MIC 102 UC Davis Exam Questions with Correct Answers

MIC 102 UC Davis Exam Questions with Correct Answers What is a microbe? - Answer-"free-living organisms so small that they are only visible under the microscope" Are their exceptions to the definition to microbes? - Answer-Yes, some microbes are hug, not free-living, or organisms What is LUCA? And how does it relate to microbes? - Answer-Last Universal Common Ancestor is thought to be what all organisms have evolved from over 4 billion years. Specifically though, the LUCA is thought to be a microbe. Can determine relationships from the small subunit (16S) rRNA gene Name three characteristics of LUCA - Answer-The LUCA and common species today share 1) DNA as genetic material 2)Protein and RNA 3) Lipid Membrane Explain how the three domain tree is different from the ring of life. - Answer-The three domain tree groups the organisms into their three appropriate lineage (Bacteria, Archaea, and Eukarya), Each developing linearly and separating with different adaptations. Whereas a ring of life includes lineage from lateral gene transfer - the organisms are really intertwined with one another and creating new species. What are the pros and cons for microbes being small? - Answer-Pro: microbes can maintain a high surface-to-volume ratio to maximize nutrient exchange. Con: Easy targets for larger microbes/species. How does cell shape influence cell metabolism? - Answer-High surface are to volume ratio can increase metabolism of nutrients, which will in affect increase growth and reproduction. Compare and contrast the general structures of archaea, bacteria and eukaryotic bacteria. - Answer-Prokaryotics: no nucleus bacteria: have rod shaped, sphere shaped, and helixcal shapes archaea: have sphereical and rod shaped organiams Eukaryotes: have fungi, slime molds mircroscopic algae, and protozoa...Organelles include nuclus, mitcochondria, and chloroplast. Explain why cells must have a membrane - Answer-To make a selective barrier for chemical diffusion and allow the primitive biological molecules to replicate and catalyze reactions in a protected , favored environment. Provide evidence for two cases of convergent evolution between bacteria and archaea cell exteriors. - Answer-1. flagella, but they differ in their assembly and structure. 2. Pili: filamentous appendages, which will attach to host cells, transfer proteins and nucleic acids to other cells and motility. Why must bacteria cells be stained to cell them? - Answer-Because it is hard to contrast the colorless cell and can;t be seen readily under the microscope. gram postive stains purple and gram negative will stain red. List advantages and disadvantages of light microscopy, fluorescence microscopy, and electron microscopy. - Answer--Light microscopy: pro can see the small microbes and structural makeup, cons need to gram stain the bacteria to differentiate the species, which will kill them -fluorescence microscopy: pro can target components in the cell or tissues by using dye and emitting light at specific wavelength, con ? -electron microscopy: pro can determine fine structural detail to make a 3D picture, con:distort structure because shot with electron/proton. Compare and contrast the cell envelopes of gram negative and gram positive bacteria. - Answer-Gram Positive: have a thick cell wall/peptidoglycan layer then a cell membrane. Have teichoic acid and lipoteichoic acid. Gram negative: have two outer membranes with a thin cell wall/peptidoglycan layer in the middle. Have lipopolysaccharide What are some roles of the bacterial murein cell wall? - Answer-1. thicker walls limits the passage of hydrophobic compounds. 2. Act as amour, and structural support. Differences and similarities in the bacterial and archaeal cell membranes. - Answer-The bacterial phospholipid bilayer has ester linkages, and two phospholipids (hydrophillic heads and hydrophobic tails with two fatty acid chains). The archaeal cell membrane can have either a phospholipid bilayer or monolayer connected by ether linkages. The monolayer here however, with have 40 carbon isopreniod groups(one straight chain from the outsides) Predict mechanisms that could allow gram positive bacteria to become resistant to penicillins. - Answer-Gram positive bacteria maybe could have developed thicker peptidoglycan layers, or have developed another enzyme that cross-links the layers together. Differences and similarities in the bacterial and archaeal cell wall. - Answer-Archaea do not have murein cell walls and protect themselves with just an S-layer. Cell walls of archaea could be made up off pseudomurein (made up of polysasccarides or a type of peptidoglycan.) - these will also stain gram positive. Importance of hopanoids for bacteria. - Answer-Hopanoids are unsual lipids made by only bacteria. These add rigidity and stability to the cell membrane. These are useful for detecting bacteria. How can acid-fast bacteria can withstand membrane-damaging chemicals? - Answer- The cell walls contains large amount of waxes called mycolic acids (made of long, complex fatty acids). This robust, thick wall is hydrophobic, which are impervious to harsh chemicals/acid/soap. Con of this is that it slows down the nutrient uptake and growth. Why would a bacteria or an archaea invest in making an S-layer when it already has a cell envelope? - Answer-The crystalline surface layer is anchored to murein cell wall of gram positive, to the out membrane of gram negative and to archaeal directly to cell walls or to cell membrane. The purpose is to act as an external layer of protection and can recrystallize on their own (self-assemble). Describe three main functions of the structure and function of bacterial flagella. - Answer-Structure includes a basal body(complex structure. 15 proteins to make rings and a rod), a hook ("joint", made of a single protein, then a filament (helical, hollow, and singel protein). They are synthesized from the bottom to top (body to filament. There function is used for locomotion