AP Bio S1 Final Part 1
Which of the following best describes the role that water plays in the reaction depicted above?
As a reactant, water cleaves the covalent bond that holds the dimer together.
A group of biology students wants to study the effects of pH on enzyme activity. They measure the activity of enzymes A and B at various pHs and record their data in the graph below. Based on the graph, what is the approximate optimal pH for enzyme B?
10
The physical characteristics of a cell influence how it functions. For example, the surface area and volume of a cell affect how efficiently waste is removed from the cell via diffusion. The table below shows data for four different cuboidal cells. Cell A 2, Cell B 4, Cell C 6, Cell D 8 Using the information from the table, what is the surface-area-to-volume ratio for the cuboidal cell that removes waste via diffusion most efficiently?
3
Which of the following best describes how the internal environment of a lysosome compares to the environment of the cytosol?
The internal environment of a lysosome is more acidic than the cytosol.
A group of biology students weighed several potato cubes and placed them in open beakers containing various sucrose solutions at 26º C. The following day, the students weighed the potato cubes again and calculated the differences in mass. It was determined that solute potential equilibrium was reached at 0.60 M. What is the solute potential of the potato cubes?
-15 bar
A student places a zucchini cube into an open container containing a 0.70 M sucrose solution. The temperature of the solution is kept steady at 20º C. What is the water potential of the zucchini cube?
-17 bars
A student places a zucchini cube into an open container containing a 0.20M sucrose solution. The temperature of the solution is kept steady at 27º C. What is the water potential of the zucchini cube?
-5.0 bar
The solute potential of a plant cell is 6.5 bar, and its pressure potential is 1.5 bar. The plant cell is placed into a solution with a water potential of −2.5 bar. What is the water potential of the cell, and in which way will water move?
-5.0 bar; water will move into the cell
An oocyte is an immature reproductive cell found in many sexually reproducing organisms. A crawfish oocyte has a radius of approximately Assuming both cell types are perfectly spherical, how many times larger is the surface area of a crawfish oocyte compared to the surface area of a human oocyte?
400
In the reaction above, two glucose monomers combine to form the dimer maltose. Which of the following best explains the process of this reaction?
A covalent bond forms through dehydration synthesis, which results in the formation of maltose and water.
Which of the following describes the most likely way in which two water molecules will interact?
A hydrogen bond will form between the hydrogen atom of one water molecule and the oxygen atom of the other water molecule.
Acetylcholine (ACh) is an important signaling molecule in the nervous system. After it transmits a signal, ACh is broken down by the enzyme acetylcholinesterase (AChE) in a reaction known as ACh hydrolysis. Which of the following best describes the effect AChE has on the hydrolysis of ACh?
AChE decreases the activation energy of ACh hydrolysis, increasing the rate of this reaction.
An embedded membrane protein spans the entire cell membrane of a single cell. Which of the following must be true about the amino acids that make up the protein?
Amino acids with charged side groups are in contact with the phosphate region of the cell membrane.
Which of the following is true about the amino acids that make up a transmembrane protein?
Amino acids with nonpolar side groups are in contact with the fatty acid region of the cell membrane.
Which of the following questions would best help identify a compartmentalized cell?
Are there membrane-bound organelles within the cell?
Methotrexate is a drug that is commonly used to treat cancers and autoimmune diseases in humans. It functions by binding to the active site of the enzyme DHFR, preventing both DNA synthesis and excess cell proliferation. Which of the following terms best describes methotrexate?
Competitive inhibitor
Consider the following molecular model. Based on its elemental composition, which of the following molecules does the model most likely represent?
Glucose, a simple carbohydrate (red, grey, and white)
In order to develop antibiotics, scientists need to understand how bacteria grow and reproduce. One factor that is essential for bacterial growth and reproduction is protein synthesis. By understanding how bacteria synthesize proteins, scientists can then attempt to develop antibiotics that block bacterial protein synthesis during an infection. Which of the following questions will best direct an investigation on how to develop an antibiotic that inhibits protein synthesis in bacteria?
How can the carboxyl (-COOH) terminus of a growing polypeptide chain be blocked?
Which of the following best explains how substances are transported across the cell membrane?
Hydrophilic amino acids move across the cell membrane through embedded transport proteins.
Based on the reaction depicted above, which of the following statements is true?
If water is not added to the reaction, hydrolysis will not occur.
Which of the following best describes how substances move across the cell membrane?
Ions move across the cell membrane through embedded channel proteins.
Which of the following questions would a researcher most likely ask if they wanted to know whether a hydrolysis reaction or a dehydration synthesis reaction is occurring?
Is water a reactant or product of the reaction?
The model below depicts the movement of several ions and molecules across a cell membrane. For each ion or molecule, the relative concentration on each side of the membrane is shown. Which of the following statements accurately describes one of the movements shown in the model?
K+ movement into the cell requires ATP hydrolysis.
Consider a reaction in which reactants X and Y combine to form the product Z. The diagram below compares the reaction coordinates for the catalyzed and uncatalyzed pathways of this reaction.Which of the following statements about letter B is true?
Letter B represents the activation energy of the catalyzed reaction pathway.
Maltase is an enzyme found in the small intestine. It helps break down maltose during the process of digestion. Which of the following best describes what happens when maltose binds with maltase?
