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Traditionally, oral drugs in pill or capsule form have been designed to release the dose of medicine in the upper gastrointestinal tract, where drugs are more readily dissolved and absorbed. New research has targeted the colon as an ideal environment for drug absorption to treat certain illnesses. To reach the colon, the drug must first pass through the stomach and small intestine. Table 1 details several drug-delivery systems.
The following experiments test two of the drug-delivery systems:
Bacteria-dependent delivery. This experiment measured the average time it took a coated tablet to travel from the stomach (gastric emptying) through the small intestine (small intestine transit) to arrive in the colon. Twelve healthy men aged 23 to 25 years old and weighing between 55 and 70 kilograms (kg) who had fasted overnight were divided into 3 groups. They each swallowed 1 tablet, which contained a tracer (A or B) and 1 of 2 natural coatings (1 or 2). The location of the tracer was measured every half-hour for 12 hours. The average times are recorded in Table 2.
Time-dependent delivery. The methods were the same as those used in Experiment 1, except that the tablets all contained the same tracer and 1 of 2 outer coatings (A or B) and one of two inner coatings (1 or 2). The average times are recorded in Table 3.
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Several scientists considered some different environmental factors and their influence on the growth of certain bacteria. The following experiments used Salmonella bacteria to measure the effect of pH levels, nutrients, and temperature on the number of bacteria produced within a given time period.
1. According to Table 1, what might best contribute to the growth of Salmonella bacteria?
A. A pH level above 9
B. A pH level below 5
C. A pH level near 7
D. A pH level near 5
2. According to the results of the three experiments, which combination of the three factors studied would be expected to produce the highest percent growth?
F. pH level of 5, organic compound in Dish 2, temperature of 40◦C
G. pH level of 7, organic compound in Dish 2, temper- ature of 10◦C
H. pH level of 5, organic compound in Dish 1, temper- ature of 40◦C
J. pH level of 9, organic compound in Dish 1, temper- ature of 90◦C
3. Which of the following conclusions is strengthened by the results of Experiment 1?
A. Salmonella bacteria reproduce most efficiently in an acidic environment.
B. Salmonella bacteria reproduce most efficiently in a neutral environment.
C. Salmonella bacteria cannot reproduce in a basic environment.
D. Salmonella bacteria cannot reproduce in an acidic environment.
4. Bacteria will generally reproduce until all of the nutrients available have been depleted. How could the experiment be altered to maximize the length of time that bacteria will reproduce?
F. Change the observation time from 6 hours to 12 hours.
G. Regularly re-supply each group of bacteria with unlimited nutrients.
H. Increase the rate of growth by decreasing the pH levels.
J. Do not test the effect of different nutrient combinations on growth.
5. Which of the following was the independent variable in Experiment 3?
A. pH level
C. organic compound
D. percent growth
6. The experiments recorded the percent growth that occurred over a 6-hour period. Bacteria often repro- duce at a rate that drastically varies from one stage to the next. The best way to study the different stages of growth would be to record the percent growth:
F. after 2 hours only.
G. after 4 hours, then again after 6 hours.
H. after 8 hours only.
J. every 15 minutes for 3 hours.
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Dopamines serve as enhancers or catalysts (a substance that initiates or increases the rate of impulses during a chemical reaction, but is not depleted during the process) to certain reactions involved in the activity of human thought. The dopamine intropin is involved in the stimulation of the neurotransmitters in the brain when thought is initiated. A student investigated the effects of dopamine activity on a specific neurotransmitter.
To each of 10 test tubes, 7 milliliters (mL) of a peptide (a neurotransmitter) solution was added. Two mL of an intropin solution was added to each of Tubes 1–9. Tube 10 received 2 mL of water without intropin. The tubes were then stirred at a constant rate in water baths at various temperatures and incubated (heated) from 0 to 15 minutes (min). At the end of the incubation period, 0.3 mL of NaCl solution was added to each tube. The NaCl stopped the reaction between the intropin and the peptide. The precipitates, solids formed in a solution during a chemical reaction, which in this case were caused by the reaction of NaCl and the pep- tide, were removed from the tubes and dried. The masses of the precipitates, in milligrams (mg), were measured to determine the relative amount of enhancer that remained in the tube. The results are shown in Table 1.
Peptide solution (8 mL) was added to an additional 8 test tubes to which 2 mL of intropin solution was then added. The tubes were incubated at 10 degrees Celsius and stirred at a constant rate for 15 min. The effect of acidity on the neurotransmitter was observed by varying the acidity levels (using the pH scale). The relative amount of neurotransmitter present in each tube was determined in the same manner as Experiment 1, by adding NaCl solution to each test tube. The results are in shown in Table 2.
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A group of students conducted several experiments using a variety of nonstick cookware, a spring scale, and several different weighted objects. Their goal was to determine which brand of cookware products had the best nonstick surface by measuring the coefficient of static friction, which is a measure of how resistant a stationary object is to movement.
A student connected the spring scale to a weighted object that was placed inside a piece of nonstick cookware as shown in Figure 1.
The students planned to calculate the coefficient of static friction by determining the force required to disturb an object from rest. During the experiment, one student anchored the nonstick cookware be holding tightly to the handle while the other student attached a weighted, smooth steel object to the spring scale. The student pulled on the spring until the object began to move. A third student recorded the force in newtons, N, indicated on the spring scale at the moment the object began to move across the nonstick surface.
This procedure was repeated for 3 different brands of cookware; each brand of cookware was tested with various weighted objects. The coefficient of static friction was calculated by dividing the average force required to move the object by its weight (mass × g, the gravitational constant). The results are shown in Table 1.
The students performed an experiment similar to Experiment 1, except three different brands of cooking spray were applied to the same cookware surface before the weights were put in place. The results are shown in Table 2.
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Earth’s habitability is sustained by the sun. Currently, the sun provides enough light and warmth to maintain temperature conditions that can support life on our planet. It is undisputed that the sun is a star. All stars go through phases where they change in size, temperature, and brightness. Two scientists present their views on how long Earth will remain habitable.
Earth’s sun has another 7 billion years before it enters the Red Giant phase. Currently, Earth could not sustain human life during the Red Giant phase. However, it is important not to believe that human life on Earth will immediately cease to exist as we know it in 7 billion years. Technology has played a huge role in helping humans adapt to conditions on this planet.
We humans have 7 billion years to advance technology and find solutions to adapt to the atmospheric changes the Red Giant phase would bring. For instance, creating a large sunshade to protect Earth would allow life to continue even when the sun enters the Red Giant phase. Another solution would be to develop technology that would stir the sun and bring new hydrogen to the sun’s core. This would greatly extend the current phase that our sun is in. There is enough time and incentive to discover ways to thwart the natural progress of nature. Therefore, I believe that human life on this planet will exist indefinitely.
The sun will enter its Red Giant phase in about 7 billion years. However, new models suggest that Earth has less than a billion years before atmospheric carbon dioxide levels drop to levels that can no longer support photosynthesis. This would lead to a dramatic temperature increase. Once Earth’s average temperature rises to above 70◦C, the oceans will evaporate and Earth’s water sources will be almost completely eliminated.
One billion years is not long enough for humans to evolve in order to meet large atmospheric and environmental changes, or to develop the technology needed to make Earth habitable. In a billion years, atmospheric changes will eliminate all life on Earth as we know it. Humans need to accept the reality that advanced life flourishes for only a limited period of time. Science fiction inspired plans to create space colonies or massive sunshades are unrealistic and will not likely be developed in the next billion years.