- Which of the following is responsible for the cohesive property of water?
- Hydrogen bonds between the oxygen atoms of two adjacent water molecules
- Covalent bonds between the hydrogen atoms of two adjacent water molecules
- Hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule
- Covalent bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule
- Hydrogen bonds between water molecules and other types of molecules
C
2 A typical bag of fertilizer contains high levels of nitrogen, phosphorus, and potassium but trace amounts of magnesium and calcium. Which of the following best matches the fertilizer component with the molecule in which it will be incorporated by organisms in the area?
A. Nitrogen will be incorporated into nucleic acids.
B Phosphorus will be incorporated into amino acids.
C Potassium will be incorporated into lipids.
D Magnesium will be incorporated into carbohydrates.
A
- Amylase is an enzyme that converts carbohydrate polymers into monomers. Glycogen synthase is one of the enzymes involved in converting carbohydrate monomers into polymers.
Which of the following best explains the reactions of these enzymes?
A. Amylase aids in the removal of a water molecule to break covalent bonds whereas glycogen synthase aids in the addition of a water molecule to form covalent bonds.
B Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen synthase aids in the removal of a water molecule to form covalent bonds
C. Amylase aids in the addition of a water molecule to form covalent bonds whereas glycogen synthase aids in the removal of a water molecule to break covalent bonds.
D Amylase aids in the removal of a water molecule to form covalent bonds whereas glycogen synthase aids in the addition of a water molecule to break covalent bonds.
B
- A mutation in the gene coding for a single-polypeptide enzyme results in the substitution of the amino acid serine, which has a polar R group, by the amino acid phenylalanine, which has a nonpolar R group. When researchers test the catalysis of the normal enzyme and the mutated enzyme, they find that the mutated enzyme has much lower activity than the normal enzyme does.
Which of the following most likely explains how the amino acid substitution has resulted in decreased catalytic activity by the mutated enzyme?
A The substitution decreased the mass of the enzyme so that the mutated enzyme binds more weakly to the substrate than the normal enzyme does.
B The substitution altered the secondary and tertiary structure of the enzyme so that the mutated enzyme folds into a different shape than the normal enzyme does
C The substitution caused many copies of the mutated enzyme to cluster together and compete for substrate to bind
D The substitution caused the directionality of the enzyme to change such that the amino terminus of the normal enzyme has become the carboxy terminus of the mutated enzyme
B
5 Ultraviolet (UV) radiation can damage DNA by breaking weak bonds. Which of the following best explains how this occurs
A Responses UV radiation disrupts the double helix structure by breaking the covalent bonds between the nitrogenous base pairs
B U V radiation disrupts the double helix structure by breaking the covalent bonds between the nitrogenous base pairs.
C UV radiation is able to break DNA strands in two by breaking covalent bonds between the sugar-phosphate backbone molecules
D UV radiation is able to break DNA strands in two by breaking hydrogen bonds between the sugar-phosphate backbone molecules.
B
If 30% of the nucleotides in a single-stranded RNA molecule are adenine, then what percent are expected to be thymine?
A 0%
B 20%
C 30%
D 70%
A
Prokaryotic and eukaryotic cells generally have which of the following features in common?
A A membrane-bound nucleus
B A cell wall made of cellulose
C Ribosomes
D Flagella or cilia that contain microtubules
E Linear chromosomes made of DNA and protein
C
Which of the following processes is most likely to occur as a result of an animal cell receiving a signal to initiate apoptosis?
A Ribosomes will translate mRNA to produce proteins.
B Vesicles will release extracellular growth factors via exocytosis.
C Lysosomes will release digestive enzymes into the cytosol.
D Vacuoles will fuse with the cellular membrane.
C
9 The primary function of the kidney is to exchange molecules across a membrane between the blood and the urine. One type of kidney cell has a basic rectangular shape, except for a single surface, which is lined with tiny, finger-like projections that extend into the surrounding extracellular space
Which of the following best explains the advantage these projections provide the cell?
A The projections increase the volume of the cell without affecting the surface area, which increases the metabolic needs of the cell.
B The projections increase the surface area–to-volume ratio of the cell, which allows for more efficient nutrient exchange with the environment.
C The projections increase the speed at which an individual molecule can move, resulting in faster nutrient exchange with the environment.
D The projections increase the selectivity of the membrane because the small size of the projections limits the number of transport proteins that can be embedded in the membrane.
B
Which of the following describes the most likely location of cholesterol in an animal cell?
