SAT II Biology E : Enzymes

Study concepts, example questions & explanations for SAT II Biology E

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Example Questions

Example Question #1 : Enzymes

Which of the following statements about enzymes is true?

Possible Answers:

Enzymes work best only at certain temperatures.

Enzymes are lipids.

Enzymes are useful for slowing down reactions in living things.

Enzymes will work at any pH value.

Correct answer:

Enzymes work best only at certain temperatures.

Explanation:

Enzymes have an "optimal temperature," or best temperature that they work at. If that temperature is below or above its optimal temperature, the enzyme will decrease in activity; if the temperature change is great enough, the enzyme could even denature (no longer work).

Example Question #2 : Enzymes

Cellular respiration involves a series of chemical reactions. Which of the following is a primary way that enzymes affect these reactions?

Possible Answers:

They increase the rate of reactions

They take the place of oxygen as a reactant

They decrease the pH of the products

They change the location of the reactions in the cell

Correct answer:

They increase the rate of reactions

Explanation:

The questions is asking how enzymes affect reactions. The function of an enzyme is to speed up chemical reactions, which will increase the overall rate of the reaction, thus "increasing the rate of the reaction" is the correct answer. 

Example Question #3 : Enzymes

The role of an enzyme in a chemical reaction is to change which of the following?

Possible Answers:

The type of reaction

The activation energy of the reaction

The temperature at which the reaction occurs

The pH at which the reaction occurs

Correct answer:

The activation energy of the reaction

Explanation:

The function of an enzyme is to speed up chemical reactions. They do this by lowering the activation energy, which is the minimum energy that must be available for a chemical reaction to occur. If the energy required is lowered, the reaction can go faster. Thus the correct answer is an enzyme changes "the activation energy of the reaction."

Example Question #4 : Enzymes

The reactants in an enzyme-catalyzed reaction are known as __________.

Possible Answers:

products

substrates

active sites

pHs

Correct answer:

substrates

Explanation:

A reactant is a substance that undergoes change during a reaction. During an enzyme reaction specifically, the reactant is called the substrate, as a substrate is the substance in which an enzyme acts on and changes. 

Example Question #5 : Enzymes

What can affect the productivity of an enzyme?

Possible Answers:

pH

None of these

Both pH and temperature

Temperature

Correct answer:

Both pH and temperature

Explanation:

Both pH and temperature can affect how productive an enzyme is. If an enzyme is functioning in an environment that is not at its optimal pH or optimal temperature, the enzyme's activity will decrease. 

Example Question #6 : Enzymes

If enzymes stop working, they have __________.

Possible Answers:

reached their optimal temperature

reached their optimal pH

turned into a substrate 

denatured

Correct answer:

reached their optimal temperature

Explanation:

Denature means to destroy the properties of a protein or other biological macromolecule. If an enzyme (which is a protein) stops working, it has denatured.

Example Question #7 : Enzymes

Why are enzymes necessary for most cellular reactions?

Possible Answers:

Enzymes increase the temperature of the reaction.

Enzymes supply the water necessary for biochemical reactions.

Enzymes make it so reactions that are nonspontaneous occur spontaneously.

They help reactions occur at a rate compatible with that necessary for sustenance of life.

Correct answer:

They help reactions occur at a rate compatible with that necessary for sustenance of life.

Explanation:

An enzymes function is to speed up chemical reactions by lowering the activation energy. If our bodies did not have enzymes, the reactions would take place, but too slowly for our cells to adequately function.

Example Question #8 : Enzymes

Many enzymes have sites on them where the binding of specific molecules will increase or decrease the activity of the enzyme. What is the name of this type of site?

Possible Answers:

Binding site

Cofactor site

Active site

Catalytic site

Allosteric site

Correct answer:

Allosteric site

Explanation:

The correct answer is "allosteric site." A molecule that binds to an enzyme's allosteric site induces a conformational change in the enzyme, decreasing or increasing the affinity of the enzyme’s binding sites to the substrate. The binding site binds and orients the substrate. The catalytic site lowers the activation energy of the reaction. The binding site and the catalytic site together make up the active site. Cofactors are parts of certain enzymes and are required for those enzymes to function.

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