Bio Final

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The energy required to run the Calvin cycle reactions of photosynthesis comes from which two substances produced during the light-dependent reactions? A ATP and NADPH B ADP and PO4 C H+ and PO2 D O2 and CO2 E H2O and CO2

A ATP and NADPH

Which of the following best describes the structures of carbohydrates? A They only occur as disaccharides. B They occur as monomers, chains of monomers, and branched structures. C They only occur as long and branched structures. D They occur as chains of monomers that hydrogen bond with complementary chains of monomers.

B They occur as monomers, chains of monomers, and branched structures.

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. Site of modification and packaging of proteins and lipids prior to export from the cell A A B B C C D D E E

C C

What most likely causes the trends in oxygen concentration shown in the graph above? A The water becomes colder at night and thus holds more oxygen. B Respiration in most organisms increases at night. C More organisms are respiring at night than during the day. D Photosynthesis produces more oxygen than is consumed by respiration during the day.

D Photosynthesis produces more oxygen than is consumed by respiration during the day.

In flowering plants, plasmodesmata are narrow channels through cell walls that connect the cytoplasms of adjacent cells. An explanation of how plant cells communicate across cell walls will most likely refer to the diffusion through plasmodesmata of which of the following? A Membrane-bound organelles B Condensed, duplicated chromosomes C Branched polysaccharides D Small, water-soluble molecules

D Small, water-soluble molecules

Simple cuboidal epithelial cells line the ducts of certain human exocrine glands. Various materials are transported into or out of the cells by diffusion. (The formula for the surface area of a cube is 6 X S2, and the formula for the volume of a cube is S3, where S = the length of a side of the cube.) Which of the following cube-shaped cells would be most efficient in removing waste by diffusion?

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it. The following questions refer to the data in Figures 1 through 4 below, which were collected during a study of the growth of plant seedlings. Figure one is a graph in the first quadrant with the horizontal axis labeled days after planting and the vertical axis labeled height in centimeters. The horizontal axis is labeled form twenty to eighty in increments of ten with tick marks in increments of five, and the vertical axis is labeled from zero to one hundred in increments of twenty, with tick marks in increments of five. There are thirteen data points on the graph that are connected by a solid line. The average height of the control seedlings not treated with inhibitor is five centimeters at day twenty-five, increasing slowly to fifteen centimeters by day fifty, and then increasing rapidly to one hundred centimeters by day one-hundred. Figure two is a graph in the first quadrant with the horizontal axis labeled days after planting and the vertical axis labeled G A (subscript) one. The horizontal axis is labeled from twenty to eighty in increments of ten with tick marks in increments of five. The vertical axis is labeled nanograms of G A one per gram of plant tissue on a log ten scale from ten to the zero power to ten to the second power. There are nine data points connected by a solid line. The concentration of G A one in control seedlings not treated with inhibitor starts at three nanograms per gram of plant tissue at day thirty, increases sharply to eighty nanograms by day forty-five, then decreasing to less than one nanogram at day fifty-five, and increasing and remaining steady between one and two nanograms of G A 1 per gram of plant tissue. Figure three is a graph in the first quadrant with the horizontal axis labeled days after planting and the vertical axis labeled total gibberellins in nanograms per gram. The horizontal axis is labeled from twenty to eighty in increments of ten with tick marks in increments of five. The horizontal axis is labeled on a log ten scale from ten to the negative one power to ten to the fourth power. There are six data points connected by a solid line. At thirty days and forty days after planting, the total gibberellins are at ten to the zero power. At day forty-five, the total gibberellins increases to ten to the second power. At fifty days after planting the total number of giberellins decreases to ten to the first power. At sixty-five days after planting, the total giberellins increases to between ten to the first and ten to the second power. At seventy-five days after planting the total giberellins increases to ten to the third power. Figure four is a graph in the first quadrant with the horizontal-axis labeled days after planting and the vertical axis labeled height in centimeters. The horizontal axis is labeled from twenty to eighty in increments of ten with tick marks in increments of five. The horizontal axis is labeled from zero to one hundred in increments of twenty with tick marks in increments of five. There are four sets of data on the graph, each of which represents a treatment with or without inhibitor. There are eleven data points represented by open squares and connected with a solid line for the control seedlings that were not treated with inhibitor. The average height of the control seedlings not treated with inhibitor is identical to figure one. There are eight data points represented by solid triangles and connected by a solid line for seedlings treated with inhibitor at a concentration of zero point six milligrams per milliliter. This curve sits just below the curve of control seedlings. There are eight data points represented by solid squares and connected by a solid line for seedlings treated with inhibitor at a concentration of six point zero milligrams per milliliter. The curve stays steady at fifteen centimeters until day sixty, and then increases steadily to fifty centimeters at day eighty. There are nine data points represented by open circles and connected by a solid line for seedlings treated with inhibitor at a concentration of sixty point zero milligrams per milliliter. The curve remains steady at ten centimeters from day forty-five to day seventy, then approaches twenty centimeters by day eighty. When the concentration of GAl is highest, the average height of the control seedlings is approximately A 10 cm B 30 cm C 60 cm D 85 cm E 95 cm

A 10 cm

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. In type 2 diabetes, the cellular response to insulin is disrupted, and individuals with type 2 diabetes cannot properly regulate their blood glucose levels. In an investigation of the insulin signaling pathway, samples of skeletal muscle were isolated from individuals who have type 2 diabetes and from individuals who do not. The results of several experiments that were performed on the muscle samples are shown in Figure 2, Figure 3, and Figure 4. Based on the information presented, which of the following genetic changes in an individual without diabetes is most likely to result in a disrupted cellular response to insulin signaling similar to that of an individual with type 2 diabetes? A A deletion in the gene encoding the insulin receptor that removes only the cytoplasmic domain of the protein B Duplication of the gene encoding a PI-3 kinase that results in synthesis of a muscle-specific variant of the enzyme in skin cells as well as in muscle cells C A mutation in the gene encoding IRS-1 that causes the protein to be active in muscle cells even in the absence of insulin signaling D Insertion of a small segment of DNA into the promoter of the Glut4 gene that results in increased synthesis of GLUT4 proteins in muscle cells

A A deletion in the gene encoding the insulin receptor that removes only the cytoplasmic domain of the protein

Which of the following best describes the numbered areas? A Areas 1 and 3 are polar, since the membrane molecules are aligned with water molecules. B Area 2 is polar, since water has been excluded from this area of the membrane. C Areas 1 and 3 are hydrophilic, since membrane molecules formed covalent bonds with water. D Area 2 is nonpolar, since hydrogen bonds between the adjacent lipids hold the membrane together.

A Areas 1 and 3 are polar, since the membrane molecules are aligned with water molecules.

What is produced during the oxidation of pyruvate? A Carbon dioxide B NAD+ C NADH D ATP

A Carbon dioxide and C NADH

The diagram below shows energy changes in a specific chemical reaction with and without the addition of an enzyme to the reaction. Which of the following questions can best be answered by the diagram? A Does the addition of an enzyme reduce the activation energy required for a reaction? B Does the addition of an enzyme result in the formation of covalent bonds? C Does the addition of an enzyme produce a greater amount of products? D Does the addition of an enzyme change the pathway for the reaction?

A Does the addition of an enzyme reduce the activation energy required for a reaction?

All eukaryotic cells contain at least one Golgi complex, typically located in the cytoplasm and near the endoplasmic reticulum. Which of the following best describes a process that occurs within the Golgi complex? A Enzymatic modification of newly synthesized integral membrane proteins B Synthesis of cytosolic proteins based on the nucleotide sequences of mRNAsmRNAs C Degradation of proteins by hydrolytic enzymes contained within the complex D Synthesis of various types of lipids

A Enzymatic modification of newly synthesized integral membrane proteins

Which of the following best explains why a cell's plasma membrane is composed of two layers of phospholipids rather than just a single layer? A Having two oppositely oriented layers of phospholipids allows only the hydrophilic heads to interact with water inside and outside of the cell. B Having two oppositely oriented layers of phospholipids allows the hydrophilic heads to repel water both inside and outside of the cells. C Having two identically oriented layers of phospholipids gives cells more protection from the exterior environment than just a single layer would. D Having two identically oriented layers of phospholipids allows for the production of vacuoles while still maintaining a protective barrier.