Maltose binds to the active site of maltase, causing the conformation of the active site to change slightly.
The model below depicts the movement of several ions and molecules across a cell membrane. For each ion or molecule, the relative concentration on each side of the membrane is shown. The model below depicts the movement of several ions and molecules across a cell membrane. For each ion or molecule, the relative concentration on each side of the membrane is shown.
Na+ is transported out of the cell by active transport.
Pepsin, a proteolytic enzyme found in the stomach, is essential for digestion. Pepsin functions optimally at approximately 37º C. Which of the following would most likely result if pepsin's environmental temperature was lowered from 37º C to 25º C?
Pepsin would be less efficient at catalyzing reactions.
Which of the following is true about the transportation of substances across the lipid region of the cell membrane?
Small nonpolar molecules can freely dissolve across the lipid region of the cell membrane.
In the reaction depicted above, maltose is broken down into two molecules of glucose. Which of the following best explains the process of this reaction?
The addition of a water molecule cleaves the covalent bond holding maltose together.
A single step reaction is represents below. A + B —> AB + heat Which of the following best explains how the addition of an enzyme would affect the above reaction?
The enzyme would decrease the activation energy of the reaction, increasing its rate.
Based on the information above, which of the following best describes the functional conformation of barnase?
The functional conformation of barnase has a tertiary structure because it consists of a polypeptide chain folded into a three-dimensional shape.
ATP synthase is a protein complex that is highly conserved across eukaryotes. This protein complex helps generate ATP, which the cell uses as a source of energy. The ATP synthase complex is made up of multiple protein subunits that are required for its function. One of these subunits, ATPsynC, is encoded by the ATPsynC gene. Which of the following claims is best supported by the results of the study described above?
The level of ATP in mutant flies is correlated with the severity of the phenotype seen in those flies.
The plant Sorghum bicolor produces an anti-herbivory chemical called dhurrin. Dhurrin is synthesized from the amino acid tyrosine in a three-step metabolic pathway. Which of the following claims is best supported by the experimental results described above?
The product of the reaction catalyzed by Enzyme 2 is efficiently transferred to Enzyme 3.
The endoplasmic reticulum (ER) is a structure found in eukaryotic cells. It is composed of two parts: the smooth ER and the rough ER. Which of the following best describes a difference between the rough ER and the smooth ER?
The rough ER has ribosomes on its surface, but the smooth ER does not.
In the reaction depicted above, two amino acids have combined to form a dipeptide. Which of the following best explains the process occuring in this reaction?
Through dehydration synthesis, a covalent bond forms to connect the dipeptide together, and a water molecule forms as a product.
Which of the following best describes how organelles within the endomembrane system function together to transport proteins?
Vesicles bud off from one organelle and then fuse with others to transport proteins through the endomembrane system.
Which of the following biological activities best demonstrates water's adhesive properties?
Water travels through vascular tissue from the roots to the leaves of a plant, moving against the force of gravity.
Which of the following best describes how the central vacuole helps support the structure of a plant cell?
When the central vacuole is full of water, it applies pressure to the cell wall and maintains the shape of the cell.
Which of the following best describes the role that water plays in the reaction depicted above?
When water condenses out of the reaction, a dimer is created as a covalent bond forms between two monomers.
Which of the following describes how regions of phospholipids are arranged in the cell membrane?
Hydrophobic fatty acid regions face each other within the interior of the cell membrane.
A student places a zucchini cube into an open container containing a 0.50 M sucrose solution. The temperature of the solution is kept steady at 25º C. What is the water potential of the zucchini cube?
-12 bars
The physical characteristics of a cell influence how it functions. For example, the surface area and volume of a cell affect how efficiently waste is removed from the cell via diffusion. The table below shows data for four different spherical cells. Spherical cell Cell A 1, Cell B 2, Cell C 3, Cell D 4 Using the information from the table, what is the surface-area-to-volume ratio for the spherical cell that removes waste via diffusion most efficiently?
3
Which of the following best describes the permeability of the cell wall?
The cell wall is a semipermeable structural boundary that allows some substances to enter the internal environment.
Humans are made up of many types of cells, and these cells have a broad range of sizes. For example, an immune system cell called a neutrophil has a radius of approximately 4μm, while a type of connective tissue cell called a fibroblast has a radius of about 8μm. Assuming both cell types are perfectly spherical, how many times larger is the surface area of a fibroblast compared to the surface area of a neutrophil?
4
Which of the following observations is best explained by water's high surface tension?
A leaf floats on the surface of a puddle.
The images below show the 3D space-filling models of two lipids. One lipid has a straight structure and the other lipid has a kinked, or bent structure. Which of the following best describes how kinks within lipids contribute to the fluidity of the cell membrane?
The hydrocarbon tails of unsaturated fatty acids form kinks that prevent dense packing of components within the cell membrane.
Which of the following best explains why enzymatic reactions within the lysosome are compartmentalized?
The hydrolytic enzymes of the lysosome function best within an environment that differs from the cytosol
Which of the following statements accurately describes an energy-releasing process that is coupled to an energy-requiring process in the cell?
The movement of motor proteins is powered by the formation of ADP and inorganic phosphate from ATP.
