Biology 110 Exam 4

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¬¬¬Biology Exam 4

Energy III – Cellular Respiration (Krebs Cycle and Electron Transport Chain) A.The Krebs Cycle
a.Energy
i.The net gain of 2 ATP and 2 NADH represents an effective transfer of 20 kcal of energy to ATP (about 10 kcal each) about 80 kcal of energy to NADH (about 40 kcal each), for a total of about 100 kcal ii.Complete oxidation of glucose results in the release of 684 kcal of energy, significant energy still remaining in pyruvate b.Eukaryotes

i.Pyruvate is transported across mitochondrial membrane, then converted t acetyl CoA (with production of NADH and carbon dioxide) c.Acetyl CoA
i.Is oxidized by a series of enzymes which make up cyclical series of reactions (Krebs Cycle) d.Krebs Cycle
i.Electrons are removed from acetyl CoA and these electrons reduce more NAD+ along with FAD (electron carrier) ii.Each NADH and FADH2 molecule formed is an important source of energy which will be used to generate ATP B.The Role of NADH and FADH2

a.Glucose
i.Catabolism- ends during kerbs cycle
ii.Not all energy contained n glucose was used in the production of ATP b.Cellular respiration
i.High energy electrons within NADH and FADH2 will be passes to a set of membrane-bound enzymes in the mitochondrion (electron transport chain) 1.Electrons provide energy to do work
2.Involve with the movement of protons
ii.The movement of the protons across the inner mitochondrial membrane creates a charge differential (voltage) which is used to synthesize ATP C.The Electron Transport Chain
a.Composition
i.Electron transport chain (ETC) is composed of a number of molecules (mostly proteins) that re located in the inner membrane fo the mitochondrion ii.The ore electronegative the molecule, the more energy required to keep the electron away from it iii.Electrons reduce oxygen and addition of hydrogen ions, water is produced as a waste product b.Steps of ETC

i.Each step has a –ΔG with each oxidation/reduction reaction energy s made available to do work ii.Involves movement of protons
c.Oxygen
i.The most electronegative atom
ii.When oxygen acts as the terminal electron acceptor, there is a maximal amount released – more protons can be transported – greater charge buildup occurs across the inner mitochondrial membrane D.Chemiosmosis

a.Movement
i.During movement of electrons through ETC – protons accumulate on the inside of the inner membrane 1.Creates voltage across inner membrane – stored as energy that is used to synthesize ATP b.Mitochondrial matrix

i.Part of the mitochondrion enclosed within the inner membrane ii.Houses the enzymes and substrates for the Krebs Cycle
E.Oxidative Phosphorylation and ATP yield
a.Generation of ATP from chemiosmosis at the end of ETC is referred to as oxidative phosphorylation b.Oxygen’s oxidative property allows large amount of free energy to be made available for synthesis of ATP c.The process generates large amount of ATP for cell when compared to substrate-level phosphorylation F.Summary

G.This tutorial focused on the final steps of cellular respiration; the Krebs cycle and the Electron Transport Chain and chemiosmosis. Recall that at the end of glycolysis there is a net production of two molecules of ATP and two molecules of NADH. The ATP is produced via substrate-level phosphorylation; in this reaction, a phosphate group on an organic molecule is transferred directly (along with high-energy electrons) onto a molecule of ADP. Substrate-level phosphorylation also occurs once during the Krebs cycle.For those organisms that completely oxidize glucose, the end product of glycolysis (pyruvate) is further oxidized by enzymes associated with the Krebs cycle (also known as the citric acid cycle and the tricarboxylic acid cycle or TCA cycle). In eukaryotes, the enzymes associated with the Krebs cycle are found in the mitochondria. Pyruvate moves into the mitochondria via specific carrier proteins located in the mitochondrial...
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