LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick The Cytoskeleton Chapter 6

Concept 6.6: The cytoskeleton is a network of fibers that organizes structures and activities in the cell Network of fibers throughout the cytoplasm It organizes the cell’s structures & activities Anchors many organelles Composed of –Microtubules –Microfilaments –Intermediate filaments © 2011 Pearson Education, Inc.

Roles of the Cytoskeleton: Support and Motility The cytoskeleton helps to support the cell and maintain its shape It interacts with motor proteins to produce motility Inside the cell, vesicles can travel along “monorails” provided by the cytoskeleton Recent evidence suggests that the cytoskeleton may help regulate biochemical activities © 2011 Pearson Education, Inc.

Figure 6.21 ATP Vesicle (a) Motor protein (ATP powered) Microtubule of cytoskeleton Receptor for motor protein 0.25  m Vesicles Microtubule (b)

Tubulin dimer 25 nm  Column of tubulin dimers 10  m Table 6.1a

10  m Actin subunit 7 nm Table 6.1b

5  m Keratin proteins Fibrous subunit (keratins coiled together) 8  12 nm Table 6.1c

Centrosome Longitudinal section of one centriole Centrioles Microtubule 0.25  m Microtubules Cross section of the other centriole Figure 6.22

Direction of swimming (b) Motion of cilia Direction of organism’s movement Power stroke Recovery stroke (a) Motion of flagella 5  m 15  m Figure 6.23

Microtubules Plasma membrane Basal body Longitudinal section of motile cilium (a) 0.5  m 0.1  m (b) Cross section of motile cilium Outer microtubule doublet Dynein proteins Central microtubule Radial spoke Cross-linking proteins between outer doublets Plasma membrane Triplet (c) Cross section of basal body Figure 6.24

Figure 6.25 Microtubule doublets Dynein protein ATP (a) Effect of unrestrained dynein movement Cross-linking proteins between outer doublets ATP Anchorage in cell (b) Effect of cross-linking proteins (c) Wavelike motion 1 2 3

Figure 6.27a Muscle cell Actin filament Myosin filament (a) Myosin motors in muscle cell contraction 0.5  m head

Figure 6.27b 100  m Cortex (outer cytoplasm): gel with actin network Inner cytoplasm: sol with actin subunits (b) Amoeboid movement Extending pseudopodium

Figure 6.27c 30  m (c) Cytoplasmic streaming in plant cells Chloroplast