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Description
Flashcards by Darcey Griffiths, updated about 2 months ago
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Created by Darcey Griffiths
about 2 months ago
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| Question | Answer |
| Aerobic Respiration | The release of large amounts of energy made available as ATP- produced from breakdown of molecules, w/ oxygen as terminal electron acceptor |
| Anaerobic Respiration | breakdown of molecules in the absence of oxygen , releasing relatively little energy, making a small amount of ATP by substrate- level phosphorylation. There’s obligate aerobes, facultative anaerobes and obligate anaerobes |
| Anaerobic respiration | breakdown of molecules in the absence of oxygen , releasing relatively little energy, making a small amount of ATP by substrate- level phosphorylation. There’s obligate aerobes, facultative anaerobes and obligate anaerobes |
| Dehydrogenation | The removal of one or more hydrogen atoms from a molecule |
| Decarboxylation | The removal of a carboxyl group from a molecule, releasing CO2. |
| Metabolism | all reactions of an organism- respiration= metabolic pathway- sequence of enzyme controlled reactions where product of one reaction is substrate for the next- reactions of respiration= catabolic- break down energy rich macromolecules eg glucose + fatty acids |
| Metabolism pt 2 | in respiration C-C, C-H and C-OH bonds are broken- lower energy bonds formed. Energy difference allows phosphorylation of ADP to ATP- ATP does not ‘produce’ energy- but when hydrolysed releases energy. Energy= available to use by cell or is lost as heat. |
| Oxidative phosphorylation | occurs on inner membranes of mitochondria in aerobic respiration- energy for making ATP comes from oxidation- reduction reactions- released in the transfer of electrons- along a chain of electron carrier molecules. |
| Photophosphorylation | Photophosphorylation- occurs in thylakoid membranes of the chloroplasts in the light- dependent stage of photosynthesis- energy for making ATP comes from light- is released in transfer of electrons along a chain of electron carrier molecules- photophosphorylation does not occur in respiration. |
| Substrate level phosphorylation | Substrate level phosphorylation- occurs when phosphate groups are transferred from donor molecules e.g. glycerate 3- phosphate to ADP to make ATP in glycolysis or when enough energy is released from a reaction to bind ADP to inorganic phosphate eg in krebs. |
| More on respiration- processes/ aerobic formula | Processes that require energy- active transport, movement, formation of complex molecules eg proteins- comes from respiration Formula for aerobic respiration of glucose C6H1206 +6CO2—> 6CO2 +6H2O+ energy (ATP) Glucose + oxygen—> carbon dioxide + water But can also use lipids and proteins in respiration |
| ATP | Critical molecule in energy transfer- Ribose and adenine part of molecule together is called adenosine Energy carrying molecule- if we react ATP with water the end phosphate can leave-this reaction releases energy- energy can then be used for processes in the cell |
| ATP- more | Reacting ATP with water is an example of a hydrolysis reaction catalysed with with ATP hydrolase also called ATPase ATP + water —> ADP + Pi + energy At end of the reaction made adenosine diphosphate (ADP) and released phosphate ion Given symbol Pi- i tells us it’s inorganic- not bonded to a carbon containing molecule -2 processes in respiration that can reform ATP- substrate level phosphorylation and oxidative phosphorylation- oxidative phosphorylation produces the vast majority of ATP during respiration |
| ATP formation | Once ATP is hydrolyzed has to be reformed to be used again ATP is formed in respiration in the energy stored in glucose- when ATP is reformed- energy from glucose is used is used to add a phosphate ion back on to ADP- process is called phosphorylation |
