unit 2 questions

Cholesterol is an important component of animal cell membranes. Cholesterol molecules are often delivered to body cells by the blood, which transports the molecules in the form of cholesterol-protein complexes. The complexes must be moved into the body cells before the cholesterol molecules can be incorporated into the phospholipid bilayers of cell membranes.

Based on the information presented, which of the following is the most likely explanation for a buildup of cholesterol molecules in the blood of an animal.

A. The animal's body cells are defective in exocytosis.

B. The animal's body cells are defective in endocytosis.

C. The animal's body cells are defective in cholesterol synthesis.

D. The animal's body cells are defective in phospholipid synthesis.

Correct. The cholesterol-protein complexes are most likely moved into the body cells by endocytosis. A defect in endocytosis is likely to result in a buildup of cholesterol in the blood.

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 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

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

Evolved from a photoautotrophic prokaryote?

A.) Mitochondria

B.) Chloroplast

C.) Golgi Apparatus

D.) Cell Membrane

E.) Vacuole

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

Correct. The mitochondria and chloroplasts contain DNA more similar to prokaryote DNA in structure and function than to eukaryotic DNA. Eukaryotic DNA 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.

Contains hydrolytic enzymes associated with the intracellular digestion of macromolecules?

A. Centriole

B. Lysosome

C. Nucleolus

D. Peroxisome

E. Ribosome

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.

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.

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

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.

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

In the first step of an experiment, rat liver cells were exposed for 5 minutes to amino acids labeled with a radioactive isotope. The cells were then washed to stop any further incorporation of radioactive amino acids. The cells were sampled periodically thereafter, and the radioactivity of a certain protein (protein X) was measured in various cell components, as shown below.

In graphing the data from this experiment, the sampling time would be shown on the x-axis because

A. cell components were shown on the y-axis

B. radioactivity level shows the most variation

C. time values are always located on the horizontal axis

D. all quantitative values are represented on the x-axis

E. sampling time is the independent variable

Changing the shape or morphology of the mitochondrial inner membrane can change the efficiency of the 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.

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.