Topic 1 , 2 , 3 , 4 , 5 Q&A
Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown solution (1-6) contained one of the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and -1.0 M. Cubes of sweet potato (1 cm3) were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions. From the data provided, which unknown solution has a molarity that most closely reflects the molarity of sweet potato cells?
4
Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown solution (1-6) contained one of the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and 1.0 M. Cubes of sweet potato (1 cm3) were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions. Which unknown solution contains the highest concentration of sucrose?
4
Which of the following statements is consistent with the second law of thermodynamics?
A constant input of energy is required to maintain the high level of organization associated with living cells.
Disruption of the active site of an enzyme would most likely result in which of the following?
A decreased ability of the enzyme to bind substrates.
Which of the following statements best describes some aspect of the function of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.
Which of the following would be a fact?
Bats with white noses have been observed in the wild.
Which of the following statements best describes induced fit?
Binding of substrate to the active site changes the shape of the active site of an enzyme.
Which component in the figure above represents a microfilament of the cytoskeleton?
C
The volume and surface area for three different cells are listed in the following table: Based on data from the table above, which of the following statements best explains which cell will be able to eliminate wastes most efficiently?
Cell 2 because it has the highest ratio of surface area to volume, which facilitates the exchange of materials between a cell and its environment.
The genetic material used for reproduction by those organisms conventionally considered to be living is ________.
DNA
Which of the following statements best describes the first law of thermodynamics?
Energy cannot be created or destroyed.
Which of the following statements best describes enzyme function?
Enzymes increase the rate of chemical reactions by lowering activation energy barriers.
A direct and repeatable observation of any aspect of the natural world can be considered a scientific ________.
Fact
Which of the following organelles is primarily responsible for the production and modification of polysaccharides that will be secreted?
Golgi apparatus
Which of the following statements best summarizes a consequence of the second law of thermodynamics?
If entropy of a system decreases, there must be a corresponding increase in the entropy of the universe.
Which of the following statements best describes a characteristic feature of a carrier protein in a plasma membrane?
It exhibits specificity for a particular type of molecule.
Which of the following statements best describes a characteristic feature of diffusion?
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
When chemical, transport, or mechanical work is performed by an organism, what happens to the heat that is generated?
It is lost to the environment.
When ATP is hydrolyzed to activate a target protein, what is often the fate of the inorganic phosphate that is released?
It may be used to form a phosphorylated intermediate.
Which of the following statements best describes the function of the nuclear pore complex found in eukaryotic cells?
It regulates the movement of proteins and RNAs into and out of the nucleus.
Use the following information when answering the following question.In 1668, Francesco Redi performed a series of experiments on spontaneous generation. He began by putting similar pieces of meat into eight identical jars. Four jars were left open to the air, and four were sealed. He then did the same experiment with one variation: Instead of sealing four of the jars completely, he covered them with gauze (the gauze excluded the flies while allowing the meat to be exposed to air). In both experiments, he monitored the jars and recorded whether or not maggots (young flies) appeared in the meat. What hypothesis was being tested in the initial experiment with open versus sealed jars?
Maggots do not arise spontaneously, but from eggs laid by adult flies.
Agrobacterium infects plants and causes them to form tumors. You are asked to determine how long a plant must be exposed to these bacteria to become infected. Which of the following experiments will provide the best data to address that question?
Measure the number of tumors formed on plants, which are exposed to Agrobacterium for different lengths of time.
Researchers hypothesized that a North American fungus not only caused symptoms of white-nose syndrome (WNS) but also caused death. The results from their experiment are shown in the graph below. Based on this graph, which of the following hypotheses would be the MOST logical hypothesis for further studies?
Other species of bats injected with European fungus will experience death.
Which of the following statements best describes a characteristic of biological membranes?
Phospholipids move laterally within the plane of the membrane.
Which of the following statements best describes some aspect of protein secretion from prokaryotic cells?
Proteins secreted by prokaryotes are likely synthesized on ribosomes bound to the cytoplasmic surface of the plasma membrane.
Why is a scientific topic best discussed by people of varying points of view, from different subdisciplines, and representing diverse cultures?
Robust and critical discussion between diverse groups improves scientific thinking.
In presenting data that result from an experiment, a group of students shows that most of their measurements fall on a straight diagonal line on their graph. However, two of their data points are "outliers" and fall far to one side of the expected relationship. Which of the following is the most reasonable way to handle the outliers when analyzing the data?
Show all results obtained and then try to explore the reason(s) for the variation in data.
Which of the following statements best describes the normal tonicity conditions for typical plant and animal cells in their native environments?