Which of the following statements best explains how the cell membrane is selectively permeable?
The movement of specific substances into and out of the cell is controlled by the cell membrane.
A student uses a microscope to compare a human skeletal muscle cell and a human epithelial cell. The student observes that the muscle cell has more mitochondria than the epithelial cell. Which of the following conclusions is best supported by this observation?
The muscle cell requires more ATP than the epithelial cell.
The following table shows the relative percentages of elements in a certain biological molecule. Which of the following best describes the biological molecule? C46% N0% P0% O51% S0% H3%
The molecule is a complex carbohydrate.
Which of the following best describes the biological molecule? C38%, N17%, P10%, 31%, S0%, H4%
The molecule is a nucleic acid.
The following table shows the relative percentages of elements in a certain biological molecule. Which of the following best describes the biological molecule? (C54%, N17%, P0%, O21%, S1%, H7%) Which of the following best describes the biological molecule?
The molecule is a protein.
The diagram below represents a rough endoplasmic reticulum. Which of the following best describes the function of the structures labeled X? (Pointing at ribosomes)
They translate mRNA into amino acid sequences.
In order to develop antibiotics, scientists need to understand how bacteria grow, divide, and spread during an infection. An essential part of bacterial growth is RNA synthesis because RNA must be synthesized before proteins can be assembled. If RNA synthesis is blocked, bacteria will not be able to survive and reproduce. Which of the following questions will best direct an investigation on how an antibiotic that inhibits RNA synthesis in bacteria can be developed?
Which chemical compounds block the 3' end of a growing RNA strand?
The image above depicts the signal transduction pathway of epinephrine. During one step in the pathway, the enzyme glycogen phosphorylase is phosphorylated, which activates the enzyme. If an inhibitor prevents glycogen phosphorylase from being activated during this pathway, which of the following will most likely occur?
Blood glucose levels will not increase in response to epinephrine.
Which of the following most accurately describes the movement of substances across the lipid region of the cell membrane?
Gases such as N2, O2, and CO2 can freely dissolve across the lipid region of the cell membrane.
Which of the following statements is true for both prokaryotic and eukaryotic cells?
Ribosomes synthesize proteins using mRNA sequences.
Eukaryotic cells contain an intricate endomembrane system that includes the nucleus, endoplasmic reticulum (ER), and Golgi complex. The Golgi complex and rough ER are often near each other, which is essential for their roles in the endomembrane system. Which of the following most accurately explains why the Golgi complex is often near the rough ER?
The Golgi complex modifies and packages proteins that are produced in the rough ER.
Cyanide is a toxin that can affect cellular respiration. It functions by binding to an allosteric site on the enzyme cytochrome c oxidase, disrupting the electron transport chain. Cyanide is able to bind to cytochrome c oxidase whether or not the enzyme is bound to a substrate. Which of the following terms best describes cyanide?
noncompetitive inhibitor
A group of biology students weighed several potato cubes and placed them in open beakers containing various sucrose solutions at 45º C. The following day, the students weighed the potato cubes again and calculated the differences in mass. It was determined that solute potential equilibrium was reached at 0.50 M
-13 bar
The solute potential of a plant cell is -15 bar, and its pressure potential is 7 bar. The plant cell is placed into a solution with a water potential of −8 bar. What is the water potential of the cell, and in which way will water move?
-8 bar; there will be no net movement of water
A group of biology students weighed several potato cubes and placed them in open beakers containing various sucrose solutions at 30º C. The following day, the students weighed the potato cubes again and calculated the differences in mass. It was determined that solute potential equilibrium was reached at 0.35 M. What is the solute potential of the potato cubes?
-8.8 bar
The solute potential of a plant cell is -12 bar, and its pressure potential is 3 bar. The plant cell is placed into a solution with a water potential of -10 bar. What is the water potential of the cell, and in which way will water move?
-9.0 bar; water will move out of the cell
The physical characteristics of a cell influence how it functions. For example, the surface area and volume of a cell affect how efficiently waste is removed from the cell via diffusion. The table below shows data for four different spherical cells. Cell A 3, Cell B, Cell C 5, Cell D 6 Using the information from the table, what is the surface-area-to-volume ratio for the spherical cell that removes waste via diffusion most efficiently?
1
Humans are made up of many types of cells, and these cells have a broad range of sizes. For example, a type of fat cell called an adipocyte has a radius of approximately 50μm, while a type of heart muscle cell called a cardiomyocyte has a radius of about 15μm. Assuming both cell types are perfectly spherical, approximately how many times larger is the surface area of an adipocyte compared to the surface area of a cardiomyocyte?
11
Cell A has a surface area of 50μm^2 and a volume of 10μm^3. Cell B has a surface area of 14μm^2 and a volume of 7μm^3. 3 7, mu, start text, m, end text, cubed. Using the information above, determine the surface-area-to-volume ratio of each cell. What is the SA:V ratio of the cell that will exchange materials with its environment at the fastest rate of diffusion?
5
The figure above depicts an agar cube with a side length of 12 mm. In an experiment, students submerged the cube in blue dye for 12 hours. The blue dye permeated 2 mm on each side, as indicated by the shading in the figure. Calculate the volume of the agar cube that remained unpenetrated by the blue dye.
