2.4 Enzymes Flashcards
What are enzymes?
proteins that speed up the rate of chemical reactions and act as biological catalysts.
What are the two models ?
- Lock and key (old)
- Induced fit (new)
explain the lock and key theory.
The active site and substrate have a complimentary shape and stay the same shape.
explain the induced fit model
substrate has to fit the active site and make the active site change shape.
Go through steps from substrate to product
- substrate enters active site and forms enzyme substrate complex
- Then forms enzyme product complex
- then products released from active site
what are the factors that affect enzyme activity?
- Temperature
- PH
- enzyme concentration
- substrate concentration
How does temp affect enzyme activity?
Increase in temp increases kinetic energy and so more successful collisions happen. This increase until after optimum temp. If too high enzyme denatures and bonds of enzyme are broken so active site changes shape
How does PH affect enzyme activity?
Optimum is 7 for humans. At optimum no hydrogen bonds of enzymes tertiary structure are broken so active site stays same. If this is to high to low of a PH then these bonds break and active site changes shape.
Explain how enzyme conc affects enzyme activity.
Increased enzymes increases chances of successful collision but if substance concentration is limited then there’s a point when increasing enzyme concentration won’t have any effect.
Explain how substrate conc has an effect on enzyme activity.
Increased substrate concentration increases the rate of reaction as more successful collisions because more active sites are full and more enzyme substrate complexes are formed. However, there’s a point at which adding more makes no difference as all the active sites are full.
What is a cofactor?
A non-protein substance that binds to an enzyme to help it work.
What are inorganic co factors.
Co factors that help bind enzyme and substrate together but don’t participate in the reaction and aren’t used up in any way.
What’s an organic co factor?
Co factor that participates in the reaction and is changed. Often acts as carriers moving chemical groups between enzymes.
What’s a competitive inhibitor?
Inhibitor that has similar shape to substrate and competes with substrate to fit in the active site. Once in active site they block it. Can be overcome by increase conc of substrate.
What’s a non competitive inhibitor?
An inhibitor that binds to the allosteric site. Not active site. Changed the shape of active site so substrate can no longer fit and make enzyme substrate complex. Can’t be competed with so increasing conc of substrate won’t increase rate of reaction or make any difference.