The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.
What will happen to a red blood cell (RBC), which has an internal ion content of about 0.9%, if it is placed into a beaker of pure water?
The cell will swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC.
Gaucher disease is the most common genetic disorder affecting lipid storage in humans. The disease is caused by deficiency of an enzyme necessary for the breakdown of lipids, which leads to the accumulation of fatty material in organs of the body including the spleen, liver, kidneys, lungs, brain, and bone marrow.Which of the following statements provides the most plausible explanation for how organelles are impacted by Gaucher disease.
The lysosomes most likely lack sufficient amounts of the enzymes necessary for lipid breakdown.
Which of the following statements best explains how the membranes in winter wheat are able to remain fluid in extremely cold temperatures?
The membranes contain an increased proportion of unsaturated phospholipids.
When H. V. Wilson exposed two species of differently pigmented sponges to a chemical that disrupted intercellular junctions, the cells of the sponges dissociated. Wilson then removed the chemical that caused dissociation and mixed the cells of the two species. He found that the sponges reassembled and that the cells from one species did not interact or form associations with the cells of the other species.Which of the following statements provides the most plausible explanation for the results of this experiment?
The molecules responsible for cell-cell adhesion (cell junctions) differed between the two species of sponge.
A patient is coughing and producing a wheezing sound as she breathes; she also has a fever. She goes to the doctor who listens to her chest, takes X-rays of her chest, and determines that she probably has something called croup. Which of the following are the facts in this scenario?
The patient is coughing, wheezing, and has a fever
Human immunodeficiency virus (HIV) infects cells that have both CD4 and CCR5 cell surface molecules. The viral nucleic acid molecules are enclosed in a protein capsid, and the protein capsid is itself contained inside an envelope consisting of a lipid bilayer membrane and viral glycoproteins. One hypothesis for viral entry into cells is that binding of HIV membrane glycoproteins to CD4 and CCR5 initiates fusion of the HIV membrane with the plasma membrane, releasing the viral capsid into the cytoplasm. An alternative hypothesis is that HIV gains entry into the cell via receptor-mediated endocytosis, and membrane fusion occurs in the endocytotic vesicle. To test these alternative hypotheses for HIV entry, researchers labeled the lipids on the HIV membrane with a red fluorescent dye. What would be observed by live-cell fluorescence microscopy immediately after HIV entry if HIV enters the cell by endocytosis first, and then later fuses with the endocytotic vesicle membrane?
The red fluorescent dye-labeled lipids will appear in the infected cell's interior.
Which of the following statements best describes a primary mechanism by which the energy released in ATP hydrolysis is used directly to drive endergonic chemical reactions in a cell?
The released phosphate is used to form phosphorylated intermediates that are more reactive than the original unphosphorylated substrate.
Cell membranes have distinct inside and outside faces. Which of the following statements is the most plausible explanation for the asymmetrical nature of the two layers of the membrane?
The two layers of a cell membrane face different environments and carry out different functions.
The solutions in the two arms of a U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2 M sucrose and 1 M glucose. Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal.
The water level will be higher in side A than in side B.
When the interior of a cell is in equilibrium with its environment, which of the following statements best describes the relative movement of molecules that can diffuse through the plasma membrane?
There is random movement of molecules into and out of the cell.
An individual is suffering from a streptococcus infection in their throat. Which of the following do the individual and the streptococcus bacteria have in common?
They both are made up of cells.
The nuclear lamina is an array of intermediate filaments that line the inner surface of the nuclear membrane. Disassembly of the lamina by chemical treatment would most likely result in which of the following consequences?
a change in the shape of the nucleus
All the organisms on your campus make up ________.
a community
A newly discovered unicellular organism isolated from acidic mine drainage is found to contain a plasma membrane, two flagella, and peroxisomes. Based on this information only, the organism is most likely to be ________.
a motile eukaryote
A series of enzymes catalyze the reactions in the metabolic pathway X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. What does substance X represent in this pathway?
a substrate
What is the name of the barrier that must be overcome before products are formed in a spontaneous reaction?
activation energy
Based on the below figure, the proton pump used which process?
active transport
A series of enzymes catalyze the reactions in the metabolic pathway X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. Based on its interaction with the enzyme that converts X to Y substance A is best described as ________.
an allosteric inhibitor
A defect in which of the following molecules would dramatically reduce the rate of diffusion of water across cell membranes?
aquaporins
How does a noncompetitive inhibitor decrease the rate of an enzyme-catalyzed reaction?
