Question

why is the shape of an enzyme important for its ability to catalyze a chemical reaction? select all that apply.
the reactants fit precisely in an enzymes active site, so different reactants cannot fit into the enzyme.
the shape of the enzyme forces the reactants into spatial orientations where a chemical reaction between the reactants is more likely.
when one reactant enters an enzymes active site, the reactant can change the shape of the active site to better fit other reactants.
the shape of the enzyme affects the free energy that the enzyme provides, which makes a nonspontaneous reaction spontaneous.

Explanation:

• First option: Enzymes have specific active sites where reactants (substrates) fit precisely (lock - and - key model). Different reactants (non - complementary to the active site) cannot bind.
• Second option: The shape of the enzyme's active site can orient the reactants in a way that the chemical bonds that need to react are in close proximity and proper spatial orientation, increasing the likelihood of the reaction.
• Third option: This is in line with the induced - fit model. When a reactant (substrate) binds to the active site, it can cause a conformational change in the enzyme (active site) which can then better accommodate other reactants (if it is a multi - substrate reaction).
• Fourth option: Enzymes lower the activation energy of a reaction, but they do not change the free energy change ($\Delta G$) of the reaction. A non - spontaneous reaction ($\Delta G>0$) will remain non - spontaneous even in the presence of an enzyme.

Answer:

• The reactants fit precisely in an enzyme's active site, so different reactants cannot fit into the enzyme.
• The shape of the enzyme forces the reactants into spatial orientations where a chemical reaction between the reactants is more likely.
• When one reactant enters an enzyme's active site, the reactant can change the shape of the active site to better fit other reactants.