512
Cell Y has a surface area of 40 um^2 and a volume of 8 um^3. Cell Z has a surface area of 72 um^2 and a volume of 12 um^3. Using the information above, determine the surface-area-to-volume ratio of each cell. What is the SA:V ratio of the cell that will exchange materials with its environment at the fastest rate of diffusion?
6
The physical characteristics of a cell influence how it functions. For example, the surface area and volume of a cell affect how efficiently waste is removed from the cell via diffusion. The table below shows data for four different cuboidal cells. Cell A 1, Cell B 2, Cell C 3, Cell D 4 Using the information from the table, what is the surface-area-to-volume ratio for the cuboidal cell that removes waste via diffusion most efficiently?
6
The figure above depicts an agar cube with a side length of 12mm. In an experiment, students submerged the cube in orange dye for 12 hours. The orange dye permeated 1.5mm on each side, as indicated by the shading in the figure. Calculate the volume of the agar cube that remained unpenetrated by the orange dye.
729
The following is an excerpt from a scientific paper written by Fagarasanu & Rachubinski. This physical compartmentalization of the cytoplasm permits the coexistence of a diverse range of chemical microenvironments, each precisely tailored for a defined set of biochemical reactions. Organelles constantly communicate with one another, which leads to the establishment of an effective and cooperative division of metabolic labor. Which of the following best explains how compartmentalization within a cell leads to a "cooperative division of metabolic labor?"
A compartmentalized cell has internal membranes that minimize competing interactions within the cell.
Thyroid-stimulating hormone (TSH) is a long-distance signaling molecule released by the anterior pituitary gland. Once released, TSH travels through the bloodstream to the thyroid gland, where it binds to G protein-coupled receptors called TSH receptors. This binding initiates signal transduction pathways that produce two thyroid hormones, T3 and T4. Which of the following best explains why individuals with hypothyroidism have low levels of T3 and T4?
A mutation in their TSH receptors decreases TSH recognition, resulting in decreased signal transduction.
Which of the following best describes the process of induced fit?
A substrate binds to the active site of an enzyme, causing the conformation of the active site to change slightly.
A scientist grew Chlorella, a single-celled photosynthetic algae, for 3 weeks in a laboratory culture. The culture medium contained dissolved carbon dioxide and nitrogen compounds, but it did not contain phosphates. At the beginning and end of the 3-week period, the scientist measured the rate of synthesis for certain biological molecules. Which of the following graphs shows the most likely results of the experiment?
A. 12 12 carbohydrates, 6 6 proteins, 4 2 nucleic acids, 4 1.8 lipids
Phenytoin is a prescription drug that is used to treat patients with epilepsy. A side effect of phenytoin is that it can be toxic to mitochondria. Which of the following processes will be most immediately disrupted by this side effect?
ATP synthesis
Acetylcholine is a neurotransmitter that helps control muscle contraction. This neurotransmitter functions differently depending on which type of muscle it interacts with. For example, acetylcholine promotes muscle contraction in skeletal muscle but inhibits contraction in heart muscle. Which of the following best explains why acetylcholine leads to different cellular responses in skeletal and heart muscle?
Acetylcholine binds to different types of receptors in skeletal and heart muscle.
Which of the following statements about cell structures best supports the common ancestry of all living things?
All cells contain ribosomes.
Which of the following questions would best help determine if a cell has membrane-bound organelles?
Are there distinct environments within the cell?
Which of the following best describes how high levels of cholesterol affect the cell membrane at certain temperatures?
At high temperatures, high amounts of cholesterol decrease the fluidity of the cell membrane.
Trypsin, a proteolytic enzyme found in the small intestine, is essential for digestion. Trypsin functions optimally at approximately 37º C. At very high temperatures, the enzyme's activity stops almost completely. Which of the following best explains why trypsin is not active at high temperatures?
At high temperatures, trypsin loses its tertiary and secondary structures.
Which of the following best describes how high levels of cholesterol affect the cell membrane at certain temperatures?
At low temperatures, high amounts of cholesterol increase the fluidity of the cell membrane.
Most species of shark are strict carnivores. However, bonnethead sharks (Sphyrna tiburo) have been observed consuming seagrass within their natural habitat. Like other plants, seagrasses contain cellulose within their cell walls. Based on the information above, which of the following best supports the claim that bonnethead sharks are capable of hydrolyzing cellulose during digestion?
Cellulose is consumed as a linear polysaccharide and is broken down into glucose monosaccharides during digestion.
A lack of water can cause plant cells to become flaccid. This gives the plant a wilted appearance as shown in the figure below. Which of the following cell structures is most likely responsible for the plant's wilted appearance?
Central vacuole
Chlorophyll a is a pigment that absorbs light energy from the sun and gives plants their green color. Which of the following plant cell structures is most likely to contain chlorophyll a?
Chloroplast
Based on its elemental composition, which of the following molecules does the model most likely represent?
Cytidine, a building block of the nucleic acid DNA
Which of the following diagrams shows the most likely way that two water molecules will bond with each other? A. Vertical Diagram B. Two molecules without line C. Two molecules with line D. Diagonal molecules
D. Diagonal molecules
In the 1950s, the scientists Alfred Hershey and Martha Chase carried out an experiment using bacteriophages, which are viruses that infect bacteria. During the experiment, the scientists allowed bacteriophages that had been labeled with either radioactive phosphorus or radioactive sulfur to infect bacterial cells. After the infection process occurred, the scientists found that the bacterial cells contained significant amounts of radioactive phosphorus, but not radioactive sulfur. Based on the results of the experiment, which of the following molecules did the bacteriophages most likely inject into bacterial cells to cause infection?
DNA, which is a nucleic acid
A group of biology students wants to study the effects of pH on enzyme activity. They measure the activity of enzymes A and B at various pHs and record their data in the graph below. A solution of enzyme A has a pH of 8. Based on the graph, which pH change would result in higher enzyme activity?
Decreasing the pH of the solution to 6
The following is an excerpt from a scientific paper written by Pan & Ren. Which of the following represents the best method to decrease the virulence of a microbe capable of QS?
Develop a drug that decreases the cell density of the microbial infection.
Several essential mechanisms in the cell, including protein synthesis, require the amino acid glutamine. The formation of glutamine from glutamate and ammonia is an energy-requiring process. This process is carried out by an enzyme called glutamine synthetase. Based on the information provided, which of the following statements is true?
During glutamine synthesis, an exothermic reaction provides energy to drive an endothermic reaction.
A damaged cell is unable to properly modify proteins after they are synthesized, which causes the proteins to misfold. Which of the following structures is most likely damaged in the cell?
Endoplasmic reticulum
Which of the following best explains why there is a difference in pH between the IMS and the cytosol?
Enzymatic reactions in the IMS require an environment that is more acidic than the cytosol.
Ptyalin is a digestive enzyme found in saliva. It helps break down large starch molecules early in the digestive process. Ptyalin is unable to break down proteins. Which of the following best explains why ptyalin is able to break down starches, but not proteins?
Enzymes are specific to their substrates.
Pancreatic amylase is a digestive enzyme found in the small intestine. It helps break down large starch molecules later in the digestive process. Pancreatic amylase is unable to break down lipids. Which of the following best explains why pancreatic amylase is able to break down starches, but not lipids?
Enzymes bind only to their specific substrates.
The model below depicts the movement of several ions and molecules across a cell membrane. For each ion or molecule, the relative concentration on each side of the membrane is shown. Which of the following statements accurately describes one of the movements shown in the model?
Glucose moves into the cell by passive transport.
Several botanists are studying the effect of high temperature on chloroplast function in Arabidopsis thaliana, a species of flowering plant. The botanists find that extremely high temperatures damage the membrane of the chloroplasts. This causes the contents of the chloroplasts to leak into the cytosol, which makes them nonfunctional. Which of the following is a likely immediate consequence of this damage?
Glucose production in the cell will decrease.
The enzyme glutamine synthetase facilitates the use of energy to combine glutamate and ammonia (NH4) forming glutamine. This process occurs in two steps, as represented in the following diagram. Which of the following statements best describes the process carried out by glutamine synthetase?
Glutamine synthetase uses an exothermic reaction to drive an endothermic one by catalyzing the formation of a phosphorylated intermediate.
Based on its elemental composition, which of the following molecules does the model most likely represent? (White, red, grey, blue)
Glycine, a building block of proteins
The image above depicts the signal transduction pathway of epinephrine. During one step in the pathway, the enzyme glycogen synthase is phosphorylated, which inactivates the enzyme. If a toxin prevents the phosphorylation of glycogen synthase during this pathway, which of the following will most likely occur when epinephrine comes into contact with its receptor?
Glycogen breakdown will still occur, but glycogen synthesis will not be affected.
A cell is treated with a toxin that prevents the synthesis of new lysosomes. However, the cell continues to produce the hydrolytic enzymes normally found in lysosomes. In which of the following structures are the hydrolytic enzymes most likely to accumulate?
Golgi complex
In order to develop antibiotics, scientists need to understand how bacteria grow and reproduce. One factor that is essential for bacterial growth and reproduction is protein synthesis. By understanding how bacteria synthesize proteins, scientists can then attempt to develop antibiotics that block bacterial protein synthesis during an infection. Which of the following questions will best direct an investigation on how to develop an antibiotic that inhibits protein synthesis in bacteria?
How can the formation of covalent bonds between amino acids be blocked?
Enzymes often play a major role in signal transduction pathways. For example, enzymes can help convert an extracellular signal into an intracellular response. Specifically, adenylyl cyclase is an enzyme that catalyzes the conversion of ATP to cyclic AMP (cAMP). One competitive inhibitor of adenylyl cyclase is called MANT-ITP. Which of the following questions would best direct an investigation on how MANT-ITP impacts a signal transduction pathway?
How does MANT-ITP affect the response to intracellular signals?
Which of the following describes how phospholipid regions are positioned in the cell membrane?
Hydrophilic phosphate regions are positioned toward aqueous environments.
In the 1950s, the scientists Alfred Hershey and Martha Chase carried out an experiment using bacteriophages, which are viruses that infect bacteria. During the experiment, the scientists allowed bacteriophages that had been labeled with either radioactive phosphorus or radioactive sulfur to infect bacterial cells. After the infection process occurred, the scientists determined the locations of the radioactive elements. After carrying out their experiment, the scientists concluded that bacteriophages inject DNA (a type of nucleic acid), but not protein, into host bacterial cells during infection. Based on the scientists' conclusion, which of the following describes the most likely result of the experiment?
