Oxidation reactions in biological systems generally involve:

a. addition of electrons and hydrogen ions.
b. loss of electrons and addition of hydrogen ions.
c. loss of electrons and either addition or loss of hydrogen ions.
d. addition of electrons and loss of hydrogen ions.
e. loss of electrons and hydrogen ions.

Loss of electrons and hydrogen ions are generally involved in oxidation reactions in biological systems

Explanation:

The substrates involved in the oxidation reaction in biological systems often loss hydrogen ion detached from itself and thereafter an electron is removed. The substrates are then oxidized by the addition of oxygen to the substrates.

These processes are catalyzed by Oxidoreductases and oxidation takes place alongside with reduction.

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