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A microorganism is a microscopic organism composed of cells, and the term can be used to refer to single-celled organisms or multi-celled organisms. The type of cells and how the cells work is what determines the type of microorganism and how the microorganism works. There are two classifications of cells, prokaryotic and eukaryotic. There are several characteristics in which prokaryotic cells and eukaryotic cells differ, as well as similarities. All organisms that are prokaryotic are single-celled, meaning they are composed of only one cell. Prokaryotic cells are small and the size of the cells do not extend much larger than a few micrometers. There are three shapes typical in prokaryotes, which are spherical, rodlike, and spiral (Russell, et al., 2011). The DNA of Prokaryotic cells is cyclic, meaning the strand is connected at each end, and is held inside an organelle, which in prokaryotes is called the nucleoid (Russell, et al., 2011). This differs from eukaryotic cells, which have double-helix shaped DNA, and is housed in an organelle called the nucleus. All prokaryotic cells have a cell wall, which provides rigidity to the cell's structure. This as well is different in eukaryotic cells, which do not always have cell walls. In eukaryotic cells the presence of a cell wall is typically dependent whether the cell is of a plant. Plants are typically the only eukaryote cells with a cell wall.
In this lab session, the cells observed were of eukaryotes and prokaryotes. The cells examined ranging from plant, to animal, to fungi, to bacterial. The plant cells examined were of the genus and species Elodea Canadensis, an aquatic plant that is often considered a pest plant (Nichols & Shaw, 1986). As plant cells, they are eukaryotic in nature. The cells were rectangular in structure, and as characteristic of plant cells, had a cell wall and vacuoles busily carrying resources through the cytoplasm to and from organelles within the cell. Also observed are numerous green chloroplasts, the pigment of which allows the plant to absorb light energy, which is used in the synthesis of carbohydrates from water and carbon dioxide. The next cells examined were human cheek epithelial cells, which will be referred to as HCEC from now on, for simplicity's sake. The HCEC in this lab session were harvested form the cheeks of the experimenters and dyed for ease of identification. Of characteristics observed is a round shape made of plasma membrane, a nucleus, and cytoplasm, which bears the organelles of the cell. HCEC are similar to plant cells, in that they are eukaryotic, but in this case they are animal, which indicates the cells have no cell wall or chloroplasts. The next organism examined were Blepharisma sp., a type of single-celled organism and eukaryote referred to as ciliate protists. The Blepharisma sp. is covered in fused cilia, which is its primary method of food intake (Giese & Suzuki, 1973). The ciliate observed were pink in hue and has a large light capsule. The next protist examined was Euglena gracilis, also a single-celled and eukaryotic organism, and is a type of flagellate, which means their primary method of locomotion is using flagellum to propel themselves through fluids (Russell, et al., 2011). The last specimen examined was a slide holding a mixture of Saccharomyces cerevisiae, a yeast, and Micrococcus roseus, a bacteria, both of them stained with isosmotic methylene blue. Inside the yeast, a nucleus and a vacuole is seen in the cytoplasm, surrounded by a cell wall. All of the bacteria that is seen is the cell wall and cytoplasm.
In this experiment, the cellular structure and characteristics of various cells and microorganisms were examined and recorded, and using the data collected, the organisms were classified, to the purpose of refining the experimenter's knowledge of cells and heightening the individual's experience with microscope usage.
Numerous measurements and observations have been taken of the microorganisms and cells presented in this lab session. This data is both qualitative and quantitative, and refers to the various sizes, shapes, colours, etc. of cells and factors of the cells and microorganisms. There were six cells that were observed, some of which certain parts were measured specifically. These cells and microorganisms include Elodea Canadensis (plant), the chloroplasts of Elodea Canadensis, human cheek epithelial cells, the nucleus of the human cheek epithelial cells, Blepharisma sp. (ciliate), Euglena gracilis (flagellate), Saccharomyces cerevisiae (yeast), and Staphylococcus aureus (bacteria).
The leaf collected by the experimenter was light green and about 12 mm in length. When examined in the microscope, the cells were observed to be rectangular in structure, possess a cell wall, and to have numerous intermittent green chloroplasts distributed throughout the cytoplasm. The average cell size was 94 Âµm, whereas the group average for the particular lab session was 114 Âµm and similarly the average chloroplast size was 3.5 Âµm as opposed to the group average obtained at that time, 4.1 Âµm. Five minutes after being lit, cyclosis could be seen occurring in the cells, which is an action where the cytoplasm circulates, carrying chloroplasts in the current.
One issue with the data given is in the results section of the lab write up doesn't seem to mention a nucleus in the E. canadensis cells. It is impossible that the cells of the plant are not present, but in its current state it appears the cell much be stained or some other method of increasing the visibility of microscopic organelles must be employed.
Human Cheek Epithelial Cells
Once the human cheek epithelial cells were collected and examined, it was identified that they had a round structure and had a plasma membrane. The typical cell present was an average diameter of 24 Âµm with a nucleus of 1.4 Âµm, when the group average was 27.5 Âµm with a nucleus of 1.7 Âµm. The cytoplasm appeared speckled with dark spots, and a dark nucleus in the centre. The scraping of the cells from the cheek seems to have resulted in folding of several cells.
Blepharisma sp. is a ciliate, which means it is covered in cilia which act as the cells method food collection. When examined, the image of the ciliate is slightly obscured by the cilia covering the entire outside of the organism, making a clear image of its internals difficult. The sample cells of Blepharisma sp. were seen to be pink, with areas of dark and light spots. The length of the particular Blepharisma was 223 Âµm, whereas the accepted average was 206.4 Âµm. Several vacuoles can be seen in the cell body, with a central vacuole near the back of the organism.
Euglena gracilis is flagellum, which means its primary method of locomotion is using flagella. The flagellum is seen to have a cylindrical shape and to have a green hue on account of a high concentration of chloroplasts. A red photoreceptor organelle is seen at the end of the organism. The nucleus was apparent near the centre of the organism. The length of the organism was recorded as 59 Âµm, with an average group value of 59.4 Âµm.
Saccharomyces cerevisiae (yeast) and Staphylococcus aureus (bacteria)
Isosomotic methylene blue stain was added to the sample to make the cells more visible. The yeast is oblong and 5.5 Âµm, with a group average of 5.0 Âµm, and the bacteria present were spherical and 1.1 Âµm and a group average of 1.4 Âµm. Both did not move at all, however may have been given movement due to external forces. The difference between the two types is the large nucleus and large vacuole of the yeast cell, as well as a daughter cell attached to the yeast.
Staphylococcus aureus is a type of bacterial cell, which means it is, contrary to the other cell types examined in this lab session, a prokaryote. The bacterium being a prokaryote explains a lot of the apparent "anomalies" regarding the observations of the bacterial cell. For instance, why there is a cell wall and no apparent DNA, as well as no other noticeable organelles being present.