Cells & Tissues, Lab Report Example

Introduction

During this week of lab exercises, cells and tissues were observed under the microscope. In the cells, passive transport was observed through the process of diffusion, This information included, observing how diffusion works in agar gel by using different color dye solutions, observing diffusion in a semipermeable membrane (nonliving) with dialysis tubing, observing diffusion in slides that contained red blood cells (living membranes) using different solutions. In the tissues, the main information observed included determining the types of tissue (epithelial, connective, muscles, and nervous) and the difference between them.

Procedures

In order to learn more about cells, the lab had several activities to perform. In activity one, observing diffusion through agar gel using dye solutions, was a simple process to follow. The materials required were, two agar gelled petri dishes, graph paper, a dropper bottle of methylene blue, a dropper bottle of potassium permanganate stain, and a small medicine dropper. The two petri dishes were placed on top of the paper to prevent making a mess. The medicine dropper was used to suction out agar gel from the center of each dish. Then, the holes were filled in with a little solution, a different kind to a single dish.  Next, the timer was started and the first 15 minutes passed. At this time, the distance from the center (diffusion) was measured. This process was repeated every 15 minutes for one hour.

In activity two, observing diffusion through nonliving membranes, was a little more extensive process to follow.  The materials required were, four sections of dialysis tubing, a small syringe, a graduated cylinder, a wax marker, fine twine or dialysis tubing clamps, and four 250 ml beakers, NaCl solution, Benedict’s solution, Silver nitrate, and Lugol’s iodine, and sucrose with Congo red solution. The four beakers were then numbered from one through four. Beakers one, three, and four were half filled with distilled water. However, beaker number two was filled with 40% glucose solution. The first dialysis tube was folded and tied off, and then filled with 10 ml of glucose solution.  The second dialysis tube is constructed the same way and filled with the same glucose solution. Continuing the process, a third dialysis tube is constructed and filled with 10% NaCl solution. The last tube is constructed and filled the red sucrose solution. The weight of each sac is recorded and then each sac is dropped into the beaker in order of construction. For example, sac one went into beaker one. The sacs then sat for one hour undisturbed.

In activity three, observing diffusion through living membranes, the only items needed were the slides and the microscopes. Slide one, red blood cells were suspended in physiological saline, slide two, red blood cells were bathed in 1.5% saline (NaCl) solution, and slide three, red blood cells were suspended in distilled water. Each slide was observed under the microscope.

In activity four, phagocytosis was observed via video.

Four microscope stations were set up to examine types of tissues. In activity one, epithelial cells were observed at station one that included simple squamous, simple cuboidal, simple columnar, stratified squamous, pseudostratified ciliated columnar, and transitional epithelia.  In activity two, connective tissue was observed at station two that included adipose, areolar, reticular, dense regular connective (cartilage), and osseous connective tissue (bone). In activity three, muscle tissue was observed at station three that included skeletal, cardiac, and longitudinal sections of smooth.  Activity four was the observation of spinal cord smear (nervous tissue). Each slide was scanned for specific structures and noted functions.

Results

The results of the lab activities for cell passive transport were both expected and unexpected according to the activity. Activity one, the potassium permanganate has a lighter molecular weight than methylene blue and therefore diffuses at a faster rate. A larger heavier molecule is always slower to diffuse.

Activity two, sac 1 (40% glucose) gained weight. There should be no net weight change in sac 2.  Since the concentrations of glucose and water are the same on both sides of the membrane, there is no net movement of water or glucose. Sac 3 will increase in weight, perhaps only by a small amount.  There has been a net movement of water into the sac and the weight of the water was not completely offset by the movement of the NaCl out of the sac. Some dialysis of NaCl occurred. There should be an increase in weight in sac 4.  The water color did not turn pink; the dye was not able to diffuse out of the sac. The Benedict’s test for sugar was negative. Sucrose did not diffuse from the sac to the beaker.  The dye and sucrose are too large to diffuse through the pores in the membrane or their rate of diffusion is too slow given the allowed time.  Net osmosis occurred in situations 1, 3, and 4.   Simple diffusion occurred in situations 1, 3, and 4.  Water molecules are very small, and move quickly down a concentration gradient. Na and Cl in solution behave like slightly larger molecules, but are smaller than glucose molecules, which move slowly, if at all, through the dialysis tubing.

In activity three, the results of the red blood cells in physiological saline stayed the normal size because it is an isotonic. The red blood cells in the NaCl solution dried out and lost their disc shapes. The last part of the activity placing the blood cells in distilled water resulted in an increase in size and even some bursting.

The results of the tissue cultures was were not measurable. Instead, there was an improvement in knowledge concerning the types of tissues. The first activity was viewing epithelial tissue and noting the difference of size, shape, and structures. It was learned that each cell is designed for its functions according to the location of it in the body.  For example, simple squamous epithelial tissue is the simplest form of tissue and is found in the internal organs like the kidneys.  Activity two results were a repeat of activity one. However, on this activity connective tissue was observed.  It was learned that connective tissue contains a large number of collagen fibers.  Activity three, viewing muscle tissue, it was learned that the three types of muscle tissue differ from each other according to the location of it in the body and also, all muscle tissue contain striations. The results of the last activity was to make note of the neurons in nervous tissue, paying special attention to the composing structure of it.

Conclusion

The conclusion for the activities of the cell diffusion is this. In cell membranes, the larger and heavier the cell molecule, the slower the diffusion.  This slow or fast diffusion, depending on the outside molecule size and weight, is the same for both, nonliving and living membranes. Also, it was concluded that if a cell is in an isotonic solution, there will be no change in size.

The conclusion for the activities of the tissue cultures is this. Each different type of muscle tissue is specially designed for the body area it will be working in. Smooth muscle for the intestines, cardiac muscle for the heart, and highly striated skeletal muscle for the arms, legs, and etc.

Works Cited

Marieb, Elaine. Essentials of Human Anatomey & Physiology Laboratory Manual.  5th ed. San Francisco: Pearson, 2012.