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- 1. Multiple Choice
Which of the following is an example of a hydrogen bond?
the attraction between the oxygen of one water molecule and the hydrogen of an adjacent molecule
the bond between hydrogen and carbon in glucose or any sugar
the peptide bond between amino acids
the intramolecular bond between hydrogen and oxygen within a molecule of water
- 2. Multiple Choice
The intramolecular bond between hydrogen and oxygen within a molecule of water
There are no hydrogen ions in a strong basic solution
Pure water has a neutral pH of 7 because the concentration of hydrogen ions equals the concentration of hydroxyl ions.
The concentration of a solution with a pH f 5 is 5 times more acidic than a solution
with pH 1.
The concentration of hydrogen ions in a solution with a ph of 2 is 2,000 times more acidic than a solution with pH of 4.
- 3. Multiple Choice
Which of the following can be used to determine the rate of an enzyme-catalyzed reaction?
The rate of substrate formed
The decrease in temperature in the system
The rate of enzyme used up
The rate of substrate used up
- 4. Multiple Choice
A student analyzed a viral genome and found that the genome had the following nucleotide composition.
• 28% adenine
• 20% thymine
• 35% cytosine
• 17% guanine
Which of the following best describes the structure of the viral genome?
Double-stranded DNA
Single-stranded DNA
Double-stranded RNA
Single-stranded RNA
- 5. Multiple Choice
The CFTRCFTR protein is made up of 1,4801,480 amino acids linked together in a chain. Some humans produce a version of the CFTRCFTR protein in which phenylalanine (an amino acid) has been deleted from position 508 of the amino acid chain.
Which of the following best predicts how the amino acid deletion will affect the structure of the CFTRCFTR protein?
It will have no observable effect on the structure of the CFTRCFTR protein.
It will affect the primary structure of the CFTRCFTR protein, but the other levels of protein structure will not be affected.
It will affect the secondary and tertiary structures of the CFTRCFTR protein, but the primary structure will not be affected.
It will affect the primary, secondary, and tertiary structures of the CFTRCFTR protein.
- 6. Multiple Choice
Hydrolysis is involved in which of the following?
Formation of starch, a polysaccharide, from monomers of glucose
Hydrogen bond formation between nitrogen bases of nucleic acids
Peptide bond formation between amino acids to form a protein
The digestion of sucrose, a disaccharide to its monomers of glucose and fructose
- 7. Multiple Choice
A globular blood protein that transports vitamin A is 127 amino acids long. How many water molecules were produced in the synthesis of the protein, and by what chemical process were the amino acids joined together?
127; hydrolysis
127; dehydration
126; hydrolysis
126; dehydration
- 8. Multiple Choice
Bacteriophages are viruses that infect bacteria. In an experiment, bacteriophages were labeled with either radioactive phosphorus or radioactive sulfur. The labeled bacteriophages were incubated with bacteria for a brief amount of time and then removed. The infected bacteria cells were found to contain significant amounts of radioactive phosphorus but not radioactive sulfur.
Based on the results of the experiment, which of the following types of molecules did the bacteriophages most likely inject into the bacteria cells?
Simple carbohydrate
Amino acid
DNA
polypepetide
- 9. Multiple Choice
The molecular formula for glucose is C6H12O6. What would be the molecular formula for a polymer made by joining 10 glucose molecules together by dehydration reactions?
C60H120O60
C6H12O6
C60H102O51
C60H100O50
- 10. Multiple Choice
Enzymes are organic catalysts. How do they increase the rate of chemical reactions?
By decreasing the free-energy change of the reaction
By increasing the free-energy change of the reaction
By raising the activation energy of the reaction
By lowering the activation energy of the reaction
- 11. Multiple Choice
The carbohydrates glucose, galactose, and fructose have the same chemical formula (C6H12O6)(C6H12O6) but different structural formulas, as represented in the figure.
Which of the following statements about glucose, galactose, and fructose is most likely true?
The carbohydrates have the same properties because they have the same number of carbon, hydrogen, and oxygen atoms.
The carbohydrates have the same properties because they each have a single carbon-oxygen double bond.
The carbohydrates have different properties because they have different arrangements of carbon, hydrogen, and oxygen atoms.
