The Cytoskeleton is classified as both a muscle of the cell and it’s skeleton. Within a eukaryotic cell, the cytoskeleton is responsible primarily for the organization and movement (or restriction) of organelles throughout the cell. The Cytoskeleton also takes a vital role in Cytokinesis, cell division.
a) Microtubules: 25 nanometers in diameter, microtubules consist of polypeptide subunits of the protein Tubulin strung and stacked together to form hollow, straw-shaped filaments. These microtubules consisting of Tubulin will constantly grow and break-apart on either end of the filament, resulting in a faster growing end and a slower one, known respectively as the plus or minus ends. Tau protein assists in the formation and stability of Microtubules. The minus end of a microtubule is anchored in the Centrosome, which organizes and coordinates the Microtubule. Located adjacent to the nucleus, these Centrosomes take a vital role in cytokinesis, arranging for microtubules to pull apart duplicated chromosomes. Shortly after complete division, the Microtubule dissociates and disappears again.
Microtubules are also found in cilia and flagella, and against popular belief, cilia and flagella are in fact not protrusions from a cells membrane. Rather they are continuations of the membrane itself, and consist of cytoplasm and of microtubules. These microtubules are also considered a part of the cells cytoskeleton.
Flagella
Flagella are long whip-like structures known to propel sperm cells, consisting of 9+2 arrangements of microtubules.
Cilia
Cilia are smaller but greater in number than flagella, and consist of a 9+2 arrangement of microtubules.
Found on the cells lining our trachea, the cilia function there to sweep particles awa...
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...orylation causes Tau proteins to lose function and soon dissociate or unbind from the microtubule. Freely floating in the axon as oligomers (proteins consisting of few monomer subunits), many Tau then began to clump together. Getting denser with time, and because Tau protein build-ups are insoluble, they formed Neurofibrillary tangles, otherwise known as aggregates. Furthermore, when the Tau protein separates from the microtubule it causes it to disintegrate because the Tau is so critical to the structure of microtubules. It is currently assumed that these tangles, or aggregates, which are so characteristic to brain cells of those with Alzheimer’s, are not the main cause of the disease. The destruction of the microtubules however may be the main cause of Alzheimer’s disease, but active research is being performed on the subject.
Works Cited
wikipedia.com
The Alzheimer’s Association (2005) defines the disease as “a progressive brain disorder that gradually destroys a person’s memory and ability to learn, reason, make judgments, communicate, and carry out daily activities”. Contrary to popular belief, Alzheimer’s is not the result of normal aging, although it normally occurs more frequently in people who are over the age of 65 (Gruetzner, 1988). Studies performed on the brains of deceased Alzheimer’s patients show several irregularities. The most obvious abnormality is in the signal-transmitting chemicals, where a 40-90% decrease in the enzyme CAT is found. This enzyme lies in the cerebral cortex and hippocampus regions of the brain. When CAT is decreased, it causes cholinergic or acetylcholine-releasing nerve terminals to diminish. These chemicals are important for communication between nerves. Also found during these autopsies were double strands of neurofibullary tangles, senile plaque (decayed neural material), and granulovacular degeneration-all which are associated with mental impairment. Neurofibullary tangles normally do increase with age, but Alzheimer’s patients show a very high density of the tangles. The brain has also been found to contain abnormally high concentrations of aluminum (Weiner, 1987).
Small ribosomes scattered throughout the cytoplasm. No mitochondria hence respiration takes place on an infolding of the cell membrane
The organism does not have any appendages to aid in motility (such as flagella, cilia, or pili) so it uses it secretory organelles to facilitate a gliding type of movement. The apical, more pointed end of the cell, houses these secretory organelles. The conoid end is responsible the entrance into a host’s cell membrane.
Alzheimer’s disease or AD is an incurable disorder of the brain that results in loss of normal brain structure and function. In an AD brain, normal brain tissue is slowly replaced by structures called plaques and neurofibrillary tangles. The plaques represent a naturally occurring sticky protein called beta amyloid and in an Alzheimer’s brain, sufferer’s tend to accumulate too much of this protein. Neurofibrillary tangles represent collapsed tau proteins which, in a normal brain along with microtubules, form a skeleton that maintains the shape of the nerve cells. In Alzheimer’s disease, the tau proteins break loose from their normal location and form tangles. Without the support of these molecules, nerve cells collapse and die. As normal brain structure is lost with progression of the disease, brain function also degenerates. Patients afflicted with Alzheimer’s disease display a gradual mental decline. Initially, and most apparently, there is a loss of short-term memory. Eventually, as a patient progresses to later stages of the disease, the brain becomes so damaged that patients can no longer communicate or recognize immediate family or even themselves. They have difficulty walking and standing and frequently fall. In the final stages, they lose bladder and bowel control and have difficulty with swallowing, frequently leaving them malnourished and dehydrated. Eventually, they are forced to remain bedridden and, without the help of life-prolonging measures provided in a hospital, die. However, this level of deterioration is severe and may take as long as twenty years. Because of the disease’s slow progress and its usual later start in a person’s life, a victim of AD will usually die first of natural causes. Under the objectives ...
