unit 5-6

1. What are the three main cytoskeletal filaments and their proteins?

Microtubules – Tubulin
Microfilaments – Actin
Intermediate filaments – Keratin, vimentin, desmin

2. What are the main functions of the cytoskeleton?

Organization of cell components, cell movement, and cell division; adaptable structure.

3. What do microtubules resist?

Bending during cell compression.

4. What is the main function of microfilaments?

Generate tension through contraction.

5. What property characterizes intermediate filaments?

Elasticity; they can withstand tensile forces.

6. What is “catastrophe” in microtubules?

Sudden shrinkage of a microtubule.

7. What is “rescue” in microtubules?

When a shrinking microtubule starts growing again.

11. What are the two main myofilaments?

thick = Myosin
Thin = Actin

12. What is the MTOC?

Microtubule organizing center, located near the nucleus; minus end points toward it.

13. What transports vesicles toward the cell surface?

kinesin

14. What transports vesicles away from cell surface

dynein

17. What is the ECM?

A network of large proteins + polysaccharides secreted by cells that supports and anchors tissues.

18. Major ECM components?

Collagen, elastin, proteoglycans, fibronectin, laminin.

19. Three ECM functions/types?

Bone (stiff), cartilage (flexible), connective tissue (gel-like).

20. What is collagen’s main role?

Provides strength and support; triple helix structure.

21. Which cells produce collagen?

Fibroblasts, smooth muscle cells, epithelial cells.

23. What are proteoglycans?

Protein core + GAGs; attract water to form gel.

24. What is fibronectin’s main function?

Connects cells to ECM; binds collagen, receptors, and other matrix components.

25. What are laminins?

ECM glycoproteins that influence migration, growth, and differentiation; cross-shaped.

26. What are integrins?

Transmembrane receptors that bind ECM (collagen, fibronectin, laminin) and connect to cytoskeleton.

27. What is the Dystrophin Glycoprotein Complex (DGC)?

Links muscle cytoskeleton to ECM; important for resisting mechanical stress.

28. What are hemidesmosomes?

Cell-ECM anchor junctions in epithelial cells; use α6β4 integrins; link to keratin via plectin.

29. Three major classes of cell junctions?

Adhesive junctions, tight junctions, gap junctions.

30. What proteins mediate adherens junctions?

Cadherins (linked to actin).

31. What proteins make up desmosomes?

Plakoglobins + desmoplakins connecting to intermediate filaments (keratin).

32. What do tight junctions do?

Create watertight seal to prevent fluid/ion leakage between cells.

33. What proteins form tight junctions?

Claudins and occludins.

35. What are gap junctions?

Protein-lined pores allowing ions/small molecules to pass between cells.

36. What proteins form gap junctions?

Connexins

37. What are plasmodesmata?

Channels between plant cells allowing movement of water, ions, and small molecules (including RNA).