Difficulty and Discrimination Indices
Difficulty indices (p) of the items ranged from 0.27 to 0.98 (Table 5), with a mean of 0.65, providing a wide range of item difficulty, similar to values reported for the DODT (Odom and Barrow, 1995). The discrimination indices (d) ranged from 0.07 to 0.67, with a mean of 0.44. The discrimination index refers to how well an item differentiates between high and low scorers; it is a basic measure of the validity of an item. On ordinary tests, a low or negative discrimination index value generally indicates that the item does not measure what other items on the instrument are measuring. However, in the case of the paired items on this instrument, the first-tier “What happens?” item is often quite easy, and provides the necessary context for the more difficult second-tier “Why does this happen?” item. This can produce a low discrimination index for some of the first (odd-numbered) items, but a high discrimination index for the paired (even-numbered) items. For example, three odd-numbered ODCA “What?” items had discrimination indices of 0.07, 0.08, and 0.16—below the value of 0.20 that is typically considered as a minimum (Odom and Barrow, 1995), and the subsequent even-numbered “Why?” items had discrimination values over 0.20. Thus, on this two-tiered assessment, a correct answer on the first-tier item (content) did not predict performance on the second-tier item (reason). For purposes of this project, all ODCA test items were considered acceptable, since the item pair (and particularly the “Why?” response) is the element of interest.
Number of ODCA items within each range of difficulty and discriminationa
For evaluating the difficulty of an item, it is helpful to consider the likelihood of guessing the correct answer. For a multiple-choice item with four possible responses, there is a 25% chance of guessing the correct response. A two-tier item with two selections for the first tier and four selections for the second tier provides a 12.5% chance of guessing the correct answer combination. In the ODCA, there are two or three response options in the first tier, and three or four in the second tier. This results in chances of guessing correct answers at 8.3% to 12.5%.
For the first tier of the ODCA, the percentage of students responding with correct answers ranged from means of 48.3% to 97.8% for upper-division biology major classes, 45.0% to 95.4% for lower-division biology major classes, and 35.6% to 97.3% for nonmajor classes (Table 6 and Figure 1). The mean percentage of combined content–reason responses on the ODCA that were correct ranged from 28.2% to 92.3% for upper-division biology major classes, 19.9% to 74.7% for lower-division biology majors, and 16.8% to 85.3% for nonmajors. Results from college students taking the DODT and ODCA were strikingly similar (Table 6), especially for the highest and lowest scoring-item combinations (Figure 1).
Percentages of college students who selected the correct content response (pale bars) and the correct content plus reason combination (darker bars) on (A) ODCA items 3 and 4 compared with DODT items 2a,b, and on ODCA items 15 and 16 compared with DODT...
Percentages of college biology students who selected the correct tier 1 “What?” (content) responses and the first- and second-tier combined content–reason (“Comb”) responses on the ODCA and the DODT
Test reliability was at least 0.70 each semester using Cronbach's alpha calculation (Fall 2007: 0.70; Spring 2008: 0.74; Fall 2008: 0.73; Spring 2009: 0.70), which is considered to be an acceptable level. Test completion time ranged from 5 to 20 min per student and was not correlated with performance (r2 > 0.05; n = 71, 72, and 83 for three semesters, Fall 2007–Fall 2008).
The most striking result is the overall consistency of students’ response patterns across levels, semesters, and years (Figure 2). Students generally performed better on first-tier “What?” items (odd numbers) than on second-tier reason “Why?” items (even numbers) on both the ODCA and the DODT (Figures 1 and 2 and Table 6), indicating that they often can predict the outcome but have less understanding about the underlying mechanisms.
Radar graph shows the percentage of nonmajors (NM), by course and by semester, who selected the correct response for each item on the ODCA. Items are grouped into the three conceptual categories described in the text. Note the similarity of performance...
Radar graph shows the percentage of lower-division biology majors (LD), by course and by semester, who selected the correct response for each item on the ODCA. Items are grouped into the three conceptual categories described in the text. Note the similarity...
