Topics: Protein, Cell, Cell membrane Pages: 7 (2094 words) Published: February 28, 2013
Human Cell, protein production, cell organelles and the cell membrane. Structure and cell transport.

The cell is the basic structural and functional unit of all known living organisms (See figure 1). It is the smallest unit of life that is classified as a living thing (except virus, which consists only from DNA/RNA covered by protein and lipids), and is often called the building block of life. Organisms can be classified as unicellular (consisting of a single cell; including most bacteria) or multicellular (including plants and animals). Humans contain about 10 trillion (1013) cells.

Figure 1 showing components of a cell.

(Source: Alvis Brazma 2001)

An antibody also known as an immune globulin (Ig) is a protein that a B Lymphocyte secretes in response to a non-self antigen. Every antibody is a Y-shaped molecule, made of four polypeptide chains (quaternary). Every mammal is able to make millions of different antibodies each with a different pair of binding sites for one type of antigen only. Antibodies are produced by white blood cells; they are used to help fend of attacks by pathogens. The antibodies are created using different organelles within the cell. All organelles have different forms and functions. (See table 1) Polypeptides are produced by linking the correct sequence of amino acids as directed by the ribosomes and mRNA. mRNA is created in the nucleus inside of the white blood cell. Once the mRNA is created it is passed on to the ribosome where peptide synthesis occurs. (See figure 2) then it is secreted via the nuclear envelope, which is a double bi-layer. These polypeptides are fed into the rough endoplasmic reticulum by the ribosome binding to the rough endoplasm and secreting the protein in the organelle.

Figure 2 showing peptide synthesis occurring in a ribosome. (Boumphreyfr 1 March 2009)

|Organelle |Form |Function | |Nucleus |A membrane-enclosed organelle found in |Control gene expression and mediate the replication of DNA| | |eukaryotic cells. |during the cell cycle. The nucleus provides a site for | |Bell PJ (November 2006) | |genetic transcription that is segregated from the location| | | |of translation in the cytoplasm. | |Ribosome |Large and complex molecular |Ribosomes are the workhorses of protein biosynthesis, the | |Sandi Barkalow (no date) | |process of translating mRNA into protein. | |Vesicle |Small bubble within a cell, and are thus |Vesicles are a basic tool used by the cell for organizing | |Arthur L. Koch, (August, 2010) |a type of organelle. Enclosed by lipid |cellular substances. Vesicles are involved in metabolism, | | |bilayer |transport and enzyme storage. | |Motor Protein |Molecular motors. |Motor proteins are the driving force behind most active | |Mahdi | |transport of proteins and vesicles in the cytoplasm. | |(October 14, 2011) | | | |Rough Endoplasmic Reticlum [pic]...
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