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    Biology Biology Document Transcript

    • CytoplasmFrom Wikipedia, the free encyclopediaJump to: navigation, searchSchematic showing the cytoplasm, with major components of a typical animal cell(organelles):(3) ribosomes (indicated by purple dots)(4) vesicle(5) rough endoplasmic reticulum (ER)(6) Golgi apparatus(7) cytoskeleton(8) smooth ER(9) mitochondria(10) vacuole(11) cytosol(12) lysosome(13) centrioles within centrosomeThe cytoplasm is a thick liquid residing between the cell membrane holding all the cells internalsub-structures (called organelles), except for the nucleus. All the contents of the cells ofprokaryote organisms (which lack a cell nucleus) are contained within the cytoplasm. Within thecells of eukaryote organisms the contents of the cell nucleus are separated from the cytoplasm,and are then called the nucleoplasm.In eukaryotic cells also, the cytoplasm contains organelles, such as mitochondria, which arefilled with liquid that is kept separate from the rest of the cytoplasm by biological membranes. Itis within the cytoplasm that most cellular activities occur, such as many metabolic pathwaysincluding glycolysis, and processes such as cell division. The inner, granular mass is called theendoplasm and the outer, clear and glassy layer is called the cell cortex or the ectoplasm.The part of the cytoplasm that is not held within organelles is called the cytosol. The cytosol is acomplex mixture of cytoskeleton filaments, dissolved molecules, and water that fills much of thevolume of a cell. The cytosol is a gel, with a network of fibers dispersed through water. Due tothis network of pores and high concentrations of dissolved macromolecules, such as proteins, an
    • effect called macromolecular crowding occurs and the cytosol does not act as an ideal solution.This crowding effect alters how the components of the cytosol interact with each other.Movement of calcium ions in and out of the cytoplasm is thought to be a signaling activity formetabolic processes.[1]NUCLEOULES++From Wikipedia, the free encyclopediaJump to: navigation, searchThe nucleolus is contained within the cell nucleus.Schematic of typical animal cell, showing subcellular components. Organelles:(1) nucleolus(2) nucleus(3) Ribosomes (little dots)(4) vesicle(5) rough endoplasmic reticulum (ER)(6) Golgi apparatus(7) Cytoskeleton(8) smooth endoplasmic reticulum (ER)(9) mitochondria(10) vacuole
    • (11) cytosol (not cytoplasm as that includes all the organelles)(12) lysosome(13) centrioles within centrosomeThe nucleolus (also called nucleole) is a non-membrane bound structure[1] composed of proteinsand nucleic acids found within the nucleus. Ribosomal RNA (rRNA) is transcribed andassembled within the nucleolus. The nucleolus ultrastructure can be visualized through anelectron microscope, while the organization and dynamics can be studied through fluorescentprotein tagging and fluorescent recovery after photobleaching (FRAP). Malfunction of nucleolican be the cause for several human diseases.From Wikipedia, the free encyclopediaJump to: navigation, searchThe nucleolus is contained within the cell nucleus.Schematic of typical animal cell, showing subcellular components. Organelles:(1) nucleolus(2) nucleus(3) Ribosomes (little dots)(4) vesicle(5) rough endoplasmic reticulum (ER)(6) Golgi apparatus
    • (7) Cytoskeleton(8) smooth endoplasmic reticulum (ER)(9) mitochondria(10) vacuole(11) cytosol (not cytoplasm as that includes all the organelles)(12) lysosome(13) centrioles within centrosomeThe nucleolus (also called nucleole) is a non-membrane bound structure[1] composed of proteinsand nucleic acids found within the nucleus. Ribosomal RNA (rRNA) is transcribed andassembled within the nucleolus. The nucleolus ultrastructure can be visualized through anelectron microscope, while the organization and dynamics can be studied through fluorescentprotein tagging and fluorescent recovery after photobleaching (FRAP). Malfunction of nucleolican be the cause for several human diseases.From Wikipedia, the free encyclopediaJump to: navigation, searchThe nucleolus is contained within the cell nucleus.Schematic of typical animal cell, showing subcellular components. Organelles:(1) nucleolus(2) nucleus
    • (3) Ribosomes (little dots)(4) vesicle(5) rough endoplasmic reticulum (ER)(6) Golgi apparatus(7) Cytoskeleton(8) smooth endoplasmic reticulum (ER)(9) mitochondria(10) vacuole(11) cytosol (not cytoplasm as that includes all the organelles)(12) lysosome(13) centrioles within centrosomeThe nucleolus (also called nucleole) is a non-membrane bound structure[1] composed of proteinsand nucleic acids found within the nucleus. Ribosomal RNA (rRNA) is transcribed andassembled within the nucleolus. The nucleolus ultrastructure can be visualized through anelectron microscope, while the organization and dynamics can be studied through fluorescentprotein tagging and fluorescent recovery after photobleaching (FRAP). Malfunction of nucleolican be the cause for several human diseases.NUCLEOLUS=From Wikipedia, the free encyclopediaJump to: navigation, searchThe nucleolus is contained within the cell nucleus.
