End Landmark District Mission Hill Triangle Architectural Conservation District Aberdeen Architectural Conservation District Fort Point Channel Landmark District Fort Point was most designated in 2008 after the Boston Wharf Co.-owned 55-acre industrial area was sold to several buyers.