Question 1

An enzyme is thought to optimize the fit between substrates by restraining and stretching or squeezing them into certain shapes and moving them to the transition state as described by the __________ model of enzyme activity.

Accepted Answer

A) lock and key 
B) induced-fit 
C) template 
D) activation 
E) conformational

Question 2

The active site of an enzyme

Accepted Answer

A) is where the coenzyme is located. 
B) is a specific bulge or protuberance on an enzyme. 
C) is a groove or crevice in the structure of the enzyme complementary to the substrate. 
D) will react with only one substrate no matter how many molecules may resemble the shape of the substrate. 
E) rigidly resists any alteration of its shape.

Question 3

Enzymes

Accepted Answer

A) are very specific. 
B) act as catalysts. 
C) are organic molecules. 
D) have special shapes that control their activities. 
E) are all of these.

Question 4

All of the following result from an increase in entropy EXCEPT

Accepted Answer

A) water from a melting ice cube. 
B) destruction from a tsunami. 
C) a decomposed body from a living body. 
D) glucose molecules from photosynthesis. 
E) ashes from burning paper.

Question 5

Coenzymes such as NAD+ and NADP+

Accepted Answer

A) are tightly bound to enzymes. 
B) are associated with metal ions. 
C) diffuse freely through the cytoplasm. 
D) are not modified in reactions. 
E) all of these.

Question 6

Which of the following statements about exergonic reactions is false?

Accepted Answer

A) They release energy. 
B) Glucose metabolism is an example. 
C) Their products have more energy than the reactants. 
D) Some energy is converted to less biologically useful forms. 
E) Bonds are broken.

Question 7

All of the following are true of the process of phosphorylation EXCEPT that

Accepted Answer

A) a molecule gains a phosphate group. 
B) a molecule loses a phosphate group. 
C) molecules become less stable. 
D) it is used to prime molecules to react. 
E) it produces ADP from ATP.

Question 8

In oxidation-reduction reactions, all of the following are true EXCEPT

Accepted Answer

A) one molecule gives up electrons. 
B) one molecule gains electrons. 
C) cells release energy. 
D) the molecule that accepts electrons is oxidized. 
E) hydrogen ions are usually released.

Question 9

In some cases, inhibitors or activators of enzyme-catalyzed reactions act by

Accepted Answer

A) binding to the substrates. 
B) affecting the supply of ATP. 
C) reversibly binding to an enzyme's allosteric site. 
D) reducing or increasing the concentration of enzymes. 
E) binding to the products.

Question 10

The activation energy of a reaction refers to the minimum amount of energy

Accepted Answer

A) released by the reaction. 
B) in the reactants. 
C) in the products. 
D) necessary to cause it to proceed on its own. 
E) difference between the energy of the reactants and the energy of the products.

Question 11

Enzyme activity may be affected by

Accepted Answer

A) salinity. 
B) pH. 
C) inhibitors. 
D) the presence of cofactors. 
E) all of these.

Question 12

Questions refer to the figure above.
 
-An enzyme substrate complex is represented by

Accepted Answer

A) C. 
B) D. 
C) E. 
D) D and E. 
E) None of these.

Question 13

Enzyme activity may be affected by

Accepted Answer

A) temperature. 
B) the presence of chemicals that fit into allosteric sites. 
C) feedback inhibition. 
D) metabolic conditions in the cell. 
E) all of these.

Question 14

The activation energy for a reaction

Accepted Answer

A) is less when enzymes are present. 
B) allows greater interaction of substrate with the active site. 
C) is needed to begin a reaction. 
D) puts the substrate at its transition state. 
E) is all of these.

Question 15

Currently, the most serious drug problem on campuses is

Accepted Answer

A) methamphetamine addiction. 
B) cocaine addiction. 
C) marijuana addiction. 
D) codeine addiction. 
E) binge drinking.

Question 16

Endergonic reactions

Accepted Answer

A) result in products with less energy than the reactants. 
B) require a net input of energy. 
C) occur in the breakdown of glucose. 
D) are used by cells to provide energy for biological reactions. 
E) break down large molecules into smaller molecules.

Question 17

All of the following are factors in enzyme-catalyzed reactions that work alone or in combination to lower the activation energy EXCEPT

Accepted Answer

A) helping substrates get together. 
B) orienting substrates in positions favoring reaction. 
C) using ATP as an energy source. 
D) shutting out water molecules. 
E) inducing a fit between enzyme and substrate.

Question 18

Enzymatic reactions can be controlled by

Accepted Answer

A) the amount of substrates available. 
B) the concentration of products. 
C) activation of enzymes. 
D) inhibition of enzymes. 
E) all of these.

Question 19

Which of the following statements is true of metabolic pathways?

Accepted Answer

A) They are enzyme-mediated sequences of reactions. 
B) They may be biosynthetic or degradative. 
C) Photosynthesis is a biosynthetic pathway. 
D) Catabolism is a degradative pathway. 
E) All of these are true.

Question 20

CO2 and H2O will not form glucose on their own because

Accepted Answer

A) CO2 does not contain sufficient energy. 
B) H2O does not contain sufficient energy. 
C) neither CO2 nor H2O contain sufficient energy. 
D) the concentration of CO2 is too low in the atmosphere. 
E) the bonds of CO2 and H2O are too stable to be broken without an input of energy.

Exam 6: Ground Rules of Metabolism

An enzyme is thought to optimize the fit between substrates by restraining and stretching or squeezing them into certain shapes and moving them to the transition state as described by the __________ model of enzyme activity.

The active site of an enzyme

Enzymes

All of the following result from an increase in entropy EXCEPT

Coenzymes such as NAD⁺ and NADP⁺

Which of the following statements about exergonic reactions is false?

All of the following are true of the process of phosphorylation EXCEPT that

In oxidation-reduction reactions, all of the following are true EXCEPT

In some cases, inhibitors or activators of enzyme-catalyzed reactions act by

The activation energy of a reaction refers to the minimum amount of energy

Enzyme activity may be affected by

Questions refer to the figure above. -An enzyme substrate complex is represented by

Enzyme activity may be affected by

The activation energy for a reaction

Currently, the most serious drug problem on campuses is

Endergonic reactions

All of the following are factors in enzyme-catalyzed reactions that work alone or in combination to lower the activation energy EXCEPT

Enzymatic reactions can be controlled by

Which of the following statements is true of metabolic pathways?

CO₂ and H₂O will not form glucose on their own because