The carbohydrates have different properties because they have different numbers of carbon-carbon bonds.
- 12. Multiple Choice
When substance A was added to an enzyme reaction, product formation decreased. The addition of more substrate did not increase product formation. From this we conclude that substance A could be
product molecules
an allosteric enzyme
a competitive inhibitor
a noncompetitive inhibitor
- 13. Multiple Choice
Which of the following statements best describes how organisms such as rabbits obtain the carbon necessary for building biological molecules?
Rabbits eat plants and use energy absorbed from the plants to make carbon atoms from electrons, protons, and neutrons in the air.
Rabbits eat plants and break down plant molecules to obtain carbon and other atoms that they rearrange into new carbon-containing molecules.
Rabbits eat plants and use water absorbed from the plants to hydrolyze CO2 which the rabbits breathe in from the air and use as a carbon source.
Rabbits eat plants and make carbon-containing molecules by using carbon atoms that the plants absorbed from the soil and stored in the cells of their leaves.
- 14. Multiple Choice
You’re the manager of a factory that produces enzyme-washed blue jeans (the enzymes lighten the color of the denim, giving a faded appearance). When the most recent batch of fabric came out of the enzyme wash, however, the color wasn’t light enough to meet your standards. Your quality control laboratory wants to do some tests to determine why the wash enzymes didn’t perform as expected.
Which hypothesis is most likely to be productive for the initial investigation?
The nucleotide chain of the enzymes many be incorrectly formed.
The dye in the fabric may have hydrolyzed the fatty acids in the enzymes.
The polysaccharides in the enzymes may have separated in the wash water.
The three-dimensional amino acid structure of the enzyme may have been altered
- 15. Multiple Choice
You’re the manager of a factory that produces enzyme-washed blue jeans (the enzymes lighten the color of the denim, giving a faded appearance). When the most recent batch of fabric came out of the enzyme wash, however, the color wasn’t light enough to meet your standards. Your quality control laboratory wants to do some tests to determine why the wash enzymes didn’t perform as expected.
3. Based on your understanding of enzyme structure, which of the following would you recommend that the lab also investigate?
The temperature of the liquid in the washing vat
Washing the blue jeans in smaller vats
The manufacturer of the fabric
Switching to another product for the enzyme wash
- 16. Multiple Choice
Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified?
as a pentose
as a monosaccharide
as a disaccharide
as a polysaccharide
- 17. Multiple Choice
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?
The initial concentration of the substrate
The final concentration of the product
The three-dimensional structure of the enzyme
The temperature of the aqueous buffer solution
- 18. Multiple Choice
Which of the following characteristics of Figure 1 best shows that the fragment is RNA and not DNA?
The 5′5′ to 3′3′ orientation of the nucleotide chain
The identity of each nitrogenous base
The charges on the phosphate groups
The type of bond linking the nucleotides together
- 19. Multiple Choice
Which of the following conclusions is most clearly supported by the representations of nucleic acid #1 and nucleic acid #2 in the image?
A. Nucleic acid #1 contains only purines, whereas nucleic acid #2 contains only pyrimidines.
A. Nucleic acid #1 contains the sugar ribose, whereas nucleic acid #2 contains the sugar deoxyribose.
A. Nucleic acid #1 contains positively charged phosphate groups, whereas nucleic acid #2 does not.
A. Nucleic acid #1 contains adenine-thymine base pairs, whereas nucleic acid #2 does not.
- 20. Multiple Choice
The molecular structures of linoleic acid and palmitic acid, two naturally occurring substances, are shown in the figure.
Based on the molecular structures shown in the figure, which molecule is likely to be solid at room temperature?
Linoleic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together.
Linoleic acid, because the presence of carbon-carbon double bonds prevents the molecules from packing closely together.
Palmitic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together.
Palmitic acid, because the presence of carbon-carbon double bonds prevents the molecules from packing closely together.
- 21. Multiple Choice
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?
There will be an increase in formaldehyde because ADH activity increases.
Competitive inhibition will be terminated because ethyl alcohol will bind to methyl alcohol and decrease ADH activity.
The peptide bonds in the active site of the enzyme will be denatured, inhibiting the enzyme.