    • Schematic of typical animal cell, showing subcellular components. Organelles:(1) nucleolus(2) nucleus(3) Ribosomes (little dots)(4) vesicle(5) rough endoplasmic reticulum (ER)(6) Golgi apparatus(7) Cytoskeleton(8) smooth endoplasmic reticulum (ER)(9) mitochondria(10) vacuole(11) cytosol (not cytoplasm as that includes all the organelles)(12) lysosome(13) centrioles within centrosomeThe nucleolus (also called nucleole) is a non-membrane bound structure[1] composed of proteinsand nucleic acids found within the nucleus. Ribosomal RNA (rRNA) is transcribed andassembled within the nucleolus. The nucleolus ultrastructure can be visualized through anelectron microscope, while the organization and dynamics can be studied through fluorescentprotein tagging and fluorescent recovery after photobleaching (FRAP). Malfunction of nucleolican be the cause for several human diseases.CELL NECLUES=In cell biology, the nucleus (pl. nuclei; from Latin nucleus or nuculeus, meaning kernel) is amembrane-enclosed organelle found in eukaryotic cells. It contains most of the cells geneticmaterial, organized as multiple long linear DNA molecules in complex with a large variety ofproteins, such as histones, to form chromosomes. The genes within these chromosomes are thecells nuclear genome. The function of the nucleus is to maintain the integrity of these genes andto control the activities of the cell by regulating gene expression — the nucleus is, therefore, thecontrol center of the cell. The main structures making up the nucleus are the nuclear envelope, adouble membrane that encloses the entire organelle and separates its contents from the cellularcytoplasm, and the nuclear lamina, a meshwork within the nucleus that adds mechanical support,much like the cytoskeleton, which supports the cell as a whole. Because the nuclear membrane isimpermeable to most molecules, nuclear pores are required to allow movement of molecules
    • across the envelope. These pores cross both of the membranes, providing a channel that allowsfree movement of small molecules and ions. The movement of larger molecules such as proteinsis carefully controlled, and requires active transport regulated by carrier proteins. Nucleartransport is crucial to cell function, as movement through the pores is required for both geneexpression and chromosomal maintenance.Although the interior of the nucleus does not contain any membrane-bound subcompartments, itscontents are not uniform, and a number of subnuclear bodies exist, made up of unique proteins,RNA molecules, and particular parts of the chromosomes. The best-known of these is thenucleolus, which is mainly involved in the assembly of ribosomes. After being produced in thenucleolus, ribosomes are exported to the cytoplasm where they translate mRNA.RIBOSOMES=A ribosome is an an organelle (an internal component of a biological cell) the function of whichis to assemble the twenty specific amino acid molecules to form the particular protein moleculedetermined by the nucleotide sequence of an RNA molecule.One of the central tenets of biology, often referred to as the central dogma of molecular biology,is that DNA is used to make RNA, which is used to make proteins. The DNA sequence in genesis copied into a messenger RNA (mRNA). Ribosomes then read the information in this mRNAand use it to create proteins. This process is known as translation; the ribosome translates thegenetic information from the RNA into proteins. Ribosomes do this by binding to an mRNA andusing it as a template for determining the correct sequence of amino acids in a particular protein.The amino acids are attached to transfer RNA (tRNA) molecules, which enter one part of theribosome and bind to the messenger RNA sequence. The attached amino acids are then joinedtogether by another part of the ribosome. The ribosome moves along the mRNA, "reading" itssequence and producing a corresponding chain of amino acids.Ribosomes are made from complexes of RNAs and proteins. Ribosomes are divided into twosubunits. The smaller subunit binds to the mRNA, while the larger subunit binds to the tRNAand the amino acids. When a ribosome finishes reading a mRNA, these two subunits split apart.Ribosomes have been classified as ribozymes, because the ribosomal RNA seems to be mostimportant for the peptidyl transferase activity that links amino acids together.Ribosomes from bacteria, archaea and eukaryotes (the three domains of life on Earth), havesignificantly different structures and RNA sequences. These differences in structure allow someantibiotics to kill bacteria by inhibiting their ribosomes, while leaving human ribosomesunaffected. The ribosomes in the mitochondria of eukaryotic cells functionally resemble in manyfeatures those in bacteria, reflecting the likely evolutionary origin of this organelle.[1] [2] Theword ribosome comes from ribonucleic acid and the Greek: soma (meaning body).VESICLE=A vesicle can be visualised as a bubble of liquid within another liquid, a supramolecularassembly made up of many different molecules. More technically, a vesicle is a small
