The purpose of these experiments is to examine the driving force behind the movement of substances across a selective or semiperpeable plasma membrane. Experiment simulations examine substances that move passively through a semipermeable membrane, and those that require active transport. Those that move passively through the membrane will do so in these simulations by facilitated diffusion and filtration. The plasma membrane’s structure is composed in such a way that it can discriminate as to which substances can pass into the cell. This enables nutrients to enter the cell, while keeping unwanted substances out. Active transport requires that the cell provide energy in the form of ATP to power the transport of substances through the membrane. During passive transport the substances move through the plasma membrane because of pressure or concentration differences between the interior and exterior of the cell. Facilitated diffusion relies on carrier proteins, and occurs when molecules are either not lipid soluble or are too large to pass through the pores of the membrane. Solutes have to combine with the carrier proteins in the membrane, and then they can be transported down the concentration gradient. Filtration is the movement of solute and water molecules across a membrane due to a pressure gradient. Active transport occurs when substances are not moving along the concentration gradient, are not lipid soluble, or are too large to pass through the membrane’s pores.
The first experiment involves the facilitated diffusion of glucose. This simulation depicts the varied rates of diffusion for glucose with differing numbers of glucose carrier proteins. As the number of glucose carrier proteins increases the rate of diffusion also increases. The second experiment simulates filtration of sodium, urea, glucose, and powdered charcoal. These substances filtrate across the membrane as a result of pressure differences between the two sides of the membrane. During simulation, the pressure is altered to examine how rate of diffusion changes with the pressure change. Experiment three depicts the active transport of Na+ and K+ across the membrane using sodium-potassium pumps and ATP. ATP is altered between simulation runs to see how this affects the rates.
Human Anatomy & Physiology Laboratory Manuel
PhysioEx 8.0 Physiology Lab Simulation Program
Activity 2: Simulating Facilitated Diffusion
In the stimulating facilitated diffusion experiment, I used the PhysioEx 8.0 Physiology Lab Simulation Program on a computer and the Human Anatomy and Physiology Laboratory Manuel. I set the glucose carrier proteins in the membrane to 500. I adjusted the glucose concentration in the left beaker to 2.0 mM and dispensed only deionized water in the right beaker. The timer was set for 60 minutes. After clicking the start button, I was able to observe concentration changes between the two beakers. This same procedure was done two more times, but I changed the number of carrier proteins to 700 on Run 2 and then 900 in Run 3. The next three simulation runs were done using 8.0 mM of glucose concentration in the left beaker and deionized water only in the right beaker. Run 4 was done using 500 carrier proteins, Run 5 used 700 carrier proteins, and Run 6 used 900 carrier proteins in the membrane. All data was recorded.
Activity 4: Simulating Filtration
In the simulating filtration experiment, I used the PhysioEx 8.0 Physiology Lab Simulation Program on a computer and the Human Anatomy and Physiology Laboratory Manuel. I adjusted the dialysis membrane in the first run to 20 MWCO. The membrane was placed between the top and bottom beaker. I then dispensed 5.00 mg/ml of NaCl, urea, glucose, and powdered charcoal into the top beaker. The pressure unit atop the...