Radar graph shows the percentage of upper-division biology majors (UD), by course and by semester, who selected the correct response for each item on the ODCA. Items are grouped into the three conceptual categories described in the text. Note the similarity...
Of the nine ODCA question pairs, 3/4, 5/6, and 7/8 yielded the lowest combined content–reason values (Figure 1 and Table 6), and thus reflected the most prevalent misconceptions among our students. Excerpts from these three item pairs are shown in Table 7, along with frequencies of student responses and variance among semesters in parentheses.
Misconceptions chosen by at least 10% of students are identified below for non–biology majors, lower-division biology majors, and upper-division biology majorsa
More than 90% of all students correctly indicated that particles (dissolved substances) would move from areas of high to low concentration (response 3a; Figure 1A and Table 6). However, when asked to provide a reason for their answer, many faltered (Table 6). The correct combined content–reason ODCA responses, 3a and 4b, were selected by < 25% of nonbiology majors and lower-division biology students (Table 6). More than one-fourth (27–44%) of students at each course level chose response 4a, “crowded particles want to move to an area with more room” (Table 3, misconception #19; Table 7). That is, a substantial proportion of our undergraduates attributed anthropomorphic qualities to substances in place of scientifically accurate alternatives. Interviews corroborated these tendencies. When an interviewee was asked why she selected 4a (“… crowded particles want to move …”) rather than 4b (“the random motion of particles suspended in a fluid results in their uniform distribution”), she stated that 4a seemed more understandable and consistent with her conceptualization of the diffusion process. “I just think of diffusion as…there's bunch of particles here and there aren't any there, so it's crowded. So [the particles] just move to the other side because…they want to even out” (italicized word indicates emphasis by the speaker). When asked why she didn't choose answer 4b, the student replied that while she knew that the particles moved randomly, she didn't quite understand how such motion would result in uniform distribution.
Surveyed biology instructors similarly identified anthropomorphism as a problem for students. For example, a college instructor with 10 years of experience noted that students think molecules “want to diffuse.” Another instructor suggested that it is difficult for students to eliminate the ideas of “‘vitalism’ and ‘volition’ on the part of the particles.”
One-fourth of our students indicated that particles tend to keep moving until they are uniformly distributed and then they stop moving (response 4c). Some of the students’ follow-up statements during interviews seemed to suggest that the students conceived of particles moving around only if there was a need to do so (e.g., a concentration gradient is present). When there was not such a need, they thought that particles would stop moving and remain stationary. Surveyed biology instructors offered similar observations. For example, a high school instructor with 20 years of experience stated: “[Students have trouble with the idea] that molecules have constant motion which can vary with conditions (temperature, pressure, etc.).” Similarly, a college instructor with 15 years of experience noted that, “[Students exhibit] no prior knowledge of kinetic energy/Brownian movement.”
Regarding question pair 5 and 6 (Figure 1B; and Table 7), illustrating misconception 1 (Table 3), more than 50% of all students (including upper-division biology majors) in most semesters indicated that if a small amount of salt is added to a large volume of water and then allowed to sit still for several days, salt molecules would be concentrated at the bottom of the container. In some semesters, more than 50% of students chose this content response (Figure 2 and Table 6). Of those students, 24–28% chose reason 6a, asserting that salt would sink, because salt is heavier than water, and 10–28% chose reason 6c, indicating that salt would sink because there will be more time for settling (Table 7).
In interviews with test takers, students who selected content response 5a combined with reason response 6a or 6c were confident that, given enough time, solute particles would be concentrated on the bottom. For example, when asked why she selected her response, one senior biology major stated, “I do think that salt is heavier…When you put it in a container, it goes to the bottom.” Interviewees stated that this would be the case both for solid solutes (e.g., salt and sugar) and for liquid solutes (e.g., food coloring or dye). Thus, in the minds of many undergraduate students, even after considerable training in biology, gravity appears to be a major factor affecting dissolved substances, even when only a small amount of solute is introduced into a solvent.
