Quiz Questions
D
A drug designed to inhibit the response of cells to testosterone would almost certainly result in which of the following? A) an increase in receptor tyrosine kinase activity B) a decrease in G protein activity C) lower cytoplasmic levels of cAMP D) a decrease in transcriptional activity of certain genes E) an increase in cytosolic calcium concentration
E
An inhibitor of phosphodiesterase activity (such as caffeine) would have which of the following effects? A) block the activation of G proteins in response to epinephrine binding to its receptor B) decrease the amount of cAMP in the cytoplasm C) block the activation of protein kinase A D) block the response of epinephrine E) prolong the effect of epinephrine by maintaining elevated cAMP levels in the cytoplasm
C
Differences among organisms are caused by A) differences in the sizes of the organic molecules in each organism. B) large differences in elemental composition from organism to organism. C) differences in the types and relative amounts of organic molecules synthesized by each organism. D) differences in the elements that bond with carbon in each organism. E) differences in inorganic compounds present in each organism.
A
If a DNA sample were composed of 30% adenine, what would be the percentage of thymine? A) 30 B) 20 C) 80 D) 40 E) impossible to tell from the information given
D
If radioactive deoxythymidine triphosphate (dTTP) is added to a culture of rapidly growing eukaryotic cells, where in the cell would you expect to find the greatest concentration of radioactivity? A) endoplasmic reticulum B) nucleoid C) cytoplasm D) nucleus E) ribosomes
D
Normal hemoglobin is a tetramer, consisting of two molecules of β hemoglobin and two molecules of α hemoglobin. In sickle-cell disease, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. Based on this information alone, we can conclude that sickle-cell hemoglobin exhibits A) altered primary structure. B) altered secondary structure. C) altered tertiary structure. D) altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered. E) altered quaternary structure.
B
Particular receptor tyrosine kinases (RTKs) that promote excessive cell division are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. HER2 is sometimes excessive in cancer cells. This information can now be utilized in breast cancer treatment if which of the following is true? A) If the patient has RTKs only in cancer cells. B) If the patient's cancer cells have excessive levels of HER2. C) If HER2, administered by injection, causes cell division. D) If the patient's genome codes for the HER2 receptor. E) If Herceptin is found in the breast lymph nodes of the patient.
E
Protein kinases are enzymes that catalyze phosphorylation of target proteins at specific sites, whereas protein phosphatases catalyze removal of phosphate(s) from phosphorylated proteins. Phosphorylation and dephosphorylation can function as an on-off switch for a protein's activity, most likely through A) a change in the optimal temperature at which a reaction will occur. B) the excision of one or more peptides. C) a change in the optimal pH at which a reaction will occur. D) the change in a protein's charge leading to cleavage. E) the change in a protein's charge leading to a conformational change.
B
Select the correct statement about the process of scientific inquiry. A) The goal of scientific research is to prove the stated hypothesis. B) It is possible to test hypotheses, such as those involving historical events, without conducting experiments. C) If the results of an experiment do not support the hypothesis that is tested, the experiment is badly designed.
A
Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon? A) the release of heat by the formation of hydrogen bonds B) the change in density when it condenses to form a liquid or solid C) reactions with other atmospheric compounds D) the release of heat by the breaking of hydrogen bonds E) the high surface tension of water
A
Thalidomide and L-dopa, shown below, are examples of pharmaceutical drugs that occur as enantiomers, or molecules that A) are mirror images of one another. B) are structural isomers. C) have identical three-dimensional shapes. D) are cis-trans isomers. E) are mirror images of one another and have the same biological activity.
A
The cell walls of bacteria, fungi, and plant cells and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following is a characteristic common to all of these extracellular structures? A) They are constructed of polymers that are synthesized in the cytoplasm and then transported out of the cell. B) They must provide a rigid structure that maintains an appropriate ratio of cell surface area to volume. C) They must block water and small molecules in order to regulate the exchange of matter and energy with their environment. D) They must permit information transfer between the cell's cytoplasm and the nucleus. E) They are composed of a mixture of lipids and carbohydrates.
E
The label on a container of margarine lists "hydrogenated vegetable oil" as the major ingredient. What is the result of adding hydrogens to vegetable oil? A) The hydrogenated vegetable oil has a lower melting point. B) The hydrogenated vegetable oil is less likely to clog arteries. C) The hydrogenated vegetable oil has fewer trans fatty acids. D) The hydrogenated vegetable oil has more "kinks" in the fatty acid chains. E) The hydrogenated vegetable oil stays solid at room temperature.