by binding to an allosteric site, thus changing the shape of the active site of the enzyme
A change of a single amino acid at a position distant from the active site of an enzyme can alter the substrate specificity by changing the ________.
by changing the 3-D shape of the enzyme
Penicillin is an antibiotic that kills bacteria by binding to the active site of an enzyme involved in synthesis of the bacterial cell wall. Which of the following phenomena best describes the mechanism of action of penicillin?
competitive inhibition
Bending of cilia and flagella results from which of the following activities?
conformational changes in a motor protein called dynein
After observing that students who regularly attend class appear to be making good grades, I propose the hypothesis that regular class attendance increases the probability that students earn higher grades. If I attend classes regularly this semester, I should make higher grades than I did last semester when I often missed class. This is a ________.
correlation
A decrease in entropy is associated with which of the following types of reaction?
dehydration
Which of the following terms best describes a chemical reaction for which ΔG is positive?
endergonic
An early step in the evolution of eukaryotic cells most likely involved which of the following events?
endosymbiosis of an oxygen-using bacterium in a larger bacterial host cell-the endosymbiont evolved into mitochondria
The relationship between the breakdown of macromolecules and the biosynthesis of macromolecules is most similar to the relationship between which of the following pairs of terms?
exergonic and endergonic
Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through which of the following structures?
gap junctions
Three important research developments that have made the genomic and proteomic approaches possible are ________.
high throughput technology, bioinformatics, and interdisciplinary research teams
Several epidemic microbial diseases of earlier centuries incurred high death rates because they resulted in severe dehydration due to diarrhea. Today these diseases are usually not fatal because of the development of which of the following types of treatments?
hydrating drinks with high concentrations of salt and glucose
When scientists generate a single informed, logical, and plausible explanation for a question and observations of the natural world, they are proposing a scientific
hypothesis
Which of the following statements describes a major advantage of light microscopy over electron microscopy?
light microscopy allows the visualization of dynamic processes in living cells
In addition to activating or inhibiting enzymes through allosteric regulation, which of these mechanisms do cells also use to control enzymatic activity?
localization of enzymes into specific organelles or membranes
The voltage across a membrane is called the ________.
membrane potential
Cyanide binds with at least one protein complex involved in producing ATP. If a cell is exposed to cyanide, most of the bound cyanide is likely to be localized within which of the following organelles?
mitochondria
Which of the following structures is common to plant and animal cells?
mitochondrion
Two organisms are ________ if they share more taxonomic classification levels.
more similar in characteristics
Which of these provides evidence of the common ancestry of all life?
near universality of the genetic code
Which cell would be best for studying lysosomes?
phagocytic white blood cell
Which of the following processes is used by white blood cells when engulfing bacteria?
phagocytosis
Which of the following structures form cytoplasmic channels that connect adjacent plant cells through the cell walls?
plasmodesmata
Experimentation is the primary, but not only, means used to verify or refute the ________ made by a hypothesis.
predictions
A cell with a predominance of rough endoplasmic reticulum is most likely involved in which of the following processes?
producing large quantities of proteins for secretion
To understand the chemical basis of inheritance, we must understand the molecular structure of DNA. This is an example of the application of which concept to the study of biology?
reductionism
Which of the following is present in a prokaryotic cell?
ribosome
A newly synthesized protein destined for secretion from a eukaryotic cell will generally follow which of the pathways listed below?
rough ER → Golgi → transport vesicle → plasma membrane
When Dr. Blehert and his team set out to determine the cause of death for thousands of bats, they determined that the sick and dead bats had a strange white fuzz on their noses and wings along with depleted fat reserves and damaged wing tissue. After performing observational studies, the researchers used a branch of mathematics called ________ to quantify the reliability of their data.
statistics
A group of researchers conducted an experiment and collected the data presented in the graph below. The graph shows that the hypothesis was ________ because all members of the control group ________ while most of the members of both treatment groups ________ by the end of the study.
supported; survived; died
A new drug designed for the treatment of lung cancer must specifically enter the cytoplasm of lung cells while not entering the cells of other tissues. Which of the following characteristics would likely enhance the specificity of this drug?
the similarity of the drug molecule to other molecules normally transported lung cells
Passive leakage of partially digested material from the small intestine into the human abdominal cavity may result from defects in which of the following type of intercellular junction?
tight junctions
Students conducting research observe the rate of an enzyme-catalyzed reaction under various conditions with a fixed amount of enzyme in each sample. When will increasing the substrate concentration likely result in the greatest increase in the reaction rate?
when a competitive inhibitor is present in the reaction
