All cells follow a similar pattern of development for at least part of their lifespans: cells first grow, then divide to produce two new cells. This is true of unicellular prokaryotic and eukaryotic organisms, and it is true of the cells that make up multicellular eukaryotic organisms. Cells grow by adding materials to their cell membranes and cell walls, if present. Cells divide either by fission, as in prokaryotic organisms, mitosis, or meiosis. The process of cell division is inherently intricate – cells must partition their DNA and cell contents appropriately into the new cells that result from division. In addition, organisms need to control when and how often cells divide in order to develop properly and ultimately to survive.
The B vitamins often work together to deliver a number of health benefits to the body. B vitamins have been shown to:
1. Bolster metabolism
2. Maintain healthy skin and muscle tone
3. Enhance immune and nervous system function
4. Promote cell growth and division — including that of the red blood cells that help prevent anemia
5. Together, they also help combat the symptoms and causes of stress, depression, and cardiovascular disease
1. Understand the concept of a cell cycle, and how it plays an important role in different types of organisms.
2. Understand several differences between the eukaryotic cell cycle and the prokaryotic growth cycle.
3. Understand how the eukaryotic cell cycle is controlled, and why this is important.
Cell division is the process where a single living cell splits to become two or more distinct new cells. All cells divide at some point in their lives. Cell division occurs in single-celled organisms like bacteria, in which it is the major form of reproduction (binary fission), or in multicellular organisms like plants, animals, and fungi. Many cells continually divide, such as the cells that line the human digestive tract or the cells that make up human skin. Other cells divide only once.
There are two major ways in which biologists categorize cell division. The first, mitosis, is simple cell division that creates two daughter cells that are genetically identical to the original parent cell. The process varies slightly between prokaryotic and eukaryotic organisms. In eularyotes, mitosis begins with replication of the deoxyribonucleic acid (DNA) within the cell to form two copies of each chromosome. Once two copies are present, the cell splits to become two new cells by cytokinesis, or formation of a fissure. Mitosis occurs in most cells and is the major form of cell division.
The second process, called meiosis is the production of daughter cells having half the amount of genetic material as the original parent cell. Such daughter cells are said to be haploid. Meiosis occurs in human sperm and egg production in which four haploid sex cells are produced from a single parent precursor cell. In both mitosis and meiosis of nucleated cells, shuffling of chromosomes creates genetic variation in the new daughter cells. These very important shuffling processes are known as independent assortment and random segregation of chromosomes.
Cell division is stimulated by certain kinds of chemical compounds. Molecules called cytokines are secreted by some cells to stimulate others to begin cell division. Also, contact with adjacent cells can control cell division. The phenomenon of contact inhibition is a process where the physical contact between neighboring cells prevents cell division from occurring. When contact is interrupted, however, cell division is stimulated to close the gap between cells. Cell division is a major mechanism by which organisms grow, tissues and organs maintain themselves, and wound healing occurs. Cancer is potentially a deadly form of uncontrolled cell division.
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