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BIOL125_Ch5 Lecture Notes

BIOL125_Ch5 Lecture Notes - BIOL 125(Microbiology Lecture...

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BIOL 125 (Microbiology) Lecture Notes Chapter 5: Survey of Eukaryotic Cells and Microorganisms 1. EXTERNAL STRUCTURE a. Locomotory Appendages. i. Built form polymers of tubulin protein called microtubules, which are arranged in 9+2 configuration. There are two types that differ in size and number. 1) Flagella – long and covered in a cell membrane sheath and one per cell. Flagella are also found in prokaryotes, but they are very different in their make-up. a) In eukaryotes, flagella are made of tubulin protein. b) The purpose in eukaryotes is chemotaxis, that is movement toward food and away from toxins. 2) Cilia – short and several in number. Found only on a single group of protozoa and certain animal cells. They function in motility, feeding, and filtering. 2. EXTERNAL BOUNDARY a. Glycocalyx – an outermost boundary in direct contact with the external environment. i. Composed of polysaccharides (slime layer or capsule). ii. More commonly seen in animal cells. iii. May not be found in all cells. iv. Functions – adherence, protection, and signal reception. b. Cell Wall – provides structural support and shape. i. Fungi – composed of two layers of polysaccharide fibers. The outer layer is mixed glycans; the inner layer is chitin (amino sugar) or cellulose (glucose polymer). ii. Algae – the chemical composition varies; substances commonly found include cellulose, pectin, mannans, silicon dioxide, and calcium carbonate. iii. The cell wall is not always present (ex. it is not found in protozoa or animal cells). iv. The cell wall also prevents osmolysis. c. Cytoplasmic or Cell Membrane. i. Structure is shown by the Fluid Mosaic Model. 1) It is typically a bilayer of phospholipids and proteins. 2) Protein can be peripheral and integral membrane proteins. 3) Sterols derived from cholesterol provide rigidity. File: cf0741a1c46508e62489b9d14d4b8885dcefbbc2.doc Updated 8/14/09
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Lecture Notes Chapter 5 Page 2 a) All eukaryotes have cholesterol (or a derivative) in the cell wall. ii. The cell membrane is a selectively permeable barrier (depending on the molecule size or the charge of the molecule). 1) It also transports materials across the membrane, which is called secretion of cellular components. iii. Eukaryotic cells are comprised of membrane-bound organelles. The membrane make-up is similar in structure and function to the plasma membrane. 3. INTERNAL STRUCTURES a. Cytoplasm – fluid environment enclosed by the plasma membrane. i. Made of water (solvent), in which proteins, carbohydrates, and other macromolecules are suspended. ii. It houses the enzymes necessary for the metabolic and synthetic activities of the cell. iii. The cytoplasm suspends various organelles. b. Ribosomes – small structures found in the cytoplasm composed of rRNA and proteins. i. Built from two subunits 40S and 60S in size, to form 80S ribosomes.
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BIOL125_Ch5 Lecture Notes - BIOL 125(Microbiology Lecture...

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