BIO 308: Exam #3 Previous Years

A bacterial species uses light for energy, gains electrons from the photolysis of HS and uses organic materials as a source of carbon. What is the metabolism of this organism?

Photoheterotroph

Reduction potential is defined as:

The tendency for a compound to accept electrons

What could be a source of electrons by a chemolithotroph for energy?

NH3 and H2

What is a chemical pair that provides a metabolic strategy that is an example of anaerobic lithotrophy?

Electron donor H2; electron acceptor SO42-

Chemolithotrophs generally derive _________ ATP from oxidation of inorganic substrates because the reduction potentials of those substrates are much more ________ than the reduction of organic substrates

Less; positive

Microorganisms in the human colon are more often being described as mutualistic with human hosts rather than communalistic. Why has this change in the definition of a symbiotic relationship occurred?

As we learn more about the ecology of the human microbiome, we recognize our dependence on these organisms for immunity, vitamin production, and other essential processes

What metabolism would be favored when there is a lack of exogenous electron acceptors

Anaerobic Fermentation

You have created a small-scale ecosystem in your laboratory that exactly mimics the nitrogen cycle in nature. You accidentally release a virus into your laboratory that inserts itself into (and inactivates) the gene for nitrogenase. What would you expect to happen in your ecosystem?

Atmospheric nitrogen would increase and soil nitrates would decrease

In a redox reaction involving NAD+/NADH and pyruvate, ________ will be the electron donor and _______ will be the electron acceptor

NADH; Pyruvate

What is the correct redox reaction when the redox pair pyruvate/lactate reacts with O2/H2O?

Lactate + O2 → Pyruvate + H2O

Which feature of anaerobic and aerobic respirtation is ALWAYS DIFFERENT between the two catabolic strategies?

Final electron acceptor

What is the fate of pyruvic acid in an organism that uses fermentation as its sole source of ATP production?

It is reduced to another compound such as lactic acid

Describe how the electron transport system (ETS) functions:

Electron transport releases energy, which is used to pump protons across the cell membrane

What is labeled C?

An anaerobic lithotroph

For the carbon cycle, what bacteria could carry conversion E?

A methane-oxidizing bacterium

Why is nitrogen the limiting nutrient in most ecosystems?

It requires large amounts of energy to be fixed

Adding organic carbon compounds to an ecosystem would most likely stimulate the growth of?

Chemoorganotrophs

What is the order in which marine dead zones are formed?

1. An influx of nitrogen occurs

2. Autotrophic bacteria grows

3. Heterotrophic bacteria grow

4. Oxygen level greatly decrease

Microbe-associated molecular patterns (MAMPs) include:

LPS, teichoic acids, and peptidoglycan

How do denitrifiers obtain energy?

using nitrate as a terminal electron acceptor in anaerobic respiration

Why are nitrogen-fixing bacteria often required to support other growth in a diverse ecosystem?

Nitrogen fixing bacteria bind free nitrogen into nitrogen compounds that plants can use

Which elemental cycle is entirely dependent upon the action of microbes?

Nitrogen cycle

Mucous membranes are quite thin and fragile. how can such delicate tissues provide defense against microbial invaders?

the mucous physically traps microbes, contains a variety of antimicrobial chemicals, and is shed constantly, along with the outermost layers of cells

A Chemoorganotroph and a photoautotroph in the same environment would NOT compete for:

Carbon and oxygen

Which catabolic process does not require oxygen but can occur in the presence of oxygen?

Fermentative catabolism

The metabolic process of denitrification reduces ____.

Reduces NO3-