Question 1

Refer to the table below.  Hexokinase catalyzes the reaction between glucose and ATP to form glucose 6-phosphate and ADP.The table summarizes results of experiments using purified hexokinase.In the experiments, different sugars were substituted for glucose, and the rate of each catalytic reaction was measured and divided by the rate of reaction using glucose as substrate.These data provide evidence for which general statement that has been made about enzymes?

Accepted Answer

The table shows that hexokinase has a high specificity for glucose as a substrate, with little to no activity observed with other sugars. This supports the general statement that enzymes display high specificity with respect to their substrates. The other answer choices are also true statements about enzymes, but are not specifically supported by the data in the table.

Question 2

The molecules that are acted on by an enzyme are called

Accepted Answer

Substrates are the specific molecules that bind to and are acted on by an enzyme. They are transformed into products during the catalysis reaction. The other options, such as products, carriers, prosthetics, and effectors, are not directly involved in the enzyme-catalyzed reaction.

Question 3

Which statement about enzymes is false?

Accepted Answer

Enzymes cannot convert an endergonic reaction to an exergonic reaction. Enzymes can lower the activation energy required for a reaction to occur, but they cannot change the thermodynamics of a reaction.

Question 4

In some cases, a substrate-enzyme complex is stabilized by

Accepted Answer

Hydrogen bonds are weak bonds that can form between a substrate and an enzyme, stabilizing the substrate-enzyme complex.

Question 5

The statement "enzymes are highly specific" means that specific

Accepted Answer

Enzymes are highly specific in that they catalyze a specific reaction or set of reactions involving specific substrates. This specificity arises from the unique three-dimensional shape and chemical properties of the enzyme, which allow it to interact with only certain substrates and catalyze specific reactions. Enzymes do not require specific concentrations of substrates or reactants, as they function in the presence of a wide range of concentrations. Similarly, enzymes do not exclusively occur in specific cells or tissues, although some may be more prevalent in certain types of cells. Finally, while enzymes do catalyze reactions with specific activation energies, this is not the basis for their specificity.

Question 6

An RNA molecule that has enzyme activity is called

Accepted Answer

An RNA molecule that has enzyme activity is called a ribozyme.

Question 7

Which of the following affects the rate of a reaction?

Accepted Answer

The rate of a reaction is primarily affected by the activation energy required for the reaction to occur. The activation energy is the energy required for the reactants to overcome the energy barrier and form products. The other answer choices represent different chemical reactions or intermediate states, but they do not directly affect the rate of the reaction. The overall change in free energy (E) can affect the feasibility of a reaction, but it does not necessarily affect the rate of the reaction.

Question 8

Enzymes of the acid-base catalysis type contain

Accepted Answer

Enzymes of the acid-base catalysis type contain acidic or basic amino acid side chains (R groups) in the active site. These side chains can donate or accept protons, which can facilitate the chemical reaction being catalyzed by the enzyme. Examples of acidic amino acids that can act as proton donors include aspartic acid and glutamic acid, while examples of basic amino acids that can act as proton acceptors include lysine and histidine.

Question 9

The five reactions listed are catalyzed by enzymes in a cell.Which reaction is catalyzed by an oxidoreductase?

Accepted Answer

Oxidoreductases are enzymes that catalyze oxidation-reduction reactions, which involve the transfer of electrons between molecules. In choice C, ethanol is oxidized to acetaldehyde while NAD+ is reduced to NADH, indicating that an oxidation-reduction reaction has occurred and thus, this reaction is catalyzed by an oxidoreductase enzyme. The other choices do not involve an oxidation-reduction reaction, and therefore, are not catalyzed by oxidoreductase enzymes.

Question 10

An active site is the

Accepted Answer

The active site is the specific region of the enzyme where the substrate binds and undergoes a chemical reaction. Therefore, it is the part of the enzyme that binds with the substrate.

Question 11

The hydrolysis of sucrose to glucose and fructose is exergonic.However, if sucrose is dissolved in water and the solution is kept overnight at room temperature, there is no detectable conversion to glucose and fructose.Why?

Accepted Answer

Although the hydrolysis of sucrose to glucose and fructose is exergonic, meaning it releases free energy, it still requires an activation energy to overcome the energy barrier and proceed with the reaction. The activation energy for the hydrolysis of sucrose is relatively high, which is why the reaction does not occur spontaneously when sucrose is simply dissolved in water and left at room temperature overnight.

