enzymes

• enzymes are known as biological catalysts because they speed up chemical reactions without being used up
• an enzyme's activity can be affected by temperature, pH, concentration of reactants or inhibitors, presence of cofactors, and pressure.
• the active site is the part of an enzyme that binds to its substrate, it has a specific shape which fits only one type of molecule.
• optimum conditions are when the rate of reaction is at its highest.
• the active site is the part of an enzyme that binds to its substrate.
• substrates are molecules on which enzymes act.
• substrates fit into the active site like a key fitting into a lock.
• enzyme-catalysed reactions occur at room temperature and do not require high temperatures.
• heat is a common denaturant.
• a denaturant is something that causes proteins to unfold and lose their function.
• when the substrate enters the active site, the bonds between atoms within the substrate break down, forming products.
• cofactors are non-protein substances required for some enzymatic activities.
• substrates are the molecules on which an enzyme acts.
• pH affects the charge on amino acids within the protein, so if the pH changes too much then the structure will change.
• co-factor is a non protein substance required for some enzymes to work properly.
• cofactors may be metal ions such as zinc (Zn+) or magnesium (Mg++).
• what are the types of proteins

  globular (ball-like, coiled, folded) & fibrous (long, stringy)
• Proteins


  Long chains of amino acids
• Classes of proteins


  • Globular
  • Fibrous
• Proteins (aka polypeptides)


  • There are 20 kinds of amino acids present in human cells
• How amino acids are formed

  1. 3 "letters" on the DNA code lead to an "amino acid"

  2. They combine together to form a "long chain" and this is what forms your protein
• Enzymes are known as biological catalysts which speed up chemical reactions
• Enzymes do not get used up and can be reused millions of times
• Enzymes


  A type of specialised protein that fall into one of the two general classes of proteins
• Globular proteins


  • The peptide chains are coiled and folded into a ball-like molecule
  • Most consist of more than one polypeptide chain held loosely together
  • They often perform many regulatory processes
• Globular proteins


  • Enzymes - helicase, hormones - insulin, antibodies
• Active site of globular proteins

  The "folds" on globular proteins where the protein function occurs
• Fibrous proteins


  • They are long and stringy "rope-like" molecules
  • Most have a role in the structural and mechanical elements of the body such as muscle fibres, collagen in tendons and keratin in hair
• Fibrous proteins


  • Muscle fibres, collagen in tendons, keratin in hair
• Structure of an enzyme

  • 3D protein folded protein structure
  • Single or going with other proteins via sulfide & hydrogen bonds
  • Has an active site which joins which substrates bind to
  • Can sometimes involve a co-factor (nonprotein)
• Substrate


  The substance that an enzyme acts upon
• Enzyme name and specificity

  • Enzymes are specific in the reactions they catalyse
  • They are often named after the substance they catalyse by adding the suffix "-ase"
• Enzyme names


  • Lipase, Peroxidase, Sucrase
• Enzyme specificity


  • Due to their shape, specifically the active sites, which are linked to the substance they catalyse
• Enzyme function


  • They do not get used up in the reaction
  • They are specific
  • They control (speed up/slow down) the rate of chemical reactions
  • One enzyme can catalyse the same reaction many times, and they do it at a very fast rate
  • Their shape is maintained by weak hydrogen bonds and thus will be susceptible to denaturing at high temperatures
• Types of enzymatic reactions

  • Anabolic reactions: enzymes are used to build molecules
  • Catabolic reactions: enzymes are used to break apart molecules
• Anabolic reactions


  Endergonic (they need a net INPUT of energy)
• Catabolic reactions


  Exergonic (there is a net RELEASE of energy)
• Enzyme active site


  The location/place where an enzyme binds to a substrate
• How an enzyme works

  1. Enzyme available with empty active site

  2. Substrate binds to enzyme with induced fit

  3. Substrate is converted to products

  4. Products are released

  5. Enzyme is unchanged and can repeat the process