Which of the following statements best helps explain the reaction specificity of an enzyme immersive reader?

Aminolevulinate dehydratase (ALAD) is an enzyme that relies on zinc as a coenzyme. A zinc ion binds to the ALAD active site, where it forms favorable interactions with the side chains of three amino acids. Researchers have found that substituting a lead ion for a zinc ion in the ALAD active site causes inhibition of ALAD.
Which of the following statements best helps explain how the lead ion causes inhibition of ALAD?

a. It changes the shape and charge of the substrate so that it becomes more compatible with ALAD's active site.
b. It changes the amino acid sequence of the ALAD protein so that the enzyme catalyzes a different reaction.
c. It changes the three-dimensional structure of the active site so that ALAD is no longer compatible with its substrate.
d. It changes the enzyme-substrate complex so that the transition state is more stable and the reaction proceeds at a faster rate.

Answer C
The substitution of a lead ion for a zinc ion most likely changes the three-dimensional structure of the ALAD active site. The three-dimensional structure of the active site plays an important role in the compatibility between an enzyme and its substrate. Changing the structure of the active site will likely interfere with enzyme function by disrupting the enzyme-substrate interaction.

Acetylcholinesterase (AChE) is a protein that catalyzes the conversion of acetylcholine to acetate and choline. When the concentration of AChE in an aqueous solution is held constant, the rate of the reaction catalyzed by AChE increases with increasing concentrations of substrate. At low concentrations of acetylcholine, a small increase in the substrate concentration results in a large increase in the reaction rate. At high concentrations of acetylcholine, however, a large increase in the substrate concentration results in only a small increase in the reaction rate.
Which of the following statements correctly explains the observed effect of the acetylcholine concentration on the rate of the enzyme-catalyzed reaction?

a. The active site of AChE is specific for acetylcholine, and only one substrate molecule can occupy the active site at a time.
b. AChE begins converting product into substrate as the acetylcholine concentration changes from low to high.
c. The AChE protein becomes denatured as the acetylcholine concentration changes from low to high
d. The substrate specificity of AChE changes as the acetylcholine concentration changes from low to high.

Answer A
Acetylcholine is the substrate for AChE, and since the shape and charge of the active site is specific for acetylcholine, only one substrate molecule can occupy the active site at a time. Therefore, at high concentrations of acetylcholine, AChE becomes saturated with substrate. When an enzyme is saturated with substrate, adding more substrate to the solution will not lead to an observable increase in the reaction rate.

A researcher proposes a model to explain how enzyme-substrate interactions determine enzyme specificity. The model is based on the idea that substrate molecules form favorable interactions with the amino acid side chains in an enzyme's active site.
Based on the model, which of the following statements best explains an enzyme's specificity for a particular substrate molecule?

a. A hydrophilic molecule interacts with nonpolar side chains in the enzyme's active site.
b. A hydrophobic molecule interacts with polar side chains in the enzyme's active site.
c. A molecule with positive charges interacts with positively charged side chains in the enzyme's active site.
d. A molecule with negative charges interacts with positively charged side chains in the enzyme's active site.

Answer D
Because opposite charges attract, a molecule with negative charges will form favorable interactions with positively charged side chains in an enzyme's active site. Based on the model, the favorable interactions helps explain the enzyme's specificity for the molecule as a substrate.

Researchers investigated the effect of urea on the three-dimensional structure of a certain enzyme. The researchers dissolved the enzyme in an aqueous buffer solution and added urea to the solution. The enzyme did not appear to have a secondary or tertiary structure. The researchers carefully removed the urea from the solution and determined that the enzyme had the original secondary and tertiary structure again.
Based on the results of the experiment, which of the following statements best predicts the effect of urea on the enzyme's function?

a. Function will be disrupted by adding the urea and regained by removing the urea.
b. Function will be disrupted by adding the urea, but it will not be regained by removing the urea.
c. Function will be gained by adding the urea and disrupted by removing the urea.
d. Function will be unaffected by the addition and removal of the urea.

Answer A
Based on the information, adding the urea denatures the enzyme, which will disrupt the enzyme's function by disrupting the active site. In contrast, removing the urea causes the enzyme to refold, which will restore the active site and the enzyme's function.

A researcher claims that the incorporation of carbon dioxide into organic molecules during photosynthesis does not violate the second law of thermodynamics.
Which of the following statements best helps justify the researcher's claim?

a. Organisms contain enzymes that lower the activation energies of specific chemical reactions.
b. An ecosystem is formed by the interaction of a community of organisms with their surrounding environment.
c. Photosynthetic organisms use the organic molecules produced during photosynthesis for growth and repair.
d. The total system that includes photosynthetic organisms and the Sun becomes less ordered over time.

Answer D
Because the total system that includes photosynthetic organisms and the Sun becomes less ordered over time, the incorporation of carbon dioxide molecules into organic molecules that occurs during photosynthesis does not violate the second law of thermodynamics.

