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SIB2004 2 & 3
Oxidative Phosphorylation
| Question | Answer |
|---|---|
| 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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