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Micro Unit 5 of 14
Microbiology Study Guide for the CLEP Exam (Microbial Growth)
| Question | Answer |
|---|---|
| What are the six most abundant elements in microbes? | carbon, oxygen, nitrogen, hydrogen, phosphorus, and sulfer |
| What are the six most abundant types of molecules in a living bacterium? | water, protiens, RNA, carbohydrates, lipids, and DNA |
| What is the most abundant component of living bacteria? | Water |
| Define "autotrophs" | bacteria that can use carbon dioxide from the air as their carbon source |
| Define "heterotrophs" | bacteria that require their carbon source in an organic form (e.g. a sugar or amino acid) |
| Define "fastidious organisms" | bacteria that do not produce their own vitamins, usually because they can acquire them from the host |
| Define "auxotrophs" | mutant bacteria that are incapable of synthesizing an organic molecule, such as a vitamin |
| Define "photoautotrophs" | bacteria that derive energy from light |
| Define "halophiles" | bacteria that have adapted to growth in high salt areas |
| Define "methanogens" | bacteria that derive energy from CO2 and hydrogen to produce methane gas |
| Define "chemoautotrophs" | bacteria that derive energy from rocks or minerals rather than sunlight or organic materials |
| How are culture media produced? | agar is added to the culture broth, the entire mix is boiled to melt the agar, and the mix is poured into petri dishes where it solidifies as it cools to room tempurature |
| Distinguish defined media and complex media | The complete chemical contents of defined media are known because the are made of known chemicals. complex media includes some component that is from a biological source, animal or plant, in which some of the constituent chemicals are not known |
| Define "selective media" | selective media allow some organisms to grow while inhibiting others |
| Define "differential media" | differential media allow several kinds of organisms to grow, but the organisms appear differently; for example, the organisms might appear as different colors |
| How are pure bacterial cultures obtained? | by streaking a sample of bacteria onto a petri dish so that individual bacteria fall in well-isolated positions. The bacteria are grown into colonies so that individual colonies can be recovered as pure cultures |
| Name AND define the technique used to work with microbial cultures | Aseptic technique: handling samples so that they do not become contaminated from the outside |
| How does diffusion assist a cell nutritionally? | Because of Brownian motion, nutrient molecules are constantly moving, so they make contact with the bacterium, pass through the outer layers, and diffuse to the cytoplasmic membrane where the cell can transport them inside |
| What prevents a bacterial cell from rupturing due to internal osmotic or hydrostatic pressure? | The strength of the peptidoglycan layer. |
| Define "aerobes" | Bacteria that grow in the presence of O2 |
| Define "facultative anaerobes" | Bacteria that grow with or without O2 |
| Define "microaerophiles" | Bacteria that require reduced levels of O2 |
| Define "acidophiles" | Bacteria that grow in acidic environment |
| Define "anaerobes" | Bacteria that fail to grow in the presence of O2 |
| Define "alkalophiles" | Bacteria that grow in alkaline environments |
| Define "obligate halophiles" | Bacteria that cannot grow without salt |
| Define "psychrophiles" | Bacteria that thrive in cold temperatures |
| Define "mesophiles" | Bacteria that thrive in WARM temperatures |
| Define "thermophiles" | Bacteria that thrive in HOT temperatures |
| Define "thermoduric bacteria" | Bacteria that cannot grow in hot temperatures, but which are also not killed by hot tempuratures |
| Define "symbiosis" | A relationship in which different organisms grow with one another |
| Define "synergism" | A relationship in which the total growth of two or more organisms is more than would have resulted had they grown independently |
| Define "commensalism" | A relationship in which one organism helps another but is unaffected itself |
| Define "antagonism" | A harmful relationship between two organisms |
| Define "normal flora" | The native microbes that an individual harbors without causing disease |
| If one bacterium goes through four generations, how many bacteria will result? | Four generations of bacterium will produce sixteen bacteria |
| How long will it require ten bacteria to grow into more than one hundred bacteria if the doubling time is thirty minutes? | Two hours (1st 30 minutes, 10 doubles to twenty, at one hour there are 40, at an hour and a half 80, and at the 2 hour point there will be 160) |
| What does exponential growth mean? | Exponential growth meand that in every generation (or growth cycle) twice as many cells are formes. This is in contrast to adding one individual each generation |
| What are the four stages of cell growth? | Lag, Log, Stationary, Decline |
| What happens in the "Lag phase"? | Cells adapt to nutrients and prepare for cell division |
| What happens in the "Log phase"? | Cells double at regular intervals |
| What happens in the "Stationary phase"? | Cells maintain cell number but do not continue to grow because of nutrient depletion |
| What happens in the "Decline phase"? | Cells because to die because of lack of energy and nutrients |
| Define "autolysis" | The breakdown or an orgaism because of it's own purpose or mechanism |
| Why may a bacterium autolyse? | Some bacteria autolyse in order to spread and enhance growth of survivors |
| How can the number of viable cells in a culture be determined? | by performing dilutions at each time point, spreading aliquots on petri dishes, and countingthe number of colonies that grow |
| What is the meaning of CFU? | Colony Forming Unit, Each viable cell that can grow into a colony on a petri plate is a CFU. |
| What information does a turbimimetric assay yield? | A turbidimetric assay determines how many bacterial cells, living or dead, are present by use of a spectrophotometer. The number differs from CFU numbers, because CFU numbers only reflect viable cells. |
| Define "anabolism" | The use of energy and building blocks to make new cellular materials |
| Define "catabolism" | The breakdown of complex materials that cells use for making more cells. |
| Define "metabolism" | All the chemical processes occurring in a cell. |
| Define "enzymes" | Protien catalysts that cells use to convert some molecules into others |
| Some enzymatic reactions are controlled by negative feedback. What happens when the product of a given reaction becomes high in concentration? | When the cell is in an environment with ample amino acids, for instance, the cell gets the signal to save energy and not make its own amino acid. |
| What is activation energy? | Activiation energy refers to the amount of heat neccessary to cause a chemical reaction. Enzymes can dramatically reduce the activation energy. |
| List the 3 major pathways of catabolism in organisms | glycolysis, the Krebs cycle and electron transport |
| Name the starting compund of glycolysis | glucose |
| How many ATP's are produced by the following processes: a. glycolysis b. TCA cycle/electron transport | a: glycolysis produces two ATPs b: TCA cycle/electron transport produces thirty ATPs |
| Name the final electron acceptor in aerobic respiration | oxygen |
| Name two possible final acceptors in anaerobic respiration | nitrate and sulfate |
| List six commercially valuable products produced by fermentation | cheese, yogurt, vinegar, acetone, butyl alcohol, beer and wine |
| Name three types of macromolecules for which building blocks, or precursor molecules, are required | DNA, RNA, and amino acids |
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