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Microbiology 201 Exam 2 Study Guide Answers

by: Julianna Sickafus

Microbiology 201 Exam 2 Study Guide Answers MICRB 201

Marketplace > Pennsylvania State University > Microbiology > MICRB 201 > Microbiology 201 Exam 2 Study Guide Answers
Julianna Sickafus
Penn State

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I went through and answered (to the best of my ability) the questions from the study guide posted my the instructor. Since we did not take notes on the last section, I will upload the answers to th...
Introductory Microbiology
Dr. Steven Keating
Study Guide
DNA, transcription, nucleic acid, metabolism, anabolism, catabolism, glycolysis, krebs cycle, Krebs/TCA Cycle respiration aerobic anaerobic proton motive force ATP synthase chemolithotrophy, fermentation, anaerobic respiration
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This 5 page Study Guide was uploaded by Julianna Sickafus on Saturday October 8, 2016. The Study Guide belongs to MICRB 201 at Pennsylvania State University taught by Dr. Steven Keating in Spring 2016. Since its upload, it has received 102 views. For similar materials see Introductory Microbiology in Microbiology at Pennsylvania State University.

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Date Created: 10/08/16
Microbiology 201 Study Guide Answers Exam 2 Environmental Factors and Growth 1. An extremophile is an organism that can grow under extreme conditions such as temperature, pH, or pressure 2. Cardinal Temperatures Minimum- the lowest temperature below which a microbe will not grow Optimum- best temperature for growth Maximum- the highest temperature above which a microbe will not grow 3. Both a psychrophile and a thermophile can thrive in environments with extreme temperatures. A psychrophile grows optimally in environments with temperatures around 15C and a thermophile grows optimally in environments with temperatures 55C and higher. A psychrophile could be found deep in the ocean or in glaciers. Thermophiles could be found in hot springs. 4. Osmotic lysis and plasmolysis are the exact opposite. Osmotic lysis would occur if a cell were in an environment that had a lower solute concentration inside the cell. This kind of solution is called a hypotonic solution. To correct the solute imbalance, water would flow into the cell in greater amounts than the water flowing out. This net influx of water into the cell would cause it to swell and burst. On the other hand, plasmolysis would occur in an environment with a higher solute concentration outside the cell. This environment is called a hypertonic environment. Water would follow the solute concentration and leave the cell causing it to shrivel. 5. A halophile is an organism that can tolerate high salt concentrations whereas an alkalophile is an organism that could tolerate a basic environment. High salt refers to the concentration of solute, whereas an alkaline environment would have a high concentration of molecules to make a solution basic, such as OH-. 6. Oxygen is not required for the growth of all microbes. In fact, for some microbes, oxygen is actually toxic. These organisms are called anaerobes. Metabolism (General Features) 1. An endergonic reaction is one that requires energy input. Biosynthetic reactions are examples of endergonic reactions. An exergonic reaction is one that releases energy; therefore, catabolic reactions are exergonic. 2. NAD+ and FAD can act as electron/energy carriers and can pass off that energy. 3. An oxidant is an electron acceptor. A reductant is an electron donator. A redox couple is an oxidant and its corresponding reductant. For instance, NAD+ is the oxidant and NADH would be the reductant. The standard reduction potential (E )0is the equilibrium constant of the redox couple. Redox couples with more negative E val0es donate electrons to couples with more positive values. In this process, energy is generated and can be captured to synthesize ATP. 4. An enzyme is a biological catalyst that increases the rate of reaction by lowering the activation energy of a reaction. Many are proteins; however, there are some that are RNAs or a combination of protein and RNA. 5. Activation energy is the energy required to form the transition state intermediate. 6. Competitive inhibitors and non-competitive inhibitors bind to different sites on the enzyme. Competitive inhibitors bind at the active site of the enzyme thus inhibited the substrate the enzyme acts on directly. Non-competitive inhibitors bind at a site different than the active site. This action causes a change in the enzyme’s shape which prohibits the substrate from binding. Catabolism 1. Anabolism: the synthesis of complex macromolecules and cells from simpler precursors -> building up Catabolism: the breakdown of complex to simpler products -> breaking down Amphibolic: pathways that can function anabolically or catabolically 2. The 2 main functions of catabolic reactions are to oxidize substrates to produce energy and to break down substrates to produce smaller substrates for biosynthesis. 3. The key substrates for glycolysis are 1 glucose molecule (or one of its derivatives) and 2 ADP and 2 NAD. The key products are 2 pyruvate molecules, 2 ATP, and 2 NADH. 4. The Pentose Phosphate pathway is considered to be an important biosynthetic pathway because it provides the main reductant for biosynthesis, NADPH. 5. The substrate pyruvate from glycolysis is converted into acetyl coenzyme A (by decarboxylation of pyruvate) before it joins the TCA cycle. 