Chapter 4.11

1. Chapter 4.11 How Do Cells Move? AP Biology Fall 2010

2. Objectives • Describe the differences between psudopods, cilia, and flagella • Understand the mechanism which moves cilia and flagella

3. Moving Along with Motor Proteins • Kinesines, dyneins, myosins, and other motor proteins function as the freight engines • Energy from ATP fuels the movement • Some motor proteins move chromosomes • Others slide one microtubule over another and others inch along tracks inside nerve cells

4. Cilia, Flagella, and False Feet • Both flagella and cilia are motile structures that extend from the surface of many cells and is completely sheathed by an extension of the plasma membrane

5. Cilia • Cilia: short, numerous, and provide locomotion for free-living cells or may move surrounding water and particles if the ciliated cell is anchored

6. Cilia • Ciliated protists swim by beating their many cilia in synchrony • Cilia in certain areas of the lungs beat nonstop

7. Flagella • Flagella: quite long, not usually numerous, and are found on one-celled protistans and animal sperm cells

8. 9 + 2 Array • Microtubular extensions of the plasma membrane have a 9 + 2 cross-sectional array that arises from a centriole extending below the array as a basal body • 9 pairs of microtubules form a ring around a central pair, all stabilized by protein spokes and links

9. 9 + 2 Array • Centrosome gives rise to a centriole • Barrel shaped structure produces and organizes microtubules into the 9 + 2 array, then it remains below the finished array as a basal body

10. Cilia and Flagella Movement • Move by sliding mechanism • Dynein arms project from each pair in the outer ring • When ATP energizes them, arms grab microtubule pair in front of them, tilt in short, downward stroke, then let go • Bound pair slides down, its arms bind the pair in front of it, forcing it to slide down • and so on around the ring • Microtubules cannot slide too far, but bends a bit • Sliding motion converted to bending motion

12. Psudopods • Pseudopods (flase feet): temporary lobes that project from the cell, used in locomotion and food capture • Macrophages and amoebas • Advance in steady direction as microfilaments inside them are elongated • Motor proteins attached to microfilaments are dragging the plasma membrane along with them in direction of interest

14. Review • What is the difference between cilia, flagella, and false feet?

15. Answers • Flagella are quite long, not usually numerous, and are found on one-celled protistans and animal sperm cells. Cilia short, numerous, and provide locomotion for free-living cells or may move surrounding water and particles if the ciliated cell is anchored. Pseudopods are temporary lobes that project from the cell, used in locomotion and food capture.