lect2-ddg sel.ppt
TRANSCRIPT
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Dinding Sel
• FUNCTION of the wall:
– Memberi bentuk, – Untuk proteksi sel,– Membatasi pertumbuhan, – Sebagai barrier, – lokasi adhesins, – contributes to motility...
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Dinding Sel tumbuhan
• Tebal, kuat kaku; pelindung sel• Bertautan antara sel 1 dg sel lain plasmodesmata• Sel muda ddg sel tipis lunak = ddg sel
primerdinamis• Sel dewasa ddg sel tebal, kuat, kaku = ddg sel
sekunder• Ssn molekuler tdr atas molekul protein & polisakarida
pd tumb tinggi : serabut = selulosa, matrix ddg sel berupa glikoprotein & 2 jns polisakarida yi. Hemiselulosa & pektin
• Selain selulosa, hemiselulosa, pektin & glikoprotein, ddg sel tumb jg mengandung lignin, kitin & suberin
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In the absence of a cell wall, plant cells adopt a spherical shape
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Ddg sel primer & sekunder
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Komponen penyusun ddg sel primer
• Polisakarida :– Selulose– Matrix polisakarida (hemiselulose, pektin)
• Protein :– Protein struktural : arabinogalaktan, ekstensin– Enzimatik : ekspansin, pektin methylesterase
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• Ddg sel fungi & bakteri berbeda dg ddg sel tumb tinggi
• Pd fungi struktur ddg sel berlapis2 tgt tk kedewasaan fungi, & tdpt kitin & β glukan yg membedakan ddg sel fungi dg ddg sel tumb tk tinggi.
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Ddg sel bakteri
• Ddg sel bakteri semi kaku krn mengandung peptidoglikan
• Pd bakteri Gr + kandungan peptidoglikan 40-90% & sbg ciri khas tdpt asam teikoat 20-50% berat kering ddg sel.
• Pd bakteri Gr – kandungan peptidoglikan 1%
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• Note:
– Protoplast: sel bakteri / fungi yg sensitive sec osmotik akibat hilangnya ddg sel. Membran sitoplasma tetap kokoh.
– Spheroplast: Sel bakteri yg sec osmotik sensitive akibat hilangnya sebagian ddg sel.
– L-form: n [Lister Institute, London, where it was first isolated] (1948) : suatu varian bakteri dg btk L dibwh kondisi stress & tidak mempunyai ddg sel.
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By electron microcopy…
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Peptidoglycan (murein) umum pd bakteri Gram positif & Gram negatif.
• peptidoglycan memiliki 2 komponen– glycan
• N-acetylglucosamines & N-acetylmuramic acids dihubungkan oleh -1,4 glycosidic bonds
– peptide• tetrapeptide (in its mature form) dg dua btk D- & dua
btk L• Variasi ikatan peptida
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Susunan…
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Organization…
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What we need to examine about composition
• Components:– N-acetylglucosamine– N-acetylmuramic acid– D and L amino acids– Dicarboxylic acids
• Linkages: -1,4 glycoside and peptide linkages
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dicarboxylic acids:
• oxalic acid............HOOC-COOH
• maleic acid..........HOOC-CH2-COOH
• succinic acid........HOOC-CH2-CH2-COOH
• glutaric acid.........HOOC-CH2-CH2-CH2-COOH
• adipic acid...........HOOC-CH2-CH2-CH2-CH2-COOH
• pimelic acid.........HOOC-CH2-CH2-CH2-CH2-CH2-COOH
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Dua diamino acids (satu diantaranya adalah dicarboxylic)
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Susunan…
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Susunan…
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The big picture of the gram positive WALL
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What else needs to be known about G+ and G- “WALLS”?
• Gram POSITIVE– teichoic acids
– phosphodiesters of substituted polyalcohols
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What else needs to be known about G+ and G- “WALLS”?
• Gram POSITIVE– teichoic acids
– phosphodiesters of substituted polyalcohols
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Some bacteria have specialized surface proteins, e. g., the M-protein of Streptococcae spp.
• The coiled-coil dimeric nature of M protein and its relationship to the bacterial cell surface is shown. The N-terminal region of the M protein, distal to the cell surface, varies among different M types, thereby providing the molecular basis of the Lancefield method of serotyping group A streptococci.
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The big picture of the gram negative ENVELOPE
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What else needs to be known about G+ and G- “WALLS”?
• Gram NEGATIVE have LPS: LipoPolySacchrides
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…“wall” …“envelope” …???• A cell is a “discrete
mass… surrounded by a membrane…”
• Typically (except for the Mycoplasma and a few other variants), there is a wall or membrane “distal” to the cell surface.
• What is between the cell membrane and these outer structures?
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What is the periplasm?
“A space between the cytoplasmic membrane and peptidoglycan layer (gram positives) and the outer envelope (gram negatives).”
• Function?
• A repository for proteins that:
– Bind sugars, amino acids, vitamins, and minerals;
– Degrade large, impermeable macromolecules (this group includes nucleases, proteases, phosphatases);
– Detoxify noxious components (e. g., lactams [using beta-lactamases].)
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OK for the “overview”…
• There are Gram positive and Gram negative “walls” and “envelopes.”
• What variations exist?
• The previous question is effectively answered by examining the Archea.
• Interestingly, the Archea have variations in both cytoplasmic membrane and cell wall structure that substantiates the distinction between “Bacteria” and “Archea”
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Some Archea have proteinaceous surfaces…
Called an S-layer
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No Archea have an authentic murein
But some have a “pseudomurein”…
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Archea juga berbeda pd cytoplasmic membranes…