AP Bio Unit 2 progress check

Figure 1. Testosterone movement across the cellular membrane Testosterone is a small steroid hormone that is important in cell signaling. Which of the following describes where testosterone enters a cell and why it is able to cross at that point?

1, testosterone is nonpolar and can diffuse through the membrane.

A study was conducted to understand the factors controlling the rate at which molecules or ions travel across cell membranes. An artificial membrane was created that was composed of a phospholipid bilayer only. The speed at which various substances crossed this membrane was measured. Some substances can pass through an actual cell membrane much faster than they passed through the artificial membrane in this study. Which of the following statements best explains this finding?

Actual cell membranes have a variety of proteins embedded in the membrane that are absent in the artificial membrane.

Beetroot cells contain a family of dark red pigments called betalains. The selectively permeable nature of the beetroot cells keeps the internal environment of the cell separate from the external environment of the cell. Researchers are interested in determining whether the selective permeability of beetroot cells is due to the cell membrane or if it is due to the cell wall. Exposure to cellulase is known to damage the structure of the cell wall. An experiment is set up in which beetroot cells are placed in an aqueous solution with cellulase and in one without cellulase. Which of the following results best refutes the alternative hypothesis that selective permeability is a consequence of the cell wall? A When beetroot cells are placed in a solution with cellulase, the solution turns dark red. B When beetroot cells are placed in a solution with cellulase, the solution remains clear. C When beetroot cells are placed in a solution, it turns dark red with or without cellulase present. D Since plant cells contain cell membranes, not cell walls, the alternate hypothesis cannot be tested.

B When beetroot cells are placed in a solution with cellulase, the solution remains clear.

A magnesium sulfate solution taken orally can cause a net movement of water into the large intestine, which results from water molecules diffusing through aquaporins embedded in the cells of the intestinal lining. By which of the following mechanisms do the water molecules most likely move into the large intestine?

By passive transport from an area of low osmolarity to an area of high osmolarity

Aldosterone (a steroid hormone) is a small, nonpolar, hydrophobic molecule that enters a target cell by moving across the plasma membrane, down a concentration gradient. Based on the information presented, how does aldosterone most likely enter target cells?

By simple diffusion because aldersterone can enter a cell by moving across the plasma membrane and moving down the concentration gradient.

The cell membrane is selectively permeable due to its structure. Thus, the internal environment of the cell is distinct from the external environment of the cell. One biologist hypothesizes that small nonpolar molecules readily pass through the membrane. Another biologist alternatively hypothesizes that these types of molecules require channel and transport proteins that are embedded in the membrane in order to move across the membrane. Which of the following data would best refute this alternative hypothesis? A Ethanol is found in the cytosol of cells when they are briefly exposed to a ten percent ethanol solution. B Cells become oxygen deficient when membrane protein activity is blocked. C CO2 and N2 movement in and out of cells is unaffected when membrane protein activity is blocked. D Sodium ions cannot move across the cell membrane when membrane protein activity is blocked.

C CO2 and N2 movement in and out of cells is unaffected when membrane protein activity is blocked.

Some viral infections can lead to the rupture of the lysosome membrane. Which prediction of the effect of this disruption of cellular compartmentalization is most likely correct? A Enzymes will be released that will specifically target the virus. B Cellular osmotic concentrations will change, preventing viral entry into the cell. C Hydrolytic enzymes will be released, which will cause cell death. D Intracellular digestion of organic materials will increase, which will increase the energy available to the cell for fighting the virus.

C Hydrolytic enzymes will be released, which will cause cell death.

Which of the following transport mechanisms will be affected most directly by a temporary shortage of ATP molecules inside the cell? A The movement of water molecules through aquaporins B The diffusion of oxygen molecules across the plasma membrane C The transport of glucose molecules against a concentration gradient D The facilitated diffusion of Ca2+ ions into the cell

C The transport of glucose molecules against a concentration gradient

Researchers have proposed a model of chloroplast evolution. According to the model, chloroplasts evolved from a small prokaryotic organism that was engulfed by an ancestral eukaryote. The engulfed prokaryote then formed an endosymbiotic relationship with the eukaryotic host. Which of the following observations best supports the model? A Chloroplasts are separated from other subcellular compartments by semipermeable membranes. B Prokaryotic and eukaryotic organisms both acquire nutrients from the surrounding environment. C Eukaryotes evolved after prokaryotes and have more complex structures. D Chloroplasts and some prokaryotes share similar photosynthetic reactions.

D Chloroplasts and some prokaryotes share similar photosynthetic reactions.

Which of the following observations best supports the claim that mitochondria evolved from once-free-living prokaryotic cells by the process of endocytosis? A Mitochondria produce ATP. B Mitochondria contain proteins. C Mitochondria exchange substances with the cytosol. D Mitochondria are surrounded by a double membrane.

D Mitochondria are surrounded by a double membrane.

Researchers investigate the transport of a certain protein into cells by endocytosis. In an experiment, the researchers incubate the cells in the presence of the protein and measure the amount of the protein that is absorbed into the cells over a five-minute period. Based on their observations, what should the researchers do to further clarify how the availability of the protein outside the cells affects the rate of endocytosis of the protein?

Incubate the cells in the presence of several different concentrations of the protein.

In an experiment, researchers compared the growth of two different plants, plant X and plant Y. The researchers maintained the plants under nearly identical conditions and observed that plant X grew faster than plant Y. The researchers also observed that the inner mitochondrial membranes of plant X had more folds than did those of plant Y. Which of the following conclusions about increasing the number of folds in the inner mitochondrial membrane is best supported by the results of the experiment?

It increases the surface area available for ATP production, which results in faster cell growth.