The Tunica is divided by fibrous tissues to form web shaped lobes. Each lobe is 3 to 10 coiled tubules called seminiferous tubules surrounded by connective tissue. (David, 2014)
Alzheimer's Disease is the result of what occurs when nerve cells in the brain begin to deteriorate and die. A neuron's primary role in the brain is to communicate with other neurons, transmitting information to different regions of the brain and body. Neuron cells are also responsible for creating memories, both short-term and long-term memories. The hippocampus, which is a small area in the brain that holds a key role in the formation of memories (Mandal). As provided by Dr. Ananya Mandal, the association between the hippocampus and Alzheimer's Disease is that the neurons located in the hippocampus are suggested to be the first cells to be damaged in the way of the disease (Mandal). It is unknown at what point in time that neuron cells begin to degenerate. Nevertheless, when neurons do deteriorate within the brain, the occurrence of plaque and tangles - abnormal proteins - begin to appear as a result of a weakening in the connection between neurons. According to information gathered by Richard Mayeux, a Professor of Neurology at Columbia University ...
Alzheimer’s disease comes from the last name of a neuro-psychiatrist from Germany, Alois Alzheimer. The disease was first diagnosed when a woman in her early fifties began experience memory problems. “Alzheimer recounted the now famous case of ‘Auguste D.’ a 51-year-old housewife who had been failing mentally for several years. As a result she had been admitted to his care in the Asylum for the Insane and Epileptic…” (Maurer and Maurer 1). After her death, he continued to examine her brain to find causes and explanations for her behavior. He discovered “…classic neuro-pathological signs of plaques and tangles” (Maurer and Maurer 1). “Plaques are chains of amino acids that are pieces of the amyloid precursor protein…tangles are aggregates of the protein tau” (Secko 1). As plaques develop they produce tangles and “these two abnormalities ultimately lead to loss of cognitive function” (Secko 1) Alois Alzheimer’s research has allowed many specialist to conclude that the apolipoproetein E gene may contribute to the disease.
carry signals toward the cell body. They are usually more, shorter and more branched than axons.
Alzheimer’s disease got its name from the German doctor, Dr. Alois Alzheimer. In 1906, he noticed that there were abnormal clumps and bundles of fibers i...
Alzheimer’s disease affects the brain cells which are called neurons. Neurons send messages from one to another, which allows us to think, remember and speak. In each of the neurons there is a branch like structure. Some carry impulses away from neurons (afferent), and some bring impulses to the neurons (efferent). The relaying of impulses from neuron to neuron in the brain makes it possible for one to carry out physical and mental tasks. When plaques and tangles form in the brain, they disrupt the flow of messages to the neurons. This happens when people age, but with an Alzheimer’s patient there are many more that disrupt, which allows them to forget simple tasks. Plaques are abnormally sticky clusters of protein. They disrupt pathways that carry signals from neuron to neuron. Plaque is a deposit of protein mixed with fragments of dead or dying neurons found in the brains of patient who have Alzheimer’s. A tangle is a set of twisted nerve cell fibers found in the cell bodies of neurons in the brains of the patients who ha...
Scientists know that Alzheimer disease is characterized by a gradual spread of sticky plaques and clumps of tangled fibers that disrupt the organization of nerve cells in the brain. However , a definite cause, prevention, or cause has not been found.
Cells are able to grow and reproduce. Cells reproduce by splitting and passing on their genes (hereditary information) to Daughter cells. The nucleus always divides before the rest of the cell divides. Therefore each daughter cell contains their own nucleus. The nucleus controls the cells activities through the genetic material DNA. The cells in a body are all the same except the gametes they were all made from one cell, the Zygote. This is the cell that was formed when two gametes from your parents fused.
The cytoskeleton is a highly dynamic intracellular platform constituted by a three-dimensional network of proteins responsible for key cellular roles as structure and shape, cell growth and development, and offering to the cell with "motility" that being the ability of the entire cell to move and for material to be moved within the cell in a regulated fashion (vesicle trafficking)’, (intechopen 2017). The cytoskeleton is made of microtubules, filaments, and fibres - they give the cytoplasm physical support. Michael Kent, (2000) describes the cytoskeleton as the ‘internal framework’, this is because it shapes the cell and provides support to cellular extensions – such as microvilli. In some cells it is used in intracellular transport. Since the shape of the cell is constantly changing, the microtubules will also change, they will readjust and reassemble to fit the needs of the cell.
These cells can be round or irregular shapes maintained by the plasma membrane. Animal cells have certain organelles that are not found in plant cells such as centrioles, lysosomes, cilia, and flagella. All of these organelles have specific jobs to help the cell function. For example, the centrioles organize the assembly of microtubules during cell division, and the cilia aids cellular locomotion. Animal cells store energy in the structure of complex carbohydrates, and can only produce ten of the twenty amino acids needed to produce
The main role for cell division if the ability to reproduce. The cell cycle allows multicellular organisms to grow and divide and single-celled organisms to reproduce. From some multicellular organisms, cell division can reproduce an entire organism. It is also primary to the progress of a multicellular organism that commences as a fertilized egg or zygote. These same organisms also benefit from cell division to reconstruct and renew cells that die