A Embedded in the plasma membrane
B Dissolved in the cytosol
C Suspended in the stroma of the chloroplast
D Bound to free ribosome
A
Which of the following best explains how the phospholipid bilayer of a transport vesicle contributes to cellular functions?
A The phospholipid bilayer allows the vesicle to fuse with the Golgi apparatus and the plasma membrane, allowing the exocytosis of proteins.
B The phospholipid bilayer physically connects the nuclear envelope to the rough endoplasmic reticulum, thus increasing the rate of transcription and translation.
C The phospholipid bilayer of a transport vesicle contains chemicals that digest the proteins made in the rough endoplasmic reticulum.
D The phospholipid bilayer contains enzymes that catalyze the conversion of hydrogen peroxide to water and oxygen.
A
Which of the following accurately describes a model of active transport?
A A membrane channel protein facilitates the movement of molecules from an area of high concentration on the outside of the cell to an area of lower concentration on the inside.
B A cell in a hypotonic solution swells as water moves into it.
C A membrane protein binds a specific molecule outside of the cell and moves the molecule into the cell where there is already a high concentration of the molecule compared with the outside.
D A membrane protein binds a specific molecule on the inside of the cell and moves the molecule to an area of lower concentration on the outside of the cell.
C
If ATP breakdown (hydrolysis) is inhibited, which of the following types of movement across cell membranes is also inhibited?
A Movement of oxygen into a cell
B Movement of water through aquaporins
C Passage of a solute against its concentration gradient
D Facilitated diffusion of a permeable substance
C
Water enters and leaves the plant cells primarily by
A endocytosis
B phagocytosis
C osmosis
D active transport
E facilitated diffusion
C
15 What evolutionaA nucleus, ribosomes, and cell wallsry advantage does compartmentalization of core metabolic processes offer eukaryotes?
A Evolution of the mitochondria allowed eukaryotes to perform respiration.
B With the evolution of mitochondria in eukaryotes, the Krebs cycle and electron transport chain also evolved.
C Evolution of a nucleus in eukaryotes separates the processes of transcription and translation and they can be regulated separately.
D A nucleus in bacteria provides separation of respiration from transcription.
C
16 Which of the following groups of cellular components are found in eukaryotic cells but not prokaryotic cells?
A Ribosomes, a nucleus, and chloroplasts
B Circular chromosomes, mitochondria, and an endoplasmic reticulum
C A nucleus, ribosomes, and cell walls
D An endoplasmic reticulum, mitochondria, and a nucleus
D
17 Which of the following can be used to determine the rate of enzyme-catalyzed reactions?
A Rate of disappearance of the enzyme
B Rate of disappearance of the substrate
C Rate of disappearance of the product
D Change in volume of the solution
E Increase in activation energy
B
A student is investigating photosynthesis in plants. The student planted grass seeds in a tray with three sections and grew the grass under artificial lights for 14 days (Figure 1). After
14 days, the student collected all of the grass from section I and recorded its mass (Table 1). The student then placed a clear cover over section II and placed an aluminum foil cover over section
III (Figure 2). The student then placed the tray back under the artificial lights for seven additional days. On day 21 , the student collected and measured the mass of the grass from sections
II and III (Table 1).
Which of the following best explains the connection between energy, growth, and the maintenance of an ordered system in the experiment?
A Energy input from light is required for the grass to grow and maintain an ordered structure.
B The grass obtains the energy for growth and maintenance of order from nutrients from the soil.
C The grass couples the release of energy from the light reactions with the production of oxygen (O2) used to produce sugars for growth
D Energy is required for the growth of the grass but not the maintenance of order.
A
Which of the following is an important difference between light-dependent and light-independent reactions of photosynthesis?
A The light-dependent reactions occur only during the day; the light-independent reactions occur only during the night.
B The light-dependent reactions occur in the cytoplasm; the light-independent reactions occur in chloroplasts
C The light-dependent reactions utilize CO2 and H2O; the light-independent reactions produce CO2 and H2O.
D The light-dependent reactions depend on the presence of both photosystems I and II; the light-independent reactions require only photosystem I
E The light-dependent reactions produce ATP and NADPH; the light-independent reactions use energy stored in ATP and NADPH..
E
ATP serves as a common energy source for organisms because
A it is the smIt acts as a secondary messenger.allest energy molecule
B it stores the least energy of any energy source
C its energy can be easily transferred to do cellular work
D it is extremely stable and can be stored in the cell for long periods of time
E traces of it have been found in fossils of ancient organisms dating back to the beginning of life on Earth
C
Insulin is a protein hormone that is secreted in response to elevated blood glucose levels. When insulin binds to its receptors on liver cells, the activated receptors stimulate phosphorylation cascades that cause the translocation of glucose transporters to the plasma membrane.
