Chapter 23, Problem 23.88EP

(a)

Interpretation Introduction

Interpretation: To indicate whether ${\text{FMNH}}_2$ is in its oxidized form or its reduced form.

Concept introduction: Electron transport chain is a sequence of biochemical reactions in which electrons and hydrogen atoms from the citric acid cycle are transferred to various intermediate carriers and finally reacts with molecular oxygen to form a water molecule.

There are four complexes associated with the electron transport chain that is present in the inner mitochondrial membrane. The four complexes that help in the electron transfer in the electron transport chain are:

Complex I: $\text{NADH-coenzyme}\text{Q reductase}$

Complex II: $\text{Succinate-coenzyme}\text{Q reductase}$

Complex III: $\text{Coenzyme}\text{Q-cytochrome c reductase}$

Complex IV: $\text{Cytochrome c oxidase}$

An overview of the electron transport chain is as follows:

Redox reactions involve oxidation and reduction reaction occurring simultaneously so that one species is oxidized and the other one is reduced. The species that gain hydrogen or electron is known as reduced form and the species that loss hydrogen or electron is known as oxidized form. The general representation of redox reaction is

$\text{A}+{\text{H}}^{\text{+}}{\text{+e}}^{\text{-}}\to \text{AH}$

Here A is oxidized form and AH is reduced form.

Answer to Problem 23.88EP

${\text{FMNH}}_2$ is the reduced form of the flavin mononucleotide.

Explanation of Solution

${\text{FMNH}}_2$ is the structural component of the complex I of the electron transport chain. Flavin mononucleotide exists in two forms: FMN (oxidized form) and ${\text{FMNH}}_2$ (reduced form). The redox reaction for this change is:

${\text{FMNH}}_2\stackrel{\text{Oxidation}}{\to }{\text{FMN+2H}}^{+}+2{\text{e}}^{-}$

Here, ${\text{FMNH}}_2$ gains electrons and hydrogen and leads to the formation of FMN.

(b)

Interpretation Introduction

Interpretation: To indicate whether $\text{Fe}\left(\text{II}\right)\text{SP}$ is in its oxidized form or its reduced form.

Concept introduction: Electron transport chain is a sequence of biochemical reactions in which electrons and hydrogen atoms from the citric acid cycle are transferred to various intermediate carriers and finally reacts with molecular oxygen to form a water molecule.

There are four complexes associated with the electron transport chain that is present in the inner mitochondrial membrane. The four complexes that help in the electron transfer in the electron transport chain are:

Complex I: $\text{NADH-coenzyme}\text{Q reductase}$

Complex II: $\text{Succinate-coenzyme}\text{Q reductase}$

Complex III: $\text{Coenzyme}\text{Q-cytochrome c reductase}$

Complex IV: $\text{Cytochrome c oxidase}$

An overview of the electron transport chain is as follows:

Redox reactions involve oxidation and reduction reaction occurring simultaneously so that one species is oxidized and the other one is reduced. The species that gain hydrogen or electron is known as reduced form and the species that loss hydrogen or electron is known as oxidized form. The general representation of redox reaction is

$\text{A}+{\text{H}}^{\text{+}}{\text{+e}}^{\text{-}}\to \text{AH}$

Here A is oxidized form and AH is reduced form.

Answer to Problem 23.88EP

$\text{Fe}\left(\text{II}\right)\text{SP}$ is in its reduced form and iron present in $\text{Fe}\left(\text{II}\right)\text{SP}$ is in $+2$ oxidation state.

Explanation of Solution

$\text{Fe}\left(\text{II}\right)\text{SP}$ is a structural component of the complex I and consists of iron that changes its oxidation state from $+2$ to $+3$ in the complex. Iron in $\text{Fe}\left(\text{II}\right)\text{SP}$ undergoes oxidation and leads to the formation of $\text{Fe}\left(\text{III}\right)\text{SP}$. The reaction to this change is:

$\text{Fe}\left(\text{II}\right)\text{SP}\stackrel{\text{Oxidation}}{\to }\text{Fe}\left(\text{III}\right)\text{SP}+2{\text{e}}^{-}$

(c)

Interpretation Introduction

Interpretation: To indicate whether $\text{cyt}{\text{c}}_1{\text{ (Fe}}^{2+})$ is in its oxidized form or its reduced form.