A Having two oppositely oriented layers of phospholipids allows only the hydrophilic heads to interact with water inside and outside of the cell.

Figure 1. Pathway activated by insulin binding to the insulin receptor Figure 2: Blood insulin levels in normal mice and EspEsp mutant mice after exposure to glucose Hormones are chemical signals that are released by cells in one part of the body that travel through the bloodstream to signal cells in another part of the body. Insulin is a hormone that is released by the pancreas that induces the uptake of glucose molecules from the bloodstream into cells. In this way, insulin lowers the overall blood glucose levels of the body. Osteoblasts and osteoclasts are two types of bone cells that play a role in regulating blood glucose levels (Figure 1). Binding of insulin to the insulin receptor on osteoblasts activates a signaling pathway that results in osteoblasts releasing a molecule, OPGOPG, that binds to neighboring osteoclasts. In response, the osteoclasts release protons (H+H+) and create an area of lower pHpH outside the cell. This low pHpH activates osteocalcin, a protein secreted in an inactive form by osteoblasts. The EspEsp gene encodes a protein that alters the structure of the insulin receptor on osteoblasts and interferes with the binding of insulin to the receptor. A researcher created a group of osteoblasts with an EspEsp mutation that prevented the production of a functional EspEsp product (mutant). The researcher then exposed the mutant strain and a normal strain that expresses EspEsp to glucose and compared the levels of insulin in the blood near the osteoblasts (Figure 2). Which of the following best describes the effect of insulin binding to the receptor on the osteoblast cells? A Insulin binding ultimately increases pancreatic secretion of additional insulin. B Insulin binding blocks the release of osteocalcin from the osteoblasts. C Insulin binding inhibits the expression of EspEsp. D Insulin binding increases the pHpH of the extracellular matrix.

A Insulin binding ultimately increases pancreatic secretion of additional insulin.

A model of the plasma membrane showing several biological molecules, including a transmembrane protein, is shown in Figure 1. Figure 1. Phospholipid bilayer with transmembrane protein Which statement best explains why correct protein folding is critical in the transmembrane protein shown above? A Interactions of the hydrophobic and hydrophilic amino acids help to anchor the protein in the membrane. B Interactions of the peptide bonds of the protein with the membrane will affect the rate at which substances can cross the membrane. C Interactions of the protein and phospholipids increase membrane fluidity. D Interactions of the quaternary structure of the protein will increase hydrogen bonding in the membrane and make the membrane less fluid.

A Interactions of the hydrophobic and hydrophilic amino acids help to anchor the protein in the membrane.

Which of the following statements is true regarding the movement of substances across cell membranes? A Ions are unable to move through the phospholipid bilayer because the nonpolar tail regions of the phospholipids are hydrophobic. B Ions are able to move through the phospholipid bilayer because the polar head regions of the phospholipids are charged. C Water is able to move through the phospholipid bilayer because the nonpolar tail regions of the phospholipids are charged. D Water is unable to move through the phospholipid bilayer because the polar head regions of the phospholipids are charged.

A Ions are unable to move through the phospholipid bilayer because the nonpolar tail regions of the phospholipids are hydrophobic.

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 ligand.

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 Nitrogen will be incorporated into nucleic acids.

For following group of questions first study the description of the data and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet. To study the actions of the enzyme catalase on hydrogen peroxide, students performed the following experiment. Catalase was extracted from potatoes by blending raw potatoes in a blender with cold distilled water. The filtrate was stored on ice. The following hydrogen peroxide solutions were made: 1 percent, 5 percent, 10 percent, and 15 percent. Filter paper disks were soaked in the catalase filtrate and dropped into beakers containing the various solutions. The activity of the enzyme was measured by the amount of time it took for the disks to float to the surface of the solution on the bubbles produced by the reaction. The following data were obtained. Which of the following experimental designs should the students use as a control for the experiment? A Place a catalase-soaked disk in a beaker of water. B Drop the disks from different heights into the solution. C Poke the floating disks back down to the bottom of the beaker and retime the rise of the disks. D Shake the beakers during the time the disks are rising. E Dip the disks in the 5% solution before putting them in any other solution.

A Place a catalase-soaked disk in a beaker of water.

A student placed a semipermeable membrane inside a U-shaped channel with two chambers, as shown. The membrane permits the movement of water but not salt. The student wants to vary the rate of osmosis that occurs across the membrane. Which of the following experimental designs will result in the fastest net rate of water movement into chamber A? A Placing salt water in chamber A and distilled water in chamber B B Placing distilled water in both chambers C Placing distilled water in chamber A and salt water in chamber B D Placing salt water in both chambers

A Placing salt water in chamber A and distilled water in chamber B

A student claims that the Y chromosome contains the sex-determining region gene, known as the SRY gene, which causes male fetuses to develop testes. Which of the following provides correct information about cell signaling that supports the claim? A The SRY gene produces a protein that binds to specific regions of DNA in certain tissues, which affects the development of these tissues. B The SRY gene produces a protein that deletes portions of the X chromosome in males so that male characteristics can develop. C The SRY gene produces an RNA segment that is exported from specific cells and targets the developing gonads. D The SRY gene is found only in tissues of the developing gonads.

A The SRY gene produces a protein that binds to specific regions of DNA in certain tissues, which affects the development of these tissues.

In an experiment, the efficiency of oxygen exchange across the plasma membrane is being assessed in four artificial red blood cells. The table above lists some properties of those artificial cells. Other conditions being equal, which artificial cell is predicted to be the most efficient in exchanging oxygen with the environment by diffusion? A The cuboidal cell B The tetrahedral cell C The cylindrical cell D The spherical cell

A The cuboidal cell

A team of biologists develop a new drug, and one team member hypothesizes that the drug is incapable of freely passing across the plasma membrane and requires the help of membrane proteins to enter cells. Alternatively, another biologist on the team hypothesizes that the drug can diffuse passively across the plasma membrane like O2O2 and CO2CO2 can. Which of the following, if true about the drug, best supports the alternative hypothesis that the new drug will exhibit simple diffusion across plasma membranes? A The drug is a small nonpolar molecule. B The drug is a small charged molecule. C The drug is a large polar molecule. D The drug is a large charged molecule.

A The drug is a small nonpolar molecule.

Muscle cells have high ATPATP demands. Which of the following is a scientific claim about how the structure of the mitochondria in muscle cells should be different than it is in other cells because of the high energy demands of mitochondria? A The inner membrane of the mitochondria in muscle cells should have more folds to increase the surface area, allowing more ATPATP to be synthesized. B The inner membrane of the mitochondria in muscle cells should be more permeable to large enzymes, allowing the same reactions to occur in both compartments of the mitochondria. C The outer membrane of the mitochondria in muscle cells should be thicker, allowing more rapid diffusion of molecules into the mitochondria. D The outer membrane of the mitochondria of muscle cells should have more folds, increasing the surface area for faster diffusion of molecules from the cytoplasm.

A The inner membrane of the mitochondria in muscle cells should have more folds to increase the surface area, allowing more ATPATP to be synthesized.

An experiment to measure the rate of respiration in crickets and mice at 10oC and 25oC was performed using a respirometer, an apparatus that measures changes in gas volume. Respiration was measured in mL of O2 consumed per gram of organism over several five-minute trials and the following data were obtained. According to the data, the mice at 10oC demonstrated greater oxygen consumption per gram of tissue than did the mice at 25oC. This is most likely explained by which of the following statements? A The mice at 10oC had a higher rate of ATP production than the mice at 25oC. B The mice at 10oC had a lower metabolic rate than the mice at 25oC. C The mice at 25oC weighed less than the mice at 10oC. D The mice at 25oC were more active than the mice at 10oC.