Item pair 7/8 (Figure 1B, Table 7, and Supplemental Material) presents an illustration and description of a container divided by a semipermeable membrane, with dye plus water on the left and pure water on the right. The problem states that only water can move through the membrane; the dye cannot pass through. In some semesters, half of our students selected content response 7c, indicating that water will maintain at equal levels on both sides of the membrane. Of those selecting response 7c, 26–29% of students across all semesters choose the reason response 8b, that water flows freely and maintains equal levels on both sides of the membrane (Table 7).
Among upper-division students who were interviewed, those who selected responses 7c and 8b indicated that atmospheric pressure overrides water's ability to move through the membrane during osmosis. In the words of a senior biology major, “I’m assuming that water's not going to rush in and…go against pressure to…dilute the dye side of things…Atmospheric pressure is going to override the system, as far as water's desire to dilute that.” Thus, students apparently have difficulty weighing and integrating the different factors affecting the movement of molecules in solution. Their intuition about the effects of atmospheric pressure tends to override the less familiar concept of osmotic pressure.
About 10–20% of students across course levels who thought that water levels would be different (correct content response, 7a: “Side 1 is higher than Side 2”) chose reason 8a (incorrect): “Water will move from high to low solute concentration.” These results indicate a major lack of understanding of the basic principles of osmosis and diffusion.
Diffusion and Osmosis
...Diffusion and Osmosis: A Full Analysis on the Concentration of Solutes and the Molecular Weight of Substances in a Dialysis Tubing and Potato Experiment Alejandro Gonzalez October 30, 2012 Biology 1500 Professor Raja Abstract The purpose of the diffusion and osmosis lab experiments is to determine the contents present before and after leaving a dialysis tubing in a beaker of solution and to test water potential by determining the percent change in mass of potatoes when left in different concentrations of sucrose in numerous beakers. In the first experiment, what occurred was that we put contents into the dialysis tubing and in a solution in a beaker and we were to set the tubing in the beaker for a set amount of time and see what contents are present in the beaker and in the dialysis after the amount of time. In the second experiment, we were to test if a mass change would occur if we set potatoes in different concentrations of sucrose. My alternate hypothesis in the first experiment with the dialysis tubing was accepted due to the fact that glucose and sodium sulfate diffused across the pores of the tubing, but starch and protein could not be. My alternate hypothesis in the second experiment was also accepted due to the fact that there was a mass change in the potatoes when put in different concentrations of glucose. Introduction Diffusion and osmosis are two terms that actually coincide with each other in the big picture and in this particular set of......
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Ap Biology Diffusion + Osmosis Lab
...Diffusion And Osmosis Introduction: There are several valuable aspects of this lab that must be understood before it is conducted. The first of these concepts is called diffusion. Molecules are constantly moving and as they are moving they tend to move from areas of higher concentration to areas of lower concentration. Diffusion can be defined as the net movement of molecules from higher to lower concentrations. One example, of diffusion is when an item like perfume is opened in a room. Shortly after it is opened the smell can be detected throughout the entire room. Diffusion can occur through a membrane such as that of a cell which explains how something can enter the cell. One special type of diffusion is called osmosis or the diffusion of water. Osmosis describes how water moves through a membrane from areas that have high water potential to areas that have lower potential. Water potential is defined as the measure of free energy of water in a solution. Biologists use this term to help describe why water moves from one area to another. Water potential can be affected by two major aspects pressure and the amount of solute. Water potential can be calculate by the pressure potential added to the solute potential. In order to calculate the solute potential one must multiply the ionization constant, the molar concentration, the pressure constant, and the temperature. When looking at a solution one can categorize it into several different relationships......
