The Electron Transport Chain

The Electron Transport Chain In the electron transport chain, electrons flow downward in energy from coenzyme NADH and flavoprotein FADH2 to the terminal electron acceptor, molecular oxygen, O2. Electrons move spontaneously from carriers of lower reduction potential (Eo) to carriers of higher reduction potential. Molecules involved in the ETC have reduction potentials between the values for NAD+/NADH couples and oxygen/H2O couples. Energy extracted from the transfer of electrons is most efficiently conserved when it is released in a step wise fashion, and is accomplished with four distinct protein complexes in the mitochondrial membrane: Complex I = NADH-coenzyme Q reductase (NADH dedhydrogenase) Complex II = succinate-conenzyme Q reductase (succinate dehydrogenase) Complex III = coenzyme Q-cytochrome c reductase Complex IV = cytochrome c oxidase Complex I oxidizes NADH and reduces coenzyme Q (UQ), transferring a pair of electrons from NADH to UQ. The oxidation of one NADH and reduction of UQ results in a net transport of protons from the matrix side to the intermembrane space. Complex II oxidizes succinate and reduces UQ, yielding a net reduction potential of +0.029 V, which does not contribute to the transport of protons across the inner mitochondrial membrane. Complex III facilitates the transfer of electrons from UQ to cytochrome c (cyto c) via the Q cycle, which oxidizes UQH2 and reduces cyto c, releasing four protons into the intermembrane space for every two electrons that pass through the Q cycle. Complex IV accepts electrons from cyto c and reduces oxygen to form H2O, driving proton transport across the inner mitochondrial membrane into the intermembrance space. For every four electrons used to reduce oxygen, four protons are released into the intermembrance space. Components of the ETC are arranged in line with the flow of electrons from donors with lower affinity for electrons toward acceptors with higher affinity for electrons. Affinity for electrons is measured by the reduction potential. The transfer of electrons does not occur in a simple linear sequence. Electrons can enter the ETC at different entry points, either through Complex I or Complex II, and then the pathways converge at Complex III. As Fig. 1 shows, electrons move from more negative to more positive reduction potentials on the energy scale. Table 13-7 presents the following reduction potentials for reactions that occur in the ETC: NAD+ + 2H+ 2e- Æ’Â   NADH + H+ ΔEo = -0.320 V FAD + 2H+ +2e- Æ’Â   FADH2 ΔEo = -0.219 V Fumarate + 2H+ + 2e- Æ’Â   Succinate ΔEo = +0.031 V Q + 2H+ + 2e- Æ’Â   QH2 ΔEo = +0.045 V cyt c1(Fe3+) + e- Æ’Â   cyt c1(Fe2+) ΔEo = +0.220 V cyt c(Fe3+) + e- Æ’Â   cyt c(Fe2+) ΔEo = +0.254 V Â ½ O2 + 2H+ + 2e- Æ’Â   H2O ΔEo = +0.816 V As mentioned, molecules involved in the ETC have reduction potentials between the values for NAD+/NADH couples and oxygen/H2O couples. Electrons move from more negative to more positive reductions potentials in the following order: NADH Æ’Â   Q Æ’Â   cytochrome c1 Æ’Â   cytochrome c Æ’Â   O2 Reactions that have positive reduction potentials have negative free energy and are energetically favorable. Complex III has a more positive reduction potential than Complex I and II, and Complex IV has a more positive reduction potential than Complex III. The reduction potential for each complex can be estimated with the half reactions and reduction potentials provided in Table 13-7. Below are the net equations for each complex: Complex I NADH + 5H+N + Q ↔ NAD+ + QH2 + 4H+P Complex II Succinate + Q ↔ fumarate + QH2 Complex III QH2 + 2 cyt c1 + 2H+N ↔ Q + 2 cyt c1 + 4 H+P Complex IV 4 cyt c + 8 H+N + O2 ↔ 4 cyt c + 4 H+P + 2 H2O For example: Complex I NADH + 5H+N + Q ↔ NAD+ + QH2 + 4H+P NAD+ + 2H+ 2e- Æ’Â   NADH + H+ ΔEo = -0.320 V Q + 2H+ + 2e- Æ’Â   QH2 ΔEo = +0.045 V ΔEo = Eoacceptor Eodonor ΔEo = 0.045 (-0.320) = +0.365 V Complex III QH2 + 2 cyt c1 + 2H+N ↔ Q + 2 cyt c1 + 4 H+P Q + 2H+ + 2e- Æ’Â   QH2 ΔEo = +0.045 V cyt c1(Fe3+) + e- Æ’Â   cyt c1(Fe2+) ΔEo = +0.220 V ΔEo = [2 x 0.220] 0.045 = +0.395 V The reduction potential for Complex III is greater than that of Complex I, correlating to flow of electrons in the ETC. Electrons move from more negative to more positive reductions potentials. In addition, both overall reactions for NADH/FADH2 to O2 are positive values, another indication that electrons moving from Complex I/II to Complex IV is energetically favorable. The calculations are provided below. This is the overall reaction for electrons that travel from NADH to O2 NADH + H+ + Â ½ O2 Æ’Â   NAD+ + H2O NAD+ + 2H+ 2e- Æ’Â   NADH + H+ ΔEo = -0.320 V Â ½ O2 + 2H+ + 2e- Æ’Â   H2O ΔEo = + 0.816 V ΔEo = 0.816 (-0.320) = +1.136 V This is the overall reaction for electrons that travel from FADH2 to O2 FADH2 + Â ½ O2 Æ’Â   FAD + H2O FAD + 2H+ +2e- Æ’Â   FADH2 ΔEo = 0.219 V Â ½ O2 + 2H+ + 2e- Æ’Â   H2O ΔEo = + 0.816 V ΔEo = 0.816 (-0.219) = +1.035 V As a result of the ETC, the net reaction for the transfer of two electrons from NADH through the respiratory chain to molecular oxygen is highly exergonic (positive reduction potentials and negative free energy). For each pair of electrons transferred to O2, four protons are pumped out of the matrix into the intermembrane space by Complex I, four by Complex III and two by Complex IV, producing a proton gradient that drives ATP synthesis (Fig.2).

