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Cytoskeleton
Medical Cell Biology
| Term | Definition |
|---|---|
| Functions of Cytoskeleton | Provides structural integrity, cell motility/contraction of muscles, change in cell shape, and movement of organelles |
| 3 Types of Muscle | skeletal, cardiac, and smooth |
| Skeletal Muscle | striated, multi-nucleated, consist of actin and myosin |
| Sacromere | Functional contractile unit of a skeletal muscle |
| 3 Layers of connective tissues surround skeletal muscle | Epimysium, Perimysium, and Endomysium |
| Epimysium | Surround the whole muscle (group of muscle fasciculi) |
| Perimysium | Surround muscle fasciculous (bundle of muscle fibers) |
| Endomysium | Surround individual muscle fiber. |
| Z Disk | actin thin filaments |
| A band | Remain constant during contraction |
| I Band | Shortens during contraction |
| H Band | Center of A band, overlapping of thick and thin filament (thick filament) |
| M Line | Anchor thick filament (myosin) |
| Actin | composed of F-actin (polymerize) and G actin (globular protein) |
| What is important about the G-protein? | Binds to ATP to polymerize F-actin. Polymerization: need ATP and Mg2+ |
| Tropomyosin | Wrap around the thin filament |
| Troponin | Bind to tropomyosin (block the myosin head binding site) TnC, TnI, TnT |
| Tropomodulin | Cap slow growing end (-) |
| Polymerization of actin | Lag phase, polymerization phase, and Steady Phase, |
| Steady Phase | Also known as tread milling Effect. Monomers added is equal to the number of monomers removed. Addition of G-actin ATP (+ end) = loss of G-actin ADP (-end) |
| Tropomyosin | Wrap around the thin filaments for stability of F-actin |
| Z disk proteins | Cap Z and alpha actinin (anchored thin filament) |
| Cap Z | bind to + end of F-actin prevent growth and depolymerization |
| Alpha actinin | Space b/w thin filaments so thick filaments won't bind |
| Titin | Keep myosin thick filament centered |
| Nebulin | extended from Z-disk to (-) end of thin filament |
| Desmin | Stabilize the Z-disk |
| Myosin | consists of 2 heavy chains and 2 light chains. Formed in coiled-coil helix fashion with a repeat sequence of amino acids- to avoid aqueous solution |
| Papain | Cleave myosin heads |
| Rigor Mortis | Occurs when there is no ATP. The myosin head remain binding to the actin filament - Stiffness |
| Calcium regulation | Troponin complex bound to tropomyosin, block the binding site for myosin head. |
| What happens when Ca binds to Troponin C? | Moves troponin away from the tropomyosin. This exposes actin to the myosin head |
| Sarcroplasmic Reticulum | Stores Ca++, consists of 2 terminal cisternae and one T-tubule (triad) |
| DHPR (Dihydropyridine receptor) | Locates along the T-Tubule, which will undergoe a conformational change. |
| Ryanodine receptor | Ca2+ channel of the SR. This SR Ca2+ channel open and release Ca2+ into the cytosol |
| Calsequestrin | Takes back Ca into the SR by Ca2 ATPase |
| Cardiac Muscle Cell | Location of the nuclei is in the center where as the location of the nuclei in a skeletal muscle is in the periphery. Contraction is the same as skeletal muscle |
| Intercalated disks | Only present in Cardiac cells |
| Gap Junctions | Located in intercalated disks. It is for synchronizing the contraction (allow rapid exchange of solutes and ions) |
| Desmosome (macula adherens) | Hold cells together |
| Fascia adherens | Hold actin thin filament together like Z-disk |
| Familial Hypertrophy Cardiomyopathy | Defect in cardiac B-myosin |
| Familial Dilated Cardiomyopathy | Defect in cardia a-actin |
| Smooth Muscles | No sarcomere, no troponin, not striated. Has dense bodies, lots of IFs (desmin, vimentin). Ratio of thin to thick 12:1. Made up of Dense bodies |
| Dense Bodies | Made up of a-actinin |
| Myosin Light Chain Kinase | Phosphorylates Myosin Light chain |
| Ca2+ Calmodulin - Contraction | Myosin light chain kinase is inactive when Ca-calmodulin complex form. This will phosphorylate myosin light chain and become active |
| Ca2+ Calmodulin - Relaxation | Dephosphorylation of myosin light chain by removing pi by phosphatase |
| Catcholamine | Binds to Beta adrenergic receptors. Cause an increase in cAMP, which phosphorylates protein Kinase A |
