TLS Online TPP Program

#Id: 3302

#Unit 6. System Physiology – Plant

In actively respiring mitochondria, 0.1% to as much as 4% of the O2 used in respiration forms •O2^2- — more than enough to have lethal effects unless the free radical is quickly disposed of.

TLS Online TPP Program

#Id: 3304

#Unit 6. System Physiology – Plant

Factors that slow the flow of electrons through the respiratory chain increase the formation of superoxide, perhaps by prolonging the lifetime of ^• O ₂ ^- generated in the Q cycle,

TLS Online TPP Program

#Id: 3305

#Unit 6. System Physiology – Plant

To prevent oxidative damage by • O2 2 , cells have several forms of the enzyme superoxide dismutase, which catalyzes the formation of hydrogen peroxide (H2O2)

TLS Online TPP Program

#Id: 3307

#Unit 6. System Physiology – Plant

Glutathione contains γ-Glu-Cys-Gly

TLS Online TPP Program

#Id: 3308

#Unit 6. System Physiology – Plant

The hydrogen peroxide (H 2 O 2 ) thus generated is rendered harmless by the action of glutathione peroxidase.

TLS Online TPP Program

#Id: 3310

#Unit 6. System Physiology – Plant

Glutathione probably helps maintain the sulfhydryl groups of proteins in the reduced state and the iron of heme in the ferrous (Fe 2+ ) state, and it serves as a reducing agent for glutaredoxin in deoxy ribonucleotide synthesis.