    • membrane-enclosed sack that can store or transport substances. Vesicles can form naturallybecause of the properties of lipid membranes (see micelle), or they may be prepared. Artificiallyprepared vesicles are known as liposomes. Most vesicles have specialized functions dependingon what materials they contain.Because vesicles tend to look alike, it is very difficult to tell the difference between differenttypes.The vesicle is separated from the cytosol by at least one phospholipid bilayer. If there is only onephospholipid bilayer, they are called unilamellar vesicles; otherwise they are calledmultilamellar.Vesicles store, transport, or digest cellular products and waste. The membrane enclosing thevesicle is similar to that of the plasma membrane, and vesicles can fuse with the plasmamembrane to release their contents outside of the cell. Vesicles can also fuse with otherorganelles within the cell.Because it is separated from the cytosol, the inside of the vesicle can be made to be differentfrom the cytosolic environment. For this reason, vesicles are a basic tool used by the cell fororganizing cellular substances. Vesicles are involved in metabolism, transport, buoyancycontrol,[1] and enzyme storage. They can also act as chemical reaction chambers.ENDOOLASMIC RETICULUM=The endoplasmic reticulum (ER) is a eukaryotic organelle that forms an interconnectednetwork of tubules, vesicles, and cisternae within cells. Rough endoplasmic reticula synthesizeproteins, while smooth endoplasmic reticula synthesize lipids and steroids, metabolizecarbohydrates and steroids (but not lipids), and regulate calcium concentration, drug metabolism,and attachment of receptors on cell membrane proteins. Sarcoplasmic reticula solely regulatecalcium levels.The lacey membranes of the endoplasmic reticulum were first seen by Keith R. Porter, AlbertClaude, and Ernest F. Fullam in 1945.[1]GOLGI APPERATUS=The Golgi apparatus (also Golgi body or the Golgi complex) is anorganelle found in most eukaryotic cells.[1] It was identified in 1897 by the Italian physicianCamillo Golgi, after whom the Golgi apparatus is named.[2]It processes and packages macromolecules, such as proteins and lipids, after their synthesis andbefore they make their way to their destination; it is particularly important in the processing ofproteins for secretion. The Golgi apparatus forms a part of the cellular endomembrane system.CYTOSKELETON=
    • The cytoskeleton (also CSK) is a cellular "scaffolding" or "skeleton" contained within thecytoplasm and is made out of protein. The cytoskeleton is present in all cells; it was once thoughtto be unique to eukaryotes, but recent research has identified the prokaryotic cytoskeleton. It hasstructures such as flagella, cilia and lamellipodia and plays important roles in both intracellulartransport (the movement of vesicles and organelles, for example) and cellular division. Theconcept of a protein mosaic that dynamically coordinated cytoplasmic biochemistry wasproposed by Rudolph Peters in 1929 [1] while the term (cytosquelette, in French) was firstintroduced by French embryologist Paul Wintrebert in 1931.[2]MITOCHODRIAN=In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organellefound in most eukaryotic cells.[1] These organelles range from 0.5 to 10 micrometers (μm) indiameter. Mitochondria are sometimes described as "cellular power plants" because theygenerate most of the cells supply of adenosine triphosphate (ATP), used as a source of chemicalenergy.[2] In addition to supplying cellular energy, mitochondria are involved in a range of otherprocesses, such as signaling, cellular differentiation, cell death, as well as the control of the cellcycle and cell growth.