Question

reaction to occur, and 2) lower activation energies?
the answer is one word: enzymes.
enzymes are proteins that act as catalysts, meaning that they make reactions go faster but arent changed by them--the structure of an enzyme is the same before and after the reaction. more specifically, proteins have areas called active sites where a particular chemical reaction takes place.
each enzyme catalyzes one particular reaction because the size, shape, and chemical composition of the active site is such that the reactants fit into the space, bind to r-groups in the active site in a way that places them 1) in the correct orientation to each other, and 2) in close proximity to charges or protons or other components of r-groups that stabilize the transition state and lower the reactions activation energy.
the active site is where reactants encounter each other in the correct spatial orientation, and where bonds that are being broken are stabilized by interactions with specific r-groups, so the activation energy threshold goes down.
one more key point about enzymes: they dont change the free energy of the reactants or the products, meaning that they dont make nonspontaneous reactions spontaneous or vice versa. they just make it much more likely that a spontaneous reaction will actually occur.
why is it appropriate to call an active site \active?\ select the single best answer.
o because of its size, shape, and chemical activity, the site is specific to one particular reaction.
o its the place where a nonspontaneous reaction becomes an active, spontaneous one.
o its the location where chemical activity--a reaction--takes place.
enzymes make nonspontaneous reactions go.
o true
o false

Explanation:

• For the first question: The text clearly states that the active site is where a particular chemical reaction takes place. The first option is about specificity (not about being "active"), and the second option is wrong as enzymes don't make non - spontaneous reactions spontaneous.
• For the second question: The text says "they don't make nonspontaneous reactions spontaneous or vice versa".

Answer:

• First question: It's the location where chemical activity—a reaction—takes place.
• Second question: False