Enzymes Flashcards
What is an enzyme?
A protein or RNA that acts as a catalyst and so alters the speed of a biochemical reaction.
What is the difference between the induced fit model and the lock and key model of enzyme action?
Induced fit model: The active site forms as the enzyme and substrate interact.
Lock and key model: A substrate will only fit the active site of one specific enzyme
Why are enzymes specific?
Enzymes, being globular proteins, have a specific 3D shape that is result of their primary protein structure.
What is the effect of enzyme concentration on an enzyme controlled reaction?
Enzymes are not used up in enzyme-controlled reactions and therefore work efficiently at very low concentrations. If the substrate is limiting then any increase in enzyme concentration will have no effect on the rate of reaction.
What is the effect of substrate concentration on an enzyme controlled reaction?
Concentration of enzyme is fixed and the substrate concentration is slowly increased: Rate of reaction increases
Excess of substrate: The graph would level off.
What is the effect of pH on an enzyme controlled reaction?
An increase or decrease in pH away from the optimum reduces the rate of enzyme action. If the change in pH is beyond a certain pH the enzyme becomes denatured.
How does a change in pH affect an enzyme?
Alters the charges on the amino acids that make up the active site of the enzyme. As a result, the substrate can no longer become attached to the active site and so the enzyme substrate complex cannot be formed.
What is the effect of temperature on an enzyme controlled reaction?
Increases the kinetic energy of molecules. This means that more enzyme substrate complexes are formed, thus increasing the rate of reaction.
What is denaturation? (In relation to temperature)
A temperature rise begins to cause the hydrogen and other bonds in the enzyme molecule to break. This results in the enzyme, including its active site, changing shape.
What is the effect of denaturation on an enzyme controlled reaction?
At first, the substrate fits less easily into the changed active site, slowing the rate of reaction.
