Exam 2: Topic 11 Flashcards
Differentiate between autotroph (and photo- and chemo-) and heterotroph with
respect to source of energy and source of carbon. Which nutritional strategy
applies to pathogenic microbes?
v Autotroph: convert inorganic carbon dioxide (CO2) into organic carbon compounds
v Photoautotroph: light & inorganic
v Chemoautotroph: chemical & inorganic
v Heterotroph: rely on more complex organic carbon compounds as nutrients; these are provided to them initially by autotrophs.
Distinguish between the following terms: obligate aerobe, obligate anaerobe and
facultative anaerobe. List the energy pathways that each type of microbe uses.
v Obligate aerobe: require O2 for life. Aerobic respiration.
v Obligate anaerobe: O2 is toxic. Anaerobic respiration
v Facultative anaerobe: Prefer O2 (aerobic respiration), but can survive without it (fermentation).
What is anaerobic respiration? How does anaerobic respiration differ from aerobic
respiration? What are the consequences in terms of how much ATP is generated
per glucose molecule?
Anaerobic differs from aerobic due to the final electron acceptor being NO3-, SO4-2, Fe+3, CO2 as opposed to oxygen, respectively. Also, the amount of ATP generated in aerobic respiration total 38 molecules (2 for glycolysis, 2 for Krebs cycle, and 34 for ETP) as opposed to a smaller amount for anaerobic respiration totaling 1-32 molecules (2 for glycolysis, 2 for Krebs cycle, and 1-32 for ETP/chemiosmosis).
Some pathogenic bacteria are obligate anaerobes. Name two pathogens that are obligate anaerobes and how their intolerance of oxygen contributes to the disease process
Clostridium tetani and Clostridium perfringens; require oxygen free environments to survive and can cause infections in areas within the body with limited oxygen access
Define ‘fermentation’. How does it differ from anaerobic respiration?
v An enzyme catalyzed, metabolic process whereby organisms convert starch or sugar to alcohol or an acid anaerobically releasing energy
v In the absence of O2, NADH is full in its reduced state and no oxidized NAD+ is available to facilitate glycolysis.
v The goal of fermentation is to oxidize NADH–>NAD+ so that glycolysis can continue and the cell can get 2 ATP per glucose
v Fermentation only utilizes the glycolysis stage of cellular respiration, producing a limited amount of ATP and organic byproducts like alcohol or lactic acid, whereas anaerobic respiration encompasses the entire cellular respiration process, including the electron transport chain, using a different final electron acceptor than oxygen to generate more ATP
What conditions promote fermentation? Why is fermentation NOT a viable
strategy as an exclusive pathway for motile organisms such as animals (that have
a high energy need)?
a. The cell lacks a sufficient amount of any appropriate, inorganic, final electron acceptor to carry out cellular respiration (O2).
b. The cell lacks genes to make appropriate complexes and electron carriers in the electron transport system.
c. The cell lacks genes to make one or more enzymes in the Krebs cycle.
○ Fermentation only yield 2 ATP molecules per glucose during glycolysis.
Briefly outline the role of Lactobacilli and Saccharomyces in sourdough bread.
Which species makes the acid, which species makes CO2?
v Saccharomyces is used to make bread, because during alcoholic fermentation the yeast produces CO2 which increases the volume of the bread.
v Lactobacilli is used in sourdough bread, because the lactic acid fermentation pathway generates the acid portion of the bread giving it the acidic sour flavor that is iconic for sourdough.
