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78 Cards in this Set
- Front
- Back
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Background Define respiration |
The release of chemical energy from glucose or other substances by oxidation; most of the energy is used to make ATP; respiration takes place in most living cells. |
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Background Why do organisms need to respire? |
All organisms need energy to drive metabolic reactions. For example, organisms need energy to... - build polypeptides from amino acids - make copies of DNA molecules - move chromosomes in meiosis/mitosis - move muscle cells |
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Background Draw the structure of ATP |
ATP is a phosphorylated nucleotide: Adenosine Triphosphate |
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Background Draw the hydrolysis of ATP |
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Background What is the function of ATP? |
To act as an immediate source of energy for biological processes |
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Background Why use ATP and not glucose? |
ATP provides small amounts of energy in small packages and can be released quickly and easily. Glucose would contain too much energy and much of it would be wasted. |
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Background Define coenzyme |
A non-protein molecule that is required for an enzyme to catalyse a reaction |
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Background What are the functions of coenzymes in respiration? |
They help enzymes carry out oxidation and reduction reactions of respiration - hydrogