Term Definition
Active site Site on surface of the enzyme to which the substrate binds
Substrate A molecule which after combining with an enzyme is converted to a
product
How do enzymes lower activation energy
- Enzyme binds to substrate
- Lowers activation energy
- By wearing bonds
- Making substrate more likely to react
Outline how lock and key model catalyse reactions
- It explains the ability of specific enzymes to bind to specific substrates
- Substrates fits exactly into the complementary shape to the active site of enzyme to form an
enzyme substrate complex by lowering the activation energy
- The active site can be changed by different chemicals/temperature/oH, so substrate can’t bind
Outline how induced fit model catalyse reactions
- It explains the ability of some enzymes to bind to several substrates
- Active site of enzyme binds to substrate, but they do not match up exactly
- Enzyme changes shape once bound, and this change in shape facilitates bond breaking by
reducing activation energy
- Once complete, products leave and enzyme works again
How active sites promotes enzyme-substrate specificity
- Shape of active site matches that of the substrate
- Active site can change to induce fit of substrate
Explain enzyme-substrate specificity
- Enzyme shape is specific to substrate
- Lock and key model
- Lipid and Lipase
- Has specific 3D shape essential to functioning
- Active site on enzyme binds to substrate
- Substrate and active site complementary due to structure
- Enzyme substrate complex forms
- Denaturation changes enzyme’s binding ability
Explain the effects of pH on enzyme catalysed reactions
- Enzymes has a optimum pH
- Active sites work best at this pH
- Activity decreases above and below the optimum
- By interfering with H-bonds
- Denaturing by extremes of pH so enzyme activity stops
- The formation of the enzyme-substrate complex and binding to active site
Effect to enzyme when exposed to increasing temperatures
- Rate of reaction increases when temperature increases as there is a greater proportion of
molecules with energy greater than the activation energy
- Maximum rate is achieved at optimum temperature
- Rate decreases above optimum temperature as enzymes are denatured at high temperature
- Heat causes vibration inside the enzyme which breaks bonds for maintaining the structure of
enzyme
- To form enzyme substrate, substrate should fit in active site of enzyme
- Since shape of active site has changed, substrate cannot bind to the enzyme
Explain the effect of change of pH, substrate concentration and
temperature on enzyme activity
pH:
- Enzymes have an optimum pH
- Activity increase as pH gets closer to optimum pH
- Extreme pH denatures enzymes by breaking bonds and altering structure
Substrate:
- As substrate concentration increases, activity increases
- As substrate concentration increases, the collisions between substrate and enzyme increases
- Till a plateau is reached and/or all active sites are occupied
Temperature:
- Enzymes have an optimum temperature
- Activity increases as it gets closer to optimum temperature
- High temperatures stop enzyme activity due to irreversible changes in structure by breaking
bonds
Explain the production of lactose-free milk
- Lactase added to milk
- Lactose hydrolysed into glucose and galactose
- For those who are lactose intolerant
- Increases sweetness and smooth texture
Discuss the use of lactase in the production of lactose-free milk
- Lactose is a disaccharide present in milk
- Lactase digests lactose into galactose and glucose
- Lactase produced naturally by yeast
- Biotechnology companies isolate lactase for use in food processing
- Lactase can be added to milk to reduce the level of lactose in the milk
- Immobilised enzymes may be used
- Lactose intolerant people cannot drink milk
- Galactose and glucose are sweeter than lactose
- So less sugar is need in food production
- Bacteria ferment glucose and galactose more quickly than lactose
- Galactose and glucose are more soluble so improve the texture of foods