Concept introduction: Electron transport chain is a sequence of biochemical reactions in which electrons and hydrogen atoms from the citric acid cycle are transferred to various intermediate carriers and finally reacts with molecular oxygen to form a water molecule.

There are four complexes associated with the electron transport chain that is present in the inner mitochondrial membrane. The four complexes that help in the electron transfer in the electron transport chain are:

Complex I: $\text{NADH-coenzyme}\text{Q reductase}$

Complex II: $\text{Succinate-coenzyme}\text{Q reductase}$

Complex III: $\text{Coenzyme}\text{Q-cytochrome c reductase}$

Complex IV: $\text{Cytochrome c oxidase}$

An overview of the electron transport chain is as follows:

Redox reactions involve oxidation and reduction reaction occurring simultaneously so that one species is oxidized and the other one is reduced. The species that gain hydrogen or electron is known as reduced form and the species that loss hydrogen or electron is known as oxidized form. The general representation of redox reaction is

$\text{A}+{\text{H}}^{\text{+}}{\text{+e}}^{\text{-}}\to \text{AH}$

Here A is oxidized form and AH is reduced form.

Answer to Problem 23.88EP

$\text{Cyt}{\text{c}}_1{\text{ (Fe}}^{2+})$ is in its oxidized form and iron present in $\text{cyt}{\text{c}}_1{\text{ (Fe}}^{2+})$ is in $+3$ oxidation state.

Explanation of Solution

$\text{Cyt}{\text{c}}_1{\text{ (Fe}}^{2+})$ is a structural component of the complex III and consists of iron that changes its oxidation state from $+2$ to $+3$ in the complex. Iron in $\text{cyt}{\text{c}}_1{\text{ (Fe}}^{2+})$ undergoes oxidation and leads to the formation of $\text{cyt}{\text{c}}_1{\text{ (Fe}}^{3+})$. The reaction to this change is:

$\text{cyt}{\text{c}}_{\text{1}}{\text{ (Fe}}^{2+})\stackrel{\text{Oxidation}}{\to }\text{cyt}{\text{c}}_{\text{1}}{\text{ (Fe}}^{3+})+{\text{e}}^{-}$

(d)

Interpretation Introduction

Interpretation: To indicate whether ${\text{NAD}}^{+}$ is in its oxidized form or its reduced form.

Concept introduction: Electron transport chain is a sequence of biochemical reactions in which electrons and hydrogen atoms from the citric acid cycle are transferred to various intermediate carriers and finally reacts with molecular oxygen to form a water molecule.

There are four complexes associated with the electron transport chain that is present in the inner mitochondrial membrane. The four complexes that help in the electron transfer in the electron transport chain are:

Complex I: $\text{NADH-coenzyme}\text{Q reductase}$

Complex II: $\text{Succinate-coenzyme}\text{Q reductase}$

Complex III: $\text{Coenzyme}\text{Q-cytochrome c reductase}$

Complex IV: $\text{Cytochrome c oxidase}$

An overview of the electron transport chain is as follows:

Redox reactions involve oxidation and reduction reaction occurring simultaneously so that one species is oxidized and the other one is reduced. The species that gain hydrogen or electron is known as reduced form and the species that loss hydrogen or electron is known as oxidized form. The general representation of redox reaction is

$\text{A}+{\text{H}}^{\text{+}}{\text{+e}}^{\text{-}}\to \text{AH}$

Here A is oxidized form and AH is reduced form.

Answer to Problem 23.88EP

${\text{NAD}}^{+}$ is the oxidized form of the nicotinamide adenine dinucleotide.

Explanation of Solution

In complex I, electrons are transferred from the $\text{NADH}$ molecule produced in the citric acid cycle. Initially $\text{NADH}$ interacts with complex I and gets oxidized to form ${\text{NAD}}^{+}$. The reaction of the reduction of ${\text{NAD}}^{+}$ is:

${\text{NAD}}^{+}+2{\text{H}}^{+}+2{\text{e}}^{-}\stackrel{\text{Reduction}}{\to }\text{NADH}+{\text{H}}^{+}$