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10 Cards in this Set
- Front
- Back
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What’s a pure culture? |
A culture containing cells of only one species |
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How are pure cultures obtained & maintained? |
Pure cultures are isolated using serial dilution, followed by streak plating, or pour plating allowing growth that can be isolated further. They’re maintained by subculturing & isolating the culture from possible contamination |
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Defined media is? |
Culturing medium of which the exact chemical composition is known |
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How can oxygen be essential for one group of organisms & yet be a a fatal toxin for others? |
O2 is an important e- acceptor for most organisms b/c of this, it’s an important part of glycolysis & energy generation. However, in organisms lacking catalases & dimutases to remove superoxide it’s fatal as a superoxide is very e- hungry that disrupts the flow of e- ions. |
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How can aerobes protect themselves against toxic oxygen products? |
Most toxic O2 products like free radicals & superoxides are neutralized by antioxidants. The antioxidant donates 1 e- to free radical in order to stabilize them & oxidize itself. It’s then no longer harmful |
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Why is nitrogen essential? |
-It makes up about 14% of the dry weight of microbial cells -Constitutes about 79% of the atmosphere -contained in the amine group of amino acids & as part of nucleotide bases |
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Describe the key events in DNA replication. |
1. Helicase & other enzymes unwind parental DNA strand 2. Proteins stabilize unwound parental DNA 3. Leading strand is synthesized continuously by DNA polymerase 4. Lagging strand’s synthesized discontinuously 5. RNA polymerase synthesizes a short primer which is then extended by DNA polymerase 6. DNA polymerase digests RNA, replacing it w/ DNA 7. DNA ligase joins the discontinuous fragments of lagging strand |
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DNA replication in a prokaryotic cell |
-occurs in the cytosol -large okazaki fragments -faster replication process -DNA polymerase I removes RNA promer |
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DNA replication in a eukaryotic cell |
-occurs in nucleus -multiple origins of replication -small okazaki fragments DNA polymerase B (beta) removes primwr DNA gyrase is required |
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How does RNA know where to begin transcription? |
A polypeptide subunit of RNA polymerase called the sigma factor is necessary for recognition of the promoter RNA polymerase unzips & unwinds DNA |
