Unit 2 Practice Test 𖦹⋆｡°✩

Question 1

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?

Answer 1

A. They have rigid, non-fluid 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.

Question 2

✩CORRECT ANSWER FOR 2.1, 1✩

Answer 2

B

Question 3

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?

Answer 3

A. Enzymatic modification of newly synthesized integral membrane proteins

B. Synthesis of cytosolic proteins based on the nucleotide sequences of

C. Degradation of proteins by hydrolytic enzymes contained within the complex

D. Synthesis of various types of lipids

Question 4

✩CORRECT ANSWER FOR 2.1, 2✩

Answer 4

A

Question 5

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 is explained by the structural differences between them?

Answer 5

A. Rough ER breaks down toxic substances, and smooth only transports them out of the cell.

B. Rough ER can synthesize and package lipids for export, and smooth ER cannot.

C. Rough ER can produce ATP, and smooth ER cannot.

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

Question 6

✩CORRECT ANSWER FOR 2.1, 3✩

Answer 6

D

Question 7

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?

Answer 7

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.

Question 8

✩CORRECT ANSWER FOR 2.2, 1✩

Answer 8

B

Question 9

Muscle cells have high ATP Ademands. 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?

Answer 9

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

Question 10

✩CORRECT ANSWER FOR 2.2, 2✩

Answer 10

A

Question 11

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. Based on the model, the newly synthesized protein is transported directly from the endoplasmic reticulum to which of the following?

Answer 11

A. The nucleus

B. The plasma membrane

C. The Golgi complex

D. The extracellular space

Question 12

✩CORRECT ANSWER FOR 2.2, 3✩

Answer 12

C

Question 13

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?

Answer 13

A. 650 micrometers

B. 875 micrometers

C. 925 micrometers

D. 1150 micrometers

Question 14

✩CORRECT ANSWER FOR 2.3, 1✩

Answer 14

A

Question 15

A spherical bacterial cell has a radius of
3microm The human egg cell has a radius of 100microm. Which statement correctly indicates the cell that is able to more efficiently exchange materials with the external environment and provides a correct explanation?

Answer 15

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.

Question 16

✩CORRECT ANSWER FOR 2.3, 2✩

Answer 16

D

Question 17

Two different models of a living cell are represented in the figure. Of the two cells represented in the figure, which would likely be more efficient at exchanging substances with the surrounding environment?

Answer 17

A. Cell A, because it has the larger surface-area-to-volume ratio.

B. Cell A, because it has the smaller surface-area-to-volume ratio.

C. Cell B, because it has the larger surface-area-to-volume ratio.

D. Cell B, because it has the smaller surface-area-to-volume ratio.

Question 18

✩CORRECT ANSWER FOR 2.3, 3✩

Answer 18

A

Question 19

✩CORRECT ANSWER FOR 2.4, 1✩
…diagram

Question 20

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?

Answer 20

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.

Question 21

✩CORRECT ANSWER FOR 2.4, 2✩

Answer 21

B

Question 22

A model of the plasma membrane showing several biological molecules, including a transmembrane protein, is shown in Figure 1. Which statement best explains why correct protein folding is critical in the transmembrane protein shown above?

Answer 22

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.

Question 23

✩CORRECT ANSWER FOR 2.4, 3✩

Answer 23

A

Question 24

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?

Answer 24

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.

Question 25

✩CORRECT ANSWER FOR 2.5, 1✩

Answer 25

D

Question 26

Plant cell walls are composed of cellulose, while fungal cell walls are composed of chitin. A group of scientists hypothesize that this difference means the cell wall has largely different functions in plant cells and fungal cells. Alternatively, another group of scientists hypothesize that despite their biochemical differences, plant and fungal cell walls serve similar functions. Which of the following observations would best support the alternative hypothesis described above?

Answer 26

A. Plant cell walls are found just outside the plasma membrane, while fungal cell walls are found just beneath the plasma membrane.

B. In both plant cells and fungal cells, the cell wall surrounds the outside of the cell membrane.

C. Some plant cells have secondary cell walls that confer additional rigidity, while fungal cells do not.

D. Photosynthesis occurs in plant cells, but it does not occur in fungal cells.

Question 27

✩CORRECT ANSWER FOR 2.5, 2✩

Answer 27

B

Question 28

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?

Answer 28

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.

Question 29

✩CORRECT ANSWER FOR 2.5, 3✩

Answer 29

A

Question 30

Figure 1 shows a model of how a channel protein influences the movement of a particle across a cell’s plasma 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?

Answer 30

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 ATP from the intracellular space and measure the rate of the particle movement into the intracellular space.

Question 31

✩CORRECT ANSWER FOR 2.6, 1✩

Answer 31

C

Question 32

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?

