Question

The active site of an enzyme a. is identical to that of any other enzyme. b. is the part of the enzyme where the substrate can fit. c. can be used over and over. d. is where the coenzyme binds. e. Both b and c are correct.

Short answer

The correct answer is e. Both b and c are correct, as the active site is the part of the enzyme where the substrate can fit, and it can be used over and over.

Step-by-step solution

Option a

The statement says, the active site of an enzyme is identical to that of any other enzyme. This statement is incorrect because the active site of each enzyme is unique to its specific substrate, making it specific to its function.

Option b

The statement says, the active site is the part of the enzyme where the substrate can fit. This statement is correct because the active site is the region of an enzyme where the substrate binds, and the enzyme's specific shape allows the substrate to fit.

Option c

The statement says, the active site can be used over and over again. This statement is correct because, in most cases, the active site of an enzyme can be reused multiple times without being permanently altered, allowing the enzyme to catalyze many reactions.

Option d

The statement says, the active site is where the coenzyme binds. This statement is incorrect because the coenzyme usually binds to a different site on the enzyme called the allosteric site, not the active site. The active site is where the substrate binds to undergo a chemical reaction.

Option e

This statement says that both Option b and Option c are correct. As we have discussed, Option b is correct, and Option c is also correct. Therefore, Option e is the correct answer to this exercise. In conclusion, the correct answer to this exercise is: e. Both b and c are correct.

Key concepts

Enzyme Specificity

Enzyme specificity refers to the unique capability of enzymes to select their specific substrate, much like a lock and key mechanism. This specificity arises from the distinct shape and functional groups of the enzyme's active site. Only the specific substrate, which acts like a key, can fit into the precise lock formed by the active site. This ensures that each enzyme catalyzes only one particular reaction. - Ensure you remember that every enzyme is specialized for a specific reaction.
- This specialization minimizes errors and increases efficiency in biochemical pathways.

Substrate Binding

Substrate binding occurs at the enzyme's active site, where the substrate fits snugly due to complementary shapes. When a substrate arrives at the active site, various interactions such as hydrogen bonds, ionic bonds, or van der Waals forces facilitate binding.
A good analogy is fitting a puzzle piece into its respective spot, meaning only the right substrate can fit into the active site of the enzyme, just like only a correctly-shaped puzzle piece fits into place. - Think of this as a precision fit that activates the enzyme.
- This binding is critical because it positions the substrate correctly for the chemical reaction to occur.

Enzyme Reusability

Enzymes have an impressive ability to be used over and over again, making them efficient tools for catalysis. After a substrate has been converted into a product, the enzyme remains unchanged and is ready to bind another substrate molecule. This reusability allows a single enzyme molecule to process thousands of substrate molecules. - Reusability is a key property distinguishing enzymes from many other catalysts.
- Think of enzymes as industrious workers that don't tire after completing a task, instead, they're ready to jump onto the next task without any delay.

Allosteric Site

The allosteric site is a different location on an enzyme, distinct from the active site. Binding of molecules, such as coenzymes or regulators, at this site can modify the enzyme's activity. This effect is often non-catalytic, but it can either activate or inhibit the enzyme's function. - A crucial point is understanding that regulation through allosteric sites helps control metabolic pathways.
- These sites act like switches, turning the enzyme's activity on or off based on cellular needs.
Overall, the interplay between active sites and allosteric sites ensures precise regulation of enzyme activity, vital for maintaining homeostasis.