Mind map

Enzymes

Shehzeb basharat BY1 as English

Map content

Enzymes

Biological catalysts
- 'Biological' because they are made by living cells
- 'Catalysts' because they speed up reactions without being changed/used up in the reaction
- Types of Reactions
  - Anabolic
    - Building up molecules
      - E.g protein synthesis
  - Catabolic
    - Breaking down molecules
      - Digestion
- Metabolic pathways
  - A sequence of enzyme controlled reactions in which the product of one reaction becomes the reactant in the next
- They lower the amount of activation energy needed to make a reaction happen
Structure
- Tertiary Structure proteins
  - Have:
    - Hydrogen bonds
    - Ionic Bonds
    - Disulphide Bridges
    - Hydrophobic interactions
  - If any of the bonds are broken the shape of the active site will change
  - 3d Shape
- Globular (Metabolically active)
- Soluble because hydrophilic R groups are on the outside of the structure
- Sites of enzyme action
  - Extracellular
    - Enzymes are secreted from cell via exocytosis
      - E.g Amylase & Saprotrophic Fungi
        Amylase made in salivary glands and released into mouth to act on food. Saprotrphic Fungi- secretes amylase,lipase and proteases on their food to be digested
  - Intracellular, in solution
    - E.g the enzymes that catalyse glucose breakdown in glycosis
  - Intracellular, Membrane bound
    - Attached to the membrane
      - E.G cristae in mitochondria
Active site models
- Temporary bonding creates an enzyme-substrate complex which allows for the reaction
- Lock & Key Model
  - Emil Fischer-1894
  - Each enzyme is substrate-specific
    - Enzymes can only catalyse 1 type of reaction
      - Needs to be a successful collision between the enzyme & substrate
- Induced Fit model
  - Where the active site changes shape to accommodate the substrate
  - E.g Lysozymes
General Process
- Enzyme & Substrate mixed together
  - Enzymes & Substrate in constant motion & collide
    - Substrate binds w/active site (in a successful collision)
      - Substrate is modified & then released
        Active sites refill w/more substrate
        The rate of reaction depends on No. of free enzymes
        if all other conditions are optimal The enzyme concentration becomes the limiting factor in the above scenario
        As reaction proceeds there is less substrate & more product
        The the substrate concentration will become the limiting factor
        Eventually, all substrate used up & graph line flattens out
Factors affecting enzyme action
- Tempurature
  - Increasing temp will increase K.E of enzyme & substrate
    - Leading to more successful collisions
      - This can increase the rate of reaction
        The optimum for most enzymes is roughly 37'c
        Above this temp the increasing vibrations break the weak hydrogen bonds
        Causing the enzymes to denature
        At Low temps the enzyme is inactivated
- pH
  - Range of optimum pH is small
    - Changes affect the ionic & hydrogen bonds
      - Small deviations cause minor changes which are reversible & only inactivate the enzyme
        Large Deviations cause denaturation
- Substrate Concentration
  - IF ENZYME CONCENTRATION IS CONSTANT
  - It is a key limiting factor
    - Higher concentrations means quicker rate of reaction until a point
      - As all the active sites are saturated adding more substrate will not increase the rate
- Enzyme Concentration
  - As the enzyme concentration increases the rate of reaction increases
Enzyme Inhibition
- Competitive
  - Have a molecular shape complementary to the active site
    - Temporarily taking the position of the substrate
      - The effect of the inhibitor can be overcome by increasing the substrate concentration
- Non-competitive
  - Bind to the allosteric site of enzymes (i.e a site other than the active site)
    - Therefore they do not compete w/the substrate
      - They affect bonds and alter the overall shape of the enzyme
        Meaning the substrate cannot bind with active site
        As the inhibitor concentration increases, more enzymes denature
        Leading to a slower rate & less product produced
        E.g Heavy metal ions (Pb lead, arsenic As)/Cyanide
        Some non-competitive inhibitors bind reversibly & irreversibly
Immobilised Enzymes
- Are enzymes that are trapped on an inert matrix
  - E.g a gel capsule or in alginate beads
- Example of reactions
  - Fermentation
  - Making lactose-free milk
  - In washing powders
    - Some people are allergic to biological washing powders. By encapsulating the enzymes. These are released only when being washed 
  - Making Baby food
    - Pectinases break down pectin in cell walls releasing the fruit juice etc
  - In Biosensers
- Advantages
  - Products can be easily recovered without contaminating the enzyme
  - The immobilised enzymes can be reused (lowering costs)
  - They can tolerate a wider range of conditions enzymes are more stable when immobilised
    - E.g temp and pH
  - Enzymes can be removed & added which means that there is more control over the rate of reaction
  - Can be used in a continuous production systems
- Disadvantages
  - Works more slowly than free enzymes
  - If encapsulated in beads- Substrate has to penetrate beads to contact enzyme: meaning sometimes only surface enzymes catalyse reactions
Biosensors
- Devices which measure the concentration of a specific metabolite in a mixture
  - When the mixture passes over the enzyme, a reaction occurs
    - The energy released is proportional to the concentration of the substrate
      - This is converted into an electrical impulse
        An accurate digital display is shown
        Because enzymes are specific to a given substrate the results are highly accurate even at low concentrations
        This can be used to diagnose & monitor those w/diabetes
- Advantages
  - Can be quantitive
  - Can detect very small amounts of molecules
  - Detects only a specific product
  - Accurate