78 WJEC Biology AS Level - Marianne Izen - 2nd Edition (1.4 Enzymes And Biological Reactions) Flashcards
What are the factors affecting enzyme action
- Temperature
- pH
- Substrate concentration
- Enzyme concentration
What does environmental condition do to the rate of reaction?
Environmental conditions, such as temperature and pH, change the three-dimensional structure of enzyme molecules.
Bonds are broken and the configuration of the active site is altered, changing the rate of the reaction.
What does the concentration of enzyme and substrate do to the rate of reaction
The concentrations of enzyme and substrate also affect the rate of reaction by changing the number of enzyme-substrate complexes formed.
How does temperature affect the rate of reaction?
Increased temperature increases the kinetic energy of enzyme and substrate molecules.
Hence they collide with enough energy more often, increasing the rate of reaction.
What happens to the rate of reaction for every 10 degrees centigrade rise in temperature?
In general, the rate of reaction doubles for each 10 degrees centigrade rise in temperature up to a particular temperature, about 40°C for most enzymes.
What happens to the rate of reaction when the temperature increases beyond 40 degrees centigrade?
- Above this temperature, molecules have more kinetic energy.
- However the reaction rate goes down because their increasing vibration breaks hydrogen bonds, changing the tertiary structure.
- This alters the shape of the active site and the substrate will not fit.
- The enzyme is denatured, a permanent change in structure.
What happens to enzymes at low temperatures?
At low temperatures, the enzyme is inactivated as the molecules have very low kinetic energy.
However, the shape is unchanged and the enzyme will work again if the temperature is raised.
What is the effect of pH on the rate of enzyme action?
Most enzymes have an optimum pH, at which the rate of reaction is highest.
Small pH changes around the optimum cause small reversible changes in enzyme structure and reduce its activity.
Extremes of pH denature enzymes.
Explain in detail how ph changes affect enzyme action
The charges on the amino acid side-chains of the enzyme’s active site are affected by hydrogen ions or hydroxide ions.
At low pH, excess H+ ions are attracted to negative charges and neutralise them.
At high pH, excess OH+ ions neutralise the positive charges.
When the ph changes are minimal, the shape of the active site is maintained.
At extremes of pH, the ionic and hydrogen bonds are disrupted. The shape changes, denaturing the enzyme. No enzyme-substrate complexes form and enzyme activity is lost.
Why do you need to take care with units of temperature
Denaturation (Key-Term)
The permanent damage to the structure and shape of a protein molecule, eg, an enzyme molecule, due to, for example, high temperature or extremes of pH.
Inactivation (Key-Term)
Reversible reduction of enzyme activity at low temperature as molecules have insufficient kinetic energy to form enzyme-substrate complexes.
What happens to the primary structure of an enzyme when it is denatured?
When an enzyme molecule is denatured, its primary structure, the order of amino acids, is unaffected but it loses higher levels of structure.
How does higher temperature denature enzymes?
How does extremes of pH denature enzymes?
How do some chemicals denature enzymes?
High temperature denatures enzymes by breaking hydrogen bonds.
Extremes of pH denature enzymes by breaking hydrogen and tonic bonds.
Some chemicals denature enzymes by also breaking disulphide bonds.