ACT Success - Science - Practice #4
There are several passages in this test. Each passage is followed by several questions. After reading a passage, choose the best answer to each question. You may refer to the passages as often as necessary. You are NOT permitted to use a calculator on this test.
Group 1
Researchers conducted an experiment to investigate how the concentration of propylene glycol (PG) in a solution affects the permeation of four different substances (P1, P2, P3, and P4) across a membrane over 24 hours. Method: For each substance, a solution was prepared with varying concentrations of PG, ranging from 0% to 100%. These solutions were then applied to a membrane, and the amount of each substance that permeated through the membrane was measured after 24 hours. The cumulative permeation was recorded in micrograms (µg) for each PG concentration level. Conclusion: The data suggest that PG concentration has a variable impact on the permeation rates of different substances, with P3 and P4 showing increased permeation at higher PG levels, while P2 is unaffected.
Question 1a
Based on the data presented in the graph, which of the following hypotheses about the interaction between PG concentration and membrane composition would best explain the varying permeation behaviors of P1, P2, P3, and P4?
High PG concentrations increase permeation rates universally across all substances.
PG concentration primarily affects substances with smaller molecular structures, explaining the variability in permeation for each substance.
P2’s permeation is independent of PG concentration because its molecular structure prevents interaction with PG.
The substances with greater molecular polarity are more affected by PG concentration, increasing their permeation rates at higher PG levels.
Question 1b
Suppose a similar experiment was conducted using the same substances but with a membrane that had a higher porosity. Predict how the overall pattern of permeation for P3 would likely change, and justify your answer based on the trends shown in the graph.
P3 would likely reach a higher permeation level across all PG concentrations, suggesting an exponential increase as PG concentration rises.
P3’s permeation would stay relatively constant, as membrane porosity would have no impact on a PG-dependent process.
P3 would show a quicker initial increase in permeation at low PG concentrations, with diminishing returns at higher concentrations.
P3 would likely decrease in permeation at high PG concentrations due to the increased porosity allowing PG to bypass the membrane.
Question 1c
If another substance, P5, was tested and its permeation data closely resembled that of P2, what might this suggest about the molecular characteristics of P5 in relation to PG concentration, and how would you design a follow-up experiment to verify this hypothesis?
P5 likely has a large molecular weight that prevents it from being affected by PG concentration. A follow-up experiment could vary the membrane thickness to see if permeation changes.
P5 might share similar polarity and solubility properties with P2, making it unaffected by PG. A follow-up experiment could vary the temperature to test permeation response.
P5 and P2 could both be hydrophobic, reducing their interaction with PG. A follow-up experiment could test different solvents besides PG.
P5 may have a structure that makes it too large to pass through the membrane, regardless of PG concentration. Testing at higher pressures could determine if pressure influences permeation.
Group 2
Scientists aimed to compare how different formulations (immediate-release and extended-release) of two drug ingredients, labeled Ingredient A and Ingredient B, affect the concentration of the drugs in the bloodstream over time. Method: Subjects were administered each of the four formulations (Ingredient A immediate-release, Ingredient A extended-release, Ingredient B immediate-release, and Ingredient B extended-release) at the start of the experiment. Blood samples were then taken at various time intervals over 24 hours to measure the concentration of each ingredient in ng/mL (nanograms per milliliter). Conclusion: This experiment demonstrates that the release type (immediate vs. extended) affects how long each drug ingredient remains at an effective concentration level in the bloodstream. Ingredient A reaches higher concentrations than Ingredient B, especially in its immediate-release form, while extended-release formulations provide a more prolonged concentration over time.
Question 2a
Considering the blood plasma concentration patterns for both ingredients, what does the difference in peak concentration times between the immediate-release and extended-release forms of Ingredient A suggest about the pharmacokinetics of these formulations? How might these findings influence the choice of formulation for treating a condition requiring sustained plasma concentration?
The immediate-release formulation of Ingredient A is ideal for achieving a rapid therapeutic effect, but the extended-release version would be better for maintaining a steady level of the drug for chronic conditions.
The extended-release formulation's delayed peak is due to a slower metabolic rate and would not be appropriate for treating acute conditions.
The immediate-release formulation of Ingredient A provides a more stable concentration over time, making it better suited for chronic use.
The results suggest that both forms would be equally effective for maintaining a stable plasma concentration.
Question 2b
Imagine that a patient requires a high blood plasma concentration of Ingredient B throughout a 24-hour period. Based on the data, which adjustments, if any, might make Ingredient B a more effective choice for this patient’s needs, and what rationale supports your answer?
Increase the dose of Ingredient B in its immediate-release form, as this will prolong its effective concentration throughout the day.
Administer Ingredient B in the extended-release form more frequently to increase its peak concentration without altering its release pattern.
Reformulate Ingredient B with a higher initial concentration in its extended-release form to maintain a longer effective period.
Switch to an extended-release formulation of Ingredient A instead, as Ingredient B does not provide adequate plasma concentration for extended periods.
Question 2c
Suppose a new formulation of Ingredient A was developed that combines immediate-release and extended-release mechanisms in a single dose. Predict how the plasma concentration curve for this combined formulation might appear over the 24-hour period, and discuss how this could potentially address limitations seen in the original formulations.
The curve would likely show two distinct peaks: an early sharp increase from the immediate-release component, followed by a sustained plateau from the extended-release portion, providing both immediate and prolonged effects.
