Cell Motility
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Pergerakan sel Cytoskeleton -serabut protein yg ditemukan di sel eukariotik -support bentuk sel -menjaga organela pada lokasi yg tetap -membantu perpindahan material ke dalam sel Copyright (c) by W. H. Freeman and Company
Bagian sitoplasma, di antara organela penuh anyaman benang2 halus Disebut jala2 mikrotrabekula (mirip bunga karang) Krn membentuk kerangka sel shg disebut sitoskeleton
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Cytoskeleton
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The Cytoskeleton in Action
Sel darah putih menggunakan sitokeleton untuk “meraih” bacteri. Copyright (c) by W. H. Freeman and Company
The Cytoskeleton
An animal cell cytoskeleton Copyright (c) by W. H. Freeman and Company
The Cytoskeleton in Action
Cilia on a protozoan
Beating sperm tail at fertilization
Smoker’s cough is due to destruction of cilia linking the airways.
During blood clotting, platelets change shape due to changes in the actin cytoskeleton
Figure 18-8 Copyright (c) by W. H. Freeman and Company
Komponen Penyusun Sitoskeleton Protein yg di sitosol mmbentuk benang halus disbut filamen Ada 3 macam (berdasar struktur dan garis tengah) : mikrotubula (24 nm), mikrofilamen (60 Ao), filamen intermedia (8-10 nm)
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19.6 Functions and structure of intermediate filaments distinguish them from other cytoskeletal fibers
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Figure 19-50
mikrotubula Filamen dgn diameter trbesar (24 nm) Trsusun atas 13 protofilamen Tiap protofilamen tdr dr molekul2 tubulin (tubulin alfa dan beta) Punya kutub positif yg pertumbuhannya cepat, kutub negatif prtumbuhannya lambat Copyright (c) by W. H. Freeman and Company
Heterodimeric tubulin subunits compose the wall of a microtubule
Figure 19-2 Copyright (c) by W. H. Freeman and Company
19.1 Arrangement of protofilaments in singlet, doublet, and triplet microtubules
Figure 19-3 Copyright (c) by W. H. Freeman and Company
Berfungsi memberi bentuk sel, gerakan sel, menentukan bidng pembelahan sel Membentuk flagela, silia, sentriol
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Mikrofilamen Trdiri dr mikrofilamen aktin, meosin dan tropomeosin (byk di otot) Aktin aktin mrpkan protein kontraktil terbanyak di sel eukariotik Dalam bentuk monomer disebut Aktin G Dalam bentuk filamen disebut Aktin F Copyright (c) by W. H. Freeman and Company
Bersifat labil (mudah terakit dan terurai) Terlibat dlm proses sitokinesis, aliran plasma, gerakan sel, gerakan mikrovili intestinal
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The actin cytoskeleton Filamen aktin(or microfilaments) adalah salah satu dr 3 filamen protein yg menyusun system cytoskeleton Eukaryotic cells contain abundant amounts of highly conserved actin
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Figure 18-1
18.1 The actin cytoskeleton is organized into bundles and networks of filaments
Figure 18-4 Copyright (c) by W. H. Freeman and Company
Actin cross-linking proteins bridge actin filaments to form bundles and networks
Figure 18-5 Copyright (c) by W. H. Freeman and Company
Filamen Intermedia Bersifat liat Punya daya rentang tinggi. Benang berongga terdiri 5 protofilamen Diameter 8-10 nm Banyak terdapat di inti, dan sel yg alami stress mekanik spt epitelium, akson sel saraf dan otot polos Copyright (c) by W. H. Freeman and Company
Pergerakan otot/muscle
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Microanatomy of Skeletal Muscle sel otot =
serabut otot yg mengandung myofibril
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Muscle: a specialized contractile machine
Figure 18-26 Copyright (c) by W. H. Freeman and Company
Tiap serabut otot terdiri dari ribuan myofibril Tiap myofibril terdapat 1500 filamen meosin dan 3000 filamen aktin Tiap filamen meosin terdiri dari molekul meosin BM 33.200 dan molekul aktin BM 70.000
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Dengan mikroskup cahaya : nampak gambaran gelap terang kepadatan relatif dan ada bagian yang tumpah tindih dr aktin dan miosin
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Pita cahaya I Terdiri filamen aktin saja (nampak terang) Sifat terhadap cahaya yg terpolarisasi (berkas cahaya yg datang dipancarkan ke semua jurusan krn kepadatan sama)
I band Copyright (c) by W. H. Freeman and Company
Pita A Terletak dimana aktin dan meosin tumpang tindih (shg nampak gelap) Sifat anisotropik (cahaya dipancarkan tdk merata)
A band Copyright (c) by W. H. Freeman and Company
Sarkomer Terbentuk oleh 2 garis Z (protein nonkontraktil) atau sebuah pita A dan 2 belahan pita I Sarkoplasma Sitoplasma sel2 otot Terdapat retikulum sarkopasma agranuler
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Z line
Z line
H band
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Filamen meosin Tediri 2 utas peptid yg satu sama lainnya saling melilit dalam suatu heliks yg ujungnya membntuk kepala.
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Filamen aktin Terdiri 3 unsur : troponin, tropomeosin, aktin
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Active site : suatu molekul ADP dimana filamen meosin saling mengadakan interaksi dgn filamen aktin shg terjadi kontraksi otot
Tropomeosin : merupakan protein yg akan “menutupi” active site shg tdk terjadi kontraksi
Troponin : akan berikatan dgn Ca utk permulaan kontraksi
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Ilustrasi sarkomer H Band
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18.4 Capping proteins stabilize the ends of actin thin filaments in the sarcomere
Figure 18-28 Copyright (c) by W. H. Freeman and Company
18.4 Thick and thin filaments slide past one another during contraction
Figure 18-29 Copyright (c) by W. H. Freeman and Company
18.4 Titin and nebulin filaments organize the sarcomere
Figure 18-30 Copyright (c) by W. H. Freeman and Company
18.4 A rise in cytosolic Ca2+ triggers muscle contraction (part I)
Figure 18-31a Copyright (c) by W. H. Freeman and Company
18.4 A rise in cytosolic Ca2+ triggers muscle contraction (part II)
Figure 18-31b Copyright (c) by W. H. Freeman and Company
18.4 Tropomyosin and troponin regulate contraction in skeletal muscle
Figure 18-32 Copyright (c) by W. H. Freeman and Company
18.4 Ca2+-dependent mechanisms for regulating contraction in skeletal and smooth muscle
Figure 18-33 Copyright (c) by W. H. Freeman and Company
18.4 Myosin-dependent mechanisms also control contraction in some muscles
Figure 18-34 Copyright (c) by W. H. Freeman and Company