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?
Enzymes are useful for slowing down reactions in living things.
Enzymes are lipids.
Enzymes will work at any pH value.
Enzymes work best only at certain temperatures.
Enzymes work best only at certain temperatures.
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?
They decrease the pH of the products
They change the location of the reactions in the cell
They increase the rate of reactions
They take the place of oxygen as a reactant
They increase the rate of reactions
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 #1 : Enzymes
The role of an enzyme in a chemical reaction is to change which of the following?
The temperature at which the reaction occurs
The pH at which the reaction occurs
The type of reaction
The activation energy of the reaction
The activation energy of the reaction
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 #3 : Enzymes
The reactants in an enzyme-catalyzed reaction are known as __________.
pHs
active sites
products
substrates
substrates
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 #4 : Enzymes
What can affect the productivity of an enzyme?
pH
Temperature
None of these
Both pH and temperature
Both pH and temperature
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 #5 : Enzymes
Why are enzymes necessary for most cellular reactions?
Enzymes make it so reactions that are nonspontaneous occur spontaneously.
Enzymes supply the water necessary for biochemical reactions.
They help reactions occur at a rate compatible with that necessary for sustenance of life.
Enzymes increase the temperature of the reaction.
They help reactions occur at a rate compatible with that necessary for sustenance of life.
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 #2 : 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?
Allosteric site
Catalytic site
Cofactor site
Active site
Binding site
Allosteric site
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.
Example Question #2 : Enzymes
If enzymes stop working, they have __________.
reached their optimal pH
turned into a substrate
denatured
reached their optimal temperature
denatured
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.
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