BIOL 238 Review 2009
This page provides review questions for BIOL 238 (Spring 2011). Answers may be posted by students.
Species to know
For each species of bacteria or archaea, state one or two broader categories of organism (such as gram-positive endospore-forming bacteria), the type of genome, type(s) of metabolism, habitat, and disease caused (if any).
Mycoplasma pneumoniae sp.
1. ATP and NADH are both energy carriers: What are the advantages of using one over the other?
2. When cells need to make glucose (gluconeogenesis), they "reverse glycolysis" because most steps are reversible. However, there are a couple of steps that are not reversible. How do you think they get reversed for gluconeogenesis?
3. There are 3 main pathways to form pyruvate- EMP, ED and PPS. How and why might a cell switch among these?
4. Explain why most soil bacteria grow using energy-yielding reactions with very small delta-G.
5. Why are glucose catabolism pathways ubiquitous, despite the fact that most bacterial habitats never provide glucose? Explain several reasons.
6. In glycolysis, explain why bacteria have to return the hydrogens from NADH back onto pyruvate to make fermentation products. Why can't NAD+ serve as a terminal electron acceptor, like O2?
7. Why do environmental factors regulate catabolism? Give examples. Why are amino acids decarboxylated at low pH, and under anaerobiosis?
8. Why does catabolism of benzene derivatives yield less energy than sugar catabolism? Why is benzene-derivative catabolism nevertheless widespread among soil bacteria?
1. Explain how bacteria and archaea switch among various electron acceptors depending on environmental conditions.
2. Explain how cell processes such as ATP synthesis can be powered by either the transmembrane pH difference or by the charge difference across the membrane. Which form of energy is likely to be used at low external pH? At high external pH?
3. For phototrophy, discuss the relative advantages and limitations of using PS I versus PS II.
4. What environments favor oxygenic photosynthesis, versus sulfur phototrophy and photoorganotrophy? Explain.
5. Explain why certain lithotrophs acidify their environments, to more extreme levels than fermentation. What are some practical consequences for human industry?
6. Is it surprising that an organism may switch between lithotrophy and organotrophy? What enzymes would have to be replaced, and what enzymes could be used in common for both kinds of metabolism?
7. What kind of environments favor methanogenesis? Why are methanogens widespread, despite the low delta-G of their energy-yielding metabolism?
1. Why does biosynthesis need both ATP and NADPH? Why couldn't biosynthetic pathways use just ATP, or just NADPH?
2. Compare and contrast fatty acid biosynthesis and amino acid biosynthesis. Which pathway requires more reduction? Which requires a greater number of different enzymes? Why?
3. What forms of nitrogen are available to microbes for assimilation? When fertilizer is spread on farmland to nourish crops, what problem is caused by microbes? What are the other oxidized forms that bacteria and plants take up and reduce to ammonia and ammonium ion? What about N from reduced organic compounds?
4. How are the pathways of amino acid biosynthesis organized? What common routes flow from which core pathways?
5. How and why do bacteria make "secondary products"? What are their functions?
6. How can we manipulate bacterial secondary product formation to develop new pharmaceutical agents?
1. Explain why the first kinds of metabolism on Earth involved electron donors from the sediment reacting with electron receptors from above. What geolotical and outer-space processed generated these electron donors and electron acceptors?
2. What evidence supports the "RNA world" aspect of the origin of life? What are evolutionary and medical implications of the RNA world model?
3. What is our modern definition of a microbial species? Explain the strengths and limitations of defining microbial species based on common ancestry of DNA sequence.
4. Explain the evolutionary origins of mitochondria and chloroplasts. What evidence do we see in the structures of modern microbes?
5. What is a virulence gene? How do virulence genes evolve? How can we analyze the relationship between virulent and nonvirulent strains of a bacterium?
1. Compare and contrast the major divisions of bacteria. State an example of a species of each major division.
2. Explain an example of a major division of bacteria whose species show nearly uniform metabolism but differ widely in form. Explain a different example of a division showing a common, distinctive form, but variety of metabolism.
3. Compare and contrast three different types of phototrophy found in bacteria.
4. Explain the pathology of three different gram-positive pathogens.
5. Explain two different examples of bacterial-host mutualism.
6. Identify these kinds of bacteria based on their descriptions:
a. This bacteria is irregularly shaped with peptidoglycan cell walls and a cytoskeleton containing tubulin (previously thought to only be present in Eukaryotes). They are heterotrophs living in variable environments that are usually low in salt, and most are oligotrophs.
b. This bacteria has a nucleus similar to that of a eukaryotic organism. It is most notable for its unique membrane structure. It has multiple internal membranes, with a double membrane functioning to surround the nucleoid. What am I?!
c. Bacteria in this group are filamentous photoheterotrophs. In the presence of oxygen they conduct nonphotosynthetic heterotrophy. They can be found in microbial mats together with thermophilic cyanobacteria. Some species contain chlorosomes. They are also known as green nonsulfur bacteria.
d. These bacteria are photolithotrophs that deposit sulfur on the cell surface. They use H2S as an electron donor and are known as green sulfur bacteria. These bacteria also live in strictly anaerobic conditions below the water surface.
e. This bacterium is gram positive but has permanently lost its cell wall and S-layer due to reductive/degenerative evolution. It also has the smallest genome(580 kbp) and it is parasitic.
f. This bacterial species ferments complex carbohydrates and serves as one of the major mutualists of the human gut. Has a Gram-negative structure and is an obligate anaerobe.
g. These bacteria are deep branching and come in a multitude of forms. They can be found living independently or in colonies. Often times, these different forms allow them to fix nitrogen. While these organisms can be found in both aquatic and terrestrial habitats, many species contain gas vesicles to maintain a favorable position in the water column.
1. Compare and contrast the different major groups of archaea. Which ones grow in extreme heat or cold? Extreme salt? Produce methane?
2. Explain how archaea growing in extreme environments require specialized equipment for study.
3. What kinds of archaea grow in "average" environment such as the soil? Or an animal digestive tract?
4. Archaea identification: What is it?
These archaea were once thought to be extremophiles, but it turns out they are the most abundant archaea in the ocean. Nonetheless, the thermophiles responsible for giving this false impression are found at temperatures of 113degrees. Others are found living in sulfuring springs. When gram stained, these archaea appear gram-negative.