| ATP formation- more | Cells use energy in glucose to produce ATP in respiration- during respiration a large no. chemical reactions gradually break down the glucose molecule- during some of these reactions a hydrogen ion is released - dehydrogenation or oxidation reaction- hydrogen ion has 2 electrons- hydrogen ions are rich in energy- can be used to form large quantities of ATP- takes place during oxidative phosphorylation- when H= is released it’s added to a molecule called a hydrogen carrier- good example- coenzyme NAD- by adding hydrogen with its 2 electrons to NAD - carry out a reduction reaction NAD + H —> NADH (reduced NAD) |
| Glycolysis overview | At different stages, energy contained within glucose can be transferred to other molecules Energy transfer can take place in 2 different ways- in some reactions the energy transferred can be used to produce a molecule of ATP directly releasing energy- energy is used to form a molecule of ATP from ADP and Pi (substrate level phosphorylation) - Or hydrogen and 2 electrons can be removed from a molecule- (dehydrogenation/ oxidation - hydrogen and 2 electrons are transferred to a hydrogen carrier such as coenzyme NAD, forming reduced NAD- reduced NAD is then used used later to produce ATP in process called oxidative phosphorylation. |
| Where does glycolysis take place + why | Glycolysis takes place in the cytoplasm and does not require oxygen Glycolysis consists of 10 different reactions but we learn a simplified version Initial stage of both aerobic and anaerobic respiration- occurs in cytoplasm as glucose can’t pass through mitochondrial membrane- but even if it could- enzymes for breakdown= not present in mitochondria- so glucose could not be metabolised |
| Glycolysis- steps pt 1 | glucose molecule is phosphorylated by addition of 2 phosphate groups using 2 molecules of ATP- ATP molecules each transfer 1 phosphate onto the glucose molecule- makes hexose diphosphate As a result- phosphorylated molecule= more reactive- less AE required for enzyme controlled reactions- also more polar than glucose= less likely to diffuse out of cell Hexose diphosphate converted to 2 molecules of triose phosphate- a 3 carbon sugar, glyceraldehyde-3- phosphate |
| Glycolysis pt 2 | Hydrogen is removed from the triose phosphate molecules- a dehydrogenation/ oxidation reaction- triose molecules oxidised to form pyruvate- this hydrogen is added onto NAD forming reduced NAD (hydrogen carrier molecule). - Also each phosphate group on triose phosphate is added to ADP, converting these molecules to ATP- so for each triose phosphate molecule 2 molecules of ATP is produced-4 ATP molecules produced overall- this is an example of substrate level phosphorylation- happens without redox reactions along electron transport chain- produces pyruvate |
| Overall products of glycolysis | At start used 2 ATP molecules but produced 4 ATP molecules at end- net yield- 2 ATP Produced 2 reduced molecules of reduced NAD- will be used in a later stage of respiration called oxidative phosphorylation- if O2 available each has potential for synthesis of an additional 3 molecules of ATP- making 6 altogether from electron transport chain Released 2 molecules of Pyruvate Doesn’t seem to have released too much energy- because pyruvate still contains a great deal of energy- gradually released during later stages of respiration in krebs cycle- if O2 is available |
| Link reaction- overview | What happens after glycolysis depends on amount of oxygen present- in absence of oxygen anaerobic respiration takes place in the cytoplasm If oxygen is present then cell carries out aerobic respiration- takes place in mitochondria- has a double membrane- internal region of a mitochondria= mitochondrial matrix |
| Link reaction overview pt2 | Pyruvate molecules produced by glycolysis are actively transported from cytoplasm into mitochondrial matrix- at this point the pyruvate molecules take part in the link reaction Link reaction formula Pyruvate + coenzyme A —> acetyl coenzyme A + carbon dioxide (at same time) NAD —> reduced NAD |
