BIOL 1081 Lecture Notes - Lecture 7: Middle Lamella, Cell Membrane, Microtubule
Ch. 4 LO- 3 Tuesday
• Tuesday, September 12th
Cytoskeleton, Extracellular structures, & Cell Connections Reading: Sections 4.6-4.8 in textbook
1. Compare and contrast the structure and functions of different fibers in the cytoskeleton.
• Microfilaments
o Actin
o 7nm in diameter
o 2 protein chains loosely twined together
o Polarity, + and – ends
o Form spontaneously in test tubes
o Function- cellular movements, contraction, crawling, pinching during division, cytokinesis,
formation of cellular extensions
• Microtubules
o Largest, hollow tubes
o 25 nm in diameter, 13 protein protofilaments
o Function-facilitate cellular movement, organize cytoplasm, responsible for moving
material within cell itself
• Intermediate filaments
o Most durable, tough fibrous proteins twined together in overlapping arrangement
o 8-10 nm in diameter
o keratin
o Function- do not break down
2. Describe the role of microtubules and motor proteins in intracellular transport.
• Form a polarized network allowing organelles and proteins to move throughout the cell
3. Identify the different cytoskeletal elements involved in cell movement, and describe how they
accomplish it.
• Crawling- arrangement of actin
• Flagella and cilia aid in movement- 9+2 structure, microtubules move past each other (undulates)
4. Describe the composition and functions of the cell walls and extracellular matrices surrounding the
plasma membrane of many eukaryotes. —See book chart
• Plants and protists- cellulose
o Primary walls
o Sticky middle lamella
o Secondary walls
• Fungi- chitin
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