The mitochondrial electron transport chain utilizes a series of electron transfer reactions to generate cellular ATP Adenosine triphosphate is a complex organic chemical that provides energy to drive many processes in living cells, e.g. muscle contraction, nerve impulse propagation, and chemical synthesis. Found in all forms of life, ATP is often referred to as the "molecular unit of currency" of i… Phosphorylation is the addition of a phosphoryl group (PO3) to a molecule. Phosphorylation and its counterpart, dephosphorylation, turn many protein enzymes on and off, thereby altering their function and activity. Protein phosphorylation is one type of post-translational modification.Adenosine triphosphate
Phosphorylation
What is the end result of the electron transport chain?
What is the end result of the electron transport chain? The end products of the electron transport chain are water and ATP. A number of intermediate compounds of the citric acid cycle can be diverted into the anabolism of other biochemical molecules, such as nonessential amino acids, sugars, and lipids.
Where do NADH and FADH enter the electron transport chain?
NADH and FADH2 are synthesized in the citric acid cycle (in the mitochondrial matrix) and deposit electrons into the electron transport chain at complexes I and II, respectively. This phase regenerates the oxidized carriers NAD+ and FAD for usage in the citric acid cycle.Also, some of the energy released by oxidation of these carriers can be used to generate a proton gradient across the inner ...
Why is the electron transport chain so important?
Why is the electron transport chain so important? The ETC is the most important stage of cellular respiration from an energy point of view because it produces the most ATP. When a cell needs energy, it breaks the third phosphate group bond and uses the resulting energy.
What happens to NADH in the electron transport chain?
The key steps of this process, shown in simplified form in the diagram above, include:
- Delivery of electrons by NADH and FADH. Reduced electron carriers (NADH and FADH) from other steps of cellular respiration transfer their electrons to molecules near the beginning of the transport ...
- Electron transfer and proton pumping. ...
- Splitting of oxygen to form water. ...
- Gradient-driven synthesis of ATP. ...
What is electron transport chain?
Electron Transport Chain is a series of compounds where it makes use of electrons from electron carrier to develop a chemical gradient. It could be used to power oxidative phosphorylation. The molecules present in the chain comprises enzymes that are protein complex or proteins, peptides and much more. Large amounts of ATP could be produced ...
When electrons are passed from one component to another until the end of the chain, the electrons reduce molecular?
When electrons are passed from one component to another until the end of the chain the electrons reduce molecular oxygen thus producing water. The requirement of oxygen in the final phase could be witnessed in the chemical reaction that involves the requirement of both oxygen and glucose.
How is ATP produced?
Large amounts of ATP could be produced through a highly efficient method termed oxidative phosphorylation. ATP is a fundamental unit of metabolic process. The electrons are transferred from electron donor to the electron acceptor leading to the production of ATP. It is one of the vital phases in the electron transport chain.
Which heme group is responsible for holding oxygen molecule between copper and iron until the oxygen content is reduced completely?
There are two heme groups where each of them is present in cytochromes c and a3. The cytochromes are responsible for holding oxygen molecule between copper and iron until the oxygen content is reduced completely. In this phase, the reduced oxygen picks two hydrogen ions from the surrounding environment to make water.
Which complex is responsible for pumping protons across the membrane?
Complex 3 is responsible for pumping protons across the membrane. It also passes electrons to the cytochrome c where it is transported to the 4th complex of enzymes and proteins. Here, Q is the electron donor and Cytochrome C is the electron acceptor. Complex 4- Cytochrome c oxidase: The 4th complex is comprised of cytochrome c, a and a3.
How are the first and second complexes connected?
The first and the second complexes are connected to a third complex through compound ubiquinone (Q). The Q molecule is soluble in water and moves freely in the hydrophobic core of the membrane. In this phase, an electron is delivered directly to the electron protein chain.
What is the function of the electron transport chain?
The mitochondrial electron transport chain utilizes a series of electron transfer reactions to generate cellular ATP through oxidative phosphorylation. A consequence of electron transfer is the generation of reactive oxygen species (ROS), which contributes to both homeostatic signaling as well as oxidative stress during pathology. In this graphical review we provide an overview of oxidative phosphorylation and its inter-relationship with ROS production by the electron transport chain. We also outline traditional and novel translational methodology for assessing mitochondrial energetics in health and disease.
How do electrons enter the ETC?
Electrons also enter the ETC through Complex II, which is a component of both the TCA cycle and the ETC. Electrons donated from FADH2are transferred sequentially to CoQ via the FeS cluster of Complex II, in a similar manner as at Complex I. Unlike Complex I, electron transport at Complex II is not accompanied by proton translocation from the matrix to the intermembrane space [6].
How many protons are in the intermembrane space?
In response to electron transport, a total of ten protons (H+) (two from Complex III, and four from each Complex I and Complex IV) are pumped from the matrix into the intermembrane space, where they accumulate to generate an electrochemical proton gradient known as the mitochondrial membrane potential (ΔΨ). ΔΨ combined with proton concentration (pH) generates a protonmotive force (Δp) which is an essential component in the process of energy storage during OXPHOS since it couples electron transport (complexes I-IV) (and oxygen consumption) to the activity of Complex V (ATP synthase), where protons re-enter the matrix to dissipate the proton gradient. Complex V is a multi-subunit complex comprised of two distinct domains, extra-membranous (termed F1) and transmembrane (termed FO), and functions under a rotational motor mechanism to allow for ATP production. Proton movement through FOfrom the intermembrane space is coupled to the rotation that results in the addition of a phosphate to adenosine diphosphate (ADP) to synthesize adenosine triphosphate (ATP) at sites in F1(Fig. 1) [6].
What is the role of antioxidants in the mitochondrion?