A The mice at 10oC had a higher rate of ATP production than the mice at 25oC.

In response to elevated blood glucose levels, beta (β) cells in the pancreas release insulin, a regulatory hormone. Insulin signals body cells to take up glucose from the blood, which returns blood glucose levels back to normal. Type 1 diabetes is an autoimmune disorder that destroys β-cells, resulting in elevated blood glucose levels. Researchers have proposed that diabetes could be treated by implanting human embryonic stem cells (hESCs) that have been induced to develop into β-cells (hESC-β). To test the proposed treatment, the researchers set up two groups of genetically identical mice and implanted the mice from one group with hESC-β cells. Several weeks after the hESC-β implant, both groups of mice were given a drug (STZ) that selectively destroys the naturally occurring mouse β-cells but does not affect the implanted hESC-β cells. Figure 1 shows a comparison of average blood glucose levels in both groups of mice. Figure 1. Average blood glucose levels in mice after STZ treatment. Error bars indicate standard deviation. In a continuation of the experiment, the researchers removed the hESC-β implant from one of the mice 16 weeks after STZ treatment. Figure 2 shows the blood glucose levels in the mouse over the duration of the experiment. Figure 2. Blood glucose levels for an individual mouse over the duration of the experiment. In contrast to type 1 diabetes, where there is no insulin production, type 2 diabetes is characterized by a failure of body cells to respond normally to insulin. Based on the results of the experiment, which of the following best predicts the effectiveness of using hESC-β implantation to treat type 2 diabetes? A The treatment would fail because insulin produced by implanted hESC-β cells will not stimulate glucose uptake by body cells. B The treatment would fail because the implanted hESC-β cells would require more glucose than the body can produce. C The treatment would succeed because the implanted hESC-β cells can express the gene that codes for human insulin. D The treatment would succeed because the body cells would secrete more insulin in the presence of the implanted hESC-β cells.

A The treatment would fail because insulin produced by implanted hESC-β cells will not stimulate glucose uptake by body cells.

When a substance moves across the plasma membrane along a concentration gradient at a rate faster than would be expected by simple diffusion alone but without the expenditure of metabolic energy, the process is best described as A facilitated diffusion B osmosis C active transport D pinocytosis E the work of an ion pump

A facilitated diffusion

Which of the following diagrams best represents hormone-activated gene expression? A B C D

A (Steroid Hormone)

A small protein is composed of 110 amino acids linked together in a chain. As shown in Figure 1, the first and last five amino acids in the chain are hydrophobic (have nonpolar and uncharged R-groups), whereas the remaining 100 amino acids are hydrophilic (have charged or polar R-groups). The nature of the R-group determines if the amino acid is hydrophobic or hydrophilic.A mutation results in the production of a version of the small protein that is only 105 amino acids long, as shown in Figure 2. Five of the hydrophobic amino acids are missing from one end of the chain.Which of the following best depicts the tertiary structures of the two proteins in water? The diagrams in the options are not drawn to the same scale as those in Figure 1 and Figure 2.

A (look at picture shown)

Excess intracellular iron is toxic to cells (iron-induced toxicity). Ferritin is an intracellular iron storage protein that binds excess iron. The presence of ferritin can protect cells from iron-induced toxicity. In an experiment to investigate the effects of dietary iron intake on ferritin synthesis, rats were given food containing different amounts of iron. Subsequently, the levels of ferritin protein in the liver were measured. The results are shown in Figure 1. Based on these and other data, researchers have developed the following model demonstrating how ferritin synthesis is regulated by iron. When iron levels are low, a repressor of translation, iron response protein (IRP), binds to an iron response element (IRE), which is a stem-loop structure near the 5¢ end of ferritin mRNA. When iron levels are high, intracellular iron binds to the IRP, and the iron-IRP complex dissociates from the IRE, permitting ribosomes to proceed with the translation of ferritin mRNA. Figure 2 represents the model of the regulation of ferritin mRNA translation by iron. Figure 2. Model of regulation of ferritin synthesis by iron Based on the data in Figure 1, the concentration of iron in the control diet used in the investigation is most likely within which of the following ranges? A 20-25 mg/kg B 35-40 mg/kg C 70-75 mg/kg D 100-125 mg/kg

B 35-40 mg/kg

The mechanism of action of many common medications involves interfering with the normal pathways that cells use to respond to hormone signals. Which of the following best describes a drug interaction that directly interferes with a signal transduction pathway? A A medication causes the cell to absorb more of a particular mineral, eventually poisoning the cell. B A medication enters the target cell and inhibits an enzyme that normally synthesizes a second messenger. C A medication enters the target cell's nucleus and acts as a mutagen. D A medication interrupts the transcription of ribosomal RNA genes.

B A medication enters the target cell and inhibits an enzyme that normally synthesizes a second messenger.

In mammals, an increase in the concentration of sodium in the blood triggers the release of antidiuretic hormone (ADH) from the pituitary gland. As the concentration of sodium in the blood returns to previous levels, the release of ADH from the pituitary gland is reduced. Based on the information presented, which of the following describes the most likely role of ADH in maintaining blood osmolarity? A ADH promotes an increase in the movement of sodium into the bloodstream. B ADH promotes an increase in the movement of water into the bloodstream. C ADH promotes an increase in the excretion of water from the body. D ADH promotes an increase in the secretion of additional ADH from the pituitary gland.

B ADH promotes an increase in the movement of water into the bloodstream.

A researcher claims that the synthesis of ATPATP from ADPADP and inorganic phosphate (Pi)(Pi) is essential to cellular function. Which of the following statements best helps justify the researcher's claim? A ADPADP is a small molecule that some cells release into their environment as a way of communicating with other cells. B ATPATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy. C Inorganic phosphate (Pi)(Pi) is a substance that cells typically acquire from their environment. D ATPATP synthase is a mitochondrial enzyme that catalyzes the conversion of ADPADP and PiPi to ATPATP.

B ATPATP hydrolysis is an energy-releasing reaction that is often coupled with reactions that require an input of energy.

Scientists compared the chemical structure of several molecules that various bacterial species use for quorum sensing. Quorum sensing is an ability some bacteria have to detect the number of related cells nearby. The chemical structure of some of these molecules found in certain species of bacteria are shown in Figure 1. Figure 1. The chemical structure of several molecules used for quorum sensing in three species of bacteria Which of the following research questions would best guide an investigation of the link between the structure of the signaling molecules and the evolution of quorum sensing? A Do these molecules require the same receptors in each bacteria species to generate a response? B Did these species evolve from a common ancestor that used a similar signaling molecule? C Do these species all perform the same action when the concentration of the signaling molecules is high enough? D Did these species evolve from the same common ancestor that is still living today and uses the same receptors?

B Did these species evolve from a common ancestor that used a similar signaling molecule?

The chemical reaction for photosynthesis is 6 CO2 + 12 H2O + light energy → C6H12O6 + 6 O2 + 6 H2O If the input water is labeled with a radioactive isotope of oxygen, 18O, then the oxygen gas released as the reaction proceeds is also labeled with 18O. Which of the following is the most likely explanation? A During the light reactions of photosynthesis, water is split, the hydrogen atoms combine with the CO2, and oxygen gas is released. B During the light reactions of photosynthesis, water is split, removing electrons and protons, and oxygen gas is released. C During the Calvin cycle, water is split, regenerating NADPH from NADP+, and oxygen gas is released. D During the Calvin cycle, water is split, the hydrogen atoms are added to intermediates of sugar synthesis, and oxygen gas is released.

B During the light reactions of photosynthesis, water is split, removing electrons and protons, and oxygen gas is released.

Ethylene is an organic compound produced by ripening fruits. In a controlled experiment, researchers found that ethylene gas stimulated the ripening process in newly harvested fruits. Which of the following describes the most likely connection between natural ethylene production and fruit ripening? A As a result of metabolic inactivity, newly harvested fruits are unable to absorb ethylene gas from the atmosphere. B Ethylene gas is a chemical signal through which ripening fruits trigger the ripening process in other fruits. C Because of normal phenotypic variation, only some of the fruits in a given generation are expected to produce ethylene gas. D The rate of ethylene gas production by ripening fruits is an indicator of the relative age of an ecosystem.

