The CELL THEORY‚ or cell doctrine‚ states that all organisms are composed of similar units of organization‚ called cells. The concept was formally articulated in 1839 by Schleiden & Schwann and has remained as the foundation of modern biology. The idea predates other great paradigms of biology including Darwin’s theory of evolution (1859)‚ Mendel’s laws of inheritance (1865)‚ and the establishment of comparative biochemistry (1940). Ultrastructural research and modern molecular biology have
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The cell wall is the tough‚ flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection. Just as the wall of the factory is for the factory. The wall also is the structure and strength. The cell membrane that separates the interior of all cells from the outside The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances
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1. INTRODUCTION A solar cell is a device that converts the energy of sunlight directly into electricity by the photovoltaic effect. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight‚ while the term photovoltaic cell is used when the light source is unspecified.”Photovoltaics” the field of technology and research related to the application of solar cells in producing electricity for practical use.
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body‚ there are billions of cells that are essential to living – these are called nerve cells. Nerve cells‚ also known as neurons‚ “are the basic information processing structures” (Stufflebeam). There are about 100 billion of these neurons in our nervous system and are the most essential cell in it. Located in brain as well as the spinal‚ there are different types of nerve cells; including: sensory neurons‚ motor neurons‚ and interneuron (Boeree). The neuron is a cell that is structured similarly
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treatment of many diseases. Stem cell research has provided hope and has brought optimism among the scientists and doctors in curing the patients who suffered or died due to the once called "untreatable" diseases decades ago. Stem cells are the ones which can develop into any type of a body cell including the cells of blood‚ liver‚ brain‚ muscles‚ and many more. They are found in adult bone marrow‚ embryos‚ fetuses‚ and blood from the umbilical cord (Bailey 100). Stem cell research is the latest advancement
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fundamentals of science. Title An investigation of an onion cell using a light microscope. Aim: The aim of this investigation is to identify the cells within an onion skin using a light microscope. An onion cell is a plant cell which through the light microscope‚ it should outline the cell wall‚ cell membrane and the nucleus. Introduction: Plant cells have a cell wall and cell membrane which animal cells do not have. The cell wall provides support and is relatively rigid‚ which consists of
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The Cell Theory The Cell Theory‚ formed by Anton van Leeuwenhoek‚ Robert Hooke‚ Matthias Schleiden‚ Theodore Schwann‚ and Rudolf Virchow‚ refers to the idea that cells are the basic unit of structure in every living organism. The theory justifies three principles: all living organisms are composed of one or more cells; the cell is the most basic unit of structure‚ function‚ and organization in all organisms; and all cells come from pre-existing‚ living cells. The formation of the cell theory
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The Cell Cycle Mitosis: the process by which cells reproduce themselves‚ resulting in daughter cells that contain the same amount of genetic material as the parent cell. Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Cell Division Occurs in a series of stages of phases Interphase occurs before mitosis begins Chromosomes are copied (# doubles) Chromosomes appear as threadlike coils (chromatin) at the start‚ but each chromosome and its copy(sister chromosome) change to sister
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What are stem cells and what is gene therapy respectively? These are cells that have the potential to form many different types of cells found in the body. When stem cells divide‚ can form more stem cells or other cells that perform specialized functions. Embryonic stem cells have the potential to form a complete individual‚ while adult stem cells can only form certain types of specialized cells. Stem cells to continue to divide throughout the lifetime of a person. The use of recombinant DNA
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ROD CELLS Rod cells‚ or rods‚ are photoreceptor cells in the retina of the eye that can function in less intense light than the other type of visual photoreceptor‚ cone cells. Rods are concentrated at the outer edges of the retina and are used in peripheral vision. On average‚ there are approximately 125 million rod cells in the human retina.[1] More sensitive than cone cells‚ rod cells are almost entirely responsible for night vision. STRUCTURE AND FUNCTION Rods are a little longer and leaner
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