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...What is reverse osmosis? What is reverse osmosis? Reverse osmosis is a special kind of diffusion. The word reverse means the opposite of the original direction of movement and osmosis is the movement of water molecules from where they are plentiful to less abundant over a selectively permeable membrane. Therefore, reverse osmosis can be define as when the solvent passes through the selectively permeable membrane from where they are less abundant to where they are in abundance. In other words, reverse osmosis is the flow water molecules opposing the natural direction of osmosis through a porous membrane. The reverse osmosis process happens after the osmosis process. Therefore, in order to fully grasp the process of reverse osmosis one has to understand the process of osmosis first. When a lower concentrated solution and a higher concentrated solution are separated by a selectively permeable membrane, water naturally moves across the membrane to the higher concentrated solution to dilute it. In time, the osmotic pressure will counter the diffusion process precisely and then the solutions will be at equilibrium. No net movement of water will be at this stage. This process is called osmosis. But, if there is an adequate amount of counter pressure applied to the concentrated solution to overpower the osmotic pressure, then osmosis will be reversed. The solution is now coerced through the selectively permeable membrane contrary to the natural flow of water. This is......
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...atoms that are independent, rapid, and random in motion. These molecules frequently collide with each other and with the sides of the container. In a period of time, this movement results in a uniform distribution of the molecules throughout the system. This process is called diffusion (Everett and Everett, n.d.). Diffusion is defined as the movement of molecules away from the area of their highest concentration to an area of low concentration. Net diffusion can be restated as the movement of particles along the concentration gradient. According to Meyertholen (n.d.), there are several factors which may affect the rate of diffusion of a substance. These factors include the following: (1) Temperature: higher the temp-higher the rate of diffusion, (2) Size of particle: bigger the particle-higher the energy to diffuse , (3) State of matter: solid takes more time to diffuse compared to liquids, liquids take more time to diffuse compared to gases and gases take less time to diffuse compared to liquids and solids, (4) Nature of matter: denser the matter-slower the rate of diffusion. My objective was to determine the properties of ammonia (NH3) and of hydrochloric acid (HCl) that are related to diffusion. I hypothesized that ammonia diffuse faster than hydrochloric acid. For more support we conduct also an experiment that would detect the diffusing substances in an agar plate using colored compounds; potassium permanganate, methylene blue and potassium dichromate...
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Osmosis and Diffusion
...Brad Sanford Bio 1120 Section 6 September 17, 2013 Partners: Dominique & Carleigh Lab #2: Osmosis & Diffusion Introduction Diffusion is the movement of molecules from a high concentration gradient to a low concentration gradient. This can occur in gases, liquids, and solids. Osmosis is a type of diffusion that allows water molecules to move through a semipermeable membrane freely by way of passive transport. During osmosis a semipermeable membrane will allow small water molecules to pass through freely without any help but larger molecules like proteins will not move through the semipermeable membrane without active transport. Active transport requires a chemical energy like ATP (adenosine triphosphate) to help the larger molecules move through the cell’s membrane.(Krane) When describing high and low concentrated solutions, it is useful to understand the terms hypertonic, hypotonic, and isotonic. A hypertonic solution has a higher concentration of solutes compared to a lower concentrated solution as water will move out of the solution (Dehydration). A hypotonic solution has a lower concentration of solutes compared to a solution with a higher concentration of solutes and water will move into the solution (Swelling). In a isotonic solution the solutes are at an equal concentration and there is no movement of the water. In this lab, two experiments were performed. The first one uses a small plastic bag closed up and filled with cornstarch and distilled......
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Biology 1020 Diffusion and Osmosis Lab Report
...Kristina Eskola BL 1020 L01 Diffusion and Osmosis Lab Report (Dialysis) Introduction: Dialysis Tubing is a membrane made of regenerated cellulose fibers formed into a flat tube. If two solutions containing dissolved substances of different molecular weights are separated by this membrane, some substances may readily pass through the pores of the membrane, but others may be excluded. We will be investigating the selective permeability of the tubing to reduce sugar, glucose, starch, and iodine potassium iodide. We will test this by placing a solution of glucose and starch into a dialysis tubing bag and then place this bag into a solution of iodine potassium iodide (I2KI). Prediction: The I2KI solution will turn blue when adding Benedict’s reagent. Hypothesis: The solution of water and I2KI will be the most permeable because they will mix and react with Benedict’s reagent and the heat so the cell membrane only allows certain molecules to enter and leave the cell Materials and Methods: In the experiment we will be using two tests. In the first test, we will be using I2KI to test for the presence of starch. When I2KI is added to an unknown solution, the solution will turn purple or black if starch is present. If there is no starch in the solution, it will remain pale yellow. In the second test we will be using Benedict’s test for reducing sugar. When Benedict’s reagent is added to an unknown solution and the solution is heated, it will turn green, orange or orange-red...
