cell
cell The structural and functional unit of most living organisms (compare
coenocyte;
syncytium). Cell size varies, but most cells are microscopic (average diameter 0.01–0.1 mm). Cells may exist as independent units of life, as in bacteria and certain protoctists, or they may form colonies or tissues, as in all plants and animals. Each cell consists of a mass of protein material that is differentiated into
cytoplasm and a
nucleus, which contains DNA. The cell is bounded by a
plasma membrane, which in the cells of plants, fungi, algae, and bacteria is surrounded by a
cell wall. There are two main types of cell.
Prokaryotic cells (bacteria) are the more primitive. The nuclear material is not bounded by a membrane and chemicals involved in cell metabolism are associated with the plasma membrane. Reproduction is generally asexual and involves simple cell cleavage. In
eukaryotic cells the nucleus is bounded by a nuclear membrane and the cytoplasm is divided by membranes into a system of interconnected cavities and separate compartments (
organelles), e.g.
mitochondria,
endoplasmic reticulum,
Golgi apparatus,
lysosomes, and
ribosomes (see illustration). Reproduction can be either asexual (see
mitosis) or sexual (see
meiosis). Plants and animals consist of eukaryotic cells but plant cells possess
chloroplasts and other
plastids and bear a rigid cellulose cell wall. See Chronology.
CELL BIOLOGY
1665 | English physicist Robert Hooke (1635–1703) coins the word ‘cell’. |
1831 | Robert Brown discovers the nucleus in plant cells. |
1838 | German botanist Matthias Schleiden (1804–81) proposes that plants are composed of cells. |
1839 | Theodor Schwann states that animals are composed of cells and concludes that all living things are made up of cells. |
1846 | German botanist Hugo von Mohl (1805–72) coins the word ‘protoplasm’ for the living material of cells. |
1858 | German pathologist Rudolf Virchow (1821–1902) postulates that all cells arise from other cells. |
1865 | German botanist Julius von Sachs (1832–97) discovers the chlorophyll-containing bodies in plant cells later named chloroplasts. |
1876–80 | German cytologist Eduard Strasburger (1844–1912) describes cell division in plants and states that new nuclei arise from division of existing nuclei. |
1882 | German cytologist Walther Flemming (1843–1905) describes the process of cell division in animal cells, for which he coins the term ‘mitosis’. Strasburger coins the words ‘cytoplasm’ and ‘nucleoplasm’. |
1886 | German biologist August Weismann (1834–1914) proposes his theory of the continuity of the germ plasm. |
1887 | Belgian cytologist Edouard van Beneden (1846–1910) discovers that the number of chromatin-containing threadlike bodies (subsequently named chromosomes) in the cells of a given species is always the same and that the sex cells contain half this number. |
1888 | German anatomist Heinrich von Waldeyer (1836–1921) coins the word ‘chromosome’. |
1898 | Camillo Golgi discovers the Golgi apparatus. |
1901 | US biologist Clarence McClung (1870–1946) discovers the sex chromosomes. |
1911 | Thomas Hunt Morgan produces the first chromosome map. |
1949 | Canadian geneticist Murray Barr (1908–95) discovers Barr bodies. |
1955 | Belgian biochemist Christian de Duve (1917– ) discovers lysosomes and peroxisomes. |
1956 | Romanian-born US physiologist George Palade (1912– ) discovers the role of microsomes (later renamed ribosomes). |
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MUHAMMAD GITMO PROCEEDINGS BEGIN DESPITE DEFENSE BOYCOTT
News Wire article from: US Fed News Service, Including US State News; 4/7/2006; 700+ words
; ...for suspected terrorist Binyam Ahmed Muhammad began dramatically here yesterday...essentially boycotting the proceedings and Muhammad requesting to represent himself. At the start of the proceeding, Muhammad was joined at the defense table only...
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Muhammad Is Assigned A Veteran Defense Team; Court Appearance His 2nd in Prince William
Newspaper article from: The Washington Post; 11/14/2002; ; 700+ words
; Sniper suspect John Allen Muhammad appeared in Prince William County...Greenspun and Jonathan Shapiro to Muhammad's defense team during the 10-minute...Greenspun was asked to represent Muhammad last week and stood with his client...
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Muhammad impassive as guilty verdicts read Trial moves to penalty phase as jury decides on prison or execution
Newspaper article from: Oakland Tribune; 11/18/2003; ; 700+ words
; ...a jury on Monday convicted John Allen Muhammad of murdering Dean H. Meyers at a Virginia...took just seven hours to decide that Muhammad directed a 23-day shooting spree intended...verdicts before the silent courtroom, Muhammad stood bolt upright, stared straight...