| Link reaction- steps pt1 | Pyruvate contains 3 C atoms - pyruvate now reacts with enzyme called coenzyme A- pyruvate molecule splits- A 2 C group is added to coenzyme A, forms acetyl coenzyme A- the remaining one carbon part of the pyruvate leaves as a molecule of CO2 At same time an oxidation reaction takes place- forms reduced NAD At end of a link reaction- got 3 products- one molecule of acetyl coenzyme A, one molecule of CO2, one molecule of reduced NAD |
| Link- REMEMBER | REMEMBER- glycolysis produces 2 pyruvate molecules for each molecule of glucose- so the link reaction takes place twice for each molecule of glucose entering respiration- so produces 2x of each product |
| Link- pt 3 | Also- during link reaction a CO2 molecule is released from the pyruvate- when CO2 is removed from a molecule- called decarboxylation reaction Because we have oxidation alongside decarboxylation during link reaction- called oxidative decarboxylation Link reaction doesn’t require O2 |
| Krebs pt 1 | Process liberates energy from C-C, C-H and C-OH bonds-produces ATP, containing the energy held in chemical bonds of original glucose molecule Glucose has 6C atoms - during link reaction- 2 of those atoms have left as 2 CO2 molecules - remaining 4C atoms are now in 2 molecules of remaining acetyl coenzyme A Acetyl coenzyme A now enters next stage of respiration - Krebs cycle- takes place in the mitochondrial matrix Can divide krebs cycle into 2 main stages In 1st stage acetyl coenzyme A reacts with a 4 carbon molecule - the 2 carbon part of acetyl coenzyme A moves onto this molecule, creating a 6C molecule- at same time the coenzyme A and goes back to take part in the link reaction- 2nd stage- a whole series of chemical reactions takes place: |
| Krebs pt 2 | For 6C molecule- First a decarboxylation reaction releases 1 CO2 molecule and a dehydrogenation reaction produces a molecule of reduced NAD- now have 5C molecule Another dehydrogenation reaction takes place- produces 1 molecule of reduced NAD/ another decarboxylation reaction- produces 1 CO2 molecule- 1 molecule of ATP also produced during krebs cycle- produced through substrate level phosphorylation Finally 2 more dehydrogenation reactions- produces 1 molecule of reduced FAD and 1 molecule of reduced NAD- coenzyme FAD is a hydrogen carrier similar to NAD |
| Krebs pt 3 | NOTE- during these reactions we regenerate our starting molecule (the 4 C molecule)- allows krebs cycle to continue again When Kreb’s cycle operates once we make 1 molecule of ATP, 3 molecules of reduced NAD, 1 molecule of reduced FAD, also release 2 CO2 molecules. REMEMBER- 1 glucose molecule forms 2 pyruvate molecules in glycolysis So- per glucose- link reaction produces 2 molecules of acetyl coenzyme A- krebs cycle operates x2 Acetate group from og glucose molecule now completely broken down to CO2 and water. Krebs cycle does not require oxygen |
| Coming up to oxidative phosphorylation- what's happened so far | So far in respiration created several molecules of reduced hydrogen carriers Next stage of respiration the reduced hydrogen carriers used to produce ATP- called oxidative phosphorylation Whole purpose of respiration is to generate ATP, However in reactions we’ve seen so far- only made net yield of 4 ATP molecules- per glucose- we produced a yield of 2 ATP molecules in glycolysis and 2 ATP molecules in 2 turns of Krebs cycle- These ATP molecules are formed by substrate level phosphorylation Also produced 12 molecules of reduced hydrogen carriers: 2 reduced NAD- glycolysis 2 reduced NAD link 6 reduced NAD, 2 reduced FAD- krebs |
| Oxidative phosphorylation- start | When hydrogen carrier is reduced it gains a hydrogen ion and 2 electrons- 2 e’s contain a great deal of energy- used to create ATP in oxidative phosphorylation Inner mitochondrial membrane is folded into cristae- increases SA- inbetween 2 membranes we have inter membrane space On inner mitochondrial membrane- have 2 different sets of proteins- electron transport chain and ATP synthetase |
