Chapter 6 and 7 AP BIO

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 glucose synthesis A mitochondria B chloroplast C Golgi Body D Membrane E Vacuole

Answer B

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

B

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 conversion of chemical energy of glucose to ATP A mitochondria B chloroplast C Golgi Body D Membrane E Vacuole

Answer A

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

Answer A

The illustration shows the active transport of hydrogen ions through a membrane protein. Which of the following best predicts the effect of not having ATP available to supply energy to this process? B H+H+ ions will move in the other direction through the protein. C H+H+ ions will continue to move through the protein in the original direction but at a slower rate. D H+H+ ions will begin to move through the phospholipid portion of the membrane in the original direction.

Answer A (Metabolic energy such as ATPATP is required for active transport of ions against a concentration gradient.)

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 O2 and CO2 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.

Answer A Correct. Small nonpolar molecules freely pass across the plasma membrane. If the drug is a small nonpolar molecule, this supports the alternative hypothesis.

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.

Answer A Correct. Tertiary structure of the protein resulting from hydrophobic and hydrophilic interactions plays a key role in how the protein interacts with the hydrophobic tails and hydrophilic head of the membrane phospholipids.

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 mRNAs C Degradation of proteins by hydrolytic enzymes contained within the complex D Synthesis of various types of lipids

Answer A Correct. The Golgi complex is a membrane-bound structure to which some proteins are moved from the rough endoplasmic reticulum, where they are enzymatically modified before being sent to a cellular membrane.

Researchers propose a model to explain variation in phytoplankton cell sizes in a marine environment. They base their model on the idea that smaller cells absorb nutrients more efficiently. The researchers predict that the mean diameter of phytoplankton cells will change by 50 micrometers for every 5-kilometer increase in distance from the shore because of a gradual decrease in nutrient availability. To test their model, the researchers determine that the phytoplankton cells found closest to shore have a mean diameter of 900 micrometers. Based on the model, what will be the mean diameter of the phytoplankton cells that are found 25 kilometers from shore? A 650 micrometers B 875 micrometers C 925 micrometers D 1150 micrometers

Answer A Correct. The model predicts that phytoplankton cell size will decrease with increasing distance from the shore, resulting in increased efficiency of nutrient absorption. The correct value was arrived at by subtracting 250 from 900.

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

Answer B

The salinity of a small inland lake has recently started to increase. Researchers are planning to study the lake over several decades to investigate how freshwater organisms survive significant changes in their natural habitat. Which of the following physiological mechanisms will the researchers most likely observe among the surviving organisms in the lake? A Prokaryotic organisms will use various mechanisms to counteract swelling of cells as a result of increased water uptake. B Single-celled organisms will use various mechanisms to counteract the increased flow of water from cells to the environment. C Eukaryotic organisms will use various mechanisms to counteract the diffusion of positively charged ions across the cell membrane. D Multicellular organisms will use various mechanisms to counteract the loss of cell adhesion as a result of calcium deficiencies.

Answer B

Which of the following components of the cell membrane is responsible for active transport? A Phospholipid B Protein C Lipid D Phosphate E Cholesterol

Answer B

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.

Answer B Correct. Compared with a smooth membrane, a highly folded membrane has a greater surface area that increases the rate of material transport across the membrane and provides more support for membrane-associated processes.

Which of the following statements best explains the processes of passive and active transport? A Passive transport is the net movement of substances down a concentration gradient that requires metabolic energy. Active transport is the movement of substances up a concentration gradient that does not require energy. B Passive transport is the net movement of substances down a concentration gradient that does not require metabolic energy. Active transport is the movement of substances up a concentration gradient that requires energy. C Passive transport is the net movement of substances up a concentration gradient that requires metabolic energy. Active transport is the movement of substances down a concentration gradient that does not require metabolic energy. D Passive transport is the net movement of substances up a concentration gradient that does not require metabolic energy. Active transport is the movement of substances down a concentration gradient that requires energy.

Answer B Correct. Passive transport is the net movement of substances down (with) a concentration gradient that does not require metabolic energy and active transport is the movement of substances up (against) a concentration gradient that requires energy

The model below shows the structure of a portion of a plasma membrane in an animal cell. Which statement best explains the orientation of the phospholipid molecules in this model? A The nonpolar portions of the phospholipid molecules are attracted to the internal and external environments. B The hydrophilic phosphate groups of the phospholipid molecules are attracted to the aqueous internal and external environments. C The embedded proteins attract the fatty acid tails of the phospholipids, so the tails point away from the internal and external aqueous environments. D The fatty acid tails of the phospholipid molecules are hydrophilic and are repelled by the internal and external aqueous environments.

