1. The electron transport chain is a part of cellular respiration. The diagram below shows the movement of ions in the electron transport chain within a mitochondrion. Which statement best describes the movement of ions shown in the diagram? (A) The electron transport chain is used to move hydrogen ions to the inner membrane space, where they create a highly reducing environment and hydrolyze CO 2 to produce sugar. This answer suggests the student may understand that hydrogen ions are being transferred to the inner membrane space, but does not understand that carbon dioxide is not hydrolyzed in this location or that an electrochemical gradient is generated to move hydrogen ions through ATP synthase and power the production of ATP through chemiosmosis. (B) Hydrogen ions diffuse into the inner membrane space and are pumped against an electrochemical gradient through the electron transport chain, which provides the energy needed to generate ATP through chemiosmosis. Page 1 of 8
This answer suggests the student may understand that hydrogen ions move into the inner membrane space, but does not understand that the hydrogen ions are pumped into the inner membrane space via the electron transport chain to produce an electrochemical gradient, and that the ions then flow through ATP synthase to the mitochondrial matrix to power the production of ATP. (C) The proteins in the electron transport chain create an electrochemical gradient by pumping hydrogen ions to an area of high concentration, which powers ATP production when the hydrogen ions diffuse back into the mitochondrial matrix. This answer suggests the student understands that hydrogen ions are pumped into the inner membrane space via the electron transport chain to an area of high concentration, which produces an electrochemical gradient that is used to produce ATP. (D) Hydrogen ions are reduced as they move through the electron transport chain in order to transfer electrons to ADP and phosphate to make ATP in the inner membrane space. This answer suggests the student may understand that hydrogen ions move through the electron transport chain, but does not understand that hydrogen ions are not reduced as they are pumped into the inner membrane space and that these ions provide the energy for ATP synthesis due to the generation of an electrochemical gradient. 2. A certain drug greatly disrupts cellular respiration. When the drug is introduced into the body, the following observations are made: Acetyl CoA builds up in the mitochondrial matrix; There is a decrease in the amount of CO 2 diffusing out of the mitochondria; and Low levels of NADH and FADH 2 slow oxidative phosphorylation on the inner mitochondrial membrane. Which statement best explains how this drug disrupts cellular respiration? (A) The drug prevents the movement of hydrogen ions into the inner membrane space, which prevents the formation of an electrochemical gradient. Page 2 of 8
This answer suggests the student may understand that the movement of hydrogen ions into the inner membrane space is necessary to establish an electrochemical gradient, but does not understand that the reduction of NAD + and FAD and the production of carbon dioxide are processes in the citric acid (Krebs) cycle, which occur in the mitochondrial matrix. (B) The drug prevents enzymes from splitting glucose into pyruvic acid during glycolysis and prevents the production of ATP during substrate-level phosphorylation. This answer suggests the student may understand that enzymes split glucose into pyruvic acid during glycolysis and that ATP is produced during substrate-level phosphorylation, but does not understand that carbon dioxide is not released during glycolysis and that the reduction of NAD + and FAD and the production of carbon dioxide are processes involved in the citric acid (Krebs) cycle. (C) The drug prevents the reduction of NAD + and FAD by binding to the enzymes involved in the citric acid (Krebs) cycle. This answer suggests the student understands that the observations made are all directly related to the processes involved in the citric acid (Krebs) cycle, which involves transforming pyruvate into acetyl CoA, reducing NAD + to NADH, and producing CO 2. (D) The drug prevents the oxidation of NADH and FADH 2 by blocking proteins from donating or accepting electrons in the electron transport chain. This answer suggests the student may understand the relationship among NADH, FADH 2, and the electron transport chain, but does not understand that the observations show that the reduction of NAD + and FAD and the production of carbon dioxide are processes involved in the citric acid (Krebs) cycle. Page 3 of 8
3. The diagram below shows the processes occurring in and around the inner mitochondrial membrane. Based on the diagram, which question best investigates a factor that affects the processes? (A) If water is generated in the mitochondrial matrix, will the mitochondrial matrix become hypotonic to the intermembrane space as the processes occur? This answer suggests the student may understand that a high concentration of water on one side of a plasma membrane will make that area hypotonic to another side with a lower water concentration, but does not understand that water can diffuse through plasma membranes (via aquaporins) so a hypotonic environment will not be produced. (B) If oxygen gas is being converted into water in the mitochondrial matrix, will the volume of the mitochondrial matrix change as the processes occur? This answer suggests the student may understand that oxygen gas is converted into a liquid in the matrix and changing a gas into a liquid decreases its volume, but does not understand that water and oxygen can diffuse directly through plasma membranes, so there will be no change in the volume of the mitochondrial matrix. (C) What effect will lowering the ph in the intermembrane space have on the proteins in the inner mitochondrial membrane? Page 4 of 8