Answer 32

A. Decreasing the salinity of the environment a little at a time until the ATP usage reaches a maximum

B. Decreasing the salinity of the environment a little at a time until ATP usage reaches a minimum

C. Increasing the salinity of the environment a little at a time until ATP usage reaches a maximum

D. Increasing the salinity of the environment a little at a time until the ATP usage reaches a minimum

Question 33

✩CORRECT ANSWER FOR 2.6, 2✩

Answer 33

D

Question 34

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 25C. The data from this experiment indicate that maximal rate of transport of protein X at 25C occurs at an ATP concentration of 1microm/mL. Which procedure should be done next to gather data needed to meet the scientist’s objective?

Answer 34

A. Incubate samples with the same four ATP concentrations at 30C.

B. Incubate samples containing 5microm/mL of ATP at four temperatures other than 25C.

C. Incubate samples containing 1.0microm/mL of ATP at four temperatures other than 25C.

D. Incubate samples containing 1.0microm/mL of ATP at 25C and determine the rate of transport for four other proteins.

Question 35

✩CORRECT ANSWER FOR 2.6, 3✩

Answer 35

C

Question 36

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?

Answer 36

A. H+ ions will stop moving through the protein.

B. H+ ions will move in the other direction through the protein.

C. H+ ions will continue to move through the protein in the original direction but at a slower rate.

D. H+ ions will begin to move through the phospholipid portion of the membrane in the original direction.

Question 37

✩CORRECT ANSWER FOR 2.7, 1✩

Answer 37

A

Question 38

Which statement best describes the effect on water transport across the cell membrane if the aquaporin in the figure ceases to function?

Answer 38

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.

Question 39

✩CORRECT ANSWER FOR 2.7, 2✩

Answer 39

B

Question 40

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. Based on the model presented in Figure 1, which of the following outcomes will most likely result from a loss of protein X function?

Answer 40

A. The membrane potential will be disrupted by an increase in Na+ concentration inside the cell.

B. The membrane potential will be disrupted by an increase in K+ concentration inside the cell.

C. The membrane potential will be maintained by the Na+ - K+ pump moving more K+ ions into the cell.

D. The membrane potential will be maintained by the diffusion of Na+ ions into the cell.

Question 41

✩CORRECT ANSWER FOR 2.7, 3✩

Answer 41

B

Question 42

✩CORRECT ANSWER FOR 2.8, 1✩
… short answer

Question 43

✩CORRECT ANSWER FOR 2.8, 2✩
… short answer

Question 44

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?

Answer 44

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.

Question 45

✩CORRECT ANSWER FOR 2.10, 1✩

Answer 45

D

Question 46

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?

Answer 46

A. The internal pH of the lysosomes will decrease, which will prevent the activation of hydrolytic enzymes and interfere with the intracellular digestion of food.

B. The internal pH of the lysosomes will increase, which will prevent the activation of hydrolytic enzymes and interfere with the intracellular digestion of food.

C. The internal pH of the lysosomes will decrease, which will activate hydrolytic enzymes and enhance the intracellular digestion of food.

D. The internal pH of the lysosomes will increase, which will activate hydrolytic enzymes and enhance the intracellular digestion of food.

Question 47

✩CORRECT ANSWER FOR 2.10, 2✩

Answer 47

B

Question 48

Which of the following statements best predicts the effect of increasing the permeability of the mitochondrial membranes to large molecules?

Answer 48

A. ATP production will increase because of an increase in the rate at which proteins diffuse out of mitochondria.

B. ATP production will increase because of an increase in the mixing of mitochondrial and cytosolic substances.

C. ATP production will decrease because of an increase in the occurrence of uncontrolled chemical reactions.

D. ATP production will decrease because of an increase in the surface area of the mitochondrial membranes.

Question 49

✩CORRECT ANSWER FOR 2.10, 3✩

Answer 49

C

Question 50

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?

Answer 50

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.

Question 51

✩CORRECT ANSWER FOR 2.11, 1✩

Answer 51

C

Question 52

Which of the following statements best supports the claim that certain organelles within eukaryotic cells evolved from free-living prokaryotic cells?

Answer 52

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 DNA that is more similar to prokaryotic in structure and function than to the eukaryotic DNA found in the cell’s nucleus.

Question 53

✩CORRECT ANSWER FOR 2.11, 2✩

Answer 53

D

Question 54

The endosymbiont theory proposes a model for the evolution of mitochondria. According to the model, an ancestral eukaryote engulfed a small, free-living prokaryotic organism. The engulfed prokaryote then formed an endosymbiotic relationship with the eukaryotic host. Which of the following observations best supports the model?

Answer 54

A. Prokaryotes and eukaryotes acquire nutrients from the surrounding environment.

B. Organelles such as mitochondria and the endoplasmic reticulum have membranes composed of phospholipids.

C. Mitochondria and some prokaryotes share similar metabolic reactions that produce ATP.

D. Eukaryotes evolved after prokaryotes and have more complex structures.

Question 55

✩CORRECT ANSWER FOR 2.11, 3✩

Answer 55

C