substrate

Examples of substrate in the following topics:

• Enzyme Active Site and Substrate Specificity

  • Enzymes bind with chemical reactants called substrates.
  • In others, two substrates may come together to create one larger molecule.
  • The enzyme's active site binds to the substrate.
  • A specific chemical substrate matches this site like a jigsaw puzzle piece and makes the enzyme specific to its substrate.
  • When an enzyme binds its substrate, it forms an enzyme-substrate complex.

• Substrates for Biosynthesis

  • Major metabolic pathways require substrates to be acted upon for the formation of larger, more complex products.
  • The major metabolic pathways require substrates to be acted upon for the formation of larger, more complex products.
  • These precursors are used as substrates for the biogenesis of large complex products.
  • This process is characterized by the production of various intermediates and molecules that function as substrates in additional pathways .
  • This pathway, comprised of a series of reactions, produces many intermediates and molecules utilized as substrates for biosynthesis in additional pathways.

• Enzyme Catalysis

  • They do this by binding the reactant(s), known as the substrate(s), to an active site within the enzyme.
  • At the active site, the substrate(s) can form an activated complex at lower energy.
  • This model proposes that the binding of the reactant, or substrate, to the enzyme active site results in a conformational change to the enzyme.
  • Electrostatic catalysis: electrostatic attractions between the enzyme and the substrate can stabilize the activated complex.
  • An enzyme catalyzes a biochemical reaction by binding a substrate at the active site.

• Overview of Reducing Agents

  • Note that Lithium Aluminum Hydride (LiAlH4) is the strongest reducing agent listed, and it reduces all the substrates.
  • In a similar sense, acyl chlorides are the most reactive substrate.

• Hydrogenation

  • Hydrogenation reactions, which involve the addition of hydrogen to substrates, have many important applications.
  • Hydrogenation reactions generally require three components: the substrate, the hydrogen source, and a catalyst.
  • The reaction is carried out at varying temperatures and pressures depending on the catalyst and substrate used.
  • Homogeneous catalysts are soluble in the solvent that contains the unsaturated substrate.
  • The metal binds the substrate and then transfers one of the hydrogen atoms from the metal to the substrate via migratory insertion.

• Control of Metabolism Through Enzyme Regulation

  • In competitive inhibition, an inhibitor molecule is similar enough to a substrate that it can bind to the enzyme's active site to stop it from binding to the substrate.
  • It "competes" with the substrate to bind to the enzyme.
  • Their binding induces a conformational change that reduces the affinity of the enzyme's active site for its substrate. 
  • Allosteric inhibitors modify the active site of the enzyme so that substrate binding is reduced or prevented.
  • In contrast, allosteric activators modify the active site of the enzyme so that the affinity for the substrate increases.

• Types and Functions of Proteins

  • Because form determines function, each enzyme is specific to its substrates.
  • The substrates are the reactants that undergo the chemical reaction catalyzed by the enzyme.
  • When the substrate binds to its active site at the enzyme, the enzyme may help in its breakdown, rearrangement, or synthesis .
  • Anabolic enzymes: enzymes that build more complex molecules from their substrates
  • A catabolic enzyme reaction showing the substrate matching the exact shape of the active site.

• Reactions of Coordination Compounds

  • Complexes that have unfilled or half-filled orbitals often show the capability to react with substrates.
  • Most substrates have a singlet ground-state; that is, they have lone electron pairs (e.g., water, amines, ethers).
  • These substrates need an empty orbital to be able to react with a metal center.
  • Some substrates (e.g., molecular oxygen) have a triplet ground state.
  • Metals with half-filled orbitals have a tendency to react with such substrates.

• Fermentation Without Substrate-Level Phosphorylation

  • Sugars are the most common substrate of fermentation, and typical examples of fermentation products are ethanol, lactic acid, lactose, and hydrogen.

• ABC Transporters

  • ABC transporters are transmembrane proteins that utilize the energy of adenosine triphosphate (ATP) hydrolysis to carry out certain biological processes including translocation of various substrates across membranes and non-transport-related processes such as translation of RNA and DNA repair.
  • They transport a wide variety of substrates across extra- and intracellular membranes, including metabolic products, lipids and sterols, and drugs.
  • The substrates that can be transported include ions, amino acids, peptides, sugars, and other molecules that are mostly hydrophilic.
  • The membrane-spanning region of the ABC transporter protects hydrophilic substrates from the lipids of the membrane bilayer thus providing a pathway across the cell membrane .