Bergmann’s rule: populations in colder climates tend to have greater body mass than those

in warmer climates. This pattern is so common that it has a name.

TLS Online TPP Program

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#Unit 6. System Physiology – Plant

Diazotrophs are able to catalyze the enzymatic reduction of this compound to ammonia (NH3) using the enzyme nitrogenase

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#Id: 9268

#Unit 6. System Physiology – Plant

Nitrogenase is a complex consisting of the MoFe protein (dinitrogenase or component I) a heterotetramer, and the Fe protein (dinitrogenase reductase or component II) a homodimer.

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#Id: 9269

#Unit 6. System Physiology – Plant

Fe protein 

contains 2 identical subunits (dimer) – nif H

Each subunit has MW of 30 ~ 72 kD.

Each subunit contains an Fe-S cluster (4Fe and 4S2-).

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#Unit 6. System Physiology – Plant

MoFe protein 

2 pairs of identical subunits (tetramer, nif D & nif K)

A total of MW 180 ~ 235kD

Each subunit has 2 Mo-Fe-S clusters.

Both Fe proteins and MoFe proteins are sensitive to O2. 

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#Id: 9271

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 9272

#Unit 6. System Physiology – Plant