precursors

Examples of precursors in the following topics:

• Substrates for Biosynthesis

  • There are various components deemed necessary for biosynthetic processes to occur, including: precursor compounds, chemical energy, and carious catalytic enzymes.
  • The citric acid cycle, comprised of a series of chemical reactions, provides precursors for additional biochemical pathways.
  • These precursors are used as substrates for the biogenesis of large complex products.
  • The precursors include amino acids and reducing agents such as NADH.
  • Additional pathways that require precursors formed by the TCA include amino acid and nucleotide synthesis .

• Steroids

  • Cholesterol is the most common steroid and is mainly synthesized in the liver; it is the precursor to vitamin D.
  • Cholesterol is also a precursor to many important steroid hormones like estrogen, testosterone, and progesterone, which are secreted by the gonads and endocrine glands.
  • Cholesterol is also the precursor to bile salts, which help in the emulsification of fats and their absorption by cells.

• Biosynthesis and Energy

  • The ability to synthesize sugars and polysaccharides from noncarbohydrate precursors is key to survival in numerous microorganisms.
  • The process of gluconeogenesis, characterized by the production of glucose or fructose from noncarbohydrate precursors, is an ubiquitous process.
  • This process utilizes precursors such as pyruvate, lactate, or glycerol .

• Lipid Soluble Vitamins

  • The precursors of vitamins A and D have been identified as the tetraterpene beta-carotene and the steroid ergosterol, respectively.

• Catabolic-Anabolic Steady State

  • These complex molecules are produced through a systematic process from small and simple precursors.
  • For example, an anabolic reaction can begin with relatively simple precursor molecules (created previously by catabolic reactions) and end with fairly complex products such as sugar, certain lipids, or even DNA, which has an extremely complex physical structure.
  • The increased complexity of the products of anabolic reactions also means they are more energy-rich than their simple precursors.

• The Rough Draft Outline

  • Rough draft outlines serve as a precursor to the speech's rough draft and help organize the speakers' ideas into a cohesive topic.
  • Creating rough draft outlines—i.e., an outline that serves as a precursor to the speech's rough draft—often helps organize and structure speakers' ideas into a cohesive and definitive topic.

• Writing Formulas for Polymeric Macromolecules

  • This polymer is called polyethylene rather than polymethylene, (-CH2-)n, because ethylene is a stable compound (methylene is not), and it also serves as the synthetic precursor of the polymer.
  • A listing of some important addition polymers and their monomer precursors is presented in the following table.

• Damage to the Cell Wall

  • Although both of these molecules are polymerized on the surface of the cytoplasmic membrane, their precursors are assembled in the cytoplasm.
  • Any event that interferes with the assembling of the peptidoglycan precursor, and the transport of that object across the cell membrane, where it will integrate into the cell wall, would compromise the integrity of the wall.

• Preparation of Ylides

  • Approximate pKa's for some ylide precursors and related compounds are provided in the following table.

• Polysaccharide Biosynthesis

  • UDP-glucose can also be used as a precursor of lipopolysaccharides, and peptidoglycan.
  • ADP-glucose is usually the precursor for glycogen production in bacteria.