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SIB2004 2 & 3

Oxidative Phosphorylation

What are all living organisms ultimately completely dependent on for energy? Adenosine Triphosphate (ATP)
What is ATP cleaved to for liberating energy? ADP and Pi
How much ATP can someone consume in a single day? Whole body mass.
From what is ATP synthesis coupled to energy extraction? From the food you eat.
ADP and Pi products are almost immediately recycled to... ATP ready for the release of energy again.
How many calories (k) is the amount required to increase the temperature of 1kg of water by 1°C? 1
Fat/Lipids have how many units of energy? 9 kcal/g
Ethanol has how many units of energy? 7 kcal/g
Proteins/amino acids have how many units of energy? 4 kcal/g
Carbohydrates/sugars have how many units of energy? 4 kcal/g
How is ATP made? By coupling the transfeer of high energy electrons derived from food with phosphorylation of ADP to ATP.
How many ATP molecules are synthesised when you burn one molecule of glucose to CO2 and H2O? 30: 26 from Phosphorylation 2 from anaerobic glycolysis
Where in the cell is ATP made? Mitochondria
What is the key electron acceptor? Oxygen
What does ETC stand for? Electron transport chain.
What is an electron transport chain? A series of electron carriers are used, each with slightly higher reduction potential than the previous one such that enegy is released in a quantized way.
What is an exampe of useful work when energy is released? Synthesise ATP.
Recite reduced fuel equivalents. Sugars, keto-acids (from amino acids) and fatty acids (CO2 is formed due to partial oxidation e.g. glycolysis/Krebs) are turned to FADH2 and NADH. FADH2 and NADH (O2 is released and H2O is formed due to complete oxidation) are turned to FAD, NAD + ATP.
What is redox potential? A systematic measure of 'relative electronegativity'.
What is electronegativity? How much something attracts or repels electrons compared with a known standard.
What is the difference between oxidised and reduced? X is oxidised and X- is reduced.
What can flow through the agar bridge and what can't? Electrons can but X can't.
If electrons flow in the direction of X- + H+ → X + 1/2H2 Then the half-cell reactions are: X- → X + e- and H+ + e- → 1/2H2 i.e. electrons are flowing from the sample cell to the reference cell.
What is the voltage on the metre when measuring redox potential? X:X-
What does a negative reduction potential mean? The oxidised form of a substance has a lower affinity for electrons than does H2.
What does a positive reduction potential mean? The oxidised form of a substance has a higher affinity for electrons than does H2.
What is a strong reducing agent (e.g. NADH) ready to do? Donate electrons because it has a negative reduction potential - it wants to be oxidised (to be NAD+).
What is a strong oxidising agent (e.g. O2) ready to do? Accept electrons because it has a positive reduction potential - it wants to be reduced.
What is the reaction that drives oxidative phosphorylation overall? 1/2O2 + 2H+ + 2e- → H2O (E'0 = +0.82V)A NAD+ + H+ + 2e- → NADH (E'0 = -0.32V) * B is in the wrong direction so it must be substracted from A which gives E'0 = 1.14V
What drives oxidative phosphorylation and the synethsis of ATP? Voltage difference.
What is the equation called to convert the voltage difference to Calories per mole? Free energy equation.
What is the free energy equation? ΔG0 = -nFΔE0 = 53kCal.mol-1 = 220 KJ.mol-1
Who proposed the chemiosmotic theory and when? Peter Dennis Mitchell proposed in 1961.
What is the chemiosmotic theory? Mechanism underlying oxidative phosphorylation.
What is used to generate a proton gradient and not to phosphorylate ADP directly? The energy derived from redox coupling in the ETC is used.
Where is the gradient generated? Across the inner mitochondrial membrane.
Where does oxidative phosphorylation occur? In the mitochondrion.
What is the mitochondrion? A specialised cellular organ, 2.0 x 0.5µm
What is a mitochondrion bounded by? What does it contain? Smooth outer membrane and contains an extensively invaginated inner membrane.
What are cristae? The number of invaginations in the mitochondrion which indicated the respiratory activity of the organelle and the cell in which it is situated.
What two compartments does the inner membrane divide into? Intermembrane space and the matrix.
