MELC-14-15-16

• Enzyme


  A substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process
• How enzymes work


  1. Enzymes and substrates collide at the right speed and orientation so that the substrate fits into the enzyme at the active site

  2. Enzymes are specialized in their active site to match the shape of a specific substrate that they can react with

  3. Once the substrate is inside, the reaction takes place

  4. The enzyme can either build up or break down the substrates that specifically bind to it, and the resulting item is called "products"
• Example of how enzymes work

  • Enzyme: Lock

  Substrate: Key
• Enzymes


  • They are biological catalysts that speed up the rate of reaction between substances within cells without being changed or destroyed in a chemical reaction
  • Some enzymes consist of only protein, while most of them consist of both protein and nonprotein components
  • They can be reused over again for the same chemical reaction in bodily processes
• Enzyme structure

  Enzymes are a linear chain of amino acids, which give rise to a three-dimensional structure

  The different ways in which amino acids will be arranged in the chain will influence proper protein folding for the enzyme to be functionally active

  The protein chain folds into a pocket-like structure known as the active site

  The active site is a pocket-like structure that holds the substrate
• Substrate


  A substance acted upon by an enzyme
• Activation energy


  The minimum amount of energy required for a reaction to take place
• Catalyst

  A chemical which speeds up a reaction but is not used up and can be recovered unchanged after the reaction
• Enzyme


  A protein molecule that speeds up the rate of a reaction by acting as a catalyst
• Enzymes are found all over the cell and can be used repeatedly until they wear out or break
• Enzymes


  • They are highly specific for a reaction and only catalyze substrates which can fit inside their active site
• pH

  A measure of the hydrogen ion (H+) and hydroxide ion (OH-) concentrations, ranging from pH1 to pH14

  Acid solutions have pH values below 7, while basic solutions have pH values above 7

  Different enzymes have different optimum pH values, and any change in pH above or below the optimum will quickly cause a decrease in the rate of reaction

  Extreme changes in pH can cause denaturation of enzymes, permanently losing their function
• Temperature

  Increasing temperature increases the rate of reaction due to more random collisions of enzymes with substrate molecules

  There is a certain temperature at which an enzyme's catalytic activity is at its greatest (optimum temperature)

  Above the optimum temperature, the enzyme structure begins to denature (breaking of weaker bonds)
• Substrate

  Increasing substrate concentration increases the rate of reaction, but any increase in concentration will have no effect on the rate of reaction once the enzymes become saturated and are working at their maximum possible rate
• Key concepts

  • Activation energy - the minimum energy required for a reaction to occur

  Active site - the region of an enzyme where substrate molecules bind and undergo a chemical reaction

  Amino acid - organic compounds that contain amino and carboxylate functional groups, along with a side chain specific to each amino acid

  Catalysts - a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change

  Chemical reactions - a process that leads to the chemical transformation of one set of chemical substances to another

  Enzyme - a substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process
• Substrate

  A molecule acted upon by an enzyme. A substrate is loaded into the active site of the enzyme, or the place that allows weak bonds to be formed between the two molecules.
• Activation Energy

  • The minimum energy required for a reaction to occur.
• Active Site

  The region of an enzyme where substrate molecules bind and undergo a chemical reaction.
• Amino Acid

  Organic compounds that contain amino and carboxylate −CO−2 functional groups, along with a side chain specific to each amino acid.
• Catalysts

  A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.
• Chemical Reactions

  A process that leads to the chemical transformation of one set of chemical substances to another.
• Enzyme


  A substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process.
• Enzyme-Substrate Complex


  A temporary molecule formed when an enzyme comes into perfect contact with its substrate.
• Metabolism


  The chemical reactions in the body's cells that change food into energy.
• Optimum Activity

  Is reached at the enzyme's optimum temperature. A continued increase in temperature results in a sharp decrease in activity as the enzyme's active site changes shape.
• Peptide Bond

  A chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule.
• Products

  A substance that is formed as the result of a chemical reaction.
• Protein Folding

  A process by which a polypeptide chain folds to become a biologically active protein in its native 3D structure.
• Reactant

  A substance that enters into and is altered in the course of a chemical reaction.
• Transition State


  A particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest potential energy along with this reaction coordinate.
• Any increase in concentration will have no effect on the rate of reaction since substrate concentration will no longer be the limiting factor. Enzymes will become saturated and will be working at their maximum possible rate.
• The transfer of electrons between molecules is important because most of the energy stored in atoms and used to fuel cell functions is in the form of high-energy electrons.
• The transfer of energy in the form of electrons allows the cell to transfer and use energy incrementally, that is, in small packages rather than a single, destructive burst.
• Reactions that remove electrons from donor molecules, leaving them oxidized, are oxidation reactions; those that add electrons to acceptor molecules, leaving them reduced, are reduction reactions.
• Because electrons can move from one molecule to another, oxidation and reduction occur in tandem. They are complementary processes which occur together. Thus, these reactions are now called oxidation-reduction reactions or redox reactions.
• Summary of Oxidation and Reduction


  • Oxidation involves the loss of electrons
  • Reduction involves the gain of electrons
  • The substance oxidized is the reducing agent
  • The substance reduced is the oxidizing agent
• Biological molecules


  The four classes of large biological molecules that all living things are made up of: carbohydrates, lipids, proteins, and nucleic acids
• Macromolecules


  Large molecules composed of thousands of covalently connected atoms
• Molecular structure and function are inseparable
• Carbohydrates


  • Serve as fuel and building material
  • Include sugars and the polymers of sugars