Competitive inhibition will decrease because the proportion of the active sites occupied by substrate will increase.
- 22. Multiple Choice
Water and ammonia interact to form hydrogen bonds, as represented in the figure.
Which statement best helps explain the formation of the hydrogen bond represented in the figure?
The oxygen has a partial positive charge, and the nitrogen has a partial negative charge.
The nitrogen has a partial negative charge, and the hydrogen attached to the oxygen has a partial positive charge.
The hydrogen attached to the oxygen has a partial negative charge, and the nitrogen also has a partial negative charge.
The nitrogen has a partial positive charge, and the hydrogen attached to the oxygen also has a partial positive charge.
- 23. Multiple Choice
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?
The enzyme’s active site binds to and stabilizes the reactant, which decreases the free-energy change of the reaction.
The enzyme’s active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction.
The enzyme’s active site binds to and stabilizes the product, which increases the amount of energy released by the reaction.
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.
- 24. Multiple Choice
A researcher claims that some bacteria contain factors that influence the function of a particular enzyme but other bacteria do not. To test the claim experimentally, the researcher will grow two different bacterial strains in separate liquid cultures and isolate the contents of the cells in each culture. The researcher will add different combinations of cellular contents, substrate, and enzyme to test tubes containing a buffer solution adjusted to the optimal pH of the enzyme and then measure the rate of product formation. The design of the researcher’s experiment is presented in Table.
Which of the following statements best justifies the inclusion of test tubes 3 and 7 in the experiment?
They will show whether the isolated cellular contents have enzymatic activity.
They will show whether environmental pH affects the function of the enzyme.
They will show the rate of product formation in the absence of bacterial factors.
They will show the rate of product formation in the absence of the substrate.
- 25. Multiple Choice
Gelatin is a protein that is derived from collagen which is found in the bones, skin, and connective tissue of animals. To investigate the ability of various enzymes to digest gelatin, a group of students set up an assay involving camera film. Camera film contains gelatin and appears black when exposed to light but turns clear as the gelatin gets broken down. The students incubated pieces of exposed camera film in test tubes, each containing one of three different enzyme solutions (trypsin, lipase, or amylase) as indicated in Figure 1. The students recorded the time it took for the enzymes to digest the gelatin in each test tube, turning the film from black to clear.
Which of the following would be the most appropriate control for this experiment?
A test tube containing no camera film
A test tube containing only a piece of exposed camera film
A test tube containing a piece of exposed camera film submerged in water
A test tube containing a piece of exposed camera film and all three enzyme solutions
- 26. Multiple Choice
A small protein is composed of 110 amino acids linked together in a chain. As shown in Figure 1, the first and last five amino acids in the chain are hydrophobic (have nonpolar and uncharged R-groups), whereas the remaining 100 amino acids are hydrophilic (have charged or polar R-groups). The nature of the R-group determines if the amino acid is hydrophobic or hydrophilic.
A mutation results in the production of a version of the small protein that is only 105 amino acids long, as shown in Figure 2. Five of the hydrophobic amino acids are missing from one end of the chain.
Which of the following best depicts the tertiary structures of the two proteins in water? The diagrams in the options are not drawn to the same scale as those in Figure 1 and Figure 2.
- 27. Multiple Choice
Which of the following is an accurate description of the process shown in Figure
The linking of amino acids with an ionic bond as an initial step in the protein synthesis process
The formation of a more complex carbohydrate with the covalent bonding of two simple sugars
The hydrolysis of amino acids with the breaking of covalent bonds with the release of water
The formation of a covalent peptide bond in a dehydration synthesis reaction
- 28. Multiple Choice
Which of the following best describes how amino acids affect the tertiary structure of a protein?
The number of amino acids determines the tertiary structure of the protein.
The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein.
The R-group of the last amino acid that is added to a growing polypeptide chain determines the next amino acid that is added to the chain.
The sequence of the amino acids in the polypeptide chain determines the protein’s primary structure but has no effect on its tertiary structure.
- 29. Multiple Choice
The enzyme peroxidase is found in many organisms. It catalyzes the breakdown of hydrogen peroxide into water and oxygen gas. The rate of peroxidase activity at different pH values was assessed by students in the lab. The students’ results are shown in the graph.
