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Essential Biology 02.2: Prokaryotes 1. This is an electronmicrograph of the bacterium Salmonella typhi. a. What is the maximum length of the main body of the cell? Prokaryotes are generally ranging under the 10 micrometer range. b. What are the name and function of this structure? The flagellum are used to move the cell from one area to the next using energy to rotate them. 2. S typhi and E. coli are examples of prokaryotes. What does the term ‘prokaryote’ literally mean? The term prokaryote means “before nucleus” because they have a nucleoid but no nucleus that encloses the DNA. 3. In the space below, draw and label (with names and functions), the structure of a generalized prokaryote cell. Include cell wall, plasma membrane, pili, flagella, nucleoid (naked DNA), ribosomes and a scale bar. The plasma membrane is a thin layer of phospholipids that controls entry and exit of substances in the cell, it can pump substances in our out and can also produce ATP. The cell wall is made of peptidoglycan and protects the cell and helps to keep the cells shape as well as preventing the cell from bursting. The cytoplasm is the fluid inside the plasma ribosomes. It carries out the chemical membrane that contains many enzymes and reactions of metabolism and is a jelly like substance. The nucleoid is the area of the cytoplasm that contains the DNA which is a very small amount. There are fewer ribosomes in it and less protein. The flagella is embedded in the cell wall and acts as a propeller to move the cell from one area to another using energy. Stephen Taylor http://sciencevideos.wordpress.com Bandung International School Essential Biology 02.2: Prokaryotes The ribosomes are small structures that synthesize proteins. The pilli are protein filaments that stick out from the cell wall, they can be pulled in or pushed out and are used to adhere one cell to another and are used when two cells exchange DNA. 4. Distinguish between gram-positive and gram-negative bacteria. Gram-positive bacteria has the ability to hold a purple stain while the gram-negative bacteria cannot hold a purple stain. 5. Through which method do prokaryotes divide and reproduce? Prokaryotes divide and reproduce by binary fission which produces two clones of the parent cells with the exact DNA. 6. Which structures can you identify in this diagram and EM image? You can identify (in order from top to bottom) the pilli, the nucleoid, the ribosomes, the plasma membrane, the cell wall and the flagella. Stephen Taylor http://sciencevideos.wordpress.com Bandung International School Essential Biology 02.2: Prokaryotes 7. Name the labeled structures in this transmission electronmicrograph: I -cell wall II- pilli III- nucleoid IV- cytoplasm 8. Calculate the magnification of the above image and the maximum length of the bacterium. 24/0.01 =2,400x Stephen Taylor http://sciencevideos.wordpress.com Bandung International School