MIC 102 Final Exam Questions with Correct Answers

MIC 102 Final Exam Questions with Correct Answers What are the different types of microscopy and staining and when are they used? - Answer-Types of microscopy include: light microscopy- used primarily to get an idea of the form of the bacteria, used in combination with staining to get an idea of Gram positive and Gram negative protein. Green fluorescent is used to observe cell occurrences like binary fission and movement of proteins. Electron microscopy is very detailed at getting an idea of what is occurring inside and outside of the cell (when frozen and cracked in half to see inside) Gram + turns out purple, Gram - is red. Crystal violet essentially gets stuck in the thicker cell wall of Gram +, and iodine is used to bind it, alcohol is used to rinse stain, so if its Gram- it will rinse right out. Safranin is red and used a counter stain so anything left with just red is Gram-. This is used in conjunction with light microscopy. List and outline the differences between Gram positive and Gram negative bacteria, structurally. Explain what their independent structures are functional for. Explain some unique types of outer membranes and archaea cell wall structure, too. - Answer-Gram-: Has thin cell wall with outer membrane. LPS, which acts as an antigen towards the host cell, is protective for the bacteria-- makes it difficult to be consumed by host phagocytosis. Has porins in the outer membrane available as transport channels- allows ionically charged molecules and sugars into the periplasm- unlike the phospholipid bilayer in the inner membrane. Contains lipoproteins which attach the outer membrane to the cell wall. Gram +: has a very thick peptidoglycan cell wall. Both - and + cell walls are made of murein layers. Teichoic acids are in the Gram + wall, which add stability and make the cell wall more rigid and can also be antigenic. Also contains lipo-teichnoic acidsattaches to the inner membrane and holds everything together-goes the furthest in. Both are able to have capsules, which helps for adherence and against desiccation and phagocytosis. Mycoplasma don't have a cell wall. Additionally, acid-fast envelopes are present on mycobacterium, are very waxy and hard to get rid of. Made of waxes called mycolic acids. Archaea have a crystalline S-layer (sometimes bacteria have it). Its attached to the cell wall of the archaea- also made of monomers linked together to make crystalline plate. Helps surface adherence and is protective against other microbes and host defenses (for the archaea). Archaea have ether bond linkage instead of ester (like bacteria), and their cell walls made of isoprenoids which are functioning in place of lipoproteins. Isoprenoids have a different structure from fatty acids that makes them more stable at high temperatures. Explain how hypertonic, isotonic and hypotonic solutions affect a cell- and the role that porins and channels play in mediating them . - Answer-In hypertonic solutions, the cell shrivels, and hypotonic is when there is a lot of osmotic pressure within the cell so it expands. Isotonic can be thought of as an equilibrium between the solutes outside and within the cell. Porins and channels help allow ions in and out of the cell, help lessen the steepness of the osmotic gradient. Can help establishing and utilizing electron transport gradient. Explain the organization of the prokaryotic cell interior- throughout the nucleoid and cytoplasm. - Answer-Essentially the nucleoid is almost distributed throughout the cytoplasm and there aren't distinct areas. This is because translation and transcription occur simultaneously and ribosomes are able to roam about. It is very tightly packed. There is not a high level of organization. Describe all the specialized compartments and "non-organelles" in prokaryotes. - Answer-Nucleoid: The DNA is compacted with proteins in a bottle-brush formation with local topical twisting, slightly negative. Cytoplasm: distributed with the nucleoid. Ribosomes float freely about the cell, but mostly at the cytoplasm-nucleoid interface. Carboxysomes: fixate CO2, have a protein shell for gas exchange, enhance the function of RuBisCo in some way (not clear how). Enterosomes are in heterotrophic bacteria and do not contain RuBisCo. Gas vesicles: protein shells that act as buoys and block water from entering the area, allowing the cell to float close enough to photosynthesize. Thylakoids: Do photosynthesis, have the lumen and the stacks for it. Magnetosomes: contain Fe+ crystals that interact with earths pole and move the bacteria around and attach to cell membrane. Storage granules: Store materials when the cell is hungry and needs a snack for later. Allows the cell to continue taking in nutrients beyond the concentration in the environment because it lowers their concentration inside the cell, thus changing the concentration gradient. Explain how binary fission works in bacteria. - Answer-First a cell, has a DNA replicated which is shoved to the poles of the bacterial cell. This signals the FtsZ to begin. FtsZ ring forms and operates binary fission. Min proteins prevent it from polymerizing towards the poles of the cell. MinD polymerizes at the ends and binds MinC which depolymerizes FtsZ and then MinE prevents MinC and D from polymerizing the midline. Describe the different types of mediums used to grow cells and their significance. - Answer-Rich medium is "a feast" and defined concentrations aren't known, but almost any bacteria should grow on it and in it for it is plentiful; therefore rich medium is also an undefined medium. Defined mediums are mediums with every component and its quantity is known in the medium. Used to figure out different aspects of bacterial growth (what they need to grow per bacterial species) can take things away to see if growth stops of continues as per specific variables. Minimal medium only contains absolute necessary components required for growth and nothing extra. What occurs in the 3 phases of growth? Lag, exponential and stationary. - AnswerDuring lag phase, adapting to new environment so growth is slow but still metabolically active. Exponential is when the cells are actively dividing. Stationary is when the growth is stalled due to build up of toxic waste or lack of nutrients- this is when endospore formation occurs, only for Firmicutes., also more mutations occur during this time. . And then there is death, which is self explanatory. Describe the 4 lab methods we use to measure cell growth. - Answer-Optical density: measures turbidity, measures the amount of light reflected which shows the amount of cells within the culture- but cannot differentiate between dead or alive cells. Colony counting:where they grow colonies on a medium, and only counts live cells and dilution intervals are used to count the number of cells that were alive in the original culture based off of each colony. Good for viable count. MOST accurate way to count the number of cells that are dividing. Flow cytometry: fancy lazer one. Uses fluorescent to track cell. Can simultaneously count and analyze cell characteristics of individual cells. Chemostats: used to maintain exponential growth phase for growing cells. (maintains the hemocytometer count) Hemocytometer: more accurate way to measure the number of cells per milliliter in culture, the grid is used to count cells in each grid. Used to extrapolate data for a known volume. Describe DRT and Binary Fission calculations, as well as generation times. - AnswerDRT, the rate at which you decrease a population by 1log a log being the extermination of 90% of the population. If you want to exterminate all of the population- you have to go one DRT below log 0. Generation time calculations To calculate the number of generations, n = (logN - logN0)/0.301, and generation time, g = t/n Generation time is about exponential growth, the amount of time it takes to double a population. The 4 stages of cell metabolism and the types of reactions that occur in all of them . - Answer-Fueling productsbuilding blocksmacromoleculesstructures