| Measuring enzyme-catalysed reactions
(Changes that most frequently measured) | - The formation of the products
- The disappearance of the substrate |
| Graph of the formation of products | - |
| Graph of the disappearance of the substrate | - |
| Explanation for the graphs | - Lots of substrates at first but no products
- Substrates bind to active sites, and are broken down into products
- Substrate decreases
- Product increases
- Less substrates to bind to enzymes and products get in the way
- Rate of formation of product and disappearance of substrate decreases
- Both graphs plateau as the substrates have been used up |
| Factors that affect enzymes | - Temperature
- pH
- Enzyme concentration
- Substrate concentration
- Presence of inhibitors |
| Denature meaning | - When the active site has changed shape
- Breaks hydrogen bonds holding tertiary structure together
- Enzyme and substrate don't fit together
- The enzyme no longer functions as a catalyst |
| Temperature affecting enzymes | - Increase in temperature increases rates of reaction
- Enzymes vibrate more + collide more with substrates (more kinetic energy)
- Form more enzyme-substrate complexes
- If temperature is too high, it breaks the bonds that hold the enzyme
- Enzyme is denatured
- Formation of enzyme substrate complexes decreases |
| pH affecting enzymes | - All enzymes have an optimum pH value
- Most human enzymes work at a pH of 7
- If pH is too low or too high the H+ and OH- ions found in acids and alkalis breaks the bonds holding the enzyme
- Enzyme denatures |
| Enzyme concentration affecting enzymes | - Increasing the enzyme concentration increases rates of reaction
- More collision between substrates and enzymes
- Excess enzymes has no further effect as there will be less substrates available |
| Substrate concentration affecting enzymes | - Increasing substrate concentration increases rates of reaction
- More collision between substrates and enzymes
- Excess of substrate has no further effect as all active sites used up
- This makes the initial rate of reaction the highest rate of reaction |
| Why calculate initial rate of reaction | - It is when the reaction is fastest
- Allows comparison |
| How do you use a tangent on a curve to calculate the rate | - Draw straight line on curve (90 degrees)
- Draw triangle from it
- Divide the vertical line by the horizontal line |
| How to find the rate of reaction on a line graph | - Draw a triangle from the line
- Divide the vertical line by the horizontal line |
| How to calculate pH using calculator | -Log10 (H+)
e.g. -Log10 (5.4 x 10^-3) |
