![]() Forney notes that the micronucleus contains all of the DNA that is present in the organism. ![]() The micronucleus is diploid that is, it contains two copies of each paramecium chromosome. The two types of nuclei are the micronucleus and macronucleus, according to the Encyclopedia of Microbiology. "They have two types of nuclei, which differ in their shape, their content and function." " Paramecium along with the other ciliates have this rather unique feature," said James Forney, a professor of biochemistry at Purdue University. ![]() ![]() Perhaps the most unusual characteristic of paramecia is their nuclei. When the contractile vacuole collapses, this excess water leaves the paramecium body through a pore in the pellicle. Depending on the species, water is fed into the contractile vacuoles via canals, or by smaller water-carrying vacuoles. Contractile vacuoles are responsible for osmoregulation, or the discharge of excess water from the cell, according to the authors of " Advanced Biology, 1st Ed." (Nelson, 2000). They then fuse with organelles called lysosomes, whose enzymes break apart food molecules and conduct a form of digestion. Food vacuoles encapsulate food consumed by the paramecium, according to the University of Chicago. These are membrane-enclosed pockets, which in plants and animals handle waste product, store water and offer structural support for cells, according to the National Human Genome Research institute Vacuoles take on specific functions with a paramecium cell. This region contains the majority of cell components and organelles, including vacuoles. Research published in the journal Zoological Science found that trichocysts of Paramecium tetraurelia were effective against two of the three predators that were tested: the Cephalodella species of rotifers and the Eucypris species of arthropods.īelow the ectoplasm lies a more fluid type of cytoplasm: the endoplasm. Trichocysts are a network of telescopic organelles that are used to repel and shield from any predatory attacks and propel the paramecium in unpredictable directions, according to Cell Biology magazine. When they discharge their contents, they become long, thin and spiky, according to "Biology of Paramecium." This region consists of spindle-shaped organelles known as trichocysts. Under an external covering called the pellicle is a layer of somewhat firm cytoplasm called the ectoplasm. However, the organism also contains some unique organelles. Paramecia have many organelles characteristic of all eukaryotes, such as the energy-generating mitochondria. The defining features of eukaryotic cells are the presence of specialized membrane-bound cellular machinery called organelles and the nucleus, which is a compartment that holds DNA, according to Washington University. In contrast to prokaryotic organisms, such as bacteria and archaea, eukaryotes have well-organized cells. (Image credit: Getty Images) Cell structure During the death (decline) phase the population dies exponentially from the accumulation of waste products.Paramecium and amebae under a microscope.During the stationary phase the population grows slowly or stops growing because of decreasing food, increasing waste, and lack of space.During the exponential growth phase (log phase) the population increases geometrically as long as there is sufficient food and space for growth.During the lag phase growth is relatively flat and the population appears either not to be growing or growing quite slowly as newly inoculated cells are adapt to their new environment.In a closed growth system, a bacterial population usually exhibits a predictable pattern of growth - its growth curve - that follows several stages or phases.Although bacteria are capable of replicating geometrically as a result of binary fission, this only occurs as long as their is space to grow, sufficient nutrients, and a way to dispose of waste products.The bacterial divisome is responsible for directing the synthesis of new cytoplasmic membrane and new peptidoglycan to form the division septum. ![]() Par proteins function to separate bacterial chromosomes to opposite poles of the cell during bacterial cell division.Because of binary fission, bacteria increase their numbers by geometric progression whereby their population doubles every generation time.For many bacteria the generation time ranges from minutes to hours. Generation time is the time it takes for a population of bacteria to double in number.Bacteria replicate by binary fission, a process by which one bacterium splits into two.\)), although the rate of death depends on the degree of toxicity and the resistance of the species and viable cells may remain for weeks to months. ![]()
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