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Muhammad's Bid for New Trial Rejected; Prince William Judge Denies Series of Motions, Changes Date for Sniper's Sentencing
Newspaper article from: The Washington Post; 2/21/2004; ; 700+ words
; ...judge yesterday declined to overturn John Allen Muhammad's murder conviction and ruled that the sniper...Jr. denied a series of legal motions from Muhammad's attorneys, ruling that Muhammad received a fair trial and that the evidence...
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Muhammad Prosecutors Must Share Evidence; Witnesses Discussed Malvo Relationship
Newspaper article from: The Washington Post; 8/27/2003; ; 700+ words
; Prosecutors must give John Allen Muhammad's attorneys statements from as many as...County concerned witness statements about Muhammad's relationship with co- defendant Lee Boyd Malvo. Muhammad's attorneys say they believe that the...
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MUHAMMAD DEFENDS HIMSELF ARGUING HIS OWN CASE SNIPER SUSPECT'S SURPRISE MOVE BEGINS DAY OF DRAMA.(FRONT)
Newspaper article from: The Virginian Pilot; 10/21/2003; 700+ words
; ...VIRGINIA BEACH -- Sniper suspect John Allen Muhammad made the stunning move Monday to represent...nothing to do with those crimes,'' Muhammad told the jury. ``Directly or indirectly.'' Dressed in a sport coat and tie, Muhammad looked at ease standing at the podium...
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Muhammad Planned More Shootings, Jury Is Told; Prosecutors Seeking Death Penalty Also Describe Attempted Escape
Newspaper article from: The Washington Post; 11/19/2003; ; 700+ words
; John Allen Muhammad was planning additional shootings in...testimony Tuesday in the penalty phase of Muhammad's trial. Prosecutors called 17 witnesses...effort to secure the death penalty against Muhammad. They have argued that he is the "worst...
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Muhammad introduced Malvo as sniper; Ex-Army buddy testifies.(PAGE ONE)
Newspaper article from: The Washington Times; 11/8/2003; 700+ words
; ...BEACH - A former Army buddy of John Allen Muhammad's yesterday testified that Mr. Muhammad introduced Lee Boyd Malvo to him as a sniper...auto mechanic Robert Holmes testified in the Muhammad sniper trial. "Lee just smiled." Mr...
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Muhammad gets OK to defend self; Attorneys on 'standby'.(PAGE ONE)
Newspaper article from: The Washington Times; 10/21/2003; 700+ words
; ...WASHINGTON TIMES VIRGINIA BEACH - John Allen Muhammad took charge of his own defense yesterday...nothing to do with these crimes," Mr. Muhammad told the jury. "Pay attention, please...fellow defendant Lee Boyd Malvo. Mr. Muhammad said he knew who had fired the shots...
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Muhammad Facing Old Team in Panthers
News Wire article from: AP Online; 11/16/2005; ; 700+ words
; ...N.C. Chicago Bears receiver Muhsin Muhammad (87), defended by Detroit Lions safety...in this Oct. 30, 2005 file photo. Muhammad comes face-to-face with his former...Panthers. (AP Photo/Paul Sancya) Muhsin Muhammad ended last season as the most prolific...
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Muhammad
Encyclopedia entry from: U*X*L Encyclopedia of World Biography
Muhammad Born: c. 570 Mecca, Arabia Died: 632 Medina, Arabia Arabian prophet Muhammad was the founder of the religion of Islam and...into the Arab Empire. Call to be a prophet Muhammad was born after his father's death in Mecca...
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Muhammad, Elijah
Encyclopedia entry from: U*X*L Encyclopedia of World Biography
Elijah Muhammad Born: October 7, 1897 Sandersville...African American religious leader Elijah Muhammad was the leader of the Nation of Islam...institutions, and religion. Early life Elijah Muhammad was born Elijah (or Robert) Poole on...
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Muhammad, Khallid Abdul 1951(?)—
Book article from: Contemporary Black Biography
Khallid Abdul Muhammad 1951(?) — Nation of Islam spokesperson Khallid Abdul Muhammad calls himself a “ truth terrorist...spokesman allied with the Nation of Islam, Muhammad has ignited a storm of controversy through...
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Muhammad, Idris
Book article from: Contemporary Musicians
Idris Muhammad Drummer For the Record … A drummer of great stylistic range, Idris Muhammad played on classic 1960s pop hits such as...eventually settling in Austria in the 1990s, Muhammad remained in demand on jazz and R&...
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Muhammad, Khallid Abdul 1948–2001
Book article from: Contemporary Black Biography
Khallid Abdul Muhammad 1948 – 2001 Activist, former...Malcolm X ” Khallid Abdul Muhammad called himself a “ truth terrorist...spokesman allied with the Nation of Islam, Muhammad ignited a storm of controversy through...
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