While the mitochondrion is a site for ROS production, antioxidant systems contribute to the regulation of the concentration and redox species in the organelle. Though the proximal ROS generated by the ETC is O2•−, this species is rapidly dismutated to H2O2by manganese superoxide dismutase (MnSOD) localized in the mitochondrial matrix and low concentrations of copper/zinc SOD located in the intermembrane space [6]. Notably, unlike O2•−, H2O2is stable and uncharged, and thus able to leave the mitochondrion to mediate cytosolic cell signaling. This signaling occurs predominantly through the oxidation of either metal cofactors or reduced thiols on cytosolic proteins, changing their function. It is now well recognized that mitochondrial H2O2regulates a number of signaling pathways by this mechanism. While discussion of each of these specific pathways is outside the scope of this article, we direct the reader to reviews of the essential role of mitochondrial ROS signaling in hypoxic adaptation [20,24], apoptosis [25], regulation of phosphorylation signaling [26,27], and cell growth and differentiation [28,29].
What are the two main antioxidant systems in the mitochondria?
The concentration of H2O2that leaves the mitochondrion is regulated by two main antioxidant systems in the mitochondrial matrix: the glutathione and thioredoxin/peroxiredoxin systems (Fig. 2). Glutathione (GSH) is oxidized by H2O2to form the glutathione disulfide (GSSG), a reaction catalyzed by glutathione peroxidase (GPx). GSSG is then reduced back to GSH by Glutathione Reductase (GR). Similarly, H2O2oxidizes a cysteine residue in the catalytic site of peroxiredoxin (PRx), which forms a disulfide bridge with a neighboring cysteine. The reductive power of thioredoxin (TRx) reduces PRx through a disulfide exchange reaction and TRx is then reduced by Thioredoxin reductase (TR). Importantly, both GR and TR require NADPH for their reductive activity. The pool of reduced NADPH is maintained by several enzymes in the mitochondrial matrix including malic enzyme (ME), glutamate dehydrogenase (GDH), and isocitrate dehydrogenase (IDH2) [30]. Additionally, membrane-associated nicotinamide nucleotide transhydrogenase (NNT) is particularly important in maintaining NADPH pools through its function of pumping protons into the matrix to regenerate NADPH by coupling oxidation of NADH to the reduction of NADP+. Importantly, the ability of NNT to renew the pool of available NADPH is dependent on ΔΨ. States of low ΔΨ decrease the amount of available reduced NADPH which then decreases the amount of reduced glutathione and thioredoxin to buffer H2O2.
What is the cell metabolism?
Cellular metabolism comprises the utilization of carbohydrates, fats, and proteins, to synthesize energy. The processes for the catabolism of glucose (via glycolysis and subsequent pyruvate oxidation), fatty acids (via fatty acid β-oxidation), and amino acids (via oxidative deamination and transamination) are reviewed in detail elsewhere [5]. However, the molecules derived from these processes are used in the tricarboxylic acid (TCA) cycle to generate substrates that enter the ETC for oxidative phosphorylation. Here we summarize the reactions that occur in the ETC to produce energy, but for a more detailed review, refer to Zhao et al. [6].
Where is the ETC located?
The ETC is embedded within the extensive inner membrane of the mitochondrion, in close proximity to the mitochondrial matrix in which the TCA cycle is localized (Fig. 1). NADH and FADH2generated by the TCA cycle donate electrons to the ETC at either Complex I (NADH:ubiquinone oxidoreductase) or Complex II (succinate dehydrogenase), respectively (Fig. 1). The electrons from NADH are passed to ubiquinone (CoQ) through a chain of co-factors including a flavin mononucleotide (FMN) followed by seven low to high potential iron-sulfur (FeS) clusters in Complex I to enter the Q cycle, where CoQ is reduced to ubiquinol (QH2). This electron transfer induces the pumping of protons by Complex I from the matrix into the intermembrane space. Though the mechanism linking electron transfer to proton pumping remains unclear, one hypothesis speculates an indirect pumping of two protons via a conformation-coupled manner and the direct pumping of the other two protons via the ubiquinone redox reaction, while another hypothesis suggests that changes in the conformation and density of water in Complex I dictates the proton translocation [6]. Regardless of the exact mechanism, the transfer of two electrons from NADH results in the pumping of four protons.
Which molecule can diffuse rapidly within the inner mitochondrial membrane, where it shuttles protons and electrons?
hydrophobic, lipid soluble molecule which can diffuse rapidly within the inner mitochondrial membrane, where it shuttles protons and electrons.
Which assembly is driven by the flow of protons back into the mitochondrial matrix?
by an ATP-synthesizing assembly that is driven by the flow of protons back into the mitochondrial matrix ⇒ shows that proton gradients are an interconvertible currency of free energy in biological systems.
What are some examples of electron transport inhibitors?
Inhibition of the electron-transport chain: cyanide (CN−); azide (N3−); and carbon monoxide (CO) examples. Inhibition of ATP synthase : Oligomycin, an antibiotic used as an antifungal agent, Uncoupling electron transport from ATP synthesis: 2,4-dinitrophenol (DNP) and certain other acidic aromatic compounds.
What is a series of sequentially acting electron carriers, most of which are integral proteins with prosthetic groups capable of?
a series of sequentially acting electron carriers, most of which are integral proteins with prosthetic groups capable of accepting and donating electrons.
How many keto groups are there in the fully oxidized state?
1) the fully oxidized state (Q), has two keto groups.
Which chain of electrons reduces O2 to H2O?
high-transfer-potential electrons flow through a series of large protein complexes embedded in the inner mitochondrial membrane, called the respiratory chain , to reduce O2 to H2O.
Which complex completes the sequence by transferring electrons from cytochrome C to O2?
4)Complex IV completes the sequence by transferring electrons from cytochrome c to O2.