This answer suggests the student understands that H + ions are being pumped into the intermembrane space, which lowers the ph, and that lowering the ph in this space even further may affect the structure and function (denaturing) of proteins in the membrane and prevent the proteins from pumping H + ions or transferring electrons in the electron transport chain. (D) What effect will the movement of negatively charged ions through the inner mitochondrial membrane have on the production of water? This answer suggests the student may understand that the movement of electrons through the electron transport chain results in water molecules, but does not understand that the electrons are being passed from protein to protein through reduction-oxidation reactions within the membrane, and the electrons are not being passed within the membrane itself. 4. A root cutting is placed in a sealed container. The concentrations of carbon dioxide and oxygen gas in the container are measured and recorded in millimeters of mercury (mmhg) every 6 hours over the next 24 hours. The results are shown in the table below. Which statement best explains the results of the experiment? (A) The root cutting is undergoing anaerobic fermentation because the root cutting is running out of oxygen and it is not able to undergo the citric acid cycle or oxidative phosphorylation. Page 5 of 8
This answer suggests the student may understand that an organism undergoes fermentation when oxygen levels are too low, but does not understand that oxygen is not used during fermentation and that the root cutting is undergoing cellular respiration, as evidenced by the oxygen concentration decreasing and the carbon dioxide concentration increasing. (B) The root cutting is using the Calvin cycle to generate energy and is consuming oxygen because there is not enough light available to carry out light reactions. This answer suggests the student may understand that the root cutting is consuming oxygen, but does not understand that carbon dioxide (not oxygen) is used during the Calvin cycle to produce sugar and that the plant is undergoing cellular respiration, as evidenced by the oxygen concentration decreasing and the carbon dioxide concentration increasing. (C) The root cutting is undergoing aerobic cellular respiration because the root cutting is generating carbon dioxide from organic molecules and is reducing oxygen to form water. This answer suggests the student understands that the root cutting is undergoing cellular respiration because the oxygen concentration is decreasing (oxygen is reduced to form water in cellular respiration) and the carbon dioxide concentration is increasing (carbon dioxide is generated from organic molecules during the citric acid [Krebs] cycle). (D) The root cutting is undergoing photolysis in the light-dependent reactions because oxygen is being split and combined with carbon to form carbon dioxide. This answer suggests the student may understand that photolysis occurs during the lightdependent reactions in photosynthesis, but does not understand that oxygen is not split and combined with carbon to form carbon dioxide during photosynthesis, and that the plant is undergoing cellular respiration, as evidenced by the oxygen concentration decreasing and the carbon dioxide concentration increasing. Page 6 of 8
5. The diagram below shows how the nutrients triglycerides, glucose, and amino acids are metabolized to produce ATP in a mitochondrion. Which scientific question is most appropriate to investigate the process of ATP production that is shown in the diagram? (A) How does the amount of ATP generation vary among each of the nutrients when oxygen supplies are limited? This answer suggests the student understands that cellular respiration of triglycerides and amino acids requires oxygen to generate ATP and that only glucose can continue to be catabolized when oxygen supply is limited, which may result in more ATP generated from glucose when blood oxygen levels are low. (B) How is the production of fatty acids in the cytosol affected by an excess supply of each nutrient? Page 7 of 8
This answer suggests the student may understand that excess nutrients are converted into fatty acids in the cytosol and stored as body fat, but does not understand that this question does not address the process of ATP production and therefore does not gather evidence about the production of ATP. (C) How does the Krebs cycle vary based on the nutrient being metabolized? This answer suggests the student may understand that the nutrients are metabolized by processes in the Krebs cycle, but does not understand that these processes in the Krebs cycle do not change based on the nutrient used. (D) How does NAD + and FAD oxidation vary for each of the nutrients? This answer suggests the student may understand the roles of NAD + and FAD in cellular respiration, but does not understand that the function of these molecules is the same regardless of the type of nutrient being oxidized. Page 8 of 8