1. Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – 422222, India 1© 2008, YCMOU. All Rights Reserved.

2. 2 OC-SBT082-U01-04 Introduction Programmes and Courses  SBT082 –CP01 - Unit 01

3. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.3 Credits  Academic Inputs by Arun Punaji More. M.Sc. (Microbiology) ‏ Experience: 11 Years arunmesh@hotmail.com

4. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of 40-60 minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about 40-60 minutes.  Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.  Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.  Appear several times, for all the Self-Tests, available for this course.  Student can use handouts for last minutes preparation just before end exam.

5. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to: Describe the structure of microtubules Describe the functions of microtubules.

6. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.6 Introduction  The cytoskeleton play a very important roles in the various functions of the cell for their growth and survival.  Cytoskeletons are made of with various types of protein filaments.  Each type of these filaments give the special characteristics of the cytoskeleton and determine its functions for the cells.  In this presentation we will see the characteristics and functions of microtubules filaments.

7. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.7 Structure of Microtubules-1  The microtubules are hollow rigid rods of 25nm in diameter.  They are made of with a single type of globular protein called as tubulin.  Tubulin is dimer of α- tubulin and β-tubulin polypeptides.  The γ-tubulin polypeptide is specifically located in centrosome.

8. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.8 Structure of Microtubules-2  The tubulin dimers polymerize to form microtubules when GTP molecules attach to these dimers.  The microtubules are very dynamic structures and tubulin dimers polymerize and depolymerize very rapidly.  These polymers assemble and dissemble very rapidly depending upon the cells' needs.  Binding of GTP molecules determine the assembly of microtubules.

9. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.9 Structure of Microtubules-3  Like the actin filament, the microtubule filament is polar polymer having + end and – end.  The tubulin dimers assemble when the GTP molecules get attached to the tubulin dimers which are added to the + end of microtubule filament.  Hydrolysis of GTP molecules attached to the tubulin dimers cause the disassembly of microtubules.

10. School of Science and Technology, Online Counseling Resource… Structure of Microtubules-4 10© 2008, YCMOU. All Rights Reserved.  The microtubule filament is made of with alpha tubulin and beta tubulin protein in the manner as shown below.

11. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.11 Structure of Microtubules-5  The rapid assembly and disassembly of microtubule filaments during mitosis are required for the DNA strands separation to two poles of the cell.  The two drugs i.e. Colchicine and Colemid can bind to the tubulin dimers inhibiting the polymerization of microtubules finally resulting into the arrest of mitosis.  The other drugs such as vincristine and vinblastine selectively inhibit microtubule polymerization.

12. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.12 Functions of Microtubules-1  The microtubules transport membrane vesicles and organelles through cytoplasm.  For examples, in nerve cells the mitochondria are transported from cell bodies to axon with help of kinesin and dynein microtubules.  In the cytoplasm the microtubules(kinesin) stretch the endoplasmic reticulum in the extended state toward the cell periphery.

13. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.13 Functions of Microtubules-2  Microtubules position the Golgi apparatus in the center of cell, near the centrosome.  Microtubules play crucial role in cell division by separating the replicated chromosomes.  In Anaphase A kinetochore microtubules move the chromosomes toward the spindle poles.  The kinetochore microtubules trasnsport the chromosomes toward the centrosomes.

14. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.14 Functions of Microtubules-3  During Anaphase B, microtubules separate the spindle poles by elongation of microtubules.  The microtubules are responsible for locomotory movements of variety of prokaryotic and eukaryotic cells.  For example, movement of bacterial flagella and cilia are based upon the microtubules.

15. School of Science and Technology, Online Counseling Resource… Functions of Microtubules-4 The microtubule filaments anchor its negative end into the centrosomes. Its positive ends attach to the chromosomes and pull the chromosomes towards poles of cells. 15© 2008, YCMOU. All Rights Reserved.

16. School of Science and Technology, Online Counseling Resource… Functions of Microtubules-5  Microtubules in the locomotory organs such as flagella and cilia in association with motor proteins such as Dyneins. 16© 2008, YCMOU. All Rights Reserved.

17. School of Science and Technology, Online Counseling Resource… Functions of Microtubules-6  Paramecium moves by the means of numerous cilia all over its body surface. © 2008, YCMOU. All Rights Reserved.17 Numerous cilia on the body surface of paramecium.

18. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.18 Critical Thinking Questions  Why the microtubule filaments are essential for the survival the cell?

19. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.19 Hints For Critical Thinking Questions  They are present in the centrosomes.

20. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.20 Study Tips  Book Title: Title:The Cell, A Molecular Approach Author: Geoffrey M. Cooper, Robert E. Hausman Publication: ASM press, Washington,D.C. Publication: ASM press, Washington,D.C.  Book Title: Cell and Molecular Biology Title: Cell and Molecular Biology Author: E.D.P. De Robertis and E.M.F. De Robertis, Jr. Author: E.D.P. De Robertis and E.M.F. De Robertis, Jr. Publication: Lippincott and Williams & Wilkins Publication: Lippincott and Williams & Wilkins

21. © 2008, YCMOU. All Rights Reserved.21 End of the Presentation Thank You !