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1 1 Lec 4 Macromolecules of Life Sept 1, 2008 Office phone: 231- 9708 LS-1 room 215 2 Deinococcus radiodurans : “Conan the Bacterium” Discovered in 1950 as scientists experimented with radiation as a means of food preservation Found in nature in extreme environments such as the North Pole as well as in common locations such as cow patties ¾ Can survive 3,000 times more radiation than a human can survive ¾ Survives at nuclear waste sites; assists in transforming nuclear waste to more disposable derivatives DNA Structure: redundancy – microbe can repair more than 200 double strand DNA breaks (most microbes can repair only a few double strand breaks) ¾ DNA organized in unique ways that prevents pieces of DNA broken by radiation from floating away ¾ 4 compartments with each containing one copy of DNA – once repairs have been made one damaged piece of DNA will migrate into an adjacent compartment where DNA sequences are compared between the two strands and additional repairs made if necessary ¾ Recent evidence suggests that resilience of the cell’s DNA repair proteins from oxidative damage by radiation maybe linked to presence of manganese ions which help prevent oxidative damage so proteins remain functional Out of the four copies of DNA present, there are always 2 or 3 tightly packed in a ring while the others can migrate and are open for DNA transcription 3 Covalent Bond Formation Nester et al, Microbiology: A Human Perspective Non-Polar Covalent bond formation Methane Sharing of electrons more or less Equally with other atoms
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2 4 Fig 3.1 Covalent Bonding Note the increase in the amount of energy necessary to break a triple vs a double bond. 3 ATP 16 – 24 ATP 5 Polar Covalent Bonds Nester et al 1. Unequal distribution of charge on the molecule results in polarity 2. The electrons are closer to the O than to the H atoms 3. The O is slightly negative and the H atoms are slightly positive 4. The opposite charges can form weak attractions
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This note was uploaded on 02/11/2009 for the course BIOL 2604 taught by Professor Sldaniel during the Spring '08 term at Virginia Tech.

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