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RELEVANT LEARNING OUTCOME:
(a) Explain the mode of action of enzymes in terms of an active site, enzyme-substrate complex, lowering of activation energy and enzyme specificity using the lock-and-key and induced-fit hypotheses.
🕐 Estimated time for this section: 5 minutes
How enzymes work
How enzymes work
All enzyme-catalysed reactions include at least three steps:
1. the binding of a substrate (S) to an enzyme (E) to form a short-lived enzyme-substrate complex (ES),
2. the conversion of ES to the enzyme-product complex (EP), and
3. the release of the product (P) from EP, to yield free P and free E
Note that the video is showing an anabolic reaction.
Anabolic reaction
Anabolic reaction
Enzymes catalyse anabolic reactions such as when cells build up or synthesize complex substances from simpler ones.
For example, amino acids taken into cells may be used to build proteins.
Catabolic reaction
Catabolic reaction
Enzymes catalyse catabolic reactions such as when cells break down complex substances to simple substances.
In cell respiration, glucose is broken down to release energy and form carbon dioxide and water. This process involves a chain of chemical reactions and a series of enzymes.
🖊️Check Your Understanding: Learning Goals Checkpoint
🖊️Check Your Understanding: Learning Goals Checkpoint
1. Why does formation of ES complex not necessarily translate to the formation of EP complex?
E+S and ES is in equilibrium because the formation of ES complex might not go on and form products. Instead, the ES complex may fall apart back to the reactants.
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