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...Introduction Osmosis is a key for every living organism on Earth, from humans to plants. In this lab we examined the processes of osmosis and diffusion. Osmosis is a specialized type of diffusion; “it is the process of water moving across a semi-permeable membrane, in response to a concentration gradient” (Readel, 2000). Fluid passes both in and out of the semi permeable membrane in osmosis, but usually there is a “net flow in one direction or another, depending on which side of the membrane has a higher concentration of solutes” (Smith, 2013). There are different factors that can affect the rate of osmosis such as temperature. In one experiment, my group and I used dialysis tubing to simulate a cell membrane. This tubing was filled with molasses and was immersed in water; cold, warm and hot. The bags were removed at regular intervals and measured for the amount of osmosis that occurred. We observed that the bags in the hot water experienced the highest amount of osmosis. In warmer temperatures the water particles tend to diffuse from high to low concentration, thus trying to dilute the solute concentration from the solution outside. From these observations and conclusion, my group and I hypothesized for our own experiment the level of solute concentration will affect the rate of osmosis. Diffusion is the process of “any substance moving from a region of high concentration to a region of lower concentration” (Readel, 2000). Therefore we predicted that the higher......
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Diffusion and Osmosis
...Diffusion and Osmosis Diffusion is the passive movement of molecules or particles along a concentration gradient, or from regions of higher to regions of lower concentration. Osmosis is a type of diffusion. This is the diffusion of water through a selectively permeable membrane (chooses what comes in and what goes out) from a region of higher water potential to a region of lower water potential. Water potential is the measure of free energy of water in a solution. Unlike diffusion, osmosis requires ATP to move the particles across the membrane. Hypothesis: In both experiments diffusion and osmosis will occur between the solutions. In experiment 1A the tube of glucose/starch will absorb the iodine solution in the cup. In experiment 1B the tube of distilled water will lose weight, and the tube of glucose will gain weight. The purpose of the experiments is to differentiate which test was diffusion and which was osmosis. Materials: Experiment 1A: Plastic Cup, Plastic Pipet, Iodine-Potassium Iodide, Deionized Water, Glucose Paper Strip Experiment 1B: (3) 15 cm pieces of Dialysis Tubing, beaker, 15 cm piece of white thread, 80% Glucose, 2% Starch, Plastic cup, 10% glucose, 15 cm blue thread, distilled water, 15 cm red thread, 20% glucose Procedure Experiment 1A: First cut a 15-cm length of dialysis tubing. Place the dialysis tubing in a beaker of distilled water and allow it to remain in the beaker for 1 minute. Open the dialysis tube by rolling it in between......
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...Effects on rate of Osmosis across a selectively permeable membrane for varying starch solute concentrations and water mixed with Lugol’s Iodine The contents of this document pertain to the effect of particle (starch) concentration on the rate of Osmosis through a selectively permeable membrane made visible by the use of Lugol’s Iodine indicator. The results proved that the greater the concentration of the starch solute within the membrane, the greater the rate of osmosis and change in color of the solute due to an increase of Lugol’s Iodine diffusing into the membrane and reacting with the starch. Ruba Nizam 3/18/2014 Introduction The purpose of this lab is to test the rates of osmosis on a model of a selectively permeable membrane filled with varying levels of starch concentrations using dialysis tubing. This experiment will make it possible to see how particles move from an area of high concentration to an area of low concentration due to the use of Lugol’s Iodine indicator. According to Michael McKinley, osmosis is defined as the, “movement of water molecules across a membrane from an area of high water concentration to an area of lower concentration until equilibrium” (McKinley). Diffusion is related to the movement of particles from an area of high concentration to an area of low concentration. Osmosis and diffusion are both passive transports that do not require energy although osmosis is the diffusion of water (Balmer). These transport processes occur......
