Report Example: Functions Involved in Maintaining Homeostasis

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Sewanee University of the South
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This report seeks to explain the results obtained from a laboratory experiment that aimed at explaining mechanisms with which solutes are transported in the body. The physiological transport being tested is active transport. The experiment involved putting different concentrations of solutes across a semi-permeable membrane (Shi, Kim, Caldwell & Sun, 2012). The components involved in this experiment include sodium ions (Na+), Potassium ions (K+), glucose molecules and Adenosine Triphosphate energy (ATP). Sodium and potassium ions are expected to move across the semipermeable membrane with the help of ATP energy and Na+/K+ pump. The experiment required keen observation on the concentrations of the substances at different times. Finding explanations as to why they behaved in a certain way is expected. Responses from the experiment are recorded and used for evaluation.


The laboratory experiment was set to explain what causes movement of Na+ and K+ and under which circumstances these ions move in the body. The ratio at which these ions should be maintained in the body for equilibrium to be attained. The effect of adding ATP and glucose to the rate at which these ions are transported, why some of the substances added were not transported and what causes the transportation of these substances to stop.

Materials and Methods

Materials required for this setup include sodium ions, potassium ions, and a semipermeable membrane, glucose, and ATP energy. These components would be added periodically during the experiment and observations made and recorded. There were also four questions at the beginning of the experiment, as the experiment proceeds, at the end of the experiment and review questions availed after the experiment to test understanding of the concept. Taking records of the concentrations and rates at which sodium and potassium are transported during the experiment was necessary. Sodium and potassium were placed on different sides of the semipermeable membrane with one ATP and 500 Na+/K+ pumps.


In the first run, there is a movement of sodium and potassium across the semipermeable membrane. The rate at which the ions are transported is high. Glucose does not move across the semipermeable membrane. In the second part, the concentration gradient is maintained, but more ATP energy is added. The number of Na+/K+ pumps is maintained. Observations are made for a while. There is a reduction in the rates at which the substances move across the semipermeable membrane.

The third section maintains the concentration gradient, ATP levels and some pumps as in the second run. There is no movement of sodium or potassium ions across the semi-permeable membrane. The rate is maintained at zero.

In the fourth part, the number of Na+/K+ pumps is increased. Sodium and potassium concentrations are maintained. ATP is also maintained. Pumps are increased. Increasing the number of pumps causes the substances to move across the membrane. The rate at which sodium and potassium ions move across the semipermeable membrane increases.

In the fifth run, glucose is added maintaining concentrations of sodium, potassium, ATP, and Na+/K+ as in the fourth run. There is no movement of ions across the membrane. The rate of movement of the ions does not change but remains constant as was achieved earlier in the fourth run. Glucose is transported across the semipermeable membrane.


The results from the observations are summarized in the table below.

Run number solute ATP Start Conc. L Start Conc. R Pumps Carriers Rate

1 Na+ Cl- 1 9.00 0.00 500 _ 0.0188

1 K+ Cl- 1 0.00 6.00 500 _ 0.0125

1 Glucose _ 0.00 0.00 _ 0 0.0000

2 Na+ Cl- 3 9.00 0.00 500 _ 0.0025

2 K+ Cl- 3 0.00 6.00 500 _ 0.0017

2 Glucose _ 0.00 0.00 _ 0 0.0000

3 Na+ Cl- 3 9.00 0.00 500 _ 0.0000

3 K+ Cl- 3 0.00 6.00 500 _ 0.0000

3 Glucose _ 0.00 0.00 _ 0 0.0000

4 Na+ Cl- 3 9.00 0.00 800 _ 0.0042

4 K+ 3 0.00 6.00 800 _ 0.0028

4 Glucose _ 0.00 0.00 _ 0 0.0000

5 Na+ Cl- 3 9.00 0.00 800 _ 0.0042

5 K+ Cl- 3 0.00 6.00 800 _ 0.0028

5 Glucose _ 0.00 10.00 _ 400 0.0028


Active transport requires a concentration gradient, ATP energy and pumps to occur. The rate at which sodium and potassium ions are transported is 3:2 respectively. A higher concentration of sodium is therefore needed for homeostatic balance in the body (Germain, 2012). Increasing the level of ATP energy enhances the rate at which the ions are transported. At 3mM ATP, transportation of ions is maximized. In the third section, transportation of the ions stopped because the ATP was depleted. Equilibrium is reached initially because there are more pumps to transport the ions. Addition of more pumps in the fourth part resulted into more ions being transported thus completing the process. Adding glucose does not affect the experiment as glucose is transported independently (Germain, 2012). It, therefore, does not affect transportation of ions.9mM sodium chloride is maintained within cells while 6mM potassium chloride is maintained outside cells because the Na+/K+ pump works only when the concentration of sodium to potassium is at 3:2. The ratio must be preserved no matter the quantity of sodium and potassium used.

Semi-permeability of the cell membranes is essential to enable movement of substances in and out. Glucose which is lipid insoluble is transported across the cell membranes through simple diffusion. Some of the substances that are excessive to pass through cell membranes are transported through carriers (Shi, Kim, Caldwell & Sun, 2012). The carriers then find their way into the cell membranes carrying those substances that are large with them. The cells, therefore, get to consist of a variety of substances transported into them through different means.


Homeostatic balance is maintained in the body when there is a correct balance of ions within and outside the cell. Whenever there is a concentration gradient, Na+/K+ pumps are activated. For this process to occur, it is important to have ATP. In the absence of ATP, these pumps are created to help transport ions across cell membranes. A combination of ATP and pumps results in faster achievement of homeostatic balance. ATP and pumps must be maintained at the maximum to ensure complete balance. There are different types of pumps created for various substances. Cells will, therefore, get all required components to maintain the salt water balance in the body. Homeostasis is essential for survival thus the body will always find ways of ensuring that various substances reach the cells. Understanding of homeostasis is made simple by lab experiments that provide conditions as those within the body. The cells mainly control physiological body processes. The lab experiments also highlight properties of the cells that make these processes possible.



Germain, R. (2012). Maintaining system homeostasis: the third law of Newtonian immunology. Nature Immunology, 13(10), 902-906.

Shi, Y., Kim, D., Caldwell, M., & Sun, D. (2012). The Role of Na+/H+ Exchanger Isoform 1 in Inflammatory Responses: Maintaining H+ Homeostasis of Immune Cells. Advances In Experimental Medicine And Biology, 411-418.


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