Mrs Morel, and How She Ruined Lives in Sons and Lovers Essay

Gertrude Morel, a mother whose possessive love for her sons hinders their ability to establish fulfilling relationships with other women, and her detest of her husband closes him out of their lives. Gertrude can not bear to see her children live the life that her husband Walter does so she makes sure that they detest him, especially William and Paul. Mrs Morel did ruin three lives in this novel, Walter’s, William’s, and Paul’s. Walter was a simple miner with simple needs and no motivation or want to advance, when he and Gertrude first met he had thick flowing black hair and a full beard and he also laughed a lot suggesting a happy, relaxed figure. He also portrayed himself as bold and a senior in the mines making a good stable wage, owning his own house and everything in it as well. Gertrude finds her self strangely attracted, despite being described as â€Å"opposite† to her new found love. They rush into marriage but the lust that they had soon fades as the lies that were told are uncovered. Gertrude starts to despise the man she married because he lied to her and goes and spends the money he makes on alcohol instead of on his family. When William is born Gertrude smothers him in love and tries her hardest to keep him away from her husband which makes Walter jealous and angry with her that he can not have the same connection with the child that she does. Gertrude does this with all the children that she and Walter have. The eldest boys are so enveloped by their mother that they can not hold a stable relationship when they grow older because their mother wants to keep them for herself, â€Å"..William and Paul Morel are unable to love when they come to manhood, because their dominant mother holds them back, so that a split occurs between body and soul – their sweethearts getting the former; their mother getting the latter; while the boys themselves are shattered; inwardly in the course of the struggle.† (Spilka, 51) William is the first born son and so he in the one that Gertrude idolizes, he is perfect to her and she wants him to be her little boy forever. When he grows older William soon gets a job in London and moves away leaving his mother and family behind. William send his mother a letter telling her about his new job and his new found girl-friend whom he will be engaged to. William and his betrothed come to visit his family at Christmas, they seem less than impressed with her and her lifestyle especially Gertrude because she treats his family as though they are somehow inferior to her. This does not discourage William to stop loving her. William becomes sick of her when they return to see his family on a vacation, his mother has the same feelings toward her, but he refuses to call off the marriage seeing how far they had come. Later in the year William dies of pneumonia with his mother by his side. Paul is a less important to his mother until William dies, then he becomes her favourite. Paul is more frail than his brother was, and he is very artistic rather than athletic. As Paul grows in sight of his mother her love for him grows stronger because of his stature, and he grows in a way that he cares of what other people feel, especially his mother. He develops an Oedipus Complex towards his mother. â€Å"Oedipus complex makes mother a lover of her son. During childhood it seems normal and acceptable but it is abnormal and almost absurd, when he grows up, to keep such feelings. He will surely have no real love for a woman and no marriage in his life and is doomed to have a tragic ending with his love affairs and to suffer spiritually the rest of his life when his mother is gone.† (Wang) When Paul is older he starts a relationship with a woman named Miriam who wants him to love her as she loves him, she wants his soul, for him to love her with every ounce of his being as she does. Gertrude see’s this and feels threatened by her because Paul’s soul should belong to her, she believes Miriam can have him physical but not spiritually. Gertrude confronts her son about this matter and Paul tells her that he does not love Miriam, that he loves only his mother and no one else. When Paul breaks things of with Miriam and starts a relationship with Clara, Gertrude is content with them together because Clara is only interested in a physical relationship. When the relationship with Clara fades Miriam tries her luck with Paul again, she says that she wants to marry him but Paul is so fixated with his love for his mother that when he feels the slightest feelings for Miriam he feels as though he is betraying her. He declines the proposal from Miriam and goes back to his mother. Gertrude Morel was a strong woman and mother but stubborn with her children in a way that she would want them to only look to her and not to walter, no matter what the situation was. Throughout the novel Gertrude ruins three lives, that of her her husbands, and her two eldest sons. Her husband Walter was not the best man for her but he did try to be a father to his children, but his wife made it almost impossible for him to do so. He is ostracized from the family throughout the novel, his life is ruined because Gertrude made him loose the only family he had before he had a chance of being a part of it. Her eldest son and first born child William, is so fixated on his mothers approval that he learns to hate the woman that he will be married to, that marriage would become like his parents. In that way Williams life is ruined by his own mother. Her third child and second son Paul can not have a stable relationship with women because he loves his mother too much, his life is ruined because once his mother is gone he is left with nothing and still can not hold a relationship together. References Spilka, Mark. â€Å"Counterfeit Loves† Twentieth Century Interpretations of Sons and Lovers. A Collection of Critical Essays Ed.Judith Farr, Prentice-Hall, INC., Englewood Cliffs, New Jersey: 1970. 51-63. Print. Wang, Yi . â€Å"Should I Use Underlining or Italics?† College of Foreign Languages, Hebei University, China . ,29 March 2001. Web. 21 November 2012. .

