enzymes topic 5 Flashcards
What is a catalyst
A substance which increases the rate of reaction without being used up or changed itself
A substance that speeds up a chemical reaction and is not changed by the reaction
What are enzymes
Enzymes are biological catalysts that speed up the rate of metabolic reactions
Describe the structure of enzymes
Enzymes are proteins that contain a highly specific active site that fits a specific substrate
Why are enzymes necessary in biological systems
they speed up reactions so that less energy is needed for the reaction to occur
describe enzyme action
A substrate that fits the specific active site of the enzyme binds to create an enzyme-substrate complex, a reaction occurs (catalysed by the enzyme) and then the products are released
What does the statement ‘enzymes are highly specific’ mean?
The active site of the enzyme must bind to a substrate that has a complementary shape and so only specific reactions can be catalysed
State 4 factors that affect the rate of an enzyme-controlled reaction
Temperature
pH
Substrate concentration
Enzyme concentration
Describe the effect of temperature on the rate of an enzyme controlled reaction
- As the temperature increases, so does the rate of reaction
- Once the temperature exceeds the optimum, the enzyme denature and the rate of reaction decreases
graph looks like an upside down U
Why does the rate of an enzyme-controlled reaction increase when the temperature increases?
- As the temperature increases, the particles have more kinetic energy
- this increases the chance of collisions between molecules being successful and leading to a reaction
If temperature increases above the optimum, how does this affect enzyme function?
The active site will be distorted as the enzyme denatures and so it will no longer fit the substrate
Describe the effect of pH on the rate of an enzyme-controlled reaction
The rate of an enzyme catalysed reaction is fastest at the optimum pH
If the pH is too high or low, the enzyme will work less efficiently and the active site may be denatured at extremes of pH
How does a pH that is very different to the optimum affect enzyme activity
The change in pH will distort the enzyme’s active site (denaturing it) so that it can no longer fit the specific substrate
Explain how enzymes function during a reaction.
[4 marks]
Part of an enzyme molecule is the active site. This is where the reaction takes place. The substrate molecule fits into the active site like a ‘lock and key’. This is because the substrate has a shape that is complementary to the shape of the active site. The chemical reaction takes place, e.g. the substrate is broken down to two product molecules which leave the active site.