B Ethylene gas is a chemical signal through which ripening fruits trigger the ripening process in other fruits.

Directions: This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all. This group of questions refers to molecules of the following substances. (A) Cytochrome(B) FADH2(C) NAD+(D) NADP+(E) Oxygen (O2) Coenzyme that transfers electrons from the Krebs cycle to the mitochondrial electron-transport chain at a lower energy level than that of electrons entering at the beginning of the chain A Cytochrome B FADH2 C NAD+ D NADP+ E Oxygen (O2)

B FADH2

Which of the following claims is scientifically accurate and consistent with an observation that a decrease in lysosome production within a cell leads to a decline in mitochondrial activity? A A lack of lysosomes will cause a decrease in the synthesis of enzymes necessary for cellular respiration. B Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration. C Fewer lysosomes will be available to store materials required for the functioning of the mitochondria. D Lysosomes will not be available to modify proteins so that they are targeted to the mitochondria.

B Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration.

What molecule is converted to glucose in the light independent reaction? A 3PGA B G3P C Pyruvate D RuBP

B G3P

A researcher measured the temperature at which two different samples of double-stranded DNADNA denature (separate into single strands). Sample 11 denatured at a significantly lower temperature than sample 22 did. Based on the data, the researcher claims that the DNADNA in sample 22 is composed of a higher percentage of guanine and cytosine than the DNADNA in sample 11 is. Which of the following best supports the researcher's claim? A The bonds between guanine and cytosine are covalent bonds, which require more energy to disrupt than those between adenine and thymine. B Guanine-cytosine pairs denature at a higher temperature because they have more hydrogen bonds between them than adenine-thymine pairs do. C Adenine-thymine pairs require less energy to separate because adenine and thymine are both single-ring bases. D Guanine-cytosine pairs require more energy to separate because one is a purine and one is a pyrimidine.

B Guanine-cytosine pairs denature at a higher temperature because they have more hydrogen bonds between them than adenine-thymine pairs do.

The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. The figure presents a simplified model of the epinephrine signaling pathway in muscle cells. A plasma membrane is shown with two transmembrane structures, a Beta-2 Adrenergic Receptor and Adenylyl Cyclase. Epinephrine is shown binding to the extracellular surface of the beta-2 adrenergic receptor. Bound to the cytosolic surface of the receptor is a G protein made up of alpha, beta, and gamma subunits. An arrow indicates that G D P that is bound to the alpha subunit of the G protein is now released from the subunit. A successive arrow points to the G protein subunits dissociated from the adrenergic receptor and the alpha subunit dissociated from a complex of the beta and gamma subunits. G T P is shown binding to the alpha subunit. A successive arrow points from the G T P-modified alpha subunit to the cytosolic region of adenylyl cyclase. Adenylyl cyclase intersects an arrow that points from A T P to Cyclic A M P. A series of arrows follows. An arrow from Cyclic A M P points to Protein Kinase A. An arrow from Protein Kinase A points to Phosphorylase Kinase and is paired with a curved arrow pointing from A T P to A D P. An arrow from Phosphorylase Kinase points to Glycogen Phosphorylase and is paired with a curved arrow pointing from A T P to A D P. An arrow from Glycogen Phosphorylase points to an arrow indicating the conversion of Glycogen to Glucose-1-Phosphate. A final arrow points from Glucose-1-Phosphate to Glycolysis. Figure 1. A simplified model of the epinephrine signaling pathway in muscle cells Based on Figure 1, which of the following statements best describes the epinephrine signaling pathway? A It involves the opening and closing of ion channels. B In involves enzymes activating other enzymes. C It involves changes in the expression of target genes. D It involves protons moving down a concentration gradient.

B In involves enzymes activating other enzymes.

Contains hydrolytic enzymes associated with the intracellular digestion of macromolecules A Centriole B Lysosome C Nucleolus D Peroxisome E Ribosome

B Lysosome

A researcher is investigating the effects of a chemical that makes thylakoid membranes permeable to hydrogen ions (H+H+). Which of the following is the most likely direct effect of adding the chemical to plant cells? A The plant cells will produce less NADPHNADPH. B The chloroplasts will generate less ATPATP. C Chlorophyll will require less light energy to excite its electrons. D The plant cells will split fewer water molecules into hydrogen ions and oxygen.

B The chloroplasts will generate less ATPATP.

Paramecia are unicellular protists that have contractile vacuoles to remove excess intracellular water. In an experimental investigation, paramecia were placed in salt solutions of increasing osmolarity. The rate at which the contractile vacuole contracted to pump out excess water was determined and plotted against osmolarity of the solutions, as shown in the graph. Which of the following is the correct explanation for the data? A At higher osmolarity, lower rates of contraction are required because more salt diffuses into the paramecia. B The contraction rate increases as the osmolarity decreases because the amount of water entering the paramecia by osmosis increases. C The contractile vacuole is less efficient in solutions of high osmolarity because of the reduced amount of ATP produced from cellular respiration. D In an isosmotic salt solution, there is no diffusion of water into or out of the paramecia, so the contraction rate is zero.

B The contraction rate increases as the osmolarity decreases because the amount of water entering the paramecia by osmosis increases.

A researcher proposes a model of an enzyme-catalyzed reaction in which a reactant is converted to a product. The model is based on the idea that the reactant passes through a transition state within the enzyme-substrate complex before the reactant is converted to the product. Which of the following statements best helps explain how the enzyme speeds up the reaction? A The enzyme's active site binds to and stabilizes the reactant, which decreases the free-energy change of the reaction. B The enzyme's active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction. C The enzyme's active site binds to and stabilizes the product, which increases the amount of energy released by the reaction. D The enzyme's active site binds to and stabilizes both the reactant and the product at the same time, which increases the reaction's equilibrium constant.

B The enzyme's active site binds to and stabilizes the transition state, which decreases the activation energy of the reaction.

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it. The following questions refer to the data in Figures 1 through 4 below, which were collected during a study of the growth of plant seedlings. Figure one is a graph in the first quadrant with the horizontal axis labeled days after planting and the vertical axis labeled height in centimeters. The horizontal axis is labeled form twenty to eighty in increments of ten with tick marks in increments of five, and the vertical axis is labeled from zero to one hundred in increments of twenty, with tick marks in increments of five. There are thirteen data points on the graph that are connected by a solid line. The average height of the control seedlings not treated with inhibitor is five centimeters at day twenty-five, increasing slowly to fifteen centimeters by day fifty, and then increasing rapidly to one hundred centimeters by day one-hundred. Figure two is a graph in the first quadrant with the horizontal axis labeled days after planting and the vertical axis labeled G A (subscript) one. The horizontal axis is labeled from twenty to eighty in increments of ten with tick marks in increments of five. The vertical axis is labeled nanograms of G A one per gram of plant tissue on a log ten scale from ten to the zero power to ten to the second power. There are nine data points connected by a solid line. The concentration of G A one in control seedlings not treated with inhibitor starts at three nanograms per gram of plant tissue at day thirty, increases sharply to eighty nanograms by day forty-five, then decreasing to less than one nanogram at day fifty-five, and increasing and remaining steady between one and two nanograms of G A 1 per gram of plant tissue. Figure three is a graph in the first quadrant with the horizontal axis labeled days after planting and the vertical axis labeled total gibberellins in nanograms per gram. The horizontal axis is labeled from twenty to eighty in increments of ten with tick marks in increments of five. The horizontal axis is labeled on a log ten scale from ten to the negative one power to ten to the fourth power. There are six data points connected by a solid line. At thirty days and forty days after planting, the total gibberellins are at ten to the zero power. At day forty-five, the total gibberellins increases to ten to the second power. At fifty days after planting the total number of giberellins decreases to ten to the first power. At sixty-five days after planting, the total giberellins increases to between ten to the first and ten to the second power. At seventy-five days after planting the total giberellins increases to ten to the third power. Figure four is a graph in the first quadrant with the horizontal-axis labeled days after planting and the vertical axis labeled height in centimeters. The horizontal axis is labeled from twenty to eighty in increments of ten with tick marks in increments of five. The horizontal axis is labeled from zero to one hundred in increments of twenty with tick marks in increments of five. There are four sets of data on the graph, each of which represents a treatment with or without inhibitor. There are eleven data points represented by open squares and connected with a solid line for the control seedlings that were not treated with inhibitor. The average height of the control seedlings not treated with inhibitor is identical to figure one. There are eight data points represented by solid triangles and connected by a solid line for seedlings treated with inhibitor at a concentration of zero point six milligrams per milliliter. This curve sits just below the curve of control seedlings. There are eight data points represented by solid squares and connected by a solid line for seedlings treated with inhibitor at a concentration of six point zero milligrams per milliliter. The curve stays steady at fifteen centimeters until day sixty, and then increases steadily to fifty centimeters at day eighty. There are nine data points represented by open circles and connected by a solid line for seedlings treated with inhibitor at a concentration of sixty point zero milligrams per milliliter. The curve remains steady at ten centimeters from day forty-five to day seventy, then approaches twenty centimeters by day eighty. Which of the following is a correct conclusion that can be drawn based only on the data in Figure 4? A Seedling growth rates decrease between 50 and 80 days after planting at all concentrations of the inhibitor. B The greater the inhibition of GAl synthesis, the lower the plant height after 80 days. C The spraying of GAl on seedlings results in an increase in seedling growth rates. D The inhibitor kills the seedlings when it is applied in very high concentrations. E The growth of the seedlings is directly proportional to the concentrations of inhibitor.