A researcher claims that genetic variation provides organisms with the ability to survive and reproduce in different environments. To support the claim, the researcher makes the following observation: bacteria that contain plasmids (small DNA molecules) are resistant to a wider range of antibiotics than are bacteria that contain no plasmids.
Which of the following statements best establishes a connection between the observation and the researcher's claim?

a. Some antibiotics inhibit the synthesis of bacterial cell walls.
b. Some antibiotics inhibit protein synthesis in bacteria cells.
c. Some plasmids cannot exist in a bacterial cell with certain other plasmids.
d. Some plasmids contain antibiotic resistance genes.

Answer D
Because some plasmids contain antibiotic resistance genes, bacteria that contain plasmids are more likely to be resistant to antibiotics than are bacteria that do not contain plasmids. The observation is evidence that genetic variation in the form of plasmids provides bacteria with the ability to survive and reproduce in different environments.

Phycobiliproteins are a complex of accessory pigments and proteins found in cyanobacteria but not in green algae. A researcher claims that the phycobiliprotein pigments in cyanobacteria allow the cyanobacteria to survive in certain aquatic niches better than green algae can.
Which of the following statements best justifies the researcher's claim?

a. The additional pigments allow the cyanobacteria to store light energy so that it can be used at night to continue photosynthesis.
b. The additional pigments block light and prevent it from reaching photosynthetic organisms at greater depths, so no photosynthetic organisms can live below the surface waters containing cyanobacteria.
c. The additional pigments require energy and cellular resources to produce, so they can be used as an energy source during times of insufficient light.
d. The additional pigments absorb light at wavelengths that green algae cannot absorb; this may allow cyanobacteria to capture more light energy for photosynthesis than green algae can in certain areas.

Answer D
Since the phycobiliprotein pigments absorb light wavelengths not absorbed by green algae, cyanobacteria are able to better perform photosynthesis and survive in areas where there is insufficient light at the needed frequencies for green algae to survive.

A researcher claims that budding yeast are able to survive in different environments because they produce enzymes that allow them to use different molecules as sources of matter and energy.
Which of the following statements best helps justify the researcher's claim by providing a relevant example?

a. Yeast cells produce protein kinases, which are enzymes that catalyze the transfer of phosphate groups from ATP to protein substrates.
b. Yeast cells produce DNA polymerases, which are enzymes that catalyze the conversion of free nucleotides into strands of DNA.
c. Yeast cells produce invertase, which is an enzyme that catalyzes the conversion of the disaccharide sucrose into glucose and fructose.
d. Yeast cells produce catalase, which is an enzyme that catalyzes the conversion of hydrogen peroxide into water and oxygen gas.

Answer C
The disaccharide sucrose is not transported efficiently into yeast cells. By producing the enzyme invertase, budding yeast can use the sucrose, glucose, and fructose in the surrounding environment as sources of matter and energy. As such, the production of invertase by budding yeast is a relevant example that will help justify the researcher's claim.

A researcher claims that different metabolic pathways allow bacteria to use different molecules as sources of matter and energy.
Which of the following statements best helps justify the researcher's claim by providing a relevant example?

a. Rhizobia bacteria form close associations with the roots of bean plants.
b. E. coli bacteria reproduce in liquid media containing either glucose or galactose.
c. The antibiotic rifampicin inhibits the growth of some bacterial strains but not of others.
d. Some viruses that infect bacteria reproduce by either the lysogenic cycle or the lytic cycle.
Answer

Answer B
Glucose and galactose are two different monosaccharides that can be used by organisms as sources of matter and energy. The ability of E. coli bacteria to reproduce in liquid media containing either glucose or galactose provides a relevant example that will help justify the researcher's claim.

A researcher claims that the synthesis of ATP from ADP and inorganic phosphate (Pi) is essential to cellular function.
Which of the following statements best helps justify the researcher's claim?

a. ADP is a small molecule that some cells release into their environment as a way of communicating with other cells.
b. ATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy.
c. Inorganic phosphate (Pi) is a substance that cells typically acquire from their environment.
d. ATP synthase is a mitochondrial enzyme that catalyzes the conversion of ADP and Pi to ATP.

Answer B
Many cellular processes necessary for maintaining the internal organization of the cell are coupled with the hydrolysis of ATP. Without a supply of ATP, these activities will stop and the cells will die.

A researcher claims that only a portion of the light energy captured by green plants is available for growth and repair.
Which of the following observations best helps justify the researcher's claim?

a. Light-capturing pigment molecules in green plants absorb red, blue, and violet light but reflect green light.
b. The energy of a photon of light is proportional to its frequency and inversely proportional to its wavelength.
c. As light energy is converted to chemical energy by metabolic processes, some of the energy is lost as heat.
d. Captured energy is stored in the molecular bonds of organic molecules, including simple sugars and starch.