Based on the information provided, which of the following best describes the role of insulin in this liver cell signal transduction pathway?
A It acts as a ligand.
B It acts as a receptor.
C It acts as a secondary messenger.
D It acts as a protein kinase.
A
It acts as a protein kinase.
A The growth factor binds to other cells in the same area and holds them together to form a large, multicellular structure.
B The growth factor binds to receptors on the cell surface, initiating a signal transduction pathway that activates specific target genes.
C The growth factor binds to sugar molecules in the extracellular fluid and provides them to the cell as a source of energy.
D The growth factor binds to phospholipids in the plasma membrane, creating a channel through which substances enter the cell.
B
The binding of erythropoietin to the erythropoietin receptor (EPoR) stimulates intracellular signaling in certain cells, which causes them to differentiate to red blood cells. The EPoR is a transmembrane protein with two cytoplasmic domains, each of which is bound by a kinase protein,
JAK2. The binding of erythropoietin to the
EPoR causes the cytoplasmic domains of the EPoR to undergo conformational changes that activate the bound JAK2 kinases. The JAK2 kinases then phosphorylate several intracellular proteins, including STAT5, whose resulting activity causes the cells to differentiate to red blood cells.
Which of the following explains how a mutation that removes a portion of each cytoplasmic domain of EPoR most likely affects differentiation of the cells?
A The cells will differentiate more rapidly than they typically do because the JAK2
kinases will always be active.
B The cells will mature to another cell type because the JAK2 kinases will phosphorylate inappropriate cellular proteins.
C STAT5 will not be activated because erythropoietin cannot bind to the
EPoR.
D STAT5 will not be activated because it will not be phosphorylated by the
JAK2 kinases.
D
Ethylene gas is an organic molecule that serves many cell signaling roles in flowering plants. Which of the following best explains how a positive feedback mechanism involving ethylene works?
A Cells of ripening fruit produce ethylene, which activates the ripening response in other fruit cells.
B Low water stress causes cells to produce ethylene, which binds to root cells and initiates cell division.
C Cells damaged by leaf-eating insects produce ethylene, which is released into the air, and repels insects.
D Fertilized ovules produce ethylene, which initiates apoptosis in flower petal cells.
A
25 During mitosis, which of the following normally occurs?
A Homologous chromosomes pair.
B Replicated chromosomes line up on the equatorial plate.
C Tetrads form.
D Maternal and paternal chromatids pair.Unreplicated chromosomes become oriented in the center of the cell.
B
Which of the following occurs during mitosis but not during meiosis I ?
A The chromosomes are pulled to opposite poles of the spindle apparatus.
B The chromatids of each chromosome are separated.
C The nuclear envelope breaks down
D Both synapsis and crossing-over take place
E The diploid number of chromosomes is reduced to the haploid number.
B
Which of the following best explains why triploid bananas do not produce seeds?
A The cells of the banana plant are unable to replicate DNA, thus preventing cell division and limiting growth.
B The banana plants lack enough genetic diversity to properly hybridize.
C The production of gametes is disrupted because of unequal pairing of homologous chromosomes during meiosis.
D The production of seeds is not required because triploid plants produce gametes without fertilization.
C
28 A blue-flowered African violet of unknown ancestry self-pollinated and produced 50 seeds. These seeds germinate and grow into flowering plants. Of these plants, 36 produce blue flowers and 14 produce pink flowers. What is the best explanation for the pink-flowered offspring?
A Blue flowers are incompletely dominant to pink flowers.
B Pink flower color is a trait recessive to blue flower color.
C Pink flower color is the result of somatic mutations in the flower color gene.
D A previous generation of the blue-flowered parent must have included 50 percent pinkflowered plants.
B
29 Gregor Mendel’s pioneering genetic experiments with pea plants occurred before the discovery of the structure and function of chromosomes. Which of the following observations about inheritance in pea plants could be explained only after the discovery that genes may be linked on a chromosome?
A Pea coloEnvironmental factors cause different mutations in
DNA
DNA during different seasons, resulting in seasonal changes in fur phenotype.r and pea shape display independent inheritance patterns.
B Offspring of a given cross show all possible combinations of traits in equal proportions.
C Most offspring of a given cross have a combination of traits that is identical to that of either one parent or the other.
D Recessive phenotypes can skip a generation, showing up only in the parental and F2 generations.
C
In the spring and summer, the fur of an arctic fox contains a pigment called melanin that gives the fox’s fur a dark color. In the fall and winter, the fur of the arctic fox is white
Which of the following most likely explains how the changing seasons result in changing fur color in an arctic fox?