Infected bacterial cells contained significant amounts of radioactive phosphorus, but not radioactive sulfur.
The model below depicts the movement of several ions across a cell membrane. For each ion, the relative concentration on each side of the membrane is shown. Which of the following statements accurately describes one of the movements shown in the model?
K+ moves out of the cell by passive transport.
Consider a reaction in which reactants X and Y combine to form the product Z. The diagram below compares the reaction coordinates for the catalyzed and uncatalyzed pathways of this reaction. Which of the following statements about letter C is true?
Letter C represents the activation energy of the uncatalyzed reaction pathway.
Tay-Sachs disease is a genetic disorder that causes certain lipids known as gangliosides to accumulate in the neurons of the brain and spinal cord. As the gangliosides build up, neurons rapidly degenerate. Which of the following cell structures is most likely associated with the accumulation of gangliosides?
Lysosomes
Which of the following best explains how modified proteins are transported within a compartmentalized cell?
Modified proteins are transported in vesicles that travel between membrane-bound organelles within the cell
The model below shows how several ions and molecules move between the proximal tubule lumen, an epithelial cell, and the blood in the kidney. The relative concentrations of sodium ions (Na+), potassium ions (K+), and calcium ions (CA2+) inside and outside the epithelial cell are indicated. Based on the model, which of the following movements requires an input of energy?
Na+ moving out of an epithelial cell into the blood
Although organisms are highly ordered systems that may appear to contradict the second law of thermodynamics, they don't actually violate this law. Which of the following statements provides the best explanation for why living organisms do not violate the second law of thermodynamics?
Organisms require a constant input of energy to maintain order, and some of this energy is released into the environment as heat.
Enzymes that catalyze consecutive steps in a metabolic pathway often cluster together in a cell. Which of the following statements describes a likely result of this clustering?
Pathway intermediates are prevented from entering alternative metabolic pathways.
Which of the following best describes how vacuoles differ between plant cells and animal cells?
Plant cells typically have a single vacuole while animal cells have multiple vacuoles
In the 1950s, the scientists Alfred Hershey and Martha Chase carried out an experiment using bacteriophages, which are viruses that infect bacteria. During the experiment, the scientists allowed bacteriophages that had been labeled with a radioactive element to infect bacterial cells. After carrying out their experiment, the scientists concluded that bacteriophages inject DNA (a type of nucleic acid), but not protein, into host bacterial cells during infection. To be able to form this conclusion, which of the following radioactive elements did Hershey and Chase most likely find inside infected bacterial cells?
Radioactive phosphorus
Viruses are infectious particles that usually consist of DNA or RNA inside a protein coat. A virus often hijacks a host cell's own processes in order to cross the plasma membrane and gain entry into the cell. Once inside, the virus uses the cell's parts and metabolism to multiply. Scientists studying a virus known as Semliki Forest virus (SFV) performed an experiment to learn about the mechanism by which SFV crosses the host cell plasma membrane. For the experiment, the scientists used two groups of cultured human cells. First, they applied chlorpromazine, a chemical that interferes with a certain cell process, to one of the groups. Then, they exposed both groups to equal amounts of SFV. The scientists observed that the virus was only able to enter the cells that had not been exposed to chlorpromazine. Based on the experiment described above, which of the following cell processes does chlorpromazine most likely inhibit?
Receptor-mediated endocytosis
Which of the following best describes the permeability of the cell wall?
Some substances pass across the cell wall because it is a semipermeable structural boundary.
The images below show the 3D space-filling models of two fatty acids. One fatty acid has a straight structure and the other fatty acid has a kinked, or bent structure. Which of the following correctly describes how high levels of fatty acid structures contribute to the rigidity of the cell membrane?
The cell membrane becomes more rigid as the amount of saturated fatty acids with a straight structure increases.
Which of the following statements best describes the selective permeability of the cell membrane?
The cell membrane regulates the transport of specific substances into and out of the cell.
Lactose is a dimer sugar composed of two monomeric subunits (galactose and glucose). In an investigation, researchers placed intestinal cells in a nutrient medium containing lactose. The researchers determined that the lactose had broken down to galactose and glucose in the manner depicted in the reaction below. The cells were then modified and re-exposed to the lactose medium. The researchers were no longer able to detect the presence of galactose and glucose. Which of the following conclusions best explains an outcome of this modification?
The cells were unable to hydrolyze the lactose dimer into its monomeric subunits.
Many species of bacteria regulate gene expression using a cell signaling system known as quorum sensing (QS). In this system, bacteria synthesize QS signaling molecules and release them into the surrounding environment. The effects of these molecules on gene expression depend on the density of the bacterial population. Which of the following best describes what occurs as the density of a QS bacterial population increases?
The concentration of QS signaling molecules increases, eventually triggering a change in gene expression throughout the bacterial population.
If water was removed from the reaction depicted above, which of the following describes the most likely outcome of this removal?
The covalent bond that holds the dimer together would not be cleaved because hydrolysis would not occur.
