2.1.4 Enzymes – Factors Affecting Enzyme Action Flashcards
(15 cards)
What factors affect enzymes?
- Temperature
- pH
- enzyme concentration
- substrate concentration
What effect does an increase in temperature have on enzyme activity?
An increase in temperature increases the rate of enzyme activity.
Why does an increase in temperature increase the rate of enzyme activity?
The substrate and the enzyme are provided with more kinetic energy so the frequency and force of successful collisions will increase.
What affect can high temperatures have on enzymes?
High temperatures can cause enzymes to denature.
What has happened when an enzyme has denatured due to temperature?
The high temperature has caused molecules within the enzyme to vibrate more and has broken weak ionic/hydrogen bonds holding the precise 3D tertiary structure of the enzyme in place. This irreversibly changes the shape of the active site so enzyme-substrate complexes are slower to form or even not possible to form.
What does optimum temperature mean?
The temperature when the enzyme is working at its maximum rate.
What is the temperature coefficient Q10?
The increase in rate of a process when the temperature is increased by 10°C
Q10 = rate of reaction at (T+10) ºC / rate of reaction at T
What does optimum pH mean?
The pH at which the enzyme has the best overall shape and therefore fastest rate.
What effect do small changes to pH have?
Small changes either side of the enzymes optimum will slow the rate of reaction but the active site will return to normal if the pH is corrected.
What effect do large changes to pH have?
Extreme changes to pH will permanently change the shape of the active site, denaturing the enzyme.
Why do small and large changes to pH have these effects?
Excess H+ ions interfere with the hydrogen and ionic bonds which hold the enzymes 3D shape causing a change to the active site’s shape.
What are buffers and how do they affect pH?
Buffers resist changes in pH by donating or accepting hydrogen ions. They can be found naturally in the body or can be used in investigations to keep pH constant.
Describe the effect of substrate concentration on enzyme activity?
The more substrate there is the more enzyme-substrate complexes can be formed so more product is formed until a maximum rate is achieved (Vmax) at which point all the active sites are occupied so enzyme concentration is now limiting.
Describe the effect of enzyme concentration on enzyme activity?
The greater the number of enzyme molecules the more successful collisions with the substrate molecules. There will therefore be a faster rate of reaction as more enzyme-substrate complexes can form. This will only happen if there is an excess of substrate present.
Why might there be a lack of enzymes in an organism?
- Enzyme synthesis might be slow- it sometimes depends on genes being switched on or off
- Enzyme degradation- they are constantly being remade in order to eliminate abnormally shaped molecules and to eliminate any surplus.
