Overview Introduction cellular structural protein with a hollow tubular structure Structure composed of polymerized dimers of α- and β-tubulin each dimer has 2 GTP molecules bound constant assembly (slow) and disassembly (fast) clinical importance Chédiak–Higashi syndrome (CHS) etiology a disease caused by a microtubule polymerization defect resulting in decreased chemotaxis, degranulation, phagocytosis AR inheritance presentation recurrent pyogenic infections particularly S. aureus partial albinism peripheral neuropathy Function component of many important cellular structures cilia 9+2 arrangement of microtubules axonemal dynein ATPase that attaches the peripheral 9 doublets causes bending of cilium by binding differentially to doublets also forms the core of flagella clinical importance Kartagener syndrome immotile cilia disease cause dynein arm defect presentation male and female infertility sperm are immotile (no functional flagellar tail) Fallopian tubes cannot sweep egg and sperm towards each other bronchiectasis recurrent sinusitis mucus with bacteria and particles cannot be removed associated with situs inversus mitotic spindles molecular motor proteins mediates intracellular transport 2 types kinesin cell center → periphery anterograde to microtubule e.g. transports neurotransmitter vesicles down axon towards synapse also transports Herpes zoster virus particles from the dorsal root ganglion during reactivation as shingles dynein periphery → cell center retrograde to microtubule e.g. lipid transport from synapse back to Golgi apparatus Pharmacologic importance mebendazole class: antihelminthic mechanism of action ↓ microtubule synthesis in worms griseofulvin class: antifungal mechanism of action deposits in new keratin and disrupts microtubule polymerization uses active against dermatophytes only vincristine/vinblastine class: anti-cancer mechanism of action ↓ microtubule polymerization inhibits mitosis side effects peripheral neuritis areflexia myelosuppression paclitaxel (taxol) class: anti-breast cancer mechanism ↑ stability of microtubule and does not allow disassembly inhibits mitosis colchicine class: anti-gout mechanism of action binds free tubulin ↓ microtubule polymerization inhibits leukocyte/granulocyte migration
QUESTIONS 1 of 8 1 2 3 4 5 6 7 8 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.BC.15.74) A 52-year-old man awakens in the middle of the night with excruciating pain in his right great toe. He reports that even the touch of the bed sheet was unbearably painful. His right foot is shown in figure A. He is treated with colchicine. Which of the following describes the mechanism of colchicine? QID: 106643 FIGURES: A Type & Select Correct Answer 1 Inhibition of xanthine oxidase 23% (78/346) 2 Inhibition of reabsorption of uric acid in proximal convoluted tubule 12% (42/346) 3 Nonselective inhibition of cyclooxygenase (COX) 1 and 2 5% (18/346) 4 Binds to glucocorticoid receptor 1% (5/346) 5 Decreases microtubule polymerization 57% (198/346) M 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic (M1.BC.15.74) A 29-year-old male presents with his wife to his primary care physician with a complaint of infertility. His medical history is significant for recurrent respiratory infections since he was a child. Semenalyis is ordered and reveals significantly reduced sperm motility. To confirm the suspected diagnosis, the physician orders a chest radiograph, which is shown in Figure A. Which of the following is the cause of this patient's condition? QID: 106657 FIGURES: A Type & Select Correct Answer 1 Microtubule polymerization defect 11% (12/110) 2 Kinesin protein mutation 21% (23/110) 3 Sphingomyelinase deficiency 3% (3/110) 4 Dynein arm defect 57% (63/110) 5 LFA-1 integrin (CD18) defect 3% (3/110) M 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.BC.15.70) In large neurons the nucleus can be found a large distance away from the terminal end of its axon. The body has a complex system of intracellular transporters that are able to carry essential proteins from the nucleus to the distal edge of the cell and back. Which of the following proteins are essential for this function? QID: 106481 Type & Select Correct Answer 1 Kinesin, Troponin 7% (7/106) 2 Dynein, Kinesin 90% (95/106) 3 Actin, Dynein 0% (0/106) 4 Myosin, Kinesin 2% (2/106) 5 Glucose, Actin 1% (1/106) M 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic (M1.BC.13.32) Which of the following cells in the body depends on dynein for its unique functioning? QID: 101696 Type & Select Correct Answer 1 Lower esophageal mucosal cell 4% (15/414) 2 Fallopian tube mucosal cell 69% (285/414) 3 Small intestinal mucosal cell 5% (22/414) 4 Skeletal muscle cell 18% (73/414) 5 Adipocyte 2% (9/414) M 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK
All Videos (3) Login to View Community Videos Login to View Community Videos Kartagener Syndrome (Primary Ciliary Dyskinesia) Biochemistry - Microtubules D 1/18/2019 238 views 5.0 (2) Login to View Community Videos Login to View Community Videos Microtubules Chris Robinson Biochemistry - Microtubules D 2/17/2015 187 views 5.0 (6) Login to View Community Videos Login to View Community Videos Microtubules Chris Robinson Biochemistry - Microtubules D 2/11/2015 67 views 5.0 (3) Biochemistry | Microtubules Biochemistry - Microtubules Listen Now 11:44 min 8/12/2021 32 plays 3.0 (1)