| Protein Kinase A | Phosphorylates myosin light chain kinase - cause inability to bind to calmoduline-- lead to relaxation |
| Dephosphorylation of MLCK | Causes muscle to contract by dephosphorylation of MLCK. MLCK is active |
| release of Ca+2 and DAG is stimulated by which kinase? | Protein kinase C |
| Caldesmon | Ca+2 proteins that interact with actin thin filaments |
| Contractile Ring | Present during telophase of mitosis. During mitosis, actin filaments form at cleavage site-cleavage furrow. Myosin polymerises with actin contractile ring |
| Villin and fimbrin | Bundled together and then attach to microvilli. Increase surface area for absorption at + end |
| Spectrin II and Myosin II | Link two bundles together at terminal web. Microvilli anchored at terminal web. |
| Gelsolin | Keep cytosol liquification that is triggered by increased calcium. Makes fragment filaments |
| Profilin | Polymerization. When PIP2 is bound to profilin, profilin cannot bind to actin. When PIP2 hydrolyzes to IP3 and DAG by PLP-C release profilin |
| Thymosin | Binds to G-actin and keep it in that state |
| Cytochlasin | Inhibitors of actin filament. Blocks plus end |
| Paballoidin | Stabilize microfilament does not allow depolarization |
| Protrusion | Actin polymerization. If polymerization is greater than retrograde flow = cell protrusion |
| Retrograde flow | myosin II contractile |
| Arp 2/3 nucleating complex | Branching of lamellipodia |
| Lamellipodia and filopodia | extension at leading edge for cell movement |
| WasP and Scar | Binds to Arp 2/3 - promote actin polymerization |
| Cdc42 | Activate Scar bind to Arp 2/3 form filopodia |
| Rac | Activate Wasp and PI (4) P5 kinase form lamellipodia and membrane ruffles |
| Rho | Bundling of actin with myosin II. |
| Rhokinase | Phosphorylates myosin II--contracation |
| ERM proteins | Ezrin, Radixin, Moesin |
| Defect Merlin | Leads to Neurofibromatosis |
| What attaches actin filament to plasma membrane | ERM Proteins |
| Spectrin 4.1 | Maintains biconcave shape of RBC |
| Ankyrin | Anchored spectrin to membrane. The whole complex is stabilized by protein 4.1 |
| Ubiquination | Is needed for shaping RBC |
| Dystrophin | Protein that belong to spectrin gene family. If absent - responsible for Duchenne's Muscular Dystrophy |
| Intermediate filaments | Resistance to mechanical stress. (ankyrin and spectrin II) |
| Keratin filament | Epithelial Cells |
| Neurofilament | Neurons |
| Vimentin | Containing filaments - fibroblasts/glial cells/ muscle cells |
| Nuclear Lamina | All nucleated cell (except RBC) |
| GFAP | brains |
| Microtubules | Need tubulin alpha and beta. 13 protofilament. Flagella and cilia motility, Meitotic and mitotic spindles. Vesicle transport. Need GTP |
| Drugs that Target Microtubules | Colchine, Viblastine sulphate, Nocodazole, Paclitaxel |
| Polarity | addition of subunit is faster at (+) end, (-) end is capped due to centrosome complex |
| Centrosome complex | Composed at 9 short-triplet microtubules (9+2 arrangement) |
| Kinesin | Anterograde transport (-end to +end) |
| Dynein and KRPS | Retrograde transport + end to - end |
| Dynactin Complex | Arp 1, Spectrin, Dynein |
| APP (Amyloid Precursor Protein) | Defect in MAMR (membrane associated motor receptors causes Alzheimer's disease |
| Dynein | ATPase extending towards B Tubule |
| Nexin | Attaches neighboring doublets |
| Radial Spokes | Attach doublets to the center |
| Arrangement of Microtbules in cilia and flagella | Arranged in 9+2 array. Doublet alpha tubule and beta tubule |
| Metaphase | Chromosome line in the middle - 2 forms: interpolar (overla of the spindles) and ASTRAL (GROWING AWAY FROM THE KINETOCHORE) |
| Telophase | Cytokinesis (contractile ring) - form daughter cell membrane |
| MAPs and Tau | Bind to tubulin monomoer of microtubule-allow bundling and stabilize MT |
| MAPs (EB 1 and CLIP 170) | Attach MT to kinetochore |
| Katanins and Stathmins/Op18 | Disrupt microtubules formation |
| Katanins | Prevent the additions of tubulins to MTs by binding to tubulins dimer |
| Stathmin | Detach MTs from MTOC |
Created by:
jsabangan
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