D
The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions? A) C6H10O5 B) C18H10O15 C) C18H36O18 D) C18H32O16 E) C3H6O3
B
The properties of water are most directly due to what type of bonds? A) Polar covalent bonds B) Hydrogen bonds C) Ionic bonds D) Peptide bonds
A
The structural level of a protein least affected by a disruption in hydrogen bonding is the A) primary level. B) All structural levels are equally affected. C) secondary level. D) quaternary level. E) tertiary level
E
Vinblastine, a drug that inhibits microtubule polymerization, is used to treat some forms of cancer. Cancer cells given vinblastine would be unable to A) migrate by amoeboid movement. B) extend pseudopods. C) maintain the shape of the nucleus. D) form cleavage furrows during cell division. E) separate chromosomes during cell division.
B
What types of proteins are not synthesized in the rough ER? A) endoplasmic reticulum proteins B) mitochondrial proteins C) plasma membrane proteins D) secreted proteins E) extracellular matrix proteins
E
When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur? A) The cell will burst. B) Plasmolysis will shrink the interior. C) The cell membrane will lyse. D) The cell will become flaccid. E) The cell will become turgid.
B
Which of the following best describes the structure of a biological membrane? A) a mixture of covalently linked phospholipids and proteins that determines which solutes can cross the membrane and which cannot B) two layers of phospholipids with proteins either crossing the layers or on the surface of the layers C) two layers of phospholipids (with opposite orientations of the phospholipids in each layer) with each layer covered on the outside with proteins D) a fluid structure in which phospholipids and proteins move freely between sides of the membrane E) two layers of phospholipids with proteins embedded between the two layers
D
Which of the following is a correct association? A) kinase activity and the addition of a tyrosine B) adenylyl cyclase activity and the conversion of cAMP to AMP C) phosphodiesterase activity and the removal of phosphate groups D) GTPase activity and hydrolysis of GTP to GDP E) phosphorylase activity and the catabolism of glucose
B
Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal? A) The cotransporter can also transport potassium ions. B) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose. C) Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell. D) Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient. E) Sodium and glucose compete for the same binding site in the cotransporter.
E
Which of the following is true of a scientific theory A) It must demonstrate the effect of one variable by testing control groups and experimental groups. B) It is only accepted after the person who came up with it has died. C) It is a method or device that applies scientific knowledge for some specific purpose. D) It is formulated by many scientists over drinks at a convention. E) It generates testable hypotheses, is supported by a large body of evidence, and is broad in scope.
B
Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA? A) 5´-AGCT-3´ with 5´-TCGA-3´ B) 5´-ATGC-3´ with 5´-GCAT-3´ C) 5´-GCGC-3´ with 5´-TATA-3' D) All of these pairs are correct. E) 5´-purine-pyrimidine-purine-pyrimidine-3´ with 3´-purine-pyrimidine-purine-pyrimidine-5´
A
Which of the following statements best describes the carbon atoms present in a seed-eating bird? A) The carbon atoms ultimately came from carbon dioxide incorporated into sugars through photosynthesis. B) The carbon atoms ultimately came from the soil. C) The carbon atoms are ultimately derived from coal. D) Inorganic carbon atoms in the seeds were incorporated into organic molecules by the bird. E) The carbon atoms ultimately came from simple organic compounds that formed abiotically from inorganic carbon, hydrogen, oxygen, and nitrogen atoms.
B
Which of the following takes place as an ice cube cools a drink? A) Evaporation of the water in the drink increases. B) Kinetic energy in the drink decreases. C) The specific heat of the water in the drink decreases. D) A calorie of heat energy is transferred from the ice to the water of the drink. E) Molecular collisions in the drink increase.
C
Why isn't the mitochondrion classified as part of the endomembrane system? A) It is a static structure. B) It is not attached to the outer nuclear envelope. C) Its structure is not derived from the ER or Golgi. D) It is not involved in protein synthesis E) It has too many vesicles.
a
You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells? A) similarity of the drug molecule to other molecules transported by the target cells B) lipid composition of the target cells' plasma membrane C) lack of charge on the drug molecule D) blood or tissue type of the patient E) hydrophobicity of the drug molecule