AP Bio Multiple Choice
Which of the following best describes the numbered areas?
Areas 1 and 3 are polar, since the membrane molecules are aligned with water molecules. (As indicated in the diagram, the heads of the phospholipids in areas 1 and 3 are adjacent to water molecules, which shows that the phospholipid heads are hydrophilic.)
Bacteriophages are viruses that infect bacteria. In an experiment, bacteriophages were labeled with either radioactive phosphorus or radioactive sulfur. The labeled bacteriophages were incubated with bacteria for a brief amount of time and then removed. The infected bacteria cells were found to contain significant amounts of radioactive phosphorus but not radioactive sulfur. Based on the results of the experiment, which of the following types of molecules did the bacteriophages most likely inject into the bacteria cells?
DNA
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?
Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration. (A function of the lysosomes is the breakdown and recycling of macronutrients, such as carbohydrates. Products of carbohydrate breakdown such as glucose are utilized by the mitochondria in the process of cell respiration.)
A cell is treated with a drug that prevents the formation of new lysosomes. The cell continues to transcribe the genes that code for the hydrolytic enzymes that are normally found in lysosomes and continues to translate the mRNAs for those proteins on membrane-bound ribosomes. The hydrolytic enzymes are most likely to accumulate in which of the following cellular structures?
Golgi complex
Which of the following is responsible for the cohesive property of water?
Hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule
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?
Increasing the salinity of the environment a little at a time until the ATP usage reaches a minimum. (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.)
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?
Interactions of the hydrophobic and hydrophilic amino acids help to anchor the protein in the membrane. (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.)
Which of the following statements is true regarding the movement of substances across cell membranes?
Ions are unable to move through the phospholipid bilayer because the nonpolar tail regions of the phospholipids are hydrophobic.
Which of the following correctly illustrates a dipeptide and an amino acid in the optimal position to form a tripeptide?
It demonstrates an ability to refine and/or interpret a representation to explain the synthesis of a biological polymer. Peptides or proteins are polymers of amino acid monomers arranged in a unique linear sequence. Each of the 20 amino acids consists of a carbon atom surrounded by an amine group (NH2), a carboxyl group (COOH), a hydrogen, and an R (variable) group. When two amino acids are positioned so that the carboxyl group of one amino acid backbone is adjacent to the amine group of another amino acid backbone, they can join by a dehydration reaction.
Which of the following is most directly responsible for water's unique properties?
It forms hydrogen bonds.
Contains hydrolytic enzymes associated with the intracellular digestion of macromolecules
Lysosome
Which of the following best supports the statement that mitochondria are descendants of endosymbiotic bacteria-like cells?
Mitochondria and bacteria possess similar ribosomes and DNA.
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?
Mitochondria will become less efficient because the surface area of the inner mitochondrial membranes will decrease. (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.)
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?
Na+ transport out of the cell requires ATP hydrolysis.
All of the following cell components are found in prokaryotic cells EXCEPT
Nuclear Envelope
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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?
Organelles isolate specific reactions, increasing metabolic efficiency. (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.)
Which of the following statements best explains the processes of passive and active transport?
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. (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.)
Which of the following components of the cell membrane is responsible for active transport?
Protein
Which of the following statements best describes how organisms such as rabbits obtain the carbon necessary for building biological molecules?
Rabbits eat plants and break down plant molecules to obtain carbon and other atoms that they rearrange into new carbon-containing molecules.
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?
Rough ER can synthesize and package proteins for export, and smooth ER cannot. (The ribosomes associated with rough ER synthesize proteins that are then exported from the cell.)
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?
The animal's body cells are defective in endocytosis. (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.)
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?
The bacterial cell, because it has the largest surface-to-volume ratio. (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.)
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?
The drug is a small nonpolar molecule. (Small nonpolar molecules freely pass across the plasma membrane. If the drug is a small nonpolar molecule, this supports the alternative hypothesis.)
Which of the following characteristics of Figure 1 best shows that the fragment is RNARNA and not DNADNA?
The identity of each nitrogenous base(RNA contains uracil, whereas DNA contains thymine)
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?
The organelle has a double membrane. (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 diagram above represents a typical rod-shaped bacterium. Which of the following best describes a feature shown in the diagram that is unique to archaea and bacteria?
The organism does not have a nuclear membrane surrounding its genetic material.
Which statement best describes the effect on water transport across the cell membrane if the aquaporin in the figure ceases to function?
Water molecules will still be able to move across the cell membrane but at a slower rate. (The aquaporin facilitates water passage, but water can still move across the membrane by osmosis.)
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
facilitated diffusion
The organelle that is a major producer of ATP and is found in both heterotrophs and autotrophs is the
mitochondrion
