The diagram shows how water can adhere to the xylem in the stems of plants, which contributes to water movement in the plant. Which of the following best explains how water is able to move upward from the roots of a plant, through its xylem in the stem, and out to the leaves?

A. Water is polar, and the walls of the xylem are nonpolar. Water molecules have the ability to form hydrogen bonds with one another but not with the xylem walls.

B. Water is nonpolar, and the walls of the xylem are polar. Water molecules are able to form hydrogen bonds with the xylem walls, and they are pulled up the xylem.

C. Water and the xylem are both nonpolar. Water molecules have the ability to form hydrogen bonds with one another but not with the xylem walls.

D. Water and the xylem are both polar. Water molecules have the ability to form hydrogen bonds with each other and with the walls of the xylem.

D

The amino acid in Figure 1 is found in a region of a polypeptide that folds away from water. Which part of the amino acid most likely contributes to the hydrophobic behavior of this region of the polypeptide?

A. Amine (NH2) group

B. Carboxyl (COOH) group

C. Methyl (CH3) group

D. Hydrogen (H) atom

C

The sequences for two short fragments of DNA are shown above. Which of the following is one way in which these two segments would differ?

A. Segment 1 would not code for mRNA because both strands have T, a base not found in RNA.

B. Segment 1 would be more soluble in water than segment 2 because it has more phosphate groups.

C. Segment 1 would become denatured at a lower temperature than would segment 2 because A-T base pairs have two hydrogen bonds whereas G-C base pairs have three.

D. Segment 1 must be from a prokaryote because it has predominantly A-T base pairs.

C

The figure below illustrates a eukaryotic cell. Which of the following best describes how the three structures indicated by the arrows work together?

A. To synthesize lipids and modify toxic substances in order to render them harmless

B. To synthesize and isolate proteins for secretion or for use in the cell

C. To catabolize nutrients and produce ATP for intracellular energy storage

D. To synthesize all ribosomal proteins

B

The figure above represents a rough endoplasmic reticulum. Which of the following best describes the role of the structure labeled Y?

A. Structure Y contributes the raw materials required for the synthesis of proteins.

B. Structure Y packages proteins for export from the cell.

C. Structure Y is the location where proteins are synthesized.

D. Structure Y contains enzymes that cut and activate proteins.

C

The following questions refer to the following diagram. For each phrase or sentence, select the labeled part to which it is most closely related. Each option may be used once, more than once, or not at all for each group.

A. A

B. B

C. C

D. D

E. E

D

The manner in which several different ions and molecules move through a cell membrane is shown in the diagram above. For each ion or molecule, the relative concentration on each side of the membrane is indicated. Which of the following accurately describes one of the movements taking place?

A. Glucose is transported into the cell by active transport.

B. Na+ is transported into the cell by active transport.

C. The movement of glucose through the membrane requires ATP hydrolysis.

D. Na+ transport out of the cell requires ATP hydrolysis.

D

The following questions refer to an experiment in which a dialysis-tubing bag is filled with a mixture of 3% starch and 3% glucose and placed in a beaker of distilled water, as shown below. After 3 hours, glucose can be detected in the water outside the dialysis-tubing bag, but starch cannot.

Which of the following best describes the condition expected after 24 hours?

A. The bag will contain more water than it did in the original condition.

B. The contents of the bag will have the same osmotic concentration as the surrounding solution.

C. Water potential in the bag will be greater than water potential in the surrounding solution.

D. Starch molecules will continue to pass through the bag.

E. A glucose test on the solution in the bag will be negative.

A

Which of the following best illustrates the flow of information required for the synthesis of proteins encoded in the genome of a retrovirus?

A. DNA>RNA>PROTEIN

B. RNA>DNA>PROTEIN

C. RNA>DNA>RNA>PROTEIN
D. DNA>RNA>DNA>PROTEIN

C

The diagram above represents a typical rod-shaped bacterium. Which of the following best describes a feature shown in the diagram that is unique to archaea and bacteria?