[3] Mitochondria have been implicated in several human diseases, includingmitochondrial disorders[4] and cardiac dysfunction,[5] and may play a role in the aging process.The word mitochondrion comes from the Greek μίτος or mitos, thread + χονδρίον or chondrion,granule.Several characteristics make mitochondria unique. The number of mitochondria in a cell varieswidely by organism and tissue type. Many cells have only a single mitochondrion, whereasothers can contain several thousand mitochondria.[6][7] The organelle is composed ofcompartments that carry out specialized functions. These compartments or regions include theouter membrane, the intermembrane space, the inner membrane, and the cristae and matrix.Mitochondrial proteins vary depending on the tissue and the species. In humans, 615 distincttypes of proteins have been identified from cardiac mitochondria,[8] whereas in Murinae (rats),940 proteins encoded by distinct genes have been reported.[9] The mitochondrial proteome isthought to be dynamically regulated.[10] Although most of a cells DNA is contained in the cellnucleus, the mitochondrion has its own independent genome. Further, its DNA shows substantialsimilarity to bacterial genomes.[11]CENTRIOLE=A centriole is a barrel-shaped cell structure[1] found in most animal eukaryotic cells, though it isabsent in higher plants and most fungi.[2] The walls of each centriole are usually composed ofnine triplets of microtubules (protein of the cytoskeleton). Deviations from this structure includeDrosophila melanogaster embryos, with nine doublets, and Caenorhabditis elegans sperm cellsand early embryos, with nine singlets; [3][4]. Crabs may also exhibit nine doublets, (see picture).An associated pair of centrioles, arranged perpendicularly and surrounded by an amorphous massof dense material (the pericentriolar material) constitutes the compound structure known as thecentrosome.[1]
    • VACOULE=A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and someprotist, animal[1] and bacterial cells.[2] Vacuoles are essentially enclosed compartments which arefilled with water containing inorganic and organic molecules including enzymes in solution,though in certain cases they may contain solids which have been engulfed. Vacuoles are formedby the fusion of multiple membrane vesicles and are effectively just larger forms of these.[3] Theorganelle has no basic shape or size; its structure varies according to the needs of the cell.The function and importance of vacuoles varies greatly according to the type of cell in whichthey are present, having much greater prominence in the cells of plants, fungi and certain protiststhan those of animals and bacteria. In general, the functions of the vacuole include: Isolating materials that might be harmful or a threat to the cell Containing waste products Containing water in plant cells Maintaining internal hydrostatic pressure or turgor within the cell Maintaining an acidic internal pH Containing small molecules Exporting unwanted substances from the cell Allows plants to support structures such as leaves and flowers due to the pressure of the central vacuole In seeds, stored proteins needed for germination are kept in protein bodies, which are modified vacuoles.[4]Vacuoles also play a major role in autophagy, maintaining a balance between biogenesis(production) and degradation (or turnover), of many substances and cell structures in certainorganisms. They also aid in the lysis and recycling of misfolded proteins that have begun to buildup within the cell. Thomas Boller [4] and others proposed that the vacuole participates in thedestruction of invading bacteria and Robert B Mellor proposed organ-specific forms have a rolein housing symbiotic bacteria. In protists, vacuoles have the additional function of storing foodwhich has been absorbed by the organism and assisting in the digestive and waste managementprocess for the cell.[5]CYTOSOL=The cytosol or intracellular fluid (or cytoplasmic matrix) is the liquid found inside cells. It isseparated into compartments by membranes. For example, the mitochondrial matrix separates themitochondrion into compartments.The contents of a eukaryotic cell within the cell membrane (excluding the cell nucleus), isreferred to as the cytoplasm. In prokaryotes, most of the chemical reactions of metabolism takeplace in the cytosol, while a few take place in membranes or in the periplasmic space. Ineukaryotes, while many metabolic pathways still occur in the cytosol, others are contained withinorganelles.