6. Substrate level phosphorylation, oxidative phosphorylation, and photophosphorylation all generate energy in the form of ATP, though in different amounts. Substrate level phosphorylation generates the least amount of ATP. Substrate level phosphorylation and photophosphorylation can both occur without the presence of oxygen and reduce electron carriers such as NAD+ or NADP+. Oxidative phosphorylation requires oxygen and uses electron carriers to transfer an electron which generates energy. 7. Though the TCA cycle does generate 1 ATP, that is not its main purpose. It also generates 3 NADH, 1 FADH , a2d2 CO . 2 8. The purpose of the electron transport chain is to carry electrons though many redox reactions which generate energy. This energy is used to pump H+ protons against their concentration gradient to the outside of the cristae membrane (for eukaryotes). These ions can then travel back through a specific protein channel into the cell. This movement generates energy which can be used to do work. In this case, the work done is ATP synthesis. 9. Respiration is the cell’s mechanism to produce ATP when oxygen is present. The electron transport chain can be used (for aerobic cells) when oxygen is present. Fermentation is an aerobic cell’s mechanism to produce ATP when oxygen is not present. This pathway produces much less energy and generates a lot of incompletely oxidized wastes. 10. Anaerobic respiration is only different from aerobic respiration because the final electron acceptor at the end of the electron acceptor chain is a substrate other than oxygen. It is less efficient than aerobic respiration because oxygen is very electronegative, making it an excellent electron acceptor. Fermentation is less effective than anaerobic respiration because it is a process that only occurs in aerobes when oxygen is not present. Thus, fermentation is a temporary “back-up” process until oxygen is available again. 11. Molecules other than glucose can be fed into the pathways described. Carbohydrates other than glucose can be broken down via hydrolases and phosphorylases to smaller monosaccharides which can be used in glycolysis. Lipids can be broken into its constituent glycerol and fatty acids. Glycerol can be used in glycolysis and the fatty acids can be converted to acetyl coA to be used in the TCA cycle or reduced into electron carriers to be used in the electron transport chain. Lastly, proteins can be broken into amino acids which, once deaminated, can be used in the TCA cycle. 12. Cyclic photophosphorylation produces only ATP whereas non-cyclic photophosphorylation generates ATP, NADPH, and O . 2 Anabolism 1. The main reductant used in anabolic reactions is NADPH. 2. The Calvin Cycle is the carbon fixation pathway that converts inorganic carbon to organic carbon to produce carbohydrates. Though it occurs during the light independent reactions of a cell, it requires the ATP and NADPH generated from the light reactions. 3. Both of these processes occur during anaerobic respiration. Dissimilatory reductions yield energy and their products are excreted from the cell. Assimilatory reductions use energy and their products are incorporated into the cell for use. + 4. The function of the enzyme nitrogenase is to reduce N to 2H . 3 5. Transaminases catalyze the transfer of the amine group from glutamic acid to other carbon skeleton to generate other amino acids. 6. An anaplerotic reaction is a reaction that generates intermediates that need to be replenished for biosynthesis. The glycoxylate cycle is an example of an anaplerotic reaction. It is a version of the TCA cycle that is modified to bypass the decarboxylation steps so that carbon is not lost as CO 2 Nucleic Acids 1. The parts of a nucleotide are a 5C sugar (either ribose or deoxyribose), a phosphate, and a nitrogenous base. 2. A nitrogenous base plus a sugar is a nucleoside. A nucleotide is a nucleoside plus a phosphate. 3. DNA contains a different sugar than RNA. DNA contains deoxyribose while RNA contains ribose. Also, DNA contains the bases adenine (A), guanine (G), cytosine (C), and thymine (T). In RNA, thymine is replaced with uracil (U). 4. Phosphodiester bonds are used in nucleic acids to hold together the sugar phosphate backbone. Hydrogen bonds are used to hold together nitrogenous bases on opposite strands. 5. A collection of gene constitutes a chromosome. A collection of chromosomes constitutes a genome. 6. Most prokaryotes have a single chromosome that is circular, supercoiled, and confined to the nucleoid. Eukaryotes have more than one chromosome. These chromosomes are linear and are found in the nucleus. 7. Semiconservative replication refers to the fact that when DNA replicates itself, each new copy of DNA contains an original parent strand and a newly synthesized daughter strand. 8. DNA polymerase: synthesizes daughter strands of DNA during replication DNA helicase: unzips H-bonds between base pairs so DNA polymerase has access to template strand Single-strand DNA binding proteins (SSBs): once strands are separated by helicases, SSBs keep the strands, that may otherwise H-bond with complementary pairs on its own strand apart. Topoisomerase: relieves the tension of the over winding of DNA ahead of the replication fork introduced by the unzipping action of helicase. DNA primase: lays down an RNA primer that initiates the action of DNA polymerase DNA ligase: seals nicks in sugar phosphate backbone 9. The leading strand synthesizes continuously in the 5’ to 3’ direction. Since the lagging strand has the opposite orientation, it does not synthesize continuously and must be made in short fragments called Okazaki fragments. Okazaki fragments are eventually joined together by DNA ligase to complete the lagging strand. Gene Structure and Transcription I will post the answers to this section after the notes on Monday.


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