A. The organism is surrounded by a cell wall.

B. The organism contains ribosomes.

C. The organism does not have a nuclear membrane surrounding its genetic material.

D. The organism is not capable of making or providing itself with ATP.

C

Figure 1 shows the amount of product produced in an enzyme-catalyzed reaction over five minutes. Which of the following best explains how the rate of the reaction changes over time?

A. the rate increases because more products are made over time

B. The rate increases because the ratio of product to substrate increases.

C. The rate decreases because the ratio of product to substrate increases.

D. The rate decreases because the enzyme is used up as the reaction progresses.

C

Based on the data in Figure 1, which of the following most likely represents the change in energy that occurs when ATP hydrolysis is coupled with the phosphorylation of a substrate?

A. Line 4 represents ATP hydrolysis, and line 1 represents phosphorylation of a substrate.

B. line 1 represents ATP hydrolysis, and line 4 represents phosphorylation of a substrate.

C. Line 2 represents ATP hydrolysis, and line 3 represents phosphorylation of a substrate. Line 2 represents A T P hydrolysis, and line 3 represents phosphorylation of a substrate.

D. Line 3 represents ATP hydrolysis, and line 2 represents phosphorylation of a substrate.

B

Figure 1. Diagram of the electron transport chain and ATP synthase in the membrane of mitochondria

A. NADH contributes more electrons to the electron transport chain than FADH2 does and therefore provides more energy to pump protons.

B. The electrons of FADH2 are transferred through three complexes of the electron transport chain whereas those of NADH are transferred through all four complexes

C. F A D H 2 contributes more protons to the mitochondrial matrix, which decreases the proton gradient.

D. The protons contributed by FADH2 are combined with O2 to make water and are not pumped across the membrane.

B

Which of the following best represents two different signaling pathways that share a second messenger?

(#14 on p. 2)

yea go look at the practice for this one idk how to describe the flic

Two types of cells, alpha and beta cells, produce signaling molecules that affect blood sugar levels in opposite ways (Figure 1). Epinephrine is a chemical, often released during periods of exercise, that ultimately causes an increase in blood sugar levels in the body.

Based on Figure 1, which of the following best explains how exercise causes blood glucose levels to rise?

A. Epinephrine inhibits alpha cells, causing the release of glucagon, and activates beta cells, blocking the release of insulin.

B. Epinephrine activates alpha cells, blocking the release of glucagon, and inhibits beta cells, causing the release of insulin.

C. Epinephrine activates alpha cells, causing the release of glucagon, and inhibits beta cells, blocking the release of insulin.

D. Epinephrine inhibits alpha cells, blocking the release of glucagon, and activates beta cells, causing the release of insulin.

C

Insulin, a hormone secreted by pancreatic cells, stimulates glucose uptake in skeletal muscle cells by mobilizing glucose transporter proteins (GLUT4) to the plasma membrane. As depicted in Figure 1, binding of insulin to the insulin receptor triggers an intracellular signaling cascade in which certain molecules activate other molecules in a relay of the hormone signal to cell targets. One outcome of the signaling cascade is mobilization of GLUT4 from vesicle storage sites in the cytoplasm to sites at the cell surface, where GLUT4 allows glucose to enter the cell.

Based on the experimental results, which of the following describes the most likely defect in muscle cells of patients with type 2 diabetes?

A. Insulin receptor proteins do not reach the cell surface.

B. Insulin does not activate its receptor.

C. IRS-1 activation is reduced at high insulin concentrations.

D. GLUT4 blocks glucose from entering cells.

C

Figure 1. A model of an endocrine signaling pathway showing involved body parts and hormones. GnRH = gonadotropin-releasing hormone, LH = luteinizing hormone, and FSH = follicle-stimulating hormone.

Figure 1 shows a model of the endocrine signaling pathway that regulates ovulation. Which of the following observations would provide evidence of a positive feedback mechanism in this system?

A. Estrogen from the ovaries inhibits the release of GnRH from the hypothalamus.

B. Progesterone from the ovaries stimulates the thickening of the uterine lining.

C. Progesterone from the ovaries inhibits the release of LH and FSH from the anterior pituitary. Progesterone from the ovaries inhibits the release of L H and F S H from the anterior pituitary.