| Oxidative phosphorylation- steps pt 1 | On inner mitochondrial membrane- have 2 different sets of proteins- electron transport chain and ATP synthetase Reduced NAD transfers high energy electrons to first protein in electron transport chain- first protein is reduced 2 electrons then pass to 2nd protein- 1st protein now oxidised- 2nd reduced KEY NOTE- as electrons move down the electrons transport chain, the electrons lose energy- used by electron transport chain proteins to pump protons (hydrogen ions) from matrix into intermembrane space |
| Oxidative phosphorylation- steps pt 2 | Because inner membrane is impermeable to protons- protons build up in intermembrane space Electrons continue making way down chain in series of oxidation and reduction reactions- at each stage protons are pumped into the intermembrane space |
| Oxidative phosphorylation- steps- pt 3 | At the end the 2 electrons have transferred all of their energy These 2 electrons now combine with oxygen and 2 hydrogen ions (protons) to make a molecule of water equation= 2 e- + ½ O2 + 2H+ —> H2O |
| Oxidative phosphorylation- steps pt4 | Reduced FAD operates in the same way as reduced NAD- However, the electrons from reduced FAD enter the transport chain in the middle rather than the start As we said molecule of glucose generates 10 reduced NAD molecules and 2 reduced FAD molecules- so as a result of the electron transport chain, the concentration of protons is much greater in the intermembrane space than the matrix- proton gradient is now used to generate ATP |
| Reaches ATP synthetase pt 1 | Enzyme ATP synthase is found on inner mitochondrial membrane- contains an ion channel through centre Protons now diffuse down the gradient through the ion channel into the matrix- this movement of protons is used by ATP synthase to generate ATP from ADP and Pi- process is called chemiosmosis - ADP+Pi→ ATP+ H2O At end protons combine with electrons and oxygen to form water- O2 from blood- taken to cells |
| Reaches ATP synthetase pt 2 | Oxygen is described as the final (terminal) electron acceptor-essential as it removes protons and electrons- oxygen reduced by addition of hydrogen atoms and electrons to make water Cyanide is a non competitive inhibitor of the final carrier of the electron transport chain- in its presence electrons and protons can’t be transferred to water- accumulate and so electron transport chain no longer functions- proton gradient not maintained- ATP synthetase can’t produce ATP- cell dies quickly |
| Oxidative phosphorylation - ATP products | In theory oxidative phosphorylation can provide 34 molecules of ATP per glucose molecule- but depends on conditions Substrate level phosphorylation in glycolysis and the krebs cycle provides only 4 ATP molecules per glucose- so oxidative phosphorylation provides a vast majority of ATP in aerobic respiration |
| Oxidative phosphorylation general products | ATP is the major product of oxidative phosphorylation, as it is the premier energy molecule of the cell. Oxidative phosphorylation also produces NAD+, FAD, and water. |
| Anaerobic respiration | no oxygen to remove atoms from reduced NAD and make water- electron transport chain cannot function- no oxidative phosphorylation- no ATP formed- no O2- no reduced NAD can be reoxidised - no NAD regenerated to pick up more hydrogen consequently- link and Krebs can't take place- only glycolysis is possible |
| Anaerobic respiration- how does glycolysis continue | For glycolysis to continue- pyruvate and hydrogen must be constantly removed and NAD must be regenerated Done how? Pyruvate accepts hydrogen from reduced NAD - 2 different anaerobic pathways to remove hydrogen from reduced NAD- both in cytoplasm |
| 2 anaerobic pathways- path1 | In animals- muscle cells may not get sufficient O2 during vigorous exercise-when deprived of O2 pyruvate= hydrogen acceptor- converted to lactate- regenerating NAD- lactate can build in muscle cells or be transported to liver- converted back to glucose or stored as glycogen- if O2 later becomes available- lactate can be respired to CO2 and water- releasing energy it contains |