    • The cytosol is a complex mixture of substances dissolved in water. Although water forms thelarge majority of the cytosol, its structure and properties within cells is not well understood. Theconcentrations of ions such as sodium and potassium are different in the cytosol than in theextracellular fluid; these differences in ion levels are important in processes such asosmoregulation and cell signaling. The cytosol also contains large amounts of macromolecules,which can alter how molecules behave, through macromolecular crowding.Although once thought to be a simple solution of molecules, multiple levels of organization existin the cytosol. These include concentration gradients of small molecules such as calcium, largecomplexes of enzymes that act together to carry out metabolic pathways, and protein complexessuch as proteasomes and carboxysomes that enclose and separate parts of the cytosol.LYSOSOME=Lysosomes are cellular organelles that contain acid hydrolase enzymes to break down wastematerials and cellular debris. They are found in animal cells, while in yeast and plants the sameroles are performed by lytic vacuoles.[1] Lysosomes digest excess or worn-out organelles, foodparticles, and engulfed viruses or bacteria. The membrane around a lysosome allows thedigestive enzymes to work at the 4.5 pH they require. Lysosomes fuse with vacuoles anddispense their enzymes into the vacuoles, digesting their contents. They are created by theaddition of hydrolytic enzymes to early endosomes from the Golgi apparatus. The namelysosome derives from the Greek words lysis, to separate, and soma, body. They are frequentlynicknamed "suicide-bags" or "suicide-sacs" by cell biologists due to their role in autolysis.Lysosomes were discovered by the Belgian cytologist Christian de Duve in the 1950s.The size of lysosomes varies from 0.1–1.2 μm.[2] At pH 4.8, the interior of the lysosomes isacidic compared to the slightly alkaline cytosol (pH 7.2). The lysosome maintains this pHdifferential by pumping protons (H+ ions) from the cytosol across the membrane via protonpumps and chloride ion channels. The lysosomal membrane protects the cytosol, and thereforethe rest of the cell, from the degradative enzymes within the lysosome. The cell is additionallyprotected from any lysosomal acid hydrolases that leak into the cytosol, as these enzymes arepH-sensitive and do not function as well in the alkaline environment of the cytosolCENTRIOLE=A centriole is a barrel-shaped cell structure[1] found in most animal eukaryotic cells, though it isabsent in higher plants and most fungi.[2] The walls of each centriole are usually composed ofnine triplets of microtubules (protein of the cytoskeleton). Deviations from this structure includeDrosophila melanogaster embryos, with nine doublets, and Caenorhabditis elegans sperm cellsand early embryos, with nine singlets; [3][4]. Crabs may also exhibit nine doublets, (see picture).An associated pair of centrioles, arranged perpendicularly and surrounded by an amorphous massof dense material (the pericentriolar material) constitutes the compound structure known as thecentrosome.[1]