D. Estrogen from the ovaries stimulates the hypothalamus and anterior pituitary to secrete more GnRH , LH , and FSH .

D

Figure 1. Diagram of the cell cycle with key checkpoints

Which of the following describes a mutation that would lead to an increase in the frequency of nondisjunction?

A. A mutation affecting checkpoint 1 proteins that forces cells to enter G0

B. A mutation affecting checkpoint 2 proteins that allows cells to divide with DNA damage

C. A mutation affecting checkpoint 3 proteins that prevents attachment of spindle fibers

D. A mutation affecting checkpoint 2 proteins that prevents duplication of the chromosomes

C

The diagram above illustrates which of the following processes?

A. Crossing-over

B. Base pair substitution

C. Duplication

D. Deletion

E. Posttranscriptional processing

A

In the pedigree above, squares represent males and circles represent females. Individuals who express a particular trait are represented by shaded figures. Which of the following patterns of inheritance best explains the transmission of the trait?

A. Sex-linked dominant

B. Sex-linked recessive

C. Autosomal recessive

D. Autosomal dominant

E. Incompletely dominant

D

The pedigree below shows the inheritance of a dominant allele of a gene in a family over several generations. Circles represent females and squares represent males. Shaded symbols indicate individuals carrying the allele.

The pedigree suggests that the gene is on a nuclear chromosome, and not on mitochondrial DNA, because

A. mitochondrial genes are not heritable

B. mitochondrial mutations cannot produce dominant traits

C. maternal mitochondrial mutations are inherited by all of a mother’s offspring

D. mitochondrial DNA is circular, whereas chromosomal DNAis linear

C

The diagram above depicts a karyotype of an individual human. Which of the following statements concerning the karyotype in the diagram is true?

A. The diagram illustrates a genetic condition found in females.

B. The diagram indicates a mechanism for increasing genetic diversity in subsequent generations.

C. The diagram illustrates the results of nondisjunction during gamete formation.

D. The diagram indicates Down syndrome, a genetic condition.

C

The mRNA transcribed from the DNA would read

A. 5’ TAG TTC AAA CCG CGT AAC AAT 3’

B. 5’ ATC AAG TTT GGC GCA TTG TAA 3’

C. 5’ AUC AAG UUU GGC GCA UUG UAA 3’

D. 5’ AAU CAA UGC GCC AAA CUU GAU 3’

E. 5’ AUU GUU ACG CGG UUU GAA CUA 3’

C

When DNA replicates, each strand of the original DNA molecule is used as a template for the synthesis of a second, complementary strand. Which of the following figures most accurately illustrates enzyme-mediated synthesis of new DNA at a replication fork?

(practice 2, question #24)

sorry pookle u gotta go look at the flic

Which of the following best describes an event during step 2 in the simplified model above?

A. A new RNA molecule is synthesized using a DNA template.

B. A new polypeptide is synthesized using an RNA template.

C. Thymine nucleotides in an RNA molecule are replaced with uracil nucleotides.

D. Noncoding sequences are removed from a newly synthesized RNA molecule.

D

Based on the universal genetic code, which of the following represents the correct polypeptide that will result from translation of the mRNAmolecule shown, beginning with the first available start codon?

A. Asp−Arg−Met−Val−Thr−Lys−Phe−Gly−His

B. Met−Arg−Asp−Stop−His−Gly−Phe−Lys−Thr−Val

C. Met−Val−Thr−Lys−Phe−Gly−His

D. Val−Thr−Lys−Phe−Gly−His

C

Phenotype is determined, in part, by which genes are expressed. The diagram below illustrates how the product of gene X regulates the expression of other genes.

Which of the following statements best explains how protein X regulates gene expression?

A. Protein X is responsible for processing pre-mRNA.

B. Protein X is responsible for activating transcription of some genes but not others.

C. Protein X is a member of some cytoplasmic protein complexes but not others.

D. Protein X causes specific base-pair changes to produce new alleles.

B

The p53 protein regulates a cellular response to DNA damage. Based on the diagram above, which of the following best describes the role of p53 in the response to DNA damage?