B The greater the inhibition of GAl synthesis, the lower the plant height after 80 days.

Figure 1 represents a nucleic acid fragment that is made up of four nucleotides linked together in a chain. Figure 1. Nucleic acid fragment Which of the following characteristics of Figure 1 best shows that the fragment is RNA and not DNA? A The 5′5′ to 3′3′ orientation of the nucleotide chain B The identity of each nitrogenous base C The charges on the phosphate groups D The type of bond linking the nucleotides together

B The identity of each nitrogenous base

Which of the following best describes how amino acids affect the tertiary structure of a protein? A The number of amino acids determines the tertiary structure of the protein. B The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein. C The R-group of the last amino acid that is added to a growing polypeptide chain determines the next amino acid that is added to the chain. D The sequence of the amino acids in the polypeptide chain determines the protein's primary structure but has no effect on its tertiary structure.

B The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein.

Which of the following best explains how molecules such as O2O2 and CO2CO2 can move across the membrane of a cell? A The majority of the cell membrane contains protein channels that allow this type of molecule into the cell. B The majority of the cell membrane is nonpolar, which allows small, nonpolar molecules to freely cross. C The phospholipids of the membrane are tightly packed, so only small molecules and ions can fit between phospholipids. D ATPATP is hydrolyzed to provide energy to help O2O2 and CO2CO2 move against their concentration gradient and across the membrane.

B The majority of the cell membrane is nonpolar, which allows small, nonpolar molecules to freely cross.

Water and ammonia interact to form hydrogen bonds, as represented in the figure. Which statement best helps explain the formation of the hydrogen bond represented in the figure? A The oxygen has a partial positive charge, and the nitrogen has a partial negative charge. B The nitrogen has a partial negative charge, and the hydrogen attached to the oxygen has a partial positive charge. C The hydrogen attached to the oxygen has a partial negative charge, and the nitrogen also has a partial negative charge. D The nitrogen has a partial positive charge, and the hydrogen attached to the oxygen also has a partial positive charge.

B The nitrogen has a partial negative charge, and the hydrogen attached to the oxygen has a partial positive charge.

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 The projections increase the surface area-to-volume ratio of the cell, which allows for more efficient nutrient exchange with the environment.

Organelles such as mitochondria and the endoplasmic reticulum have membranes that compartmentalize reactions and other metabolic processes. To function properly, the organelles must move substances across their membranes. Which of the following statements describes a feature shared by mitochondria and the endoplasmic reticulum that increases the efficiency of their basic functions? A They have rigid, nonfluid membranes. B They have highly folded membranes. C They have membranes composed of many carbohydrates. D They have double membranes, with one membrane enclosed within the other.

B They have highly folded membranes.

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

Which of the following best describes the role of water in photosynthesis? A Water is the only source of protons for the formation of a proton gradient. B Water molecules donate electrons to the electron transport chain. C Water molecules combine with stored carbon molecules to produce glucose. D Water is the terminal electron acceptor for electrons that pass through the electron transport chain.

B Water molecules donate electrons to the electron transport chain.

Which statement best describes the effect on water transport across the cell membrane if the aquaporin in the figure ceases to function? A Water molecules will no longer be able to move across the cell membrane. B Water molecules will still be able to move across the cell membrane but at a slower rate. C Water molecules will only be able to enter the cell by active transport. D Water molecules will move across the cell membrane at a faster rate without the aquaporin regulating their flow.

B Water molecules will still be able to move across the cell membrane but at a slower rate.

Where does the light reaction take place? A stroma of the chloroplast B thylakoid membrane C stomata of the leaf D cuticle of the leaf

B thylakoid membrane

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

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it. The following questions refer to the data in Figures 1 through 4 below, which were collected during a study of the growth of plant seedlings. Figure one is a graph in the first quadrant with the horizontal axis labeled days after planting and the vertical axis labeled height in centimeters. The horizontal axis is labeled form twenty to eighty in increments of ten with tick marks in increments of five, and the vertical axis is labeled from zero to one hundred in increments of twenty, with tick marks in increments of five. There are thirteen data points on the graph that are connected by a solid line. The average height of the control seedlings not treated with inhibitor is five centimeters at day twenty-five, increasing slowly to fifteen centimeters by day fifty, and then increasing rapidly to one hundred centimeters by day one-hundred. Figure two is a graph in the first quadrant with the horizontal axis labeled days after planting and the vertical axis labeled G A (subscript) one. The horizontal axis is labeled from twenty to eighty in increments of ten with tick marks in increments of five. The vertical axis is labeled nanograms of G A one per gram of plant tissue on a log ten scale from ten to the zero power to ten to the second power. There are nine data points connected by a solid line. The concentration of G A one in control seedlings not treated with inhibitor starts at three nanograms per gram of plant tissue at day thirty, increases sharply to eighty nanograms by day forty-five, then decreasing to less than one nanogram at day fifty-five, and increasing and remaining steady between one and two nanograms of G A 1 per gram of plant tissue. Figure three is a graph in the first quadrant with the horizontal axis labeled days after planting and the vertical axis labeled total gibberellins in nanograms per gram. The horizontal axis is labeled from twenty to eighty in increments of ten with tick marks in increments of five. The horizontal axis is labeled on a log ten scale from ten to the negative one power to ten to the fourth power. There are six data points connected by a solid line. At thirty days and forty days after planting, the total gibberellins are at ten to the zero power. At day forty-five, the total gibberellins increases to ten to the second power. At fifty days after planting the total number of giberellins decreases to ten to the first power. At sixty-five days after planting, the total giberellins increases to between ten to the first and ten to the second power. At seventy-five days after planting the total giberellins increases to ten to the third power. Figure four is a graph in the first quadrant with the horizontal-axis labeled days after planting and the vertical axis labeled height in centimeters. The horizontal axis is labeled from twenty to eighty in increments of ten with tick marks in increments of five. The horizontal axis is labeled from zero to one hundred in increments of twenty with tick marks in increments of five. There are four sets of data on the graph, each of which represents a treatment with or without inhibitor. There are eleven data points represented by open squares and connected with a solid line for the control seedlings that were not treated with inhibitor. The average height of the control seedlings not treated with inhibitor is identical to figure one. There are eight data points represented by solid triangles and connected by a solid line for seedlings treated with inhibitor at a concentration of zero point six milligrams per milliliter. This curve sits just below the curve of control seedlings. There are eight data points represented by solid squares and connected by a solid line for seedlings treated with inhibitor at a concentration of six point zero milligrams per milliliter. The curve stays steady at fifteen centimeters until day sixty, and then increases steadily to fifty centimeters at day eighty. There are nine data points represented by open circles and connected by a solid line for seedlings treated with inhibitor at a concentration of sixty point zero milligrams per milliliter. The curve remains steady at ten centimeters from day forty-five to day seventy, then approaches twenty centimeters by day eighty. The concentration of all gibberellins 65 days after planting is approximately A 5 ng/gram B 10 ng/gram C 20 ng/gram D 120 ng/gram E 150 ng/gram