If the experiment is repeated at pH 11, the observed activity level of the enzyme will most likely be
the same as the level at pH 7
lower than the level at pH 9
greater than the level at pH 9
between the levels observed at pH 5 and pH 7.
- 30. Multiple Choice
Figure is a diagram of water molecules at the air-water interface at the surface of a pond.
Based on the figure, which of the following best describes how the properties of water at an air-water interface enable an insect to walk on the water's surface?
Covalent bonds between water molecules and the air above provide cohesion, which causes tiny bubbles to form under the feet of the insect.
Ionic bonds between molecules at the surface of the water provide an electric charge, which attracts the feet of the insect, keeping it on the surface.
Polar covalent bonds between molecules at the surface of the water provide adhesion, which supports the weight of the insect.
Hydrogen bonds between molecules at the surface of the water provide surface tension, which allows the water surface to deform but not break under the insect.
- 31. Multiple Choice
Protein digestion in humans is primarily carried out by three enzymes. Pepsin is found in the stomach (pH2), where it aids in the breakdown of large proteins into smaller peptides, while trypsin and chymotrypsin are found in the small intestine (pH8), where they aid in the further breakdown of the proteins into amino acids and dipeptides that can be absorbed into the bloodstream. Graph 1 shows the effect of pH on the activity levels of the
three enzymes.
Which of the following best predicts how the structure and function of pepsin will change as it
enters the small intestine?
Pepsin will not change in shape and will continue to break down proteins in the small intestine.
It contains hydrogen atoms.
It is an ionic compound.
It forms hydrogen bonds.
- 32. Multiple Choice
Which of the following is most directly responsible for water’s unique properties?
It contains oxygen atoms.
It contains hydrogen atoms.
It is an ionic compound.
It forms hydrogen bonds.
- 33. Multiple Choice
Two groups of students attempted to re-create the primitive atmospheric conditions of early Earth using the apparatus represented below. Each group ran the experiment with different gas mixtures in the apparatus.
Which of the following statements best justifies the claim that the conditions in at least one of the experiments could generate the molecular building blocks essential for life?
The carbon dioxide ( CO2 ) gas and water ( H2O ) vapor in experiment 1 could react spontaneously to produce the phospholipids required by the first life-forms.
The nitrogen ( N2 ) gas and ammonia ( NH3 ) gas in experiment 1 could provide the elemental nitrogen required for the formation of amino acids.
The sulfur dioxide ( SO2 ) gas in experiment 2 could donate the excited electrons required to drive the process of photosynthesis.
The methane ( CH4 ) gas in experiment 2 could act as the electron acceptor required to complete the process of cellular respiration
- 34. Multiple Choice
Which of the following correctly illustrates a dipeptide and an amino acid in the optimal position to form a tripeptide?
- 35. Multiple Choice
Students investigated the effect of light on the carbon cycle in aquatic ecosystems by performing the controlled experiment summarized below. The students placed equal amounts of water (pH7) from a large aquarium in glass beakers. The students transferred aquatic plants from the aquarium to several of the beakers, and then they placed equal numbers of the beakers in the light or the dark (Figure 1: groups I and II). Similarly, the students transferred goldfish from the same aquarium to other beakers, and then they placed equal numbers of those beakers in the light or dark (Figure 1: groups III and IV). Finally, the students placed an equal number of beakers containing water only in the light or dark (Figure 1: groups V and VI)
After exposing the samples to light or dark for one hour, the students recorded the pH of the water in each beaker. Carbon dioxide dissolved in water will lower the pH of an aqueous solution. In the experiment, the students used changes in pH to monitor changes in the amount of carbon dioxide in the water. For each treatment group, the students calculated the mean pH and standard error, as documented in the table below.
Which of the following graphs is the most appropriate representation of the experimental results documented in the table?
- 36. Multiple Choice
For the enzyme-catalyzed reaction shown in Figure 2.3, which of these treatments will cause the greatest increase in the rate of the reaction, if the initial reactant concentration is 1.0 micromolar?
doubling the activation energy needed
cooling the reaction by 10°C
doubling the concentration of the reactants to 2.0 micromolar
doubling the enzyme concentration
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