In an experiment, researchers provided a radiolabeled amino acid to living plant cells. After one hour, the researchers determined the amount of the radiolabeled amino acid that was in each of several subcellular compartments. The results of the experiment are represented in the table. Which of the following conclusions about the radiolabeled amino acid is best supported by the results of the experiment?

It was mostly incorporated into proteins that regulate and manage metabolic reactions.

The figure shows a representation of a protein embedded in a cell membrane. The numbers indicate different structural regions of the protein. Based on the figure, which of the following statements best describes the relationship between regions 1 and 2 of the protein?

Region 1 is hydrophilic because it interacts with an aqueous environment, whereas region 2 is hydrophobic because it interacts with the interior of the membrane.

Intravenous (IV) therapy is used for fluid replacement in instances of dehydration in humans and other animals. One type of IV fluid is essentially a saltwater solution. To determine the best concentration for therapy in people, a team of students is researching the effects of solutions of different salt concentrations on red blood cells. The following observations were made from three different red blood cell samples viewed under a microscope. 0.3% Saline (Cells swell) 0.9% Saline (Cells unchanged) 1.5% Saline (Cells shrink) The team wants to extend the research project. What should the team of students do next to obtain data that are more conclusive?

Repeat the process with other salt concentrations.

Some membrane proteins help maintain the concentrations of ions inside a cell by transporting the ions across the cell's plasma membrane. Other membrane proteins form pores in the plasma membrane through which the ions can diffuse. A model showing the influence of membrane proteins on the movement of sodium (Na+) and potassium (K+) ions across a plasma membrane is presented in Figure 1. Based on the model presented in Figure 1, which of the following changes will most likely result from a depletion of available ATP stores inside the cell?

The Na+concentration inside the cell will increase.

Which of the following cellular deficiencies would most likely be related to mutations in mitochondrial proteins? A The cell is unable to synthesize most proteins required for normal cell functions. B The cell is unable to break down toxic materials and would accumulate large volumes of these materials. C The cell is able to synthesize proteins, but the proteins would not fold properly and would not contain the correct molecular tags for export from the cell. D The cell is unable to complete reactions related to electron transport and ATP production.

The cell is unable to complete reactions related to electron transport and ATP production.

Lysosomes digest food particles brought into a cell by endocytosis. After a vesicle containing food particles fuses with a lysosome, H+ ions are transported into the lysosome from the cytosol. This significantly lowers the pH of the lysosome relative to the cytosol and activates the enzymes that digest the particles. Which of the following best predicts what will happen to the lysosomal enzymes if the proteins that transport H+ ions from the cytosol into the lysosome are damaged?

The lysosomal enzymes will not become active, since there will be no active transport of H+ ions.

aucher disease is an inherited disorder in which cells of the body are unable to break down a particular type of lipid, resulting in a buildup of the lipid in some tissues and organs. Based on the information provided, Gaucher disease results most directly from a defect in the function of which of the following organelles?

The lysosome

A certain type of specialized cell contains an unusually large amount of rough endoplasmic reticulum (ER). Which of the following functions is this cell type most likely specialized to perform?

The production and secretion of proteins

Stomata are pores on the surfaces of the leaves and stems of plants that regulate gas exchange between the plants and the atmosphere. Researchers found that the stomata density on the leaves of a species of plant change as the concentration of CO2 in the atmosphere changes. When grown at 350 ppm CO2 the plant has an average density of 300 stomata per mm2, but when grown at 400 ppm CO2 the plant has an average density of 250 stomata per mm2. Which of the following best describes how the ratio of the density of stomata (stomata per mm2) per CO2 concentration (ppm CO2) changes as the CO2 concentration increases?

The ratio decreases from 0.86 to 0.63, because fewer stomata are needed at higher CO2 concentrations.

Hereditary spherocytosis (HS) is a disorder of red blood cells that causes the cells to be smaller and spherical instead of having the usual flattened, biconcave shape. The average diameter of normal red blood cells is 7.2um, and the average diameter of red blood cells in a person with HS was found to be 6.7um. The normal red blood cell has an average surface area of 136um2 and an average volume of 91um3. Which of the following provides an accurate calculation of the surface area to volume ratio of an HS red blood cell, as well as a prediction of its effect on the efficient transferring of oxygen compared to a normal red blood cell?

The ratio is 0.89, and the cells are less efficient at transferring oxygen.

A scientist is studying the various prokaryotic and eukaryotic species found floating in a sample of water taken from a marine ecosystem. Which cellular component will be found in the widest range of organisms in the sample?

The ribosome, since all organisms need to synthesize proteins.

Researchers conducted an experiment to investigate the effects of a valinomycin treatment on skeletal muscle cells. Valinomycin is a naturally occurring substance that can be used as a drug. The results of the experiment are presented in the table. Relative Rates of ATP Production Time after Treatment Untreated Cells Valinomycin-Treated Cells 5 minutes 1.0 0.3 10 minutes 7.7 2.7 Which of the following claims about the effects of the valinomycin treatment is best supported by the data presented in the table? A The valinomycin treatment caused an increase in the activity of the rough endoplasmic reticulum. B The valinomycin treatment caused an increase in the activity of the Golgi complex. C The valinomycin treatment caused a decrease in the activity of the lysosome. D The valinomycin treatment caused a decrease in the activity of the mitochondria.

The valinomycin treatment caused a decrease in the activity of the mitochondria.

Some cells, such as intestinal cells, exchange a lot of material with their surroundings. The surface-to-volume ratio of these cells affects the efficiency of material exchange. The table provides measurements of four different eukaryotic cells. Cell 1 2 3 4 Total surface area (um2) 40 60 80 100 Total volume (um3) 20 10 30 20 Based on the data, which cell is likely to be most effective in the exchange of materials?

cell 2