C 20 ng/gram

The graph above shows changes in glucagon and insulin secretions at different concentrations of blood glucose. Which of the following feedback mechanisms is best supported by the data? A A falling glucagon level causes a rise in the insulin level, which maintains equal amounts of both hormones in the blood. B A high glucagon level causes a rise in the insulin level, which maintains high levels of both hormones in the blood. C A low glucose level causes the release of glucagon, which stimulates the release of more glucose from tissues, which in turn lowers the amount of glucagon being released. D A low glucose level causes the release of insulin, which stimulates the release of more glucose from tissues, which in turn increases the amount of insulin being released.

C A low glucose level causes the release of glucagon, which stimulates the release of more glucose from tissues, which in turn lowers the amount of glucagon being released.

Figure 1. A model of epinephrine signaling 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 Epinephrine activates alpha cells, causing the release of glucagon, and inhibits beta cells, blocking the release of insulin.

High blood cholesterol (hypercholesterolemia, HC) can lead to cardiovascular problems such as atherosclerosis and heart attack. Exercise and monitoring of diet can often control cholesterol levels; however, in certain cases HC is inherited as an autosomal dominant disease caused by a mutation in a single gene. A man with high cholesterol levels is about to marry a woman whose total cholesterol levels are also higher than average. A physician has suggested they get tested for the HC allele. Which of the following is a valid ethical question concerning the test? A How important are the results of the test to the couple's health, since they already know they have HC? B How can they eliminate the allele for HC from their cells? C If both have the allele for HC, should an insurance company raise their rates because of the results of the test? D What cures are available for HC other than dietary changes and exercise?

C If both have the allele for HC, should an insurance company raise their rates because of the results of the test?

In a certain signal transduction pathway, the binding of an extracellular molecule to a cell-surface protein results in a rapid increase in the concentration of cyclic AMPAMP inside the cell. The cyclic AMPAMP binds to and activates cytosolic enzymes that then activate other enzymes in the cell. Which of the following statements best describes the role of cyclic AMPAMP in the signal transduction pathway? A It acts as a signaling molecule that passes the signal from the cell to other cells. B It acts as a receptor that carries the signal from outside the cell to inside the cell. C It acts as a second messenger that helps relay and amplify the signal within the cell. D It acts as a channel protein that transmits the signal across the cell's nuclear membrane.

C It acts as a second messenger that helps relay and amplify the signal within the cell.

Amylase is a protein that catalyzes the conversion of starch to simple sugars. Amylase activity in an aqueous solution can be measured by using iodine as a starch indicator. A solution containing iodine and starch will have a dark-blue color, whereas a solution containing iodine but no starch will have a light-brown color. The color change of an iodine solution from dark blue to light brown can be used to measure the rate at which starch is converted to simple sugars. A student designs an experiment to investigate the effect of environmental pHpH on amylase function. The design of the experiment is presented in Table 1. Table 1. An experiment for investigating the effect of pHpH on amylase function A It will provide a measurement of amylase activity at an acidic pHpH. B It will provide a measurement of amylase activity at a basic pHpH. C It will show the color change that occurs in the absence of enzyme activity. D It will show the color change that occurs in the absence of the amylase protein.

C It will show the color change that occurs in the absence of enzyme activity.

Figure 1. An amino acid 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 (NH2NH2) group B Carboxyl (COOHCOOH) group C Methyl (CH3CH3) group D Hydrogen (HH) atom

C Methyl (CH3CH3) group

Directions: This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all. This group of questions refers to molecules of the following substances. (A) Cytochrome(B) FADH2(C) NAD+(D) NADP+(E) Oxygen (O2) An intermediate electron acceptor for oxidations that occur in both glycolysis and in Krebs cycle reactions A Cytochrome B FADH2 C NAD+ D NADP+ E Oxygen (O2)

C NAD+

In chloroplasts, ATPATP is synthesized from ADPADP plus inorganic phosphate (Pi)(Pi) in a reaction catalyzed by ATPATP synthase molecules that are embedded in the thylakoid membrane. Which of the following statements provides evidence to support the claim that no ATPATP will be synthesized in the absence of a proton gradient across the thylakoid membrane? A Blocking electron flow from one carrier to the next in the electron transport chains blocks formation of a proton gradient in the thylakoid. B Increasing the proton concentration difference across the thylakoid membrane is not associated with a parallel increase in the rate of ATPATP synthesis. C No ATPATP is synthesized when channel proteins that allow the free passage of protons are inserted into the thylakoid membrane. D No ATPATP is synthesized while the Calvin cycle is synthesizing carbohydrates and using ATPATP and NADPHNADPH at a high rate.

C No ATPATP is synthesized when channel proteins that allow the free passage of protons are inserted into the thylakoid membrane.

Directions: This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all. This group of questions refers to the following groups of biological compounds. (A) Proteins(B) Carbohydrates(C) Nucleic acids(D) Lipids(E) Steroids Used to carry the genetic code A Proteins B Carbohydrates C Nucleic acids D Lipids E Steroids

C Nucleic acids

Protein digestion in humans is primarily carried out by three enzymes. Pepsin is found in the stomach (pH2)(pH2), where it aids in the breakdown of large proteins into smaller peptides, while trypsin and chymotrypsin are found in the small intestine (pH8)(pH8), where they aid in the further breakdown of the proteins into amino acids and dipeptides that can be absorbed into the bloodstream. Graph 1 shows the effect of pHpH on the activity levels of the three enzymes. Which of the following best predicts how the structure and function of pepsin will change as it enters the small intestine? A Pepsin will not change in shape and will continue to break down proteins in the small intestine. B Pepsin will not change in shape but may not work due to the basic environment of the small intestine. C Pepsin will change in shape because of the basic environment of the small intestine; therefore, its enzymatic activity will decrease. D Pepsin will change in shape because of the presence of trypsin and chymotrypsin in the small intestine, both of which act as competitive inhibitors.

C Pepsin will change in shape because of the basic environment of the small intestine; therefore, its enzymatic activity will decrease.

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 Ribosomes

Cell communication is critical for the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling? A Cell signaling uses the highest molecular weight molecules found in living cells. B Cell signaling has largely been replaced by other cell functions in higher mammals. C Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes. D Cell signaling functions mainly during early developmental stages.

C Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes.

Researchers have proposed a model of the process by which a newly synthesized protein is transported to the plasma membrane and secreted into the extracellular space. The model is represented in Figure 1. Figure 1. A model of the intracellular transport of a newly synthesized secreted protein Based on the model, the newly synthesized protein is transported directly from the endoplasmic reticulum to which of the following? A The nucleus B The plasma membrane C The Golgi complex D The extracellular space

C The Golgi complex

A student used a microscope to observe a wet-mount slide of red onion epidermal cells that were suspended in a 1%1% NaClNaCl solution. The student then added a 15%15% NaClNaCl solution to the slide and observed the changes that occurred. The student's observations are represented in Figure 1. Figure 1. Student's observations of onion cells Which of the following most directly explains the changes in the cells? A The degradation of DNADNA in the nuclei of the cells B The lysis of chloroplasts in the cells C The movement of water from the central vacuoles of the cells into the solution D The movement of NaClNaCl from the solution into the cytoplasm of the cells

C The movement of water from the central vacuoles of the cells into the solution

Which of the following statements best helps explain the reaction specificity of an enzyme? A The free energy of the reactants is greater than the free energy of the products. B The equilibrium constant of the reaction is much greater than 1. C The shape and charge of the substrates are compatible with the active site of the enzyme. D The concentration of the enzyme inside living cells is greater than the concentration of substrate.