Glycogen is a highly branched macromolecule usually stored in liver and muscle cells. If blood glucose levels decrease, glycogen breaks down to release glucose in a process called glycogenolysis. In this process, the glycogen polysaccharide goes through hydrolysis and breaks down into glucose monosaccharides. If a toxin were to inhibit glycogenolysis, which of the following statements best predicts a consequence of this inhibition?
The covalent bonds between individual glucose monomers will not be cleaved.
Bodies of water, such as ponds, freeze from top to bottom, forming a floating sheet of ice. This can help aquatic organisms survive during cold winter months. Which of the following statements explains why the ice floats on the surface of the pond?
The crystalline structure of solid ice makes it less dense than liquid water.
A scientist grew Chlorella, a single-celled photosynthetic algae, for 3 weeks in a laboratory culture. The culture medium contained dissolved carbon dioxide and other nutrients. At the beginning and end of the 3-week period, the scientist measured the rate of synthesis for certain biological molecules. The results are shown in the following graph. (12 12 Carbohydrates) Based on the experimental results, which of the following is most likely true about the Chlorella culture medium?
The culture medium contained a sufficient level of nitrogen-containing compounds, but lacked phosphates.
A scientist grew Chlorella, a single-celled photosynthetic algae, for 3 weeks in a laboratory culture. The culture medium contained dissolved carbon dioxide and other nutrients. At the beginning and end of the 3-week period, the scientist measured the rate of synthesis for certain biological molecules. The results are shown in the following graph. Based on the experimental results, which of the following is most likely true about the Chlorella culture medium?
The culture medium contained a sufficient level of phosphates, but lacked nitrogen-containing compounds.
The image below depicts how the bacterial protein barnase undergoes modifications that involve changing its conformation, or shape. In order to function in the cell, barnase has to be folded from a nonfunctional conformation into a functional conformation. Based on the information above, which of the following best describes the functional conformation of barnase?
The functional conformation of barnase has a tertiary structure because it consists of a polypeptide chain folded into a three-dimensional shape.
A cytologist uses a microscope to compare a human hepatocyte and a human epithelial cell. She observes that the smooth endoplasmic reticulum (ER) of the hepatocyte is larger and contains more folds than the smooth ER of the epithelial cell. Which of the following is best supported by this observation?
The hepatocyte is able to synthesize lipids more efficiently than the epithelial cell.
The air temperature ranges of several Southern California cities in August are shown in the table below. Which of the following best explains why coastal cities like San Diego often have a smaller air temperature range than inland cities?
The high heat capacity of water allows the ocean to moderate the temperature of nearby air and land.
The formation of the amino acid tryptophan is catalyzed by the enzyme tryptophan synthase. This enzyme is made up of alpha and beta subunits. Which of the following statements describes a likely effect of the channel on the process carried out by tryptophan synthase?
The indole molecule does not diffuse across the cell membrane before it can be used by the beta subunit.
A mutation causes the extracellular domain of a G protein-coupled receptor (GPCR) to be misfolded. The misfolded GPCR is packaged into a vesicle that travels to the cell membrane. Upon reaching the cell membrane, the vesicle deposits the misfolded GPCR, which fuses with the cell membrane and functions as a membrane receptor. Which of the following best predicts what will occur whenever the misfolded GPCR is in the presence of its specific ligand?
The ligand-binding domain of the misfolded GPCR will not bind with its specific ligand.
Wolman disease affects lysosomal function and results in the accumulation of lipids in the liver, spleen, intestines, adrenal glands, and lymph nodes. Which of the following best explains why excess lipids accumulate in individuals with Wolman disease?
The lysosomes contain an insufficient amount of lipid-digesting enzymes.
Leigh syndrome is a rare genetic disorder that affects the central nervous system. Most individuals with Leigh syndrome have mitochondria that cannot meet the energy demands of the cell. Which of the following is the most likely outcome of Leigh syndrome on affected mitochondria?
The mitochondria cannot produce sufficient ATP to power normal cellular processes.
Which of the following statements is true?
The organization seen in living cells, tissues, and organs is maintained by a constant input of energy.
In the early 1950's, a team of researchers led by Erwin Chargaff conducted a series of experiments related to deciphering the chemical composition of DNA. In one experiment, Chargaff's team examined samples of DNA from different species of sea urchins. The results of this experiment are summarized in the table below. Which of the following results from the experiment is most consistent with the base-pairing rules of DNA?
The percentage of adenine nucleotides is roughly equal to the percentage of thymine nucleotides across all species in the experiment.
A student places a potato cube into a beaker of distilled water as shown below. The potato has a pressure potential of 7.2 bar and a solute potential of -9.8 bar. Assuming standard atmospheric pressure, which of the following is true?
The potato cube has a water potential of -2.6 bar and the distilled water has a water potential of 0 bar.
Several scientists are studying the effect of initial substrate concentration on the activity of an enzyme. They perform a series of enzyme-controlled reactions, keeping the concentration of enzyme constant but increasing the initial concentration of substrate in each trial. The graph below shows their results. Based on the data above, which of the following best describes what happens to the rate of product formation at higher initial substrate concentrations?
The rate of product formation levels off because nearly all of the enzyme is bound to substrate.
