IB Review: Enzymes

In an enzyme-catalyzed reaction, the _____ binds to the _____ .

• Substance, enzyme

• Substrate, enzyme

• Substrate, active site

• Substrate, allosteric site

An increase in which of these factors will guarantee an increase in enzyme activity?

• Temperature

• pH

• Substrate concentration

• Amount of enzyme present

How would you expect the optimum pH of enzymes to vary between the stomach and acidic hot springs?

• The optimum pH would be roughly the same.

• The optimum pH in acidic hot springs would be much lower than the stomach

• The optimum pH in acidic hot springs would be much larger than the stomach

• Depends on the enzyme.

Catalase is an enzyme produced in the liver. It decomposes hydrogen peroxide into water and oxygen gas. Where would you expect its optimum temperature to be?

• It has no optimum temperature since the higher the temperature, the more collisions.

What type of macromolecule is an enzyme?

• Carbohydrate

• Lipid

• Protein

• Nucleic acid

Answer explanation

Enzymes are proteins that speed up chemical reactions.

Pepsin is an enzyme that is produced in the stomach to break down proteins. What would be the optimal pH for pepsin?

• 2

• 6

• 8

• 14

Answer explanation

The stomach is acidic, meaning it has a low pH. Since pepsin works in the stomach, the optimal pH should also be low (acid).

Every enzyme has a specifc shape that matches to a substrate. What is the region of the enzyme that binds to the substrate called?

• the reaction center

• the active site

• the sustrateolli

• the product-maker

Answer explanation

The active site of the enzyme is a specific shape that binds to that enzyme's substrate.

If an enzyme is denatured, what happens to the shape of the active site?

• It becomes deformed and does not match the substrate

• It becomes expanded and can fit more of the substrate

• It becomes smaller and the substrate also shrinks

• It becomes reversed and the reaction will go backwards

Answer explanation

When an enzyme is denatured it looses its shape and can no longer function.

The shape of the active site changes and so the substrate doesn't match any more.

Human body temperature is around 37 ^oC. There is a bacteria species that lives in a hot spring. The hot spring can reach temperatures of 80 ^oC What would be the optimal temperature of the enzymes in this bacteria?

• 20 ^oC

• 37 ^oC

• 80 ^oC

• 115 ^oC

Answer explanation

Optimal temperatures for enzymes depend on where they live. The bacteria lives in the hot spring so it must be adapted to survive there.

Select all that apply: Which of the following factors can cause an enzyme to become denatured?

• optimal conditions

• changes in pH

• Extreme heat

• cold

Answer explanation

High temperatures (beyond the optimal temperature) and changes to an enzyme's pH can both affect the shape.

Cold temperatures slow down an enzyme but don't make it denature.