Biology AP Classroom Chapter 11 Practice Answer Key

Which of the following diagrams best represents hormone-activated gene expression?

A

Antidiuretic hormone (ADH) is important in maintaining homeostasis in mammals. ADH is released from the hypothalamus in response to high tissue osmolarity. In response to ADH, the collecting duct and distal tubule in the kidney become more permeable to water, which increases water reabsorption into the capillaries. The amount of hormone released is controlled by a negative feedback loop. Based on the model presented, which of the following statements expresses the proper relationship between osmolarity, ADH release, and urine production? A) As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine. B) As tissue osmolarity rises, less ADH is released, causing less water to be excreted as urine. C) As tissue osmolarity rises, more ADH is released, causing more water to be excreted as urine. D) As tissue osmolarity rises, less ADH is released, causing more water to be excreted as urine.

A As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine.

Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown? A) Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP B) Epinephrine binds to a cell-surface receptor; the activated receptor catalyzes the conversion of glycogen to glucose. C) Epinephrine diffuses through the plasma membrane; the hormone dimerizes in the cytosol. D) Epinephrine is taken into the cell by endocytosis; glycogen is converted to glucose in the endocytotic vesicle.

A Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger,

Which of the following outcomes will most likely result from the irreversible binding of GDP to the G protein? A)The intracellular concentration of glycogen will increase. B) The intracellular concentration of activated protein kinase A will increase. C) The intracellular concentration of cyclic AMP will increase. D) The intracellular concentration of glucose-1-phosphate will increase.

A The intracellular concentration of glycogen will increase.

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.

The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of the following demonstrates negative feedback by the endocrine system? A) During labor, the fetus exerts pressure on the uterine wall, inducing the production of oxytocin, which stimulates uterine wall contraction. The contractions cause the fetus to further push on the wall, increasing the production of oxytocin. B) After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels. C) At high elevation, atmospheric oxygen is more scarce. In response to signals that oxygen is low, the brain decreases an individual's rate of respiration to compensate for the difference. D) A transcription factor binds to the regulatory region of a gene, blocking the binding of another transcription factor required for expression.

B After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels.

The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of the following demonstrates negative feedback by the endocrine system? A) During labor, the fetus exerts pressure on the uterine wall, inducing the production of oxytocin, which stimulates uterine wall contraction. The contractions cause the fetus to further push on the wall, increasing the production of oxytocin. B) After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels. C) At high elevation, atmospheric oxygen is more scarce. In response to signals that oxygen is low, the brain decreases an individual's rate of respiration to compensate for the difference. D) A transcription factor binds to the regulatory region of a gene, blocking the binding of another transcription factor required for expression.

B After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels. *repeat but i wanna keep the numbers the same

The model shown in the figure represents the role of two hormones, calcitonin and parathyroid hormone (PTH), in maintaining normal blood calcium levels in humans. If a dietary change results in an increase in blood calcium concentration above normal levels, which of the following is the most likely effect on calcium homeostasis? A) Calcitonin levels will decline, thus stimulating the release of PTH. B) Calcitonin levels will rise, thus promoting the deposit of calcium into bones. C) PTH levels will decline, thus stimulating the loss of calcium from bones. D) PTH levels will increase, thus preventing the release of calcitonin.

B Calcitonin levels will rise, thus promoting the deposit of calcium into bones.

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.

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.

Which of the following statements best describes how a growth factor stimulates cell division from outside a cell? A) The growth factor binds to other cells in the same area and holds them together to form a large, multicellular structure. B) The growth factor binds to receptors on the cell surface, initiating a signal transduction pathway that activates specific target genes. C) The growth factor binds to sugar molecules in the extracellular fluid and provides them to the cell as a source of energy. D) The growth factor binds to phospholipids in the plasma membrane, creating a channel through which substances enter the cell.

B The growth factor binds to receptors on the cell surface, initiating a signal transduction pathway that activates specific target genes.

Cyclic AMP phosphodiesterase is an enzyme that catalyzes the conversion of cyclic AMP to a different molecule. Which of the following best predicts the effect of inhibiting cyclic AMP phosphodiesterase in a muscle cell stimulated by epinephrine? A) The concentration of cyclic AMPAMP will decrease because adenylyl cyclase will no longer be activated. B) The G protein will diffuse out of the cell because it will no longer bind to the plasma membrane. C) Phosphorylase kinase will remain active because protein kinase A will no longer be deactivated. D) Glycolysis will stop because epinephrine signaling will no longer stimulate glycogen breakdown.

C Phosphorylase kinase will remain active because protein kinase A will no longer be deactivated.

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.

Which of the following statements best describes the role of adenylyl cyclase in the epinephrine signaling pathway? A) It converts a polymer to its monomer subunits. B) It moves substances across the plasma membrane. C) It accelerates the production of a second messenger. D) It transfers phosphate groups from ATPATP to protein substrates.

C It accelerates the production of a second messenger.

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.

Based on the model of ferritin synthesis presented in Figure 2, which of the following best describes the mechanism whereby iron most likely regulates ferritin production? A) Translation occurs under low intracellular iron concentration when the IRP recruits ribosomes to the ferritin mRNA. B) Translation occurs under low intracellular iron concentration when the IRP stabilizes the stem-loop structure in the ferritin mRNA. C) Translation occurs under high intracellular iron concentration when the IRP-iron complex dissociates from ferritin mRNA, permitting ribosomes access to the ferritin coding region. D) Translation occurs under high intracellular iron concentration when the IRP-iron complex brings the 5¢ end of the mRNA closer to the ferritin coding region.

C Translation occurs under high intracellular iron concentration when the IRP-iron complex dissociates from ferritin mRNA, permitting ribosomes access to the ferritin coding region.

The diagram above illustrates feedback control as exerted by the hormone thyroxine. Following surgical removal of the thyroid gland, the level of TSH in the blood will increase. Which of the following best explains this increase? A) Residual blood thyroxine, from prior to thyroid gland removal, will bind to cells in the anterior pituitary, signaling more TSH secretion. B) Thyroxine will remain bound to thyroxine receptors on various body cells, and these body cells will secrete additional hormones that stimulate the anterior pituitary to secrete TSH. C) Thyroxine that was stored in the anterior pituitary prior to thyroid gland removal will signal more TSH secretion. D) A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion.

D A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion.

Damaged tissue releases chemicals that activate platelets and stimulate the formation of blood clots. Which of the following predictions about the activity of platelets best describes a positive feedback mechanism? A) Activated platelets release chemicals that inhibit blood clot formation. B) Activated platelets release signaling molecules that inhibit cell division in damaged tissue. C) Activated platelets constrict the blood vessels, stopping blood flow. D) Activated platelets release chemicals that activate more platelets.

D Activated platelets release chemicals that activate more platelets.

Based on the model of ferritin synthesis presented in Figure 2, which of the following describes the role of feedback on the control of intracellular iron levels? A) A decrease in iron levels activates the IRP. The IRP in turn activates iron transport proteins in the cell membrane, thereby returning free iron levels to normal. B) A decrease in iron levels activates synthesis of ferritin protein. Ferritin protein in turn releases bound iron, thereby returning free iron levels to normal. C) An increase in iron levels activates the IRP. The IRP in turn binds iron, thereby decreasing both free iron levels and ferritin synthesis. D) An increase in iron levels activates synthesis of ferritin protein. Ferritin protein in turn binds iron, thereby decreasing both free iron levels and ferritin synthesis.

D An increase in iron levels activates synthesis of ferritin protein. Ferritin protein in turn binds iron, thereby decreasing both free iron levels and ferritin synthesis.

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.