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...lighter molecular weight value diffused at a faster rate. Thus, resulting in the formation of a white smoke in the glass tube moving closer to the side of the heavier substance Hydrochloric Acid (HCl). The agar-water gel set-up consisted of a agar-water gel in a petri dish. Potassium Permanganate (KmnO4), Methylene Blue (C16H18N3SCl) had a drop in each well. Methylene Blue, having the heaviest weight, diffused slowly. Therefore, the heavier the molecular weight, the slower the rate of diffusion. Introduction Many interesting biological facts but usually, when modifications or experiments are tried, the investigator has some reason for doing so. A substance in the gaseous or liquid state consists of molecules or atoms that are independent, rapid, and random in motion. These molecules frequently collide with each other and with the sides of the container. In a period of time, this movement results in a uniform distribution of the molecules throughout the system. This process is called diffusion. Diffusion is a process of equalization which involves movement of molecules from an area of high concentration to an area of low concentration. Materials and Methods Results Methylene Blue(MW: 320g/mole) | Potassium Permanganate(MW : 158g/mole) | Time(min) | Distance (mm) | Rate(mm/min) | Time(min) | Distance (mm) | Rate (mm/min) | 0 | 15 | 0 | 0 | 24 | 0 | 15 | 16 | 1.06 | 15 | 32.67 | 2.178 | 30 | 16.3 | 0.5 | 30 | 36.67 | 1.23 | 45 | 17 | 0.38 | 45 | 40.3 |......
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...Fatmata Diffusion Abstract dialysis tubing is, made of cellulose because it’s a selectively permeable membrane. In this experiment, we are testing to see if the solution in the beaker moves into the dialysis bag. Which because of that, Introduction Diffusion and osmosis are two types of transport mechanisms. Diffusion is the movement of molecules from areas of higher concentrations to areas of lower concentration until the molecules are evenly distributed through the area. Osmosis is the dispersion of water. Our cells are capable of absorbing nutrients because, the cell membrane is selectively permeable (some molecules can diffuse freely through the membrane while others cannot). In this experiment we used dialysis bag as a model of the cell membrane. Our hypothesis was that the glucose will diffuse out of the membrane into the beaker filled with iodine solution. To demonstrate dialysis tubing we used water, starch and iodine. When starch and iodine react together they form a dark brown color. Materials Rubber band | Dialysis bag | Beaker | Glucose solution | Iodine solution | Water, thread | Methods * Cut a piece of dialysis tubing that has been soaking in water approximately 40 cm (approx. 16 in) long, Tie the end of the dialysis tubing with two or more knots. * Fill the bag halfway with glucose solution. And add 4 full droppers of starch solution to the bag. * Hold the open end close while you mix the content o the bag. Rinse of outside the bag...
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...Osmosis Is Serious Business! by Troy R. Nash Department of Biology Presbyterian College, Clinton, SC Questions-Too Much of a Good Thing 1. The extra fertilizer created a hypertonic environment around the roots of the corn ____/ 2 pts. What sort of environment (hypotonic, hypertonic, isotonic) did the extra fertilizer create around the roots of the corn? 2. The extra fertilizer caused the soil to become hypertonic which cause water to diffuse out of the corn into the soil. This caused the crops to die from lack of water. ____/ 2pts. Keeping in mind your answer to the previous question, what do you believe caused the corn plants to wilt and eventually die? 3. If Michael would have told his dad what he had done, two things could have possibly been done.. One option would have been the removal of as much of the extra fertilizer as possible to reduce the chance of the fertilizer becoming hypertonic. The other option would to be to overwater the crops so the environment would be isotonic and no diffuse would take place because of the equal concentrations of the solutions inside and outside of the plant cells. I think just telling his father would have saved a lot of heartache and trouble. ____/ 2 pts If Michael’s mistake had been caught earlier, is there anything that could have been done to prevent the corn from dying? Questions-Too Little Too Late 1. The distilled water cause the patient’s bloodstream to become a hypotonic environment . ____/2pts. What problem......