Answer B Correct. The hydrophilic polar phosphate groups of the phospholipid molecules orient toward the polar internal and external aqueous environments, forming a bilayer that keeps the hydrophobic portions of the phospholipids away from the polar molecule

A cell's membrane potential is maintained by the movement of ions into and out of the cell. A model showing the influence of membrane proteins on the movement of sodium (Na+) and potassium (K+) ions across the plasma membrane is presented in Figure 1. Figure 1. Section of a cell's plasma membrane, showing ion concentrations and membrane proteins Based on the model presented in Figure 1, which of the following outcomes will most likely result from a loss of protein X function? A The membrane potential will be disrupted by an increase in Na+Na+ concentration inside the cell. B The membrane potential will be disrupted by an increase in K+K+ concentration inside the cell. C The membrane potential will be maintained by the Na+−K+Na+⁢−⁢K+ pump moving more K+K+ ions into the cell. D The membrane potential will be maintained by the diffusion of Na+Na+ ions into the cell.

Answer B Correct. The intracellular K+K+ concentration will increase because the Na+−K+Na+−K+ pump will continue to transport K+K+ into the cell without any diffusing out of the cell. As a result, the cell's membrane potential will be disrupted.

The figure shows a process by which a cell might absorb food from its surrounding environment and break it down for use as a source of energy and matter. The process involves lysosomes, which are membrane-bound organelles that contain hydrolytic enzymes. Activation of the hydrolytic enzymes requires an acidic pH, and lysosomes maintain an internal acidic pH by using ion pumps. Which of the following outcomes will most likely result from a loss of ion pump function in the cell's lysosomes? A The internal pHpH of the lysosomes will decrease, which will prevent the activation of hydrolytic enzymes and interfere with the intracellular digestion of food. B The internal pHpH of the lysosomes will increase, which will prevent the activation of hydrolytic enzymes and interfere with the intracellular digestion of food. C The internal pHpH of the lysosomes will decrease, which will activate hydrolytic enzymes and enhance the intracellular digestion of food. D The internal pHpH of the lysosomes will increase, which will activate hydrolytic enzymes and enhance the intracellular digestion of food.

Answer B Correct. The lysosomes rely on the ion pumps to maintain an internal acidic pHpH. A loss of ion pump function will most likely result in an increase in the internal pHpH of lysosomes from acidic to neutral, which will prevent the activation of hydrolytic enzymes and interfere with intracellular digestion of food.

If ATP breakdown (hydrolysis) is inhibited, which of the following types of movement across cell membranes is also inhibited? A Movement of oxygen into a cell B Movement of water through aquaporins C Passage of a solute against its concentration gradient D Facilitated diffusion of a permeable substance

Answer C

The following question refer to the graph below, which illustrates the percent change in the mass of pieces of plant tissue placed in solutions of different sucrose molarities. The approximate molarity of the solution in which the mass of the plant pieces would not change is A 0.0 M B 0.1 M C 0.3 M D 0.5 M E 0.7 M

Answer C

Which of the following scientific questions is most relevant to the model represented in the figure above? A Is ATP required for the transportation of sugars across the outer mitochondrial membrane? B Do the types of phospholipids in a membrane affect the rate at which molecules enter a cell by passive diffusion? C Which molecular substance is actively transported across the plasma membrane? D How does temperature affect the movement of molecules into lysosomes?

Answer C

Figure 1 shows a model of how a channel protein influences the movement of a particle across a cell's plasma membrane. Figure 1. A section of a cell's plasma membrane, showing a channel protein and a concentration gradient across the membrane An investigator wants to understand whether a newly found membrane protein is involved in membrane transport of a certain particle. Which investigation will help determine whether the new membrane protein is a channel protein involved in membrane transport? A Add small nonpolar molecules to the extracellular space and measure the direction of particle movement of the molecules. B Measure the rate of extracellular fluid movement into the intracellular space. C Add more of the proteins to the plasma membrane and measure the rate of the particle movement. D Remove ATPATP from the intracellular space and measure the rate of the particle movement into the intracellular space.

Answer C Correct. If the movement of particles is mediated by the channel protein, then an increase in proteins in the cell membrane should influence the rate of particle movement across the membrane.

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

Answer C Correct. Membrane proteins and secreted proteins are synthesized by ribosomes bound to the surface of the endoplasmic reticulum. As shown in the figure, a newly synthesized secreted protein is transported by vesicles from the endoplasmic reticulum directly to the Golgi complex.

