Exam1key.07

Exam1key.07 - Bio 221 Short Answer 5 points each Name_KEY...

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Bio 221 Name__________ KEY ___________________ Exam 1 Short Answer. 5 points each. (None of the questions requires more than a 3 sentence answer.) 1. How does hydrogen bonding contribute to the formation of biological membranes? The hydrophobic effect - Water hydrogen bonds to the phospholipid head groups and to other water molecules, forcing the tails away from the water. The tails interact with each other to form the interior of the membrane. 2. Sketch the scheme of oxygenic photosynthesis. Show where the PMF and reducing power are formed. Label the reaction centers, show the ultimate electron donor, and show why it is called “oxygenic.” 3. List three features of bacterial endospores that allow them to be highly resistant to damage from harsh environments. For each feature, also state the harsh environment protected against. 1) SASP protect DNA against drying out and keep it metabolically inactive 2) cortex peptidoglycan keeps water out of spore core 3) protein coat protects against UV and chemical damage 4. Pseudomonas aeruginosa strain A is notorious for fouling swimming pool filters. However, a mutant variety (strain B) that does not have pili does not cause fouling. It is also much easier to decontaminate filters if they contain strain B than if they contain strain A. Explain these results. Without pili, strain B cannot attach to surfaces, so cannot initiate biofilm formation. Unable to form a biofilm, strain B will not secrete slime, and will not foul the filter. Also, without being in a biofilm, strain B will be much easier to kill than strain A, since organisms in biofilms are hundreds of times more resistant to chemical damage. 5. Most antimicrobial chemicals that affect the cell membrane work by dissolving the lipids. But a new antibiotic, daptomycin, is different. It has a hydrophilic core that can be reduced, and a hydrophobic exterior that can shuttle across the membrane. How does daptomycin kill a bacterial cell? The hydrophobic core of daptomycin is reduced (accepts electrons and protons) - from the proton gradient! It can carry them across the membrane since the outside of daptomycin is hydrophobic, and dissipate the proton gradient. So daptomycin kills cells by destroying the PMF. NADP → NADPH (reducing power) PMF PS2 PS1 H 2 O (electron donor) O 2 (“oxygenic”) (Other answers may be acceptable as well)
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Multiple choice. 75 points (1.5 points each). 1. Which of the following structures is found only in Bacteria? A. cell wall B. flagellum C. cell membrane D. nucleus E. lipopolysaccharide 2. Which of the following statements about viruses is true? A. They have an active chemical metabolism. B. Viruses that infect bacteria cannot infect humans. C.
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This note was uploaded on 04/07/2008 for the course BIOL 221 taught by Professor Walter during the Spring '08 term at Purdue.

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Exam1key.07 - Bio 221 Short Answer 5 points each Name_KEY...

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