A Environmental factors cause changes in gene expression, resulting in seasonal variations in pigment production.
B Environmental factors cause different mutations in DNA during different seasons, resulting in seasonal changes in fur phenotype.
C Environmental factors cause proteins to be translated using different genetic codes during different seasons, resulting in variations in pigment production.
D Environmental factors cause enzymes to react with different substrates, resulting in the accumulation of different pigments
A
Which of the following occurs in all species of living organisms and may lead to an increase in genetic variation?
A Mutations in the genome
B Crossing-over in meiosis
C Random assortment of chromosomes
D Alternative splicing of mRNA
A
Which of the following best describes a characteristic of DNA that makes it useful as hereditary material?
A here are many different types of nucleotide bases that can be incorporated into
DNA.
B The nucleotide bases can also be used to provide the energy needed for reproduction.
C Nucleotide bases can be randomly replaced with different nucleotide bases to increase variation.
D Nucleotide bases in one strand can only be paired with specific bases in the other strand.
D
Which of the following best explains why ligase is required for DNA replication?
Responses
A The lagging strand cannot be replicated continuously, and ligase is needed to join the fragments.
B Ligase forms the hydrogen bonds between complementary bases in the two strands of DNA.
C Ligase facilitates the binding of RNA polymerase to the promoter region.
D Ligase enables the newly synthesized DNA to twist into a double helix
A
34 Which of the following best explains how the expression of a eukaryotic gene encoding a protein will differ if the gene is expressed in a prokaryotic cell instead of in a eukaryotic cell?
A No transcript will be made, because eukaryotic DNA cannot be transcribed by prokaryotic RNA polymerase.
B The protein will have a different sequence of amino acids, because prokaryotes use a different genetic code.
C The protein will be made but will not function, because prokaryotes cannot remove introns.
D The protein will not be made, because prokaryotes lack the ribosomes necessary for translation.
C
Beta thalassemia is a disorder caused by mutations in the HBB gene. Examination of the
HBB protein in an individual with beta thalassemia shows that the protein is missing many amino acids at its carboxyl terminus.
Which of the following is the most likely explanation for how a mutation in the DNA could result in the loss of the carboxyl terminus of the HBB protein?
A The mutation keeps the HBB gene wrapped tightly around histones, preventing transcription of the gene.
B The mutation changes the promoter sequence of the gene such that different transcription faThe mutation changes a codon in the coding region of the HBB transcript to a stop codon such that translation terminates earlier than it should.ctors initiate transcription of the gene.
C The mutation changes a codon in the coding region of the HBB transcript to a stop codon such that translation terminates earlier than it should.
D The mutation results in hydrogen bonds between adjacent amino acids instead of covalent bonds, resulting in the production of an unstable protein.
C
36 Which of the following best explains how the prokaryotic expression of a metabolic protein can be regulated when the protein is already present at a high concentration?
A Repressor proteins can be activated and bind to regulatory sequences to block transcription.
B Transcription factors can bind to regulatory sequences to increase RNA polymerase binding.
C Regulatory proteins can be inactivated to increase gene expression.
D Histone modification can prevent transcription of the gene.
A
Dystrophin is a protein that is expressed in certain muscle cells. In combination with other cellular proteins, dystrophin strengthens protein fibers in muscle cells to allow muscles to contract without injury.
Nucleotide deletions in the gene that encodes dystrophin are associated with the genetic disorder Duchenne Muscular Dystrophy (DMD). Individuals with DMD do not produce functional dystrophin and, as a result, the protein fibers, and then entire muscle cells, become damaged.
Which of the following best explains how the dystrophin protein is synthesized by certain muscle cells of an individual but not by other cell types?
A Each cell has different genes as a result of changes that occur during development and cell specialization.
b The presence of different transcription factors in different cell types results in differential gene expression.
C A cell can only translate mRNA transcripts that have gene-specific sequences that are recognized by the ribosomes.
D The promoter region of the gene is necessary for expression to occur, and this region is only present in certain cell types.
B
Living cells typically have biosynthetic pathways to synthesize at least some of the amino acids used in making proteins. Some strains of E. coli, a prokaryote, can synthesize the amino acid tryptophan, while other E. coli strains cannot. Similarly, some strains of the yeast S. cerevisiae, a eukaryote, can synthesize tryptophan, while other S. cerevisiae strains cannot.
Which of the following describes the most likely source of genetic variation found in the tryptophan synthesis pathways of both species?
A Exchange of genetic information occurs through crossing over.
