All cells are surrounded by a phospholipid bilayer membrane. The function of the phospholipid bilayer is to act as a barrier between the living cell and the environment. The phospholipid bilayer also regulate the passage of solutes into and out of the cell. The phospholipid bilayer membrane can differentiate which solutes to move in or not. One process by which solutes enter cells is by diffusion, which is the movement of solutes from high concentration to low concentration. Another process is osmosis, which is when water molecules diffuse across a cell membrane from regions of low solute concentration to high solute concentration.
Diffusion is defined as the movement of solute molecules from a region of high concentration to low concentration. To learn about some of the factors that affect the rate of diffusion, we will measure the distances that two colored solutes move through a gelatin agar medium. The gelatin medium is composed of agar and water; and mimics an aqueous system. The experimental plan is that we will add drops of different solutes into small test tubes containing agar. The tubes will be incubated under different environmental conditions for about 1 hour. We will compare the relative diffusion rates of the solutes by measuring the distances traveled by the solutes in each test tubes. The result is that longer distances traveled by the solutes indicate a higher diffusion rate and shorter distances traveled indicate a slower diffusion rate.
The solutes that we will used are: KMnO4 ( potassium permanganate, molecular mass = 158 grams/mole) and a dye called Aniline Blue ( molecular mass = 738 grams/mole).
The experiment will address the following questions:
1. How will increasing temperature affect diffusion rate?
2. How will increasing solute molecular weight affect diffusion rate?
3. How will increasing solute concentration affect diffusion rate?
1. Take 6 agar-filled test tube and label 1- 6.
2. Add the different solutes into the test tube 1- 6 using table 1 as a guide.
Tube # Solute Incubation Distance Moved (mm)
1 0.1 M KMnO4 4C 4
2 0.1 M KMnO4 room temp 7
3 0.1 M KMnO4 35C 12
4 0.1 M An. Blue room temp 6
5 0.02 M An. Blue room temp 8
6 0.01 M An. Blue room temp 9
Osmosis is when water molecules diffuse across a cell membranes from regions of low solute concentration to high solute concentration. Water molecule are in constant motion, and the rate of water is dependent on the temperature. Many cells embark on a situation in which the total concentration of solutes is different on the inside and on the outside of the cell. When this occurs, water will move into or out of the cell depending on the relative concenration of solutes on either side of the membrane. The solution on the side of the membrane where solute concentration is less than that of the other side is referred to as being hypotonic. The solution on the side of the membrane where solute concentrations is greater than that of the other side is referred to as being hypertonic. When the solute concentration is the same on both sides of the membrane, the solution is said to be isotonic.
To learn about osmosis, we will use a synthetic permeable membrane called a dialysis tubing to create "artificial cells". We will fill these dialysis bags ( artificial cells) with solutions of various concentration and place them in beakers with solutions of varying concentration.
1. Take 4 beakers label each with number 1, 2, 3, or 4.
2. Fill these beakers with bathing solutions that correspond with numbers on beakers. Volume here should be 200 ml
3. Obtain 4 strips of dialysis tubing and soak them in distilled water.
4. Use table 2 to create the dialysis bags with appropriate contents listed in the table.
5. After weighing and recording the weights of the bags, place them into the beaker with the number corresponding to the bag #.
6. Incubate the bags for at least one hour. At the end of the incubation time, blot the excess solution to the surface of each bag, and weigh and record the weights.
Bag or Bag Content Bathing Beginning Ending
Beaker # (approx. 10 ml) Solutions Weight (g.) Weight (g.)
1 water 40% sucrose 10 6
2 water water 10 10
3 20% sucrose water 10 15
4 40% sucrose water 10 20.
1. Define Diffusion
The movement of solute molecules from a region of high concentration to low concentration.
2. How will increasing temperature affect diffusion rate?
Increasing the temperature will increase the diffusion rate. The reason is that an increase in temperature would increase the speed of water molecule movement and thus increase the number of collisions between solutes and solvents. Since diffusion is driven by these collisions, the rate of diffusion would increase.
3. How will increasing solute molecular weight affect diffusion rate?
The following solution goes through the given experiments and discusses how the diffusion rate can be influenced by various factors, such as temperature. The process of osmosis is also detailed. This is all completed in about 380 words.
Factors influence adoption and diffusion of innovations
1. What factors influence the adoption and diffusion of innovations?
The factors that influence the adoption and diffusion of innovations are the type of advantage the innovation provides. The next is the compatibility of the innovation. For instance, if there is a new software, it is compatible with the commonly used operating systems its adoption is likely to be fast. Further, if the innovation can be observed and tried out its adoption and diffusion becomes faster. In addition, if the innovation is simple it is accepted quickly. The adoption of the innovation to individual needs is an important factor that influences adoption and diffusion of innovation. From a different perspective the relative advantage provided by the innovation leads to quick adoption and diffusion. One of the most critical factors is the cost of diffusion. This influences the rate of diffusion.
In case of diffusion if the physical distance among people is less, there is strong opinion leaders in favor of the innovation, and the similarity among members of a culture leads to speedy diffusion of innovation. There are some characteristics of the population that enhance adoption and diffusion. These characteristics are that the individuals are willing to take risk, focused on technology, willing to take risk and are communicate frequently. Even those people that are technology oriented tend to adopt innovations easily.
2. What methods of forecasting technology and markets are available, and what are their relative advantages and disadvantages?
One of the methods of obtaining forecasting technology and markets is the Delphi technique. This provides input for ideas and problem-solving. Compared to other forecasting techniques involving a group, its relative advantages are that it is conducive to independent thinking, enables sharing of information, leads to reliable forecast results, is inexpensive and allows participants to be anonymous. The relative disadvantages are that it is time consuming, requires ability to write, and needs time and participant commitment( Wallace. T, & Stahl. R2002).
Another method of forecasting technology and markets is the econometric models. These combine economic theory, model building, and statistical methods. The advantages of this method of forecasting technology and markets are that it is based on cause-affect relationships, can forecast the extent of the change, allows adjustment of the model, and provides alternative future scenarios, on the other hand the disadvantages are it may less accurate in case of short term forecasts, depends on its assumptions, and can be expensive(Porter. A 1991).
Another method that can be used for forecasting technology and markets is morphological analysis. This method enables structuring and investigating the set of relationship. Its advantages are that ambiguous parameter definitions are revealed and incomplete ranges of conditions are exposed. In an unbiased way reveals all the relationships. The disadvantages are that it requires experienced facilitation, and developing parameters is very difficult (Wallace. T & Stahl. R2002).
Porter. A (1991) Forecasting and management of technology, Wiley-IEEE,
Rogers, E.M. (1995). Diffusion of innovations (4th ed.). New York: The Free Press.
Stockdill, S.H. and Morehouse, D.L. (1992). Critical factors in successful adoption of technology: A checklist of TDC findings. Educational Technology, 32, 1, 57-58.
Wallace. T, & Stahl. R( 2002) Sales forecasting: a new approach : why and how to emphasize teamwork, not formulas, forecast less, not more, focus on process improvement, not forecast accuracy, T. F. Wallace & CO,