The combined formulation would likely show a single, high peak, as the immediate-release portion would mask the extended-release effect, resulting in a rapid decline after the initial absorption.
The concentration curve would resemble the immediate-release form but taper off more slowly, making it indistinguishable from the extended-release version.
The curve would remain flat, with no distinguishable peak, due to the canceling effects of the immediate- and extended-release components.
Question 3a
A researcher studies the solubility of various salts in water and finds that as the water temperature increases from 25°C to 75°C, the solubility of salt X increases from 30 g/L to 85 g/L. Based on this information, which of the following statements best describes the relationship between temperature and the solubility of salt X?
The solubility of salt X decreases as temperature increases.
The solubility of salt X is unaffected by temperature.
The solubility of salt X increases as temperature increases.
The solubility of salt X increases initially but then decreases at higher temperatures.
Question 3b
In an experiment, a biologist measures the growth rate of two plant species under different light intensities. Species A grows fastest at 50% light intensity, while Species B grows fastest at 75% light intensity. If the light intensity were increased to 90%, what would be the most likely outcome for the growth rates of both species?
Both Species A and Species B would grow faster at 90% light intensity.
Species A’s growth rate would likely decrease, while Species B’s growth rate may remain steady or decrease slightly.
Species B would grow faster, but Species A’s growth rate would remain constant.
Both species would experience no change in growth rate.
Question 4a
A group of chemists studied the effects of adding different catalysts (Catalyst A, B, and C) on the rate of a chemical reaction at a constant temperature. They found that the reaction rate increased significantly with Catalyst B but showed little change with Catalysts A and C. Based on these results, which of the following conclusions is most likely correct?
Catalyst B lowers the activation energy of the reaction more effectively than Catalysts A and C.
Catalyst A prevents the reaction from occurring, while Catalyst C has no effect.
Catalyst C is less stable than Catalyst B, which is why it is less effective.
Catalyst A increases the activation energy required for the reaction.
Question 4b
Scientists conducted an experiment to investigate the effects of pH on enzyme activity. They observed that Enzyme Z was most active at pH 7 and had no activity below pH 4 or above pH 10. If the experiment were repeated at pH 5, what would the scientists most likely observe?
Enzyme Z activity would be higher than at pH 7.
Enzyme Z activity would be absent at pH 5.
Enzyme Z activity would be lower than at pH 7 but still present.
Enzyme Z activity would be unaffected by pH changes.
Group 5
Coral bleaching is a phenomenon where corals lose their vibrant colors and turn white, often leading to coral death if the bleaching is prolonged. Three marine biologists have differing viewpoints on the primary causes of coral bleaching events.
Marine Biologist 1 Marine Biologist 1 argues that coral bleaching primarily results from elevated water temperatures, which are a direct consequence of global climate change. When ocean temperatures rise, corals expel the symbiotic algae, known as zooxanthellae, that live within their tissues and provide them with nutrients. Without these algae, corals lose their color and their primary source of energy, leading to bleaching. Marine Biologist 1 points to recent studies showing a strong correlation between rising ocean temperatures and the frequency of coral bleaching events, especially during periods of prolonged heatwaves. According to this viewpoint, reducing greenhouse gas emissions could help stabilize ocean temperatures and prevent future bleaching events.
Marine Biologist 2 Marine Biologist 2 believes that while high temperatures can trigger bleaching, the primary cause is actually related to water pollution, particularly from agricultural runoff. This runoff introduces excess nutrients, such as nitrogen and phosphorous, into the water, leading to an overgrowth of algae on the coral surface. This excessive algal growth competes with the zooxanthellae, ultimately causing the corals to expel them and resulting in bleaching. Marine Biologist 2 argues that coral reefs near agricultural areas experience higher rates of bleaching, regardless of ocean temperature. To mitigate bleaching, Marine Biologist 2 suggests stricter controls on agricultural practices to reduce nutrient runoff.
Marine Biologist 3 Marine Biologist 3 contends that coral bleaching is primarily driven by ocean acidification, which occurs as oceans absorb more carbon dioxide (CO₂) from the atmosphere. This absorption lowers the pH of seawater, making it more acidic and interfering with the coral’s ability to build and maintain their calcium carbonate skeletons. As the corals struggle to grow in more acidic conditions, they become stressed and are more likely to expel their zooxanthellae. Marine Biologist 3 argues that even in cooler or less polluted waters, bleaching is occurring in areas with high levels of ocean acidification. According to this viewpoint, decreasing CO₂ emissions is essential to prevent further acidification and coral bleaching.
Question 5a
If a study found that coral bleaching rates were significantly lower in waters with controlled nutrient levels, regardless of temperature or pH, this finding would most strongly support which marine biologist’s viewpoint?
Marine Biologist 1 only
Marine Biologist 2 only
Marine Biologist 3 only
Both Marine Biologists 1 and 3
Question 5b
Which of the following observations would most strongly challenge Marine Biologist 3’s viewpoint on the primary cause of coral bleaching?
Coral bleaching rates are higher in areas with warmer water temperatures, even where ocean acidity is stable.
Coral reefs located far from agricultural runoff sources experience bleaching only during periods of high acidity.
Coral reefs in colder, nutrient-poor waters exhibit higher bleaching rates when temperatures rise slightly.
Coral reefs in areas with reduced CO2 emissions show fewer instances of bleaching than those in areas with higher CO2 emissions.
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