A. Phosphorylated p53 binds to DNA and repairs the damage.

B. Phosphorylated p53 stimulates transcription of p21 , and the resulting p21 protein suppresses cell division until the DNA damage is repaired. Phosphorylated , p 53, stimulates transcription of , p 21, , and the resulting , p 21, protein suppresses cell division until the , D N A, damage is repaired.

C. Phosphorylated p53 binds cyclin−Cdk complexes, and the resulting protein complex repairs the DNA damage.

D. Phosphorylated p53 activates p21 proteins, and the p21 proteins in turn repair the DNA damage.

B

A karyotype is a representation of all the metaphase chromosomes in a sample of cells from a particular individual (Figure 1).

Which of the following most likely explains how the chromosomes circled in Figure 1 could cause a genetic disorder in the person from whom the cells were obtained?

A. The extra chromosome causes crowding in the nucleus of the cells and blocks RNA polymerase from binding to and transcribing certain genes.

B. The extra chromosome will affect the levels of RNA transcribed from certain genes and the amount of protein produced from those genes in each cell.

C. The cells will not divide and enable growth, because the extra chromosome will interfere with the pairing of homologous chromosome

D. The extra chromosome will cause other chromosomes in the cell to become triploid during future rounds of cell division.

B

In a transformation experiment, a sample of E. coli bacteria was mixed with a plasmid containing the gene for resistance to the antibiotic ampicillin (ampr). Plasmid was not added to a second sample. Samples were plated on nutrient agar plates, some of which were supplemented with the antibiotic ampicillin. The results of E. coli growth are summarized below. The shaded area represents extensive growth of bacteria; dots represent individual colonies of bacteria.

Which of the following statements best explains why there are fewer colonies on plate IV than on plate III?

A. Plate IV is the positive control.

B. Not all E. coli cells are successfully transformed.

C. The bacteria on plate III did not mutate.

D. The plasmid inhibits E. coli growth

B

The three-spined stickleback (Gasterosteus aculeatus) is a small fish found in both marine and freshwater environments. Marine stickleback populations consist mainly of individuals with armor-like plates covering most of their body surface (completely plated). Approximately 10,000 years ago, some marine sticklebacks colonized freshwater environments. After many generations in the freshwater environments, the freshwater stickleback populations lacked the armor plating (low plated) typical of marine stickleback populations.

Over the period between 1957 and 2005, one freshwater population, in Lake Washington, a lake in a coastal region of the northwestern United States, changed from having a majority of individuals of the low-plated phenotype to having more individuals of the completely-plated phenotype than of the low-plated phenotype. Figure 1 shows the distribution of plated phenotypes in Lake Washington sticklebacks at four time points between 1957 and 2005.

Which of the following best explains the differences in the armor of the Lake Washington stickleback population summarized in Figure 1 ?

A. Analysis of somatic cells using chromosomal staining and light microscopy indicates that stickleback fish have a diploid number of 42.

B. Stickleback males from natural freshwater populations are typically more aggressive when competing for mates than are stickleback males from laboratory-bred populations..

C. Fish exhibiting the low-plated phenotype were selected against in the Lake Washington stickleback population over the last 50 years.

D. Migration of individuals from other freshwater environments to Lake Washington led to gene flow between populations that were once geographically isolated.

C

Which of the following describes a scenario that would result in the phenotypic change shown in the graph?

A. A fish that has mouth parts adapted to eat moderately sized prey is introduced into a lake in which there are only large and small prey.

B. A population of mice live on the ground and in short trees. An invasive, tree-dwelling snake that preys on the mice is introduced into the area.

C. Climate change-induced warming of arctic tundra reduces average snow cover that lighter-colored arctic foxes rely on for camouflage. Darker-colored arctic foxes are better suited to the exposed moss and grass habitat.

D. House sparrows that lay smaller-than-average clutches of eggs produce fewer viable offspring, while larger-than-average clutches of eggs result in malnourished chicks that have a higher mortality rate.