In an experiment, cells were isolated from an aquatic plant and suspended in pond water, a sucrose sugar solution, or distilled water. All of the cells were then viewed under a microscope. Compared with the cell in the pond water, the cell in the sugar solution appeared shriveled, and the cell in the distilled water appeared inflated. The results of the experiment are represented in Figure 1. Figure 1. The results of an experiment using aquatic plant cells Which of the following statements best explains the observations represented in Figure 1 ? A There was a net movement of sucrose out of the cell suspended in the sugar solution and a net movement of sucrose into the cell suspended in the distilled water. B There was a net movement of sucrose into the cell suspended in the sugar solution and a net movement of sucrose out of the cell suspended in the distilled water. C There was a net movement of water out of the cell suspended in the sugar solution and a net movement of water into the cell suspended in the distilled water. D There was a net movement of water into the cell suspended in the sugar solution and a net movement of water out of the cell suspended in the distilled water.

Answer C Correct. The plasma membrane that surrounds a living cell is typically permeable to water but not sucrose. In the experiment represented in Figure 1, there was a net movement of water out of the cell suspended in the sugar solution, causing the cell to appear shriveled, and a net movement of water into the cell suspended in the distilled water, causing the cell to appear inflated.

The transport of a substance across a plasma membrane of a specific organelle requires energy. The rate at which the transport takes place also depends on temperature. A scientist isolated the specific organelle and then used the following treatments to determine the conditions that will result in the maximal transport. All treatments contained the extracted organelle and were maintained at 25°C. The data from this experiment indicate that maximal rate of transport of protein X at 25°C occurs at an ATP concentration of 1.0μm/mL. Figure 1. The four ATP concentrations used in the experiment Which procedure should be done next to gather data needed to meet the scientist's objective? A Incubate samples with the same four ATPATP concentrations at 30°C30°C. B Incubate samples containing 5.0μm/mL5.0μm/mL of ATPATP at four temperatures other than 25°C25°C. C Incubate samples containing 1.0μm/mL1.0μm/mL of ATPATP at four temperatures other than 25°C25°C. D Incubate samples containing 1.0μm/mL1.0μm/mL of ATPATP at 25°C25°C and determine the rate of transport for four other proteins.

Answer C Correct. This procedure combines the optimal ATPATP concentration for transport with data for transport rates at four other temperatures.

Membrane-bound organelles have been an important component in the evolution of complex, multicellular organisms. Which of the following best summarizes an advantage of eukaryotic cells having internal membranes? A Eukaryotic cells are able to reproduce faster because of the presence of organelles. B Some organelles, such as mitochondria and chloroplasts, are similar to prokaryotic cells in structure. C Organelles isolate specific reactions, increasing metabolic efficiency. D Compartmentalization leads to a higher mutation rate in DNA, which leads to more new species.

Answer C This option is correct. It demonstrates understanding and provides an explanation of how internal membrane-bound organelles contribute to cell function by providing a favorable local environment for metabolic reactions, and by protecting the cell from potentially damaging metabolic reactions.

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

Answer C This option is correct. The saline solution is isotonic relative to the RBC's cytoplasm. This will result in a dynamic equilibrium. View 2 shows a RBC in an isotonic environment because it would shrink in a hypertonic solution and swell in a hypotonic solution.

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.

Answer D

Which of the following best describes an advantage that eukaryote organisms have over prokaryote organisms? A Prokaryotes lack a cell membrane and therefore are unable to control what enters or exits the cell. B Eukaryotes have a nuclear envelope separating their DNA from the rest of the cell, which increases the likelihood of advantageous mutations. C Eukaryotes have mitochondria and chloroplasts that contain their own genome, which allows the cells to reproduce more rapidly. D Eukaryotes have organelles that allow for compartmentalization of cellular processes, which increases the efficiency of those processes

Answer D

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.

Answer D Correct. Even with mutated aquaporins, a small amount of water is able to enter and leave the cell. Thus, turgor pressure is not lost and the alternative hypothesis is supported.

Water is constantly diffusing into the cytosol of freshwater single-celled organisms. In order to maintain the proper solute concentrations in the cytosol, contractile vacuoles pump out the excess water. An experimenter placed single-celled organisms into various saline concentrations and recorded the ATP used by the contractile vacuole. The data are shown in the graph. Of the following, which additional investigation can be used to determine when the cells are in an isotonic solution? A Decreasing the salinity of the environment a little at a time until the ATPATP usage reaches a maximum B Decreasing the salinity of the environment a little at a time until ATPATP usage reaches a minimum C Increasing the salinity of the environment a little at a time until ATPATP usage reaches a maximum D Increasing the salinity of the environment a little at a time until the ATPATP usage reaches a minimum

Answer D Correct. If the environment is isotonic to the cell, the net flow of water due to diffusion is zero, and ATPATP is not used to pump water out of the cell.

A spherical bacterial cell has a radius of 3μm. The human egg cell has a radius of 100μm. Which statement correctly indicates the cell that is able to more efficiently exchange materials with the external environment and provides a correct explanation? A The egg cell, because it has the smallest surface-to-volume ratio. B The egg cell, because it has the largest surface-to-volume ratio. C The bacterial cell, because it has the smallest surface-to-volume ratio. D The bacterial cell, because it has the largest surface-to-volume ratio.

