APK 2105C Lecture Notes - Lecture 6: Respiratory Tract, Epithelium, Microvillus
23 May 2018
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Chapter 2, Part 4
The Cell: Structure & Function
• Non-membranous organelles = not enclosed with a membrane
o Ribosomes = makes proteins
▪ Large ribosomal subunit + small ribosomal subunit → ribosome
• Subunits are made within nucleolus
o Cytoskeleton = flexible lattice of fibrous proteins (filaments)
▪ Microfilaments (very small—7nm)
• Microvilli (increases SA)
o Used for absorption or secretion of something
o Not motile
• Motility in cells
• Actin filaments = generates muscle contraction
▪ Intermediate filaments = 8-12 nm in diameter
• Slightly larger than microfilaments
• Look like they have been twisted together
• Myosin
• Keratin = fills up epithelial cells in on the surface of the skin—
makes them hard
• Form network throughout cell
• Organelles will be attached to these filaments
▪ Microtubules = 25 nm in diametes
• Considerably larger than other two types
• Celia and flagella
o Flagella = projecting cells
▪ Sperms
o Celia = similar to microvilli but filled with microtubules
▪ ARE motile (not like microvilli)
▪ Wavelike motion to propel things along surface of
the cell
▪ Lines upper respiratory tract
• Cell-to-cell adhesions (membrane junctions)
o Tight junctions = serve to seal adjacent cells together so fluids cannot leak
between them
o Desmosomes = anchor adjacent cells together to resist pulling forces
▪ Have anchoring transmembrane proteins with enlargements on the end of
each other—acts like a zipper
o Gap junctions = provide a tunnel between adjacent cells allowing direct electrical
and metabolic coupling of the cells
▪ Allow cellular communication between ICF
▪ Reasons for coupling
• Metabolic coupling
o Avascular tissues (epithelial tissue) are connected to get
oxygen and nutrients from other cells
• Electric coupling = movements of ions between cells
o Only seen in cells that have direct contact with each other
▪ NOT neurons or CT
• General cell functions
o Metabolism = all chemical rxns in the body
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