Several scientists are studying the effect of initial substrate concentration on the activity of an enzyme. They perform a series of enzyme-controlled reactions, keeping the concentration of enzyme constant but increasing the initial concentration of substrate in each trial. The graph below shows their results. Based on the data above, which of the following best predicts how the rate of product formation will change if the initial substrate concentration is increased from 0.7 M to 1.0 M?
The rate of product formation will not change significantly.
A researcher wants to identify a newly isolated DNA strand. The first step in identifying the DNA strand is to measure its length. To do this, the researcher wants to develop a fluorescent tag that emits light once it binds to both ends of the strand. Which of the following best describes how the researcher should develop a fluorescent tag with an ability to bind to both ends of the strand?
The tag should have an affinity to bind only free 3' hydroxyl (-OH) and 5' phosphate (-PO4) functional groups.
The following passage describes a fungus in a forest ecosystem. Phlebia tremellosa is a fungus that decomposes organic matter by secreting enzymes into its surroundings. Which of the following statements best justifies the claim that the processes carried out by the fungus are consistent with the second law of thermodynamics?
The total amount of entropy in the universe increases when heat is released from the fungus into the environment.
In the cell membrane, carbohydrate chains can be covalently linked to membrane proteins to form glycoproteins. They can also be covalently linked to membrane phospholipids to form glycolipids. These two cell membrane structures are shown in the image below. During an investigation, researchers discover a new toxin that enters a cell after binding to a carbohydrate on the cell membrane. Which of the following best describes how the toxin attaches to the cell membrane?
The toxin attaches to specific monosaccharides on the cell membrane.
An unknown cell is determined to contain a nucleus, a cell wall, mitochondria, chloroplasts, and ribosomes. Which of the following statements about the unknown cell is most likely true?
The unknown cell can perform photosynthesis.
A student places a potato cube into a beaker of distilled water as shown below. The potato has a pressure potential of 0.2 bar and a solute potential of -0.4 bar. Assuming standard atmospheric pressure, which of the following is true?
The water potential of the potato cube is -0.2 bar and the water potential of the distilled water is 0 bar.
The major source of energy in a cell is adenosine triphosphate, or ATP. Most of the ATP in a eukaryotic organism is synthesized in mitochondria using ATP synthase. ATP synthase is an enzyme made up of multiple protein subunits. Some of these subunits are essential for the function of ATP synthase, while others are not. Which of the following pieces of evidence best supports the claim that the wild type version of the gene described above is not essential for ATP synthase function?
There is no lethal phenotype associated with a null mutation in the gene.
The human body is capable of digesting the complex polymer starch into simpler subunits. This digestive process requires the presence of water and the enzyme amylase in order to break down starch into maltose. This is depicted below. Which of the following statements best describes the digestion of starch into maltose?
This is a hydrolysis reaction that requires water to break down a complex polymer into simpler subunits
In the image above, a thymine nucleotide and cytosine nucleotide are connected together as a dinucleotide. A single guanine nucleotide is also shown. Which of the following best predicts how the free guanine nucleotide will attach to the dinucleotide?
Through dehydration synthesis, the guanine nucleotide will form a covalent bond at the 3' hydroxyl (-OH) of the cytosine nucleotide.
What role do the highlighted hydroxyl group (-OH) and hydrogen atom (H) play in the depicted reaction above?
Through dehydration synthesis, they condense out of the reaction as a water molecule and a covalent bond forms in their place.
A neuron stimulates muscle contraction by sending signals across the neuromuscular junction, or the point of contact between a neuron and a muscle cell. The signaling process begins when membrane-bound structures inside the neuron fuse with the cell membrane, releasing signaling molecules into the neuromuscular junction. These molecules then diffuse through the junction and binds to receptors on the surface of the muscle cell, leading to muscle contraction. Based on the information above, which of the following cell processes does botulinum toxin most likely inhibit?
Vesicle fusion during exocytosis
In the reaction depicted above, two amino acids have combined to form a dipeptide. Which of the following best describes the role of water in the reaction?
Water is a product that forms as a result of a dehydration synthesis reaction between the two amino acid monomers.
Which of the following best explains water's ability to dissolve certain substances such as glucose, but remain separate from other substances such as oils?
Water molecules are polar, consisting of two partially positive hydrogen atoms, and one partially negative oxygen atom.
Which statement best describes why water is an effective solvent?
Water's polarity allows it to dissolve ionic and polar compounds.
The model below shows how glucose, sodium ions (Na+), and potassium ions (K+) move between the intestinal lumen, epithelial cell, and the blood in the small intestine. The relative concentrations of glucose, Na+, and K+ inside and outside the epithelial cell are indicated. Based on the model, which of the following movements does not require an input of energy?
glucose moving out of an epithelial cell into the blood
The major source of energy in a cell is adenosine triphosphate, or ATP. ATP can be synthesized in mitochondria using a protein complex called ATP synthase. A group of scientists studied a collection of fruit flies that had fewer ATP synthase complexes than normal due to various gene mutations. They then used this data to generate Figure 1. A newly discovered gene mutation causes fruit flies to have ATP synthase levels that are about one-third of normal. Based on the information presented in Figure 1, which of the following describes a likely outcome for a population made up of these flies?
~70% percent of flies in the mutant population will die before reaching adulthood because the supply of ATP will not meet energy demands.