Answer D Correct. The bacterial cell is more efficient in the exchange of materials with the external environment. While the egg cell is much larger than the bacterial cell, the egg cell has a surface-to-volume ratio that is 33 times smaller than the bacterial cell's surface-to-volume ratio.

Changing the shape or morphology of the mitochondrial inner membrane can change the efficiency of mitochondrial function. Which of the following outcomes will most likely result from a change in the shape of the mitochondrial inner membrane from a highly folded surface to a smooth, flat surface? A Mitochondria will become more efficient because the inner mitochondrial membrane will become more permeable to ions. B Mitochondria will become more efficient because the total volume of the mitochondria will increase. C Mitochondria will become less efficient because the inner mitochondrial membrane will become less permeable to large molecules. D Mitochondria will become less efficient because the surface area of the inner mitochondrial membranes will decrease.

Answer D Correct. The change to the inner mitochondrial membrane will result in a decrease in the membrane's surface area, which will reduce the efficiency of mitochondrial function because there will be less surface area for reactions to occur.

Which of the following statements best supports the claim that certain organelles within eukaryotic cells evolved from free-living prokaryotic cells? A The cytoplasm of both eukaryotes and prokaryotes is surrounded by a plasma membrane. B Eukaryotes and prokaryotes both contain ribosomes, but the ribosomes of eukaryotes are more complex in structure than those of prokaryotes. C Eukaryotes exchange segments of internal membranes between the endoplasmic reticulum and Golgi apparatus, but prokaryotes have no such internal membranes. D Some organelles contain their own DNADNA that is more similar to prokaryotic DNADNA in structure and function than to the eukaryotic DNADNA found in the cell's nucleus.

Answer D Correct. The mitochondria and chloroplasts contain DNADNA more similar to prokaryote DNADNA in structure and function than to eukaryotic DNADNA. Eukaryotic DNADNA in the nucleus has additional structural proteins and a more complex process of protein synthesis. The most reasonable explanation involves the incorporation of one free-living prokaryotes that eventually integrated with the structures and processes of their eukaryotic hosts.

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 ERER breaks down toxic substances, and smooth ERER only transports them out of the cell. B Rough ERER can synthesize and package lipids for export, and smooth ERER cannot. C Rough ERER can produce ATPATP, and smooth ERER cannot. D Rough ERER can synthesize and package proteins for export, and smooth ERER cannot.

Answer D Correct. The ribosomes associated with rough ERER synthesize proteins that are then exported from the cell.

Researchers claimed that a particular organelle originated from a free-living prokaryotic cell that was engulfed by a larger cell, as shown in Figure 1. Which of the following provides evidence to best support the researchers' claim? A The organelle has a phospholipid membrane. B The organelle has protein in the membrane. C The organelle has a double membrane. D The organelle has an internal aqueous environment that is similar to the cytosol of the larger cell.

Answer: C (The organelle's double membrane could have resulted from the process of endocytosis. Based on the claim, the organelle's inner membrane originated from the plasma membrane of the smaller cell and the organelle's outer membrane originated from the plasma membrane of the larger cell.)

The following questions refer to an experiment in which a dialysis-tubing bag is filled with a mixture of 3% starch and 3% glucose and placed in a beaker of distilled water, as shown below. After 3 hours, glucose can be detected in the water outside the dialysis-tubing bag, but starch cannot. From the initial conditions and results described, which of the following is a logical conclusion? A The initial concentration of glucose in the bag is higher than the initial concentration of starch in the bag. B The pores of the bag are larger than the glucose molecules but smaller than the starch molecules. C The bag is not selectively permeable. D A net movement of water into the beaker has occurred. E The molarity of the solution in the bag and the mola

B

A student formulated a hypothesis that water-soluble pollutants damage living organisms by increasing the permeability of cellular membranes. To test the hypothesis, the student investigated the effect of isopropanol and acetone on beet root cells. The vacuoles of beet root cells contain large amounts of betacyanin, a water-soluble pigment that is released into the extracellular environment as a result of increased membrane permeability. The student prepared identical samples of beet root tissue and incubated each sample for 15 minutes in the specific solution for that group. At the end of the incubation period, the student measured the absorbance of 460 nm light for each sample. A greater concentration of betacyanin in the solution surrounding the beet root cells results in a greater absorbance of 460 nm light. The results of the experiment are shown in the table above. Which of the following is the dependent variable in the experiment? A The percent by volume of isopropanol in the treatment solutions B The percent by volume of water in the treatment solutions C The length of time each sample was incubated in the treatment solutions D The absorbance of 460 nm light by the treatment solutions

D