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Description
Flashcards by Darcey Griffiths, updated about 1 month ago
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Created by Darcey Griffiths
about 2 months ago
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| Question | Answer |
| ATP- what is it | Universal energy currency- used in all cells to drive their reactions-ATP is made when energy becomes available eg in respiration and in the light dependent reactions of photosynthesis- is broken down when cell needs energy eg in muscle contraction and powering membrane Na+ and K+ pumps |
| Why is ATP suited to its role | -its inert -can pass out of mitochondria into the cytoplasm - releases energy efficiently -releases energy in useable quantities- little wasted as heat - is easily hydrolysed to release energy - is readily reformed by phosphorylation |
| Chemiosmosis- WJEC definition | The flow of protons down an electrochemical gradient through ATP synthetase, coupled w/ the synthesis of ATP from ADP and a phosphate ion |
| Chemiosmosis- pt1 | In the synthesis of ATP, electrons and protons, derived from hydrogen atoms have different pathways - Electrons from hydrogen atoms are transferred from a donor molecule to a recipient- then a sequence of reactions transfers the electrons from one molecule to the next- each transfer= redox reaction- oxidation reactions makes energy available- energy eventually used to synthesise ATP |
| Importance of oxidation in chemiosmosis | Energy released by oxidisation pumps protons from hydrogen atoms across a membrane- more concentrated on one side of membrane than the other- difference in concentration of the protons and the charge on either side of the membrane creates an electrochemical gradient |
| Importance of oxidation in chemiosmosis pt2 | source of potential energy- protons flow back down gradient in process called chemiosmosis through enzyme ATP synthetase- energy they release as they do so- converted into chemical energy in ATP., |
| The mitochondria and chloroplast membranes | ATP synthetase makes ATP from energy associated with proton gradients across membranes- Respiration uses inner membranes of mitochondria- photosynthesis uses thylakoid membranes of chloroplast- bacteria do not have internal membranes- use cell membranes to establish proton gradient by pumping protons out of cytoplasm, into space between cell membrane and peptidoglycan layer |
| Endosymbiosis | Common function of the inner membranes of mitochondria, chloroplasts and bacteria supports theory of endosymbiosis-membranes must only let protons through and in a highly controlled way- protons= tiny/ easily pass through water molecules- so membranes must also be water tight- described as sealed membranes |
| diagrams of mitochondrion and chloroplast | p13 |
| Proton gradient- origin of life | Proton gradients occur in non living systems- naturally occuring events like these may have had great impact on origin of life as proton gradients is fundamental for all living things |
| Proton gradients- photosynthesis | The chemiosmosis on thylakoid membranes takes place during the light-dependent reactions. During this process, photoexcited electrons move through the photosystems. It involves the following steps; * The photons of light fall on the photosystems and excite the electrons. * The photoexcited electrons move through the electron transport chain. * As the electrons move down the electron transport chain, energy is liberated that is used to pump hydrogen ions from the stroma of chloroplasts into the lumen of the thylakoids. |
| Proton gradients- photosynthesis- pt2 | The energy of electrons is stored in the form of electrochemical gradient of protons across thylakoid membrane Protons move down conc gradient back down into stroma- passes via ATP synthase- creates energy Used to phosphorylate ADP in stroma NADP= final electron acceptor |
| Proton gradients- respiration | Electrons= excited by energy derived from food molecules- whole process happens- energy released by chemiosmosis as protons flow back into matrix by ATP synthetase incorporated into ATP- energy not incorporated is lost as heat |
| Disrupting proton gradients causes death pt 1 | Apoptosis= programmed cell death- occurs eg when fingers and toes grow in embryonic development- operates by preventing proton gradients from forming- |
| pt2- why is DNP fatal | DNP can cross this membrane on it's own. DNP can also grab a proton and carry the proton across the membrane. When this happens, you have a shortage of protons for ATP synthase which results in a shortage of ATP. Your body then needs to continue to burn more carbs, fat, and protein at a higher rate to make up for the shortage of ATP. When DNP transports a proton across the membrane heat is produced. (all energy released from those molecules= converted to heat- body overheats sometimes fatally |
| Electron transport chain | =Series of protein carriers on the inner membrane of mitochondria and chloroplasts - releases energy from electrons- incorporates it into ATP Hydrogen atoms derived from respiratory breakdown of glucose are transferred by dehydrogenase enzymes to co- enzymes NAD and FAD- carried to inner membrane of mitochondrion- electrons and protons have different paths but both move through electron transport chain- so system often described as transferring hydrogen atoms |
| Electron transport chain pt2 | For every 2 protons delivered by reduced NAD, enough energy is released to synthesise 3 molecules of ATP-for every 2 protons delivered by FAD- only enough for 2 molecules of ATP- Energy for proton pump and electron transport chain comes from oxidation reactions= addition of phosphate group- happens to ADP when using this energy- oxidative phosphorylation |
| Electron transport chain- photosynthesis | In photosynthesis- groups of pigments/ proteins called photosystems transfer excited electrons to electron acceptors and then to a series of proton carriers all on thylakoid membranes- protons from water and the electrons are transferred to coenzyme NADP and subsequently to glycerate- 3- phosphate in path that synthesises carbs- energy that powers proton pump/ electron transport chain comes from light- synthesises ATP by photophosphorylation |
| Electron transport chain- how ATP synthase works | ATP synthase occurs in all bacteria, arches and eukaryotes- presumably evolved in very early life as protons diffuse down electrochemical gradient through ATP synthase, energy released causes rotor and stalk to rotate-mechanical energy from rotation is converted into chemical energy as a phosphate ion Pi is added to ADP to form ATP in catalytic head- look at diagram p14 to understand |
| Table-p15 | H |
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