C The shape and charge of the substrates are compatible with the active site of the enzyme.

The Hedgehog protein (Hh) plays a critical role during a certain period of embryo development, but it normally has no role in adults except for the maintenance of adult stem cells. However, the Hedgehog protein has been detected in 70 percent of pancreatic cancer cell samples. As illustrated in the figures below, the Hedgehog protein binds to an integral membrane protein receptor known as Patched (Ptc), thus initiating a pathway of gene expression. When Hedgehog is absent, Ptc inhibits another protein known as Smoothened (Smo), which, in turn, blocks the activation of a group of proteins collectively known as the Hedgehog signaling complex (HSC). The inactivation is the result of proteolytic cleavage of one component of the HSC complex, a transcription factor known as Cubitus interruptus (Ci). When Hedgehog is present, it binds to Ptc, which prevents the inhibition of Smo by Ptc. The result is that Ci remains intact and can enter the nucleus, where it binds to and activates certain genes. One approach to treating patients with pancreatic cancer and other cancers in which the Hedgehog protein is detected is to modify the Hedgehog signaling pathway. Which of the following is the most useful approach? A Treating patients with a molecule that is structurally similar to Hedgehog and that will bind to and interact with Ptc in the same fashion as Hedgehog B Injecting patients with embryonic cells so that Hedgehog will bind to those cells instead of the cancer cells C Treating patients with a membrane-soluble compound that can bind to Smo and block its activity D Injecting patients with a preparation of purified membrane-soluble Ci that will enter the nuclei of the cancer cells and induce gene transcription

C Treating patients with a membrane-soluble compound that can bind to Smo and block its activity

A sample of human blood was placed in a test tube containing a physiological saline solution (0.9% sodium chloride). This type of solution is often used intravenously to quickly rehydrate patients. A drop of the blood from the test tube was placed on a slide and red blood cells (RBCs) were observed under a microscope. Three possible outcomes are diagrammed below. Which of the following best predicts which diagrammed microscope view the laboratory worker would see and best explains why? A View 1 because RBC membranes are freely permeable to water B View 2 because the RBCs use energy to allow sodium entry and to pump water out C View 2 because the rate of water movement into the RBCs equals the rate of water movement out of the cells D View 3 because the sodium-potassium pumps in the RBC membranes use energy to keep the sodium out but allow water to freely flow into the cells

C View 2 because the rate of water movement into the RBCs equals the rate of water movement out of the cells

A feature of organic compounds NOT found in inorganic compounds is the presence of A ionizing chemical groups B electrons C carbon atoms covalently bonded to each other D oxygen E hydrogen bonds

C carbon atoms covalently bonded to each other

ATP serves as a common energy source for organisms because A it is the smallest 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 its energy can be easily transferred to do cellular work

C larger fish consume more oxygen than smaller fish at all four temperatures

Students conducted a controlled experiment to investigate whether sawdust provides enough nutrients to support plants growth. The students separated nearly 10 identical sunflower seatings into two groups. That's enough about the question so sucks. They observe differences between the groups most likely resulted from differences in the ability of seedlings to reduce which of the following monomers.

C, and it is a picture of two molecules. One had 4h 1n 2c 2o and an r group and the other 4h 5n 5o 1p

The figure above shows a model of a ligand precursor being cleaved to produce an active ligand that binds to a specific receptor. Which of the following is most likely to reduce the binding of the active ligand to its receptor? A A change in the cytoskeletal attachment of transmembrane proteins B The presence of a large amount of the precursor form of the ligand C An increase in the ratio of the number of unsaturated to the number of saturated fatty acid tails of the membrane lipids D A mutation in the receptor gene that causes a substitution of a charged amino acid for a nonpolar amino acid in the ligand binding site of the receptor

D A mutation in the receptor gene that causes a substitution of a charged amino acid for a nonpolar amino acid in the ligand binding site of the receptor

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 An endoplasmic reticulum, mitochondria, and a nucleus

The enzyme trypsin aids in protein digestion in the small intestine. The relative activity of trypsin at different pHpH values is shown in Figure 1. Which of the following statements best explains the activity levels of trypsin shown in Figure 1 ? A The small intestine releases inhibitor molecules that block the activity of trypsin unless it is at its optimum pHpH. B The number of effective collisions between trypsin and its substrate increase at higher pHpH values. C As pHpH values increase, the substrate concentration decreases, leading to an eventual decline in the rate of the trypsin-catalyzed reaction. D At extremely low pHpH values, trypsin is denatured and cannot function efficiently.

D At extremely low pHpH values, trypsin is denatured and cannot function efficiently.

Aquaporins are channel proteins that facilitate the transport of water across the cell membrane. One group of researchers hypothesizes that without functional aquaporins, no water will be able to enter the cell. A different group proposes an alternative hypothesis, stating that even with nonfunctional aquaporins, a small amount of water will still cross the cell membrane. An experiment is set up in which plant cells with mutated (nonfunctional) aquaporins and plant cells with normally functioning aquaporins are both placed in distilled water. Which of the following data would support the alternative hypothesis? A Cells with functional aquaporins exhibit low turgor pressure and are hypertonic. B Cells with functional aquaporins exhibit high turgor pressure and are hypotonic. C Cells with mutated aquaporins exhibit an absence of turgor pressure and are completely plasmolyzed. D Cells with mutated aquaporins exhibit moderate turgor pressure and are hypertonic.

D Cells with mutated aquaporins exhibit moderate turgor pressure and are hypertonic.

Directions: This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all. (A) Glysolysis(B) Krebs cycle (citric acid cycle)(C) Calvin cycle (light-independent reactions of photosynthesis)(D) Light-dependent reactions of photosynthesis(E) Chemiosmosis Process in which O2 is released as a by-product of oxidation-reduction reactions A A B B C C D D E E

D D

The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. The figure presents a simplified model of the epinephrine signaling pathway in muscle cells. A plasma membrane is shown with two transmembrane structures, a Beta-2 Adrenergic Receptor and Adenylyl Cyclase. Epinephrine is shown binding to the extracellular surface of the beta-2 adrenergic receptor. Bound to the cytosolic surface of the receptor is a G protein made up of alpha, beta, and gamma subunits. An arrow indicates that G D P that is bound to the alpha subunit of the G protein is now released from the subunit. A successive arrow points to the G protein subunits dissociated from the adrenergic receptor and the alpha subunit dissociated from a complex of the beta and gamma subunits. G T P is shown binding to the alpha subunit. A successive arrow points from the G T P-modified alpha subunit to the cytosolic region of adenylyl cyclase. Adenylyl cyclase intersects an arrow that points from A T P to Cyclic A M P. A series of arrows follows. An arrow from Cyclic A M P points to Protein Kinase A. An arrow from Protein Kinase A points to Phosphorylase Kinase and is paired with a curved arrow pointing from A T P to A D P. An arrow from Phosphorylase Kinase points to Glycogen Phosphorylase and is paired with a curved arrow pointing from A T P to A D P. An arrow from Glycogen Phosphorylase points to an arrow indicating the conversion of Glycogen to Glucose-1-Phosphate. A final arrow points from Glucose-1-Phosphate to Glycolysis. Figure 1. A simplified model of the epinephrine signaling pathway in muscle cells A researcher claims that the epinephrine signaling pathway controls a catabolic process in muscle cells. Which of the following statements best helps justify the researcher's claim? A Epinephrine is a signaling molecule that binds to a transmembrane protein. B The G protein in the epinephrine signaling pathway consists of three different subunits. C Phosphorylase kinase catalyzes the hydrolysis of ATP. D Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate.

D Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate.