| 2 anaerobic pathways- path2 | In various microorganisms eg yeast and in plant cells under certain conditions eg roots in waterlogged soils- pyruvate is converted o CO2 and to ethanal, a hydrogen acceptor- converted by decarboxylase- Ethanal is reduced to ethanol and NAD is regenerated in alcoholic fermentation ( a process in which some sugars (as glucose) are converted into alcohol and carbon dioxide by the action of various yeasts, molds, or bacteria or carbohydrate materials) pathway= irreversible- even if O2 becomes available again ethanol is not broken down- accumulates in cells- can rise to toxic concentrations |
| Energy budget aerobic respiration | p 47- table shos how many H+ atoms and ATP molecules produced from 1 molecule of glucose- gives 2 turns of krebs cycle |
| How many ATP molecules overall respired | 38 overall per glucose molecule- theoretical total- cell is generally not this efficient as- - ATP used to move pyruvate, ADP, reduced NAD and reduced FAD across mitochondrial membrane -Proton gradient may become compromised by proton leakage across the inner mitochondrial membrane, rather than passing through ATP synthetase Molecules may also leak through membranes on average 30-32 ATP molecules tend to be produced |
| Maths | If a mole of glucose is combusted in oxygen- produces 2880 kJ energy required to make ATP= 30.6 kJ/mol-1- if theoretical max is considered- a mole of glucose makes 38 moles of ATP- equivalent to 30.6x38= 1162.8 kJ therefore efficiency of ATP production= energy made through ATP/ energy released in combustion= 1162.8/2880x 100= 40.4% |
| Anaerobic respiration- brief overview | Without ATP synthetase associated with the electron transport system- the only ATP formed is in glycolysis makes 2 molecules of ATP per molecule of glucose by substrate level phosphorylation- small compared to 38 molecules of ATP produced during aerobic- |
| anaerobic more pt2 | in anaerobic pyruvate not transferred to the mitochondria but is converted in the cytoplasm- to ethanol in plants or lactate in mammals-2H released in conversion of glucose to pyruvate reduces NAD - given up again in formation of ethanol in plant cells or lactate in animal cell- many different metabolic pathways have been identified in bacteria or archaea- many organic acids and alcohols produced by their fermentation |
| anaerobic respiration- maths | Efficiency of ATP production= energy made available through ATP/ energy released in combustion x100= 30.6x2/2880x100=2.1% much less efficient |
| Alternative respiratory pathways | Kreb's cycle- sometimes called metabolic hub as the Metabolic pathways of carbohydrates, lipids and proteins can feed into it and in some situations fats and proteins can be used as respiratory substrates - Acetyl Coenzyme A is a most significant molecule as it links the metabolism of the three types of macromolecule |
| Lipid pathways | Triglyceride molecule has 2 parts-3 carbon glycerol part and on right - 3 fatty acids- fatty acids and glycerol= joined by 3 ester bonds- when triglycerides are digested - ester bonds= hydrolysed- release glycerol and fatty acid molecules- 3 carbon glycerol molecule enters glycolysis- converted to pyruvate- pyruvate then enters link reaction and krebs cycle as previously seen |
| Lipids pt 2 electric boogaloo | fatty acid molecules broken down into 2 carbon units eg O H H H || | | | C C- C - C | | | | H H H H Start of a fatty acid chain- 2 units here each unit forms a molecule of acetyl coenzyme A |
| Lipids pt 3 | Acetyl coenzyme A now enters the krebs cycle- fatty acids contain great amount of carbon to hydrogen bonds- forms very large number of acetyl coenzyme A molecules- so triglycerides contains great amount of energy- more than glucose |
| Protein- aerobic respiration pathway | First protein must be hydrolysed to its individual amino acids during digestion- all proteins have an amino group- in first stage- amino group is removed- called deamination- carbon part of amino acid is then processed (entirety that isn't N-H-H)- |
| Protein- aerobic respiration pathway- pt 2 | pathway of this depends on amino acid- some amino acids lead to production of pyruvate- others can be converted to molecules that're part of Krebs cycle- energy value of proteins is approx same as carbs |
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