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...Investigating Osmosis in Potatoe Tissue To find out how the concentration of sucrose solution affects the rate of osmosis in a potato and what happens to the length and mass of the potato. What is osmosis? Osmosis is the movement of the water molecules across a partially permeable from a region of high water concentration to a region of low water concentration. Osmosis is a special case of diffusion The biochemical process in living cells always takes place in a solution. A solution is made up of a solvent (the dissolving fluid) and solute (the particles dissolved in the solvent). In living organisms, the solvent is water and the solution is called aqueous solution. Living cells are separated from their surroundings by the partially permeable cell surface membrane. The contents of the cell, the cytoplasm, are one aqueous solution and the surroundings of the cell, for example pond water, is another aqueous solution. If the two solutions do not have the same concentration of various substances, molecules may move away from one to the other by diffusion, if the membrane is permeable these substances. To summarise osmosis: The diffusion of water molecules, down a water potential gradiant across a partially permeable membrane. Cells and osmosis A cell is surrounded by a partially permeable membrane, and water may cross the membrane easily. If cell is placed in a solution of lower water potential, water leaves......
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Osmosis and Diffusion
...the plasma membranes processes use energy to move substances across the membrane. Osmosis Lab 2. Explain your observations in detail in terms of concentration gradient, diffusion, osmosis, osmotic pressure, passive transport, and active transport. A. The osmosis lab was a really awesome lab. It gave you the excitement for three days to see how much the egg has changed. Concentration gradient is a ongoing change in the concentration of solutes in a solution as a function of distance through a solution. The concentration gradient of the egg was almost seeing through. You could see the eggs membrane and the yellow oak that was in the center of the egg. Diffusion is the tendency of atoms, molecules, and ions in a liquid or air solution to move from areas of higher concentration to areas of low concentration to become more diffuse. For the diffusion of the egg, the egg expanded and got higher concentration of the water outside of the membrane and a lower concentration inside the osmosis. Osmosis is the movement of water across a selectively permeable membrane into a compartment containing solute that cannot cross the same membrane. The osmosis is what causes the bubbles. Osmotic pressure is the ability of osmosis to generate enough pressure to lift a volume of water. The water equilibrates in the jar. The passive transport exchanges the oxygen 02and C02 in the jar. Active transport of the osmosis lab was against the gradient. Ph.I.L.S Lab 3. Explain what happened to the......
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...Practice Problems – Osmosis and Water potential Use this key to answer all the problems below. If you choose B or C, rewrite the statement so that it is complete and true. A = TRUE B = FALSE C = NOT ENOUGH INFORMATION PROBLEM ONE: The initial molar concentration of the cytoplasm inside a cell is 2M and the cell is placed in a solution with a concentration of 2.5M. 1. Initially, free energy is greater inside the cell than outside 2. It is possible that this cell is already in equilibrium with its surroundings. 3. Initially, solute concentration is greater outside the cell than inside. 4. Water will enter the cell because solute potential is lower inside the cell than outside. 5. The cell will become flaccid because the pressure potential is greater outside the cell than inside. 6. The cell is already in equilibrium with its surroundings because of the combination of pressure potential and solute potential inside and outside the cell. 7. Initially, the cytoplasm is hypertonic to the surrounding solution. 8. Initially, the numerical value of the solute potential is more negative inside the cell than outside. 9. Net diffusion of water will be from inside the cell to outside the cell. 10. At equilibrium, the molarity of the cytoplasm will have increased. 11. At equilibrium, the pressure potential inside the cell will have increased. PROBLEM TWO: The initial molar concentration of the cytoplasm inside a cell is 1.3 M and the surrounding solution......
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