Cortisol is a hormone produced in response to stress, including starvation, in humans. Which of the following is most likely an immediate effect of a starvation-induced increase in cortisol secretion? A Increased activation of the immune system B Increased urine production by the kidneys C Increased bone and collagen formation D Increased mobilization of fatty acids from fat cells

D Increased mobilization of fatty acids from fat cells

Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model (Figure 1) in which CDK5, a protein expressed in axon terminals, inhibits the movement of synaptic vesicles to the presynaptic membrane. To test their model, the researchers used a modified version of green fluorescent protein (GFP*). In slightly alkaline conditions, GFP* exhibits a bright green fluorescence. In acidic conditions, GFP* exhibits no fluorescence. Using standard techniques, the gene encoding GFP* is easily introduced into living cells. By engineering the expression of GFP* in laboratory-cultured nerve cells, the researchers found that a bright green fluorescence was exhibited only when a presynaptic neuron was given a certain stimulus. Which of the following observations best supports the hypothesis that CDK5 negatively regulates neurotransmitter release? A Introduction of CDK5 protein into neurons results in the movement of synaptic vesicles to the plasma membrane in the absence of any stimulus. B Uptake of a gene encoding CDK5 by neurons results in the movement of synaptic vesicles to the plasma membrane in the absence of any stimulus. C Suppression of CDK5 expression in neurons inhibits the movement of synaptic vesicles to the plasma membrane in response to a specific stimulus. D Inhibition of CDK5 activity in neurons increases the movement of synaptic vesicles to the plasma membrane in response to a specific stimulus.

D Inhibition of CDK5 activity in neurons increases the movement of synaptic vesicles to the plasma membrane in response to a specific stimulus.

Which of the following is most directly responsible for water's unique properties? A It contains oxygen atoms. B It contains hydrogen atoms. C It is an ionic compound. D It forms hydrogen bonds. E It is nonpolar.

D It forms hydrogen bonds.

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 Na+ transport out of the cell requires ATP hydrolysis.

Which of the following conclusions is most clearly supported by the representations of nucleic acid #1 and nucleic acid #2? A Nucleic acid #1#1 contains only purines, whereas nucleic acid #2#2 contains only pyrimidines. B Nucleic acid #1#1 contains the sugar ribose, whereas nucleic acid #2#2 contains the sugar deoxyribose. C Nucleic acid #1#1 contains positively charged phosphate groups, whereas nucleic acid #2#2 does not. D Nucleic acid #1#1 contains adenine-thymine base pairs, whereas nucleic acid #2#2 does not.

D Nucleic acid #1#1 contains adenine-thymine base pairs, whereas nucleic acid #2#2 does not.

Steroid hormones, such as testosterone, pass through the plasma membrane and bind to an intracellular protein, as shown in the diagram below. The hormone-receptor complex then enters the nucleus, where it interacts with DNA to promote transcription of a specific gene. The figure is labeled Signaling Diagram for Steroid Hormones. It shows a cell with its plasma membrane and nucleus. There is a steroid hormone outside the plasma membrane; there is an arrow from the steroid hormone to another steroid hormone inside the plasma membrane but outside the nuclear envelope. The steroid hormone inside the plasma membrane is on a hormone-receptor complex. Next to the hormone-receptor complex there is an intracellular protein with an arrow pointing to the steroid hormone that is on the hormone-receptor complex. There is an arrow from the hormone-receptor complex pointing through the nuclear envelope to another steroid hormone on a hormone-receptor complex. Below this the diagram shows D N A. From the D N A, there is an arrow pointing to target-gene m R N A. From the target-gene m R N A, there is an arrow pointing out through the nuclear envelope to proteins being synthesized by ribosomes. Based on the information presented, which of the following will also occur in response to steroid signaling? A Histone protein synthesis will increase because histones maintain the DNA in an optimal conformation for chromosome assembly. B Ribosome production will increase because ribosomes are specific for the mRNA with which they bind during translation. C DNA replication will increase as a result of the binding of the hormone-receptor complex to the DNA. D Production of a specific mRNA will increase as a result of the binding of the hormone-receptor complex to the DNA.

D Production of a specific mRNA will increase as a result of the binding of the hormone-receptor complex to the DNA.

Cells contain smaller components called organelles that are necessary for a cell's survival. Organelle functions have often been compared to components of larger systems. Which of the following functional differences between the rough and smooth endoplasmic reticulum (ER) is explained by the structural differences between them? A Rough ER breaks down toxic substances, and smooth ERER only transports them out of the cell. B Rough ER can synthesize and package lipids for export, and smooth ERER cannot. C Rough ER can produce ATPATP, and smooth ERER cannot. D Rough ER can synthesize and package proteins for export, and smooth ERER cannot.

D Rough ERER can synthesize and package proteins for export, and smooth ERER cannot.

Pyruvate dehydrogenase is an enzyme that converts pyruvate to acetyl-CoACoA. Acetyl-CoACoA is further metabolized in the Krebs cycle. A researcher measured the accumulation of acetyl-CoACoA in a reaction containing pyruvate and pyruvate dehydrogenase under several different conditions (Figure 1). Figure 1. Accumulation of acetyl-CoACoA under different conditions Which of the following best describes the cellular location where pyruvate dehydrogenase is most likely active? A The cytosol B The lysosomes C The nucleus D The mitochondrial matrix

D The mitochondrial matrix

A human kidney filters about 200 liters of blood each day. Approximately two liters of liquid and nutrient waste are excreted as urine. The remaining fluid and dissolved substances are reabsorbed and continue to circulate throughout the body. Antidiuretic hormone (ADH) is secreted in response to reduced plasma volume. ADH targets the collecting ducts in the kidney, stimulating the insertion of aquaporins into their plasma membranes and an increased reabsorption of water. If ADH secretion is inhibited, which of the following would initially result? A The number of aquaporins would increase in response to the inhibition of ADH. B The person would decrease oral water intake to compensate for the inhibition of ADH. C Blood filtration would increase to compensate for the lack of aquaporins. D The person would produce greater amounts of dilute urine.

D The person would produce greater amounts of dilute urine.

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 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.

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it and fill in the corresponding circle on the answer sheet. Dialysis tubing is permeable to water molecules but not to sucrose. Four dialysis tubes are half filled with 5 percent, 10 percent, 20 percent, and 40 percent sucrose solutions, respectively, and two dialysis tubes are half filled with distilled water. The dialysis tubes are all sealed at both ends, and the initial masses are determined. Five dialysis tubes are placed into beakers containing distilled water, and the sixth dialysis tube, containing distilled water, is placed into a 40 percent sucrose solution. The masses of the dialysis tubes are recorded at 30-minute intervals for 90 minutes, as shown in the table below. A net movement of water into the beaker occurs in which of the following dialysis tubes? A 2 B 3 C 4 D 5 E 6

E 6

Which of the following are characteristic of both prokaryotic and eukaryotic cells? A Cytoplasm and a well-defined nucleus surrounded by a membrane B Membranous sites of ATP synthesis, Golgi complex, and ribosomes C Mitochondria, nucleus, and ribosomes D Cell wall, several chromosomes, and cytoplasm E Cell membrane, ribosomes, DNA, and RNA

E Cell membrane, ribosomes, DNA, and RNA

Which of the following statements about mitochondrial chemiosmosis is NOT true? A A proton gradient is established across the inner membrane of the mitochondrion. B The potential energy released from the mitochondrial proton gradient is used to produce ATP. C The mitochondrial proton gradient provides energy for muscle contraction. D Proteins embedded in the inner mitochondrial membrane play an important role in ATP synthesis. E Heat energy is required to establish the electron transport chain.

E Heat energy is required to establish the electron transport chain.

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 The light-dependent reactions produce ATP and NADPH; the light-independent reactions use energy stored in ATP and NADPH.

The organelle that is a major producer of ATP and is found in both heterotrophs and autotrophs is the A chloroplast B nucleus C ribosome D Golgi apparatus E mitochondrion

E mitochondrion

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