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Cell nucleus

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الكلية كلية الصيدلة     القسم  فرع العلوم الاساسية     المرحلة 1
أستاذ المادة رفاه سليم حسن المطيري       22/12/2016 07:25:49
In cell biology, the nucleus (pl. nuclei) is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell s genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these chromosomes are the cell s nuclear genome. The function of the nucleus is to maintain the integrity of these genes and to control the activities of the cell by regulating gene expression — the nucleus is, therefore, the control center of the cell.
The main structures making up the nucleus are the nuclear envelope, a double membrane that encloses the entire organelle and unifies its contents from the cellular cytoplasm. The viscous liquid within it is called nucleoplasm, and is similar in composition to the cytosol found outside the nucleus. The nucleoskeleton (which includes nuclear lamina) is a mesh work within the nucleus that adds mechanical support, much like the cytoskeleton, which supports the cell as a whole. Because the nuclear membrane is impermeable to large molecules, nuclear pores are required to allow movement of molecules across the envelope. These pores cross both of the membranes, providing a channel that allows free movement of small molecules and ions. The movement of larger molecules such as proteins is carefully controlled, and requires active transport regulated by carrier proteins. Nuclear transport is crucial to cell function, as movement through the pores is required for both gene expression and chromosomal maintenance. The interior of the nucleus does not contain any membrane-bound sub compartments, its contents are not uniform, and a number of sub-nuclear bodies exist, made up of unique proteins, RNA molecules, and particular parts of the chromosomes. The best-known of these is the nucleolus, which is mainly involved in the assembly of ribosomes. After being produced in the nucleolus, ribosomes are exported to the cytoplasm where they translate mRNA

المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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