All living things are composed of cells, they share several characteristics. Organisms are coordinated structure that consists of one or more cells. Even a simple single cell organisms are complex as inside each cell atoms made up molecules; these in tern makes up cell organelles. Organisms can respond to diverse stimuli. For example plants tends to grow in the direction of the light. Even bacteria can move forward or away from chemical. A single cell organisms reproduce by first duplicating their DNA. Then they divide it equally as the cell prepares to form new cells.
There are two major categories of cells, these includes eukaryotic cells and prokaryotic cells. Eukaryotic cells can be further distinguished as animal cells or plant cells. Prokaryotic cells are a type of cell lacking a nucleus and other organelles, these cells are found only in the domains Bacteria and Archaea. Eukaryotic cells have a membrane enclosed nucleus and other membrane enclosed organelles. The nucleus in the eukaryotic cell holds the majority of the genetic material and controls all activity within the cell, similar to that of a master blueprint.
DNA replication which can be defined as the process where two identical copies are created from one original DNA strand occurs within the nucleus of the cell. The movement of the MRNA happens in the ribosomes.
Ribosomes are cells that helps in the production of protein, they are responsible to link amino acids together. When cells need to produce protein (mRNA) is created in the nucleus. There are two subunits to every ribosomes: large and small. The large is responsible to join the amino acids together and the small is responsible to study the RNA.
The endoplasmic reticulum (ER) is a type of organelle found in the cell, it forms a chain of network of membrane enclosed tubes. There are two types of endoplasmic reticulum, rough and smooth. The smooth endoplasmic is responsible for the making and metabolism of steroids hormones and fat. On the other hand the rough endoplasmic aids in the production of protein and how it is used within the body.
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The Golgi apparatus is found in most eukaryotic cells. The Golgi packages proteins into membrane-bound vesicles inside the cell before the vesicles are sent to their destination. The single membrane is similar to the cell membrane in that it has two layers. The membrane surrounds an area of fluid where the complex molecules (proteins, sugars and enzymes) are stored and change, because the Golgi complex absorbs vesicles from rough ER.
Chloroplasts are organelles, specialized subunits in the plants cells. Their main function is to conduct the process of photosynthesis, where the photosynthesis pigment chlorophyll captures the suns energy and stores it in the energy storage molecules ATP and NADPH while releasing oxygen and water.
Mitochondria are the organelles of cellular respiration in nearly all cells, making energy from sugar and other food molecules which is used to produce another form of energy, the ATP used as energy by the cell.
Lysosomes are cell organelles that is surrounded by a membrane, containing hydrolytic enzymes that break down the food molecules, especially protein and other complex molecules. They also join with or assists the vacuoles to help with digestion. The cell membrane is made up of the phospholipid bilayer which also has proteins embedded in it.
Cellular transport can be done through active or passive transport. It is essential to produce ATP, which is the common energy source for the cell. ATP drives numerous cellular processes, including protein transport. Cellular respiration has two main phases: glycolysis which breaks down glucose to pyruvic acid and oxidation of pyruvic acid to carbon dioxide and water.
Cellular reproduction is another important process. How exactly are new cells formed? Cells reproduce through two main processes: mitosis and meiosis.
Mitosis is the process where the chromosome in a cell nucleus is separated into two identical daughter cells with two identical chromosomes and its own nucleus. These cells are responsible for the reproduction of somatic cells or non-sex cells. Mitosis is also responsible for asexual reproduction. Therefore, in adult organism mitosis plays a role in cell replacement, wound healing and tumor formation. This process is essential for day to day activity and human growth.
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On the other hand Meiosis is the process of cell division that produces haploid gametes in diploid organisms, resembles mitoses, but has two special features. Firstly, the number of chromosomes is reduce to half. Secondly the exchange of genetic material, pieces of chromosomes between homologous chromosomes. Meiosis is found in sexual reproduction of organisms, where the male and female sex cell combine to create a young. During reproduction the cells duplicate their contents and transfer them to their daughter cells. Meiosis produces four genetically different daughter cells and leads to the production of germ cells or sex cells which is also important for sexual reproduction and is a source of genetic diversity through crossing over. We are able to reproduce because of this.
Mendelian Laws tells about genes and inherence from one generation to another. One of the principles founded by Gregor Mendel during his experimental phase was the law of segregation.
The law of segregation states that during the production of gametes, the two copies of each hereditary factor segregates so that the offspring’s gets one factor from each parent.
Secondly, the principle of independent assortment where genes for different traits grows independently of one another in the formation of gametes. These traits are inherited by offspring from parents by chromosomes which carry the genetic material.
DNA is the in hereditary material in almost all organisms including human. Nearly all the cells in an individual’s body has the same DNA structure.
The cells are condensed into chromatin and chromosomes to allow it to be transferred from parents to offspring. Problems or mutations in the DNA can lead to serious problems such as cancer and other life threatening diseases. When these cells have a virus which continue to reproduce uncontrollably, this can lead to the formation of tumors which can multiply rapidly. This can most often happen at the genetic level. Cancer tends to spreads when these cells leave their place of origin and spread to neighboring tissues and organs. This can become dangerous for the human body when it begins to affect our internal organs. Gene therapy may be a possible solution to treat cancer by targeting mutations in the cancer cells. This would provide a more effective treatment than chemically treating all cells in the body via chemotherapy which can cause damage to other, healthy parts of the body.
- Eric J. Simon, Jean L. Dickley, Jane B. Reece : Campbell Essential Biology fifth edition
- http://en.wikipedia.org/wiki/Mitochondrion – Mitochondrion
- http://en.wikipedia.org/wiki/Eukaryote – eukaryote
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