Child Development Case Study - 1973 Words

From the video observation, the two three-year old children, Thomas and Riley set off on a bus journey along with their childminder; it is observed that both the children speak about their journey, in which they are able to identify various features, which include the passengers; various buildings and different types of buses. Both children observe many of the features by taking photographs to highlight what they have observed on their journey. From observation, the video looks at the way the childminder plans the experience from a child-initiated stance, which directs the children’s learning in addition with assisting them with role-play and symbolic play, which is shown towards the end of the video. Thus, this essay will focus on the†¦show more content†¦Additionally, Bruner (1986) suggests that children develop differently at equivalent stages however, agreeing with Piaget’s cognitive perspective; egocentrism may constituent towards child development, depend ing on the individual child’s cognitive process. Furthermore, Bruner indicates that both nurture and nature is a crucial part of development, which is promoted and enhanced through socialization, provided that â€Å"the child’s growing knowledge of the world is achieved principally by direct encounters with it in interacting and negotiating with others† (Bruner, 1986, p.61). 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Howard Zinn s The Vietnam War - 1446 Words

Howard Zinn says it best when he writes that â€Å"from 1964 to 1972, the wealthiest and most powerful nation in the history of the world made a maximum military effort, with everything short of atomic bombs, to defeat a nationalist revolutionary movement in a tiny peasant country – and failed† (Zinn, 460). Zinn does not mince words when expressing his thoughts about the Vietnam War, because as Zinn says, Vietnam was basically a modern portrayal of David vs. Goliath. One could even go as far as to say that Vietnam was in essence a case of mass genocide in Vietnam. Thousands and thousands of Vietnamese and America soldiers were killed along with thousands upon thousands of innocent, Vietnamese citizens. War is an infectious disease and the Vietnam War is a perfect example of how deadly of a disease war can be. Everybody involved in the Vietnam War was affected, whether it was Vietnamese citizens, Vietnamese soldiers, American soldiers, or even American citizens back home . 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