Answer C
During photosynthesis, some of the captured light energy is lost to the environment in the form of heat energy. As a result, only some of the captured light energy is converted to chemical energy and stored for later use in growth and repair.

Alcohol dehydrogenase (ADH) is an enzyme that aids in the decomposition of ethyl alcohol (C2H5OH) into nontoxic substances. Methyl alcohol acts as a competitive inhibitor of ethyl alcohol by competing for the same active site on ADH. When attached to ADH, methyl alcohol is converted to formaldehyde, which is toxic in the body.
Which of the following statements best predicts the effect of increasing the concentration of substrate (ethyl alcohol), while keeping the concentration of the inhibitor (methyl alcohol) constant?

a. There will be an increase in formaldehyde because ADH activity increases.
b. Competitive inhibition will be terminated because ethyl alcohol will bind to methyl alcohol and decrease ADH activity.
c. The peptide bonds in the active site of the enzyme will be denatured, inhibiting the enzyme.
d. Competitive inhibition will decrease because the proportion of the active sites occupied by substrate will increase.

Answer D
The increase in amount of substrate will increase the number of enzyme-ethanol complexes formed, increasing the amount of nontoxic product formed from ethyl alcohol.

A researcher designs an experiment to investigate the effect of environmental temperature on the function of an enzyme. For each trial included in the experiment, the researcher will add the enzyme and its substrate to an aqueous buffer solution and then measure the amount of product formed over 20 minutes.
Which of the following must remain the same for all trials of this experiment?

a. The initial concentration of the substrate
b. The final concentration of the product
c. The three-dimensional structure of the enzyme
d. The temperature of the aqueous buffer solution

Answer A
Keeping the initial substrate concentration constant allows the researcher to compare the reaction rates under different environmental conditions. The reaction rates will provide the researcher with information about the enzyme's function in different environments.

A researcher proposes a model of an enzyme-catalyzed reaction in which a reactant is converted to a product. The model is based on the idea that the reactant passes through a transition state within the enzyme-substrate complex before the reactant is converted to the product.
Which of the following statements best helps explain how the enzyme speeds up the reaction?

a. The enzyme's active site binds to and stabilizes the reactant, which decreases the free-energy change of the reaction.
b. The enzyme's active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction.
c. The enzyme's active site binds to and stabilizes the product, which increases the amount of energy released by the reaction.
d. The enzyme's active site binds to and stabilizes both the reactant and the product at the same time, which increases the reaction's equilibrium constant.

Answer B
An enzyme typically speeds up a reaction by stabilizing a transition state in the reaction, which decreases the reaction's activation energy. The enzyme's active site binds more tightly to the transition state than to either the substrate or the product, which speeds up the reaction and allows the enzyme to catalyze the same reaction repeatedly.

Which of the following statements best helps explain the reaction specificity of an enzyme?

a. The free energy of the reactants is greater than the free energy of the products.
b. The equilibrium constant of the reaction is much greater than 1.
c. The shape and charge of the substrates are compatible with the active site of the enzyme.
d. The concentration of the enzyme inside living cells is greater than the concentration of substrate.

Answer C
The reaction specificity of an enzyme is determined by the compatibility of the substrate with the enzyme's active site. A substrate's shape and charge affect how it fits into an enzyme's active site and whether it forms favorable interactions with the enzyme.

The enzyme hexokinase catalyzes the conversion of glucose to glucose-6-phosphate, which is an important step in glycolysis. The reaction involves the transfer of a phosphate group from ATP to glucose.
Either a glucose molecule or a water molecule can fit in the active site of hexokinase. The presence of a water molecule in hexokinase's active site would result in the hydrolysis of ATP to ADP instead of the conversion of glucose to glucose-6-phosphate.
Which of the following statements best helps explain the reaction specificity of hexokinase?

a. Both glucose and water are polar molecules that form favorable interactions with charged and polar amino acid side chains in hexokinase's active site.
b. Both glucose and water have oxygen atoms that can form covalent bonds with the phosphorus atoms of phosphate groups.
c. Glucose is an energy-rich organic molecule that can be broken down by glycolysis to produce ATP, whereas water is an inorganic molecule.
d. Glucose has the right shape and charge to cause hexokinase to undergo a structural change needed for catalysis, whereas water does not.

Answer D
Correct. Hexokinase catalyzes the conversion of glucose to glucose-6-phosphate but not the hydrolysis of ATP. Hexokinase's reaction specificity is explained by the compatibility of glucose and hexokinase's active site, which results in part from glucose's shape and charge. Because of this compatibility, hexokinase undergoes a structural change when it binds to glucose but not to water, and the structural change is necessary for hexokinase to become catalytically active.

Which of the following best explains the reaction specificity of an enzyme?

Which of the following statements best helps explain the reaction specificity of hexokinase quizlet?

Which of the following statements best explains an enzyme's specificity for a particular substrate molecule?

What is the reaction specificity of hexokinase?