How was the structure of mitochondria established? By an electron microscope (Palade and Sjostrand).
What does the matrix contain? Very high concentrations of oxidative enzymes including those of the Citric Acid Cycle and Fatty Acid Oxidation. It also contained the mitochondrial genetic machinery.
What does the outer membrane contain? Contains porins that allow the free diffusion of ions and molecules up to 10kD.
The intermembrane space equilabrates with what? Cytosol.
What is cytosol? Concentration of ions and metabolites.
What is electron transport? The pathway by which electrons from reduced fuel molecules are transferred to molecular oxygen.
What is the energy released by electron transport used for? To pump protons across the inner mitochondrial membrane.
What happens when the protons flow back? They phosphorylate ADP to yield ATP.
How is oxidation of NADH carried out? By a series of electron carriers with increasin reduction potentials.
How do electrons travel through the chain? From lower to higher reduction potentials (i.e. decreasing free energy). The electron carriers become alternatively reduced and oxidised as they accept and donate electrons.
How many complexes are the components of the chain arranged by? 4 complexes
How was the sequence of the electron carriers in the chain established? Using electron transport inhibitors, and determination of the reduction potentials of the individual electron carriers.
C1: What is Complex I also known as? NADH-Q Oxidoreductase.
C1: What big is Complex I? The largest complex in the chain.
C1: What is Complex I composed of? 43 polypeptide chains, a molecule of FMN and 6-7 ion-sulphur clusters.
C1: What does the Q in NADH-Q stand for? Ubiquinone.
C1: What can ubiquinone carry? One or two electrons per molecule.
C1: What are the iron atoms in iron-sulphur clusters and in the cytochromes? One electron carrier.
C1: How many electrons pass from NADH to Complex I, specifically FMN prosthetic group? Two electrons.
C1: What does FMN stand for? Flavin mononucleotide - the flavin derives from Vitamin B2 (riboflavin).
C1: The electrons are transported via iron-sulphur to oxidised ____ which is thereby ___? Coenzyme Q, reduced.
C1: During the electron transport from lower to higher reuction potential, how many protons are pumped from where into the what? Four, matrix and intermembrane space.
C1: How many protons are taken up by quinone? Two protons. Q → QH2
C1: What does quinone form? Quininol.
C1: How does the reduced form of coenzyme Q carry the electrons to Complex II? Through the lipid bilayer of the inner mitochondrial membrane.
C2: What is Complex II also known as? Succinate-Q reductase.
C2: Complex II has several ___-linked enzyme activities. What do they include? FAD. Citric Acid Cycle Enzyme and Succinate Dehydrogenase.
C2: What does Complex II transfer? From where? To where? Electrons from succinate to Q.
C2: What does Complex II contain? It contains iron-sulphur clusters and a molecule of cytochome b560.
C2: Does Complex II have proton-translocating activity? No.
C2: Does Complex II pump protons from the matrix to cytosolic side of the inner membrane. No.
C3: What is Complex III also known as? Q-cytochrome c oxidoreductase.
C3: Complex III passes electrons from where and to where? From reduced Q to cytochrome C.
C3: What is Complex III composed of? Two b-cytochromes, one cyctochrome c1 and one iron-sulphur cluster. Three haem groups and FeS clusters are near the cytoplasmic aspect to relate to the cytochrome c in the intermembrane space.
C3: How many proteins does Complex III pump per pair of electrons transferred? Four.
C3: Where is cytochrome c located? On the outer surface of the inner membrane.
C3: Where does cytochrome c transfer electrons between? Complexes III and IV.
C3: What does cytochrome c contain? A haem group with an iron atom whose oxidation state can be III (oxidised) or II (reduced).
C3: Where is cytochrome c always present? Respiratory chain.
C4: What is Complex IV also known as? Cytochrome c oxidase.
C4: What is Complex IV composed of? Cytochrome a, cytochrome a3, three copper atoms, a Mg2+ ion and a Zn2+ ion.
C4: How many protons does Complex IV pump per pair of electrons and where are they transferred to? Four and to oxygen.
Created by: Groberts00



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