Biological molecules

• Enzyme's active se


  Single polypeptide chan
• Amino acids


  Form the enzyme of 50 amino acids which
• Bond such as a

  Hydrogen bond
• Not forming


  Part of the active site
• Catalysts


  • Define a catalyst
• Why enzymes


  Explain why enzyme's active site could pr
• Why enzyme's active site


  Explain why also pr
• Amino acids


  • 2 of the 6 amino acids which bind to the substrate which maintains enzyme's shape
• Figure 2 Example of an enzyme-substrate complex

  • Showing the six out of the 50 amino acids that form the active site
• Induced fit model of enzyme action

  Scientists often try to explain their observations by producing a representation of how something works. This is known as a scientific model. Examples include the physical models used to explain enzyme action. The induced fit model of enzyme action proposes that the active site forms as the enzyme and substrate interact. The proximity of the substrate (a change in the environment of the enzyme) leads to a change in the enzyme that forms the functional active site (Figure 3). In other words, the enzyme is flexible and can mould itself around the substrate in the way that a glove moulds itself to the shape of the hand. The enzyme has a certain general shape, just as a glove has, but this alters in the presence of the substrate. As it changes its shape, the enzyme puts a strain on the substrate molecule. This strain distorts a particular bond or bonds in the substrate and consequently lowers the activation energy needed to break the bond.
• Any change in an enzyme's environment is likely to change its shape. The very act of colliding with its substrate is a change in its environment and so its shape changes -induced fit.
• Lock


  One earlier proposed that the same way as the lock-eac shape that a single w substrate site of on
• This model observes that specified catalys (key) the en as the
• Opposites


  The correct term is complementary
• Effect of temperature on enzyme action

  1. Rise in temperature increases kinetic energy of molecules

  2. Molecules move around more rapidly and collide more often

  3. Enzyme and substrate molecules come together more often in a given time

  4. More effective collisions

  5. More enzyme-substrate complexes formed

  6. Rate of reaction increases
• Rise in temperature


  Begins to cause hydrogen and other bonds in enzyme molecule to break
• Enzyme shape change


  Substrate fits less easily into changed active site, slowing rate of reaction
• At around 60°C, enzyme is so disrupted that it stops working altogether, it is said to be denatured
• Denaturation is a permanent change and, once it has occurred, the enzyme does not function again
• Measuring rate of change

  1. Measure gradient of tangent to curve at chosen point

  2. Tangent is line that touches curve without cutting across it

  3. Use normal line to accurately draw tangent
• Fundamental experimental technique is changing only a single variable in each experiment
• When investigating effect of a named variable, all other variables must be kept constant
• Active site and substrate are complementary, not the same