B Viral transmission of genetic information required to synthesize tryptophan occurs.
C Random assortment of chromosomes leads to genetic variation.
D Errors in DNA replication lead to genetic variation.
D
In Darwinian terms, the fittest individuals of a species are those that
A attract the most mates
B grow to the largest size
C are best equipped to cope with the predators to which they are exposed
D leave the greatest number of reproducing descendants
D
Many species of corals are threatened by the increasing temperatures and decreasing
pH of ocean waters. One species, Stylophora pistillata, has been found to thrive in water that is warmer and has a lower pH than the water that corals typically thrive in. Additionally, researchers have found that the tolerance for the new water conditions is heritable.
Which of the following statements best explains the changes seen in S. pistillata in response to the changing water conditions?
A The corals’ adaptation is an example of natural selection because the tolerance is in response to a changing environment and has a genetic basis.
B The corals’ adaptation is an example of the founder effect because the majority of corals do not have a tolerance for warmer water.
C The corals’ adaptation is an example of genetic drift because the change was a chance event and not the result of selection in response to environmental change.
D The corals’ adaptation is an example of adaptive radiation because it has resulted in a wide range of species adapting to the new ocean conditions.
A
In plants, members of the euphorbia family and the cactus family have separate origins, with the euphorbia evolving in the desert regions of Asia and Africa and the cacti in the desert regions of the Americas. Both have fleshy stems adapted for water storage, protective spines, and leaves that are greatly reduced or absent. The similarities between these two families of plants represent an example of
A coevolution
B convergent evolution
C genetic drift
D sympatric speciation
E balanced polymorphism
B
The different species of finches on the Galapagos Islands are believed to have arisen as a result of natural selection acting on populations of finches that had experienced
A convergent evolution
B gene flow
C the bottleneck effect
D geographic isolation
E hybrid sterility
D
For following group of questions first study the description of the situation and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet.
If p equals the frequency of the dominant allele and q equals the frequency of the recessive allele, which of the following terms represents the frequency of the individuals who show the dominant phenotype?
A p2
B q2
C 2pq
D p2 + 2pq
E p2 + q2
D
The placement and development of two bones of the reptilian jaw are very similar to that of two bones of the mammalian middle ear, which probably evolved from the reptile bones. The similarity of these bones is an example of
A structural homology
B speciation
C vestigial structures
D convergent evolution
E adaptive radiation
A
A number of different phylogenies (evolutionary trees) have been proposed by scientists. These phylogenies are useful because they can be used to
A determine when two similar populations of a species evolved into two separate species
B evaluate which groups of organisms may be most closely related
C
demonstrate that all photosynthetic organ-isms are members of the Kingdom Plantae
D demonstrate that natural selection is the prevailing force in evolution
E demonstrate which taxa (groups of organisms) contain the most highly evolved species
B
All of the following are density-dependent factors that limit animal populations EXCEPT
A weather
B predation
C birthright
D food competition
E mortality
A
Different species of bumblebee compete for flower nectar in their ecosystem. While the flowers vary in the length of their petals, bumblebees vary in the length of a mouth part called a proboscis. Bumblebees demonstrate a preference for flowers that correspond to the length of their proboscis. Species with proboscises of similar length tend to occupy different areas. Species that live in the same area tend to have proboscises of different lengths.
Which of the following best explains the relationship between the different bumblebee species living in the same area?
A The bumblebees have undergone allopatric speciation due to geographic isolation.
B The bumblebees have undergone niche partitioning due to competition.
C The bumblebees have a mutualistic relationship with other bumblebee species due to natural selection.
D The bumblebees have a commensalistic relationship due to the variety of niches that are available.
B
Wolves, once native to Yellowstone National Park, were hunted to the point of complete extinction in the park. As a result, the elk population in the park flourished, putting extra demands on the carrying capacity of the park. Many other species, such as certain trees and beavers, were negatively affected by the increase in elk.
Years later, wolves were reintroduced into the park. While the elk population decreased after the wolves returned, the beaver and songbird populations began to increase as did the populations of various plant species.
Which of the following best explains how wolves are a keystone species in this ecosystem?
- Wolves help balance the population sizes of other species, allowing more species to thrive in the wolves’ presence than in their absence.
- Wolves prey on certain species, increasing competition among other species, which results in a decrease in biodiversity in the ecosystem.
- Wolves are not affected by factors that typically limit the population size; therefore their population can grow exponentially, increasing the demand on the parks’ resources.
- Wolves prey on other species without having any natural predators themselves; therefore their presence significantly decreases many populations within the community.
A