D

question #33 on p.2 GO LOOK TO LEARN

too complicado to copy and paste

Portions of the amino acid sequences of some dehydrogenase enzymes found in bacteria, yeast, corn, horses, and sheep are shown in Figure 1. Each letter represents a different amino acid in the sequence.

Based on Figure 1, which of the following conclusions about the enzymes is most likely correct?

A. Corn and horse dehydrogenase enzymes arose separately during each organism’s evolution and now exhibit strong sequence similarity as a result of their similar catalytic roles.

B. These enzymes all evolved from a common prokaryotic dehydrogenase enzyme, so they exhibit regions of sequence similarity.

C. Any evolutionary relationship is unlikely, because there is little sequence similarity between these enzymes.

D. No conclusion can be drawn based on amino acid sequence, because there are twenty amino acids and only four nucleotides.

B

The gene encoding the catalytic subunit of cytochrome c oxidase (MT-CO1 ) is found in the mitochondria of all animals. The gene evolves rapidly and is often used to determine evolutionary relationships among species. Table 1 shows DNA sequence differences among four animal species (I , II , III , and IV ). Which of the following cladograms best represents the evolutionary relationships among the four species?

(practice 2 questoin #35 go look to leanr its flics)

sowwy

Over many generations, two populations of the same species can diverge into separate species through reproductive isolation. The figures below represent a model of speciation and show the results of matings between individuals from two diverging populations at four different stages of speciation. The males represented in the model are heterogametic, which means they have two different sex-determining chromosomes, (e.g., XY). The females are homogametic, which means they have two similar sex-determining chromosomes, (e.g.,XX). The offspring from each mating are labeled interpopulation hybrids.

Based on the model of speciation presented, which of the following describes the most likely consequence to the populations over time?

A. Hybrid individuals are less likely to pass their genetic information on to subsequent generations.

B. Hybrid individuals living together are physically unable to mate with each other.

C. Geographically isolated populations gradually acquire similar heritable traits

D. Differences between hybrid individuals of a species disappear over time.

A

As depicted in the diagram, honeybees communicate the location of flower patches to members of their hives with waggle dances that give information about the direction and distance to the flowers. Which of the following statements about how honeybees communicate the position of flower patches is most consistent with the model?

A. The number of repetitions of the waggle dance indicates the quality of the pollen source.

B. The total area covered by any waggle dance leads bees to the target flowers.

C. The angle of the waggle phase relative to the vertical plane indicates the position of the target flowers relative to another beehive.

D. The farther the target flowers from the hive, the longer the waggle phase.

D

Based on Figure 1, which of the following is the most likely short-term effect of a decrease in the killer whale population?

A. The sea otter and kelp populations will increase, while the sea urchin population will decrease.

B. The sea otter and sea urchin populations will increase, while the kelp population will decrease.

C. The sea otter population will stay the same, while the sea urchin and kelp populations will increase

D. There will be no change to the sea otter, sea urchin, and kelp populations because another predator species will fill the niche previously occupied by the killer whales.

A

Which of the following changes to the environment will most likely lead to more energy entering the meadow community represented above?

A. Increasing the number of nesting sites for hawks and owls

B. Removing squirrels from the area

C. Increasing the light available to the plants

D. Applying a chemical pesticide that is specific for spiders

C

In an investigation, the relationship between black bears, salmon, and influx of marine nitrogen into the area around a southwestern Alaskan stream was studied. The investigators established several test plots of the same size along the stream with the following species composition: no salmon or black bears (N), bears but not salmon (B), salmon but not bears (S), and a plot where salmon and bears interact (SB). Nitrogen influx in the different sampling areas was measured as a means of assessing the impact of the different species on the health of the ecosystem. The data are plotted in Figure 1.

Which of the following statements is best supported by the data?

A. Black bears are a keystone species.

B. Salmon are a keystone species.

C. Black bear urine is a significant source of nitrogen in the environment.

D. The presence of black bears and salmon correlates with a significant increase in nitrogen influx.

D