Question 12

Which will not increase the rate of conversion of reactant A to product B in the presence of enzyme C?

Accepted Answer

The addition of a molecule that competes with the substrate (A) for the enzyme's (C) active site would inhibit the reaction rather than increase the rate of conversion of A to B. This is because the competing molecule (D) would decrease the availability of the active site for the substrate (A), thus slowing down the reaction.

Question 13

Trypsin and elastase are both enzymes that catalyze hydrolysis of peptide bonds.However, trypsin only hydrolyzes peptide bonds next to lysine, and elastase only hydrolyzes peptide bonds next to alanine.Why?

Accepted Answer

The shapes of the active sites for the two enzymes are different. The specificity of trypsin and elastase for lysine and alanine, respectively, is due to the shape and complementary nature of their respective active sites. Trypsin has a catalytic triad composed of Asp, His, and Ser residues and a deep, narrow pocket that accommodates the basic side chain of lysine. Elastase, on the other hand, has a smaller pocket with a hydrophobic surface that preferentially binds the small side chain of alanine.

Question 14

The presence of a catalyst affects the

Accepted Answer

Catalysts work by lowering the activation energy (free energy of the transition state) for a reaction, thus increasing the rate at which the reaction reaches equilibrium. They do not affect the position of equilibrium, the overall energy change of the reaction, or the energy of the reactants or products.

Question 15

The enzyme $\alpha$-amylase increases the rate at which starch is broken down into smaller oligosaccharides by _______ of the reaction.

Accepted Answer

Enzymes such as F1F1F1S1F1F1F10-amylase lower the activation energy required to initiate a chemical reaction, making it more likely to occur. In this case, the enzyme increases the rate at which starch is broken down into smaller oligosaccharides by lowering the activation energy required for the reaction to occur.

Question 16

Mechanisms used by enzymes to catalyze reactions are similar in that they all

Accepted Answer

Enzymes catalyze reactions by lowering the activation energy barrier, which stabilizes the transition state of the substrate. Therefore, it is common for all mechanisms used by enzymes to involve the stabilization of the transition state of the substrate. This is the fundamental principle behind enzyme catalysis. While some enzymes do involve transient chemical changes or require cofactors or coenzymes, these are not universal mechanisms used by all enzymes. Similarly, permanent chemical changes are often not desirable as they would affect the enzyme's ability to function over time.

Question 17

The enzyme glyceraldehyde 3-phosphate dehydrogenase catalyzes the reaction glyceraldehyde 3-phosphate $\rightarrow$ 1,3-diphosphoglycerate.The binding of the glyceraldehyde 3-phosphate to the enzyme creates a(n)

Accepted Answer

The binding of glyceraldehyde 3-phosphate to the enzyme forms an enzyme-substrate complex, which is a temporary intermediate in the reaction pathway. The other options are not directly related to this step in the reaction.

Question 18

Refer to the figure below.  Which type of mechanism used by an enzyme to catalyze a reaction is illustrated in the figure?

Accepted Answer

The answer of Refer to the figure below.  Which...

Question 19

The enzyme glucose oxidase binds the six-carbon sugar glucose and catalyzes its conversion to glucono-1,5-lactone.Mannose is also a six-carbon sugar, but glucose oxidase cannot bind mannose.The specificity of glucose oxidase is based on the

Accepted Answer

The specificity of glucose oxidase is determined by the three-dimensional shape and structure of its active site, which can only accommodate glucose due to specific interactions between glucose and the amino acid residues in the enzyme's active site. Mannose, being a different sugar with a slightly different structure, cannot bind to the active site and therefore cannot be catalyzed by glucose oxidase. The other answer choices are not directly related to enzyme specificity.

Question 20

The enzyme sucrase increases the rate at which sucrose is broken down into glucose and fructose.Sucrase works by

Accepted Answer

Enzymes like sucrase lower the activation energy of biochemical reactions, which means that they speed up the reaction by requiring less energy to get started. By lowering the activation energy, the enzyme helps the substrate (in this case, sucrose) convert into products (glucose and fructose) at a faster rate, without being used up or altered in the process.

