Week 2: Why are microorganisms important? Flashcards
Aside from water, what comprises most of the mass of a cell?
Macromolecules
List the four major classes of macromolecules.
Lipids, proteins, carbohydrates, & nucleic acids.
Biological macromolecules are comprised almost entirely of which six elements?
C,H,N,O,P,S
In a single sentence, summarize the nutrient needs of living organisms.
Organisms must obtain Carbon, Hydrogen, Oxygen, Phosphorus and Sulfur from to stay alive.
What is an inorganic reservoir? (also known as an “abiotic reservoir”)
It’s the form that most organic elements exist in naturally, however it is unavailable to most organisms.
What is a biogeochemical cycle, and how does it relate to inorganic reservoirs?
They cycle by converting inorganic reservoirs into usable biotic reservoirs and ultimately back to abiotic reservoirs.
The skeletons of all organic molecules are built of what element?
Carbon
What is the key inorganic reservoir of carbon?
CO2
What biological process converts this inorganic carbon into an organic form? What groups of organisms perform this process?
Photosynthesis, performed by photoautotrophs “producers”.
What biological process oxidizes this organic carbon, converting it back into an inorganic form? What groups of organisms perform this process?
Cellular respiration, performed by “consumers”
What is meant by the term carbon fixation?
Conversion of CO2 into sugars via photosynthesis.
Once an organism fixes carbon, in what ways is this carbon used by the organism?
Used by the autotroph itself to fuel cellular respiration, convert into other organic molecules, converted to fructose for the fruit, joined to make starch, combined with other nutrients to promote growth, converted into fats and oils, and jointed to make cellulose for cell wall.
Describe the conversion of biomass in a producer to biomass in a consumer. How efficient is this process? What is the fate of the “lost” biomass?
Carbon fixation builds biomass of the “producers”. However for the “consumer” little biomass is gained, only 10-15%. Much of the carbon is waste that is decomposed by various microbes and turned back into CO2. Overall not a very efficient process relating to biomass.
What biological process produces oxygen gas? What groups of organisms perform this process?
O2 is a waste product of photosynthesis performed by mostly microorganisms.
For what key biological process do many organisms require oxygen gas?
Cellular respiration
Which classes of macromolecules are rich in the element nitrogen?
Proteins and nucleic acids
What is the key abiotic reservoir of nitrogen?
N2
What is accomplished by the process of nitrogen fixation?
N2 is converted to usable NH3
What is a diazotroph? Try dissecting the word (di-azo-troph). What does each of these roots mean and how are they relevant to the process performed by diazotrophs?
Two-nitrogen-eat, eaters if 2 nitrogen. Used to describe the bacterial species that are capable of nitrogen fixation.
What characteristic of molecular nitrogen (N2) makes it difficult to convert into anything else?
The triple bond between the nitrogens is an extremely strong bond thar requires a lot of energy to break.
What enzyme catalyzes nitrogen fixation?
Nitrogenase
Briefly describe the functions of each of the two components of nitrogenase.
- Iron (Fe) Protein: Smaller component composed of two separate homodimers, hydrolyzes ATP and provides electrons.
- Molybdenum-orpm (Mo-Fe)Protein: larger component composed of single heterotetramer (alph2beta2), active site of nitrogen fixation.
How many genes are required to encode nitrogenase? Explain.
3 separate genes. Iron is homodimer so counts as 1, Mo-Fe is heterotetramer and sounds as 2.
Did the nitrogenase enzyme evolve independently in the various species able to fix nitrogen? Justify your answer.
No, they are homologous and derived from a common ancestor.
Why do you think the nitrogenase enzymes of different species use different cofactors?
Because they evolved in different environments that have different availability of the needed elements (molybdenum, vanadium, or iron).
What effects does carbon monoxide (CO) have on the enzyme nitrogenase?
similar enough to fit in and bind to the activation site.
Describe the interaction of carbon monoxide (CO) with the enzyme nitrogenase.
Competitive inhibitors
What effect does molecular oxygen (O2) have on the enzyme nitrogenase?
Binding results in irreversible inhibition of nitrogenase because it oxidizes iron ions. As a result nitrogen fixation has to occur in an oxygen free environment.
Bacillus and Clostridium
Anaerobic soil bacteria, lives in an environment lacking O2 because other organisms use any O2 present.
Azotobacter
Aerobic heterotrophic soil bacteria, key nitrogen fixer in grasslands, high respiratory rate rapidly consumes O2 creating low O2 environment.
Anabaena and Nostoc
cyanobacteria, filamentous aerobic oxygenic photosynthetic bacteria, fix nitrogen in specialized heterocysts that lack photosystem II so no O2 produced.
Azospirillum
alphaproteobacterium, attached to the outer surface of roots and tropical grasses to form beneficial (but not symbiotic) relationships. Supplies nitrogen to the grass which stimulates growth and bacteria has more surface space. Plant consumes much of the O2.