Quiz 8: Energy, Enzymes, and Metabolism

The molecules that are acted on by an enzyme are called

Which statement about enzymes is false?

In some cases, a substrate-enzyme complex is stabilized by

The statement "enzymes are highly specific" means that specific

An RNA molecule that has enzyme activity is called

Which of the following affects the rate of a reaction?

Enzymes of the acid-base catalysis type contain

The five reactions listed are catalyzed by enzymes in a cell.Which reaction is catalyzed by an oxidoreductase?

An active site is the

The hydrolysis of sucrose to glucose and fructose is exergonic.However, if sucrose is dissolved in water and the solution is kept overnight at room temperature, there is no detectable conversion to glucose and fructose.Why?

Which will not increase the rate of conversion of reactant A to product B in the presence of enzyme C?

Trypsin and elastase are both enzymes that catalyze hydrolysis of peptide bonds.However, trypsin only hydrolyzes peptide bonds next to lysine, and elastase only hydrolyzes peptide bonds next to alanine.Why?

The presence of a catalyst affects the

The enzyme $\alpha$ -amylase increases the rate at which starch is broken down into smaller oligosaccharides by _______ of the reaction.

Mechanisms used by enzymes to catalyze reactions are similar in that they all

The enzyme glyceraldehyde 3-phosphate dehydrogenase catalyzes the reaction glyceraldehyde 3-phosphate $\rightarrow$ 1,3-diphosphoglycerate.The binding of the glyceraldehyde 3-phosphate to the enzyme creates a(n)

Refer to the figure below. Which type of mechanism used by an enzyme to catalyze a reaction is illustrated in the figure?

The enzyme glucose oxidase binds the six-carbon sugar glucose and catalyzes its conversion to glucono-1,5-lactone.Mannose is also a six-carbon sugar, but glucose oxidase cannot bind mannose.The specificity of glucose oxidase is based on the

The enzyme sucrase increases the rate at which sucrose is broken down into glucose and fructose.Sucrase works by

Quiz 8: Energy, Enzymes, and Metabolism

The molecules that are acted on by an enzyme are called

Which statement about enzymes is false?

In some cases, a substrate-enzyme complex is stabilized by

The statement "enzymes are highly specific" means that specific

An RNA molecule that has enzyme activity is called

Which of the following affects the rate of a reaction?

Enzymes of the acid-base catalysis type contain

The five reactions listed are catalyzed by enzymes in a cell.Which reaction is catalyzed by an oxidoreductase?

An active site is the

The hydrolysis of sucrose to glucose and fructose is exergonic.However, if sucrose is dissolved in water and the solution is kept overnight at room temperature, there is no detectable conversion to glucose and fructose.Why?

Which will not increase the rate of conversion of reactant A to product B in the presence of enzyme C?

Trypsin and elastase are both enzymes that catalyze hydrolysis of peptide bonds.However, trypsin only hydrolyzes peptide bonds next to lysine, and elastase only hydrolyzes peptide bonds next to alanine.Why?

The presence of a catalyst affects the

The enzyme α\alphaα -amylase increases the rate at which starch is broken down into smaller oligosaccharides by _______ of the reaction.

Mechanisms used by enzymes to catalyze reactions are similar in that they all

The enzyme glyceraldehyde 3-phosphate dehydrogenase catalyzes the reaction glyceraldehyde 3-phosphate →\rightarrow→ 1,3-diphosphoglycerate.The binding of the glyceraldehyde 3-phosphate to the enzyme creates a(n)

Refer to the figure below. Which type of mechanism used by an enzyme to catalyze a reaction is illustrated in the figure?

The enzyme glucose oxidase binds the six-carbon sugar glucose and catalyzes its conversion to glucono-1,5-lactone.Mannose is also a six-carbon sugar, but glucose oxidase cannot bind mannose.The specificity of glucose oxidase is based on the

The enzyme sucrase increases the rate at which sucrose is broken down into glucose and fructose.Sucrase works by

The enzyme $\alpha$ -amylase increases the rate at which starch is broken down into smaller oligosaccharides by _______ of the reaction.

The enzyme glyceraldehyde 3-phosphate dehydrogenase catalyzes the reaction glyceraldehyde 3-phosphate $\rightarrow$ 1,3-diphosphoglycerate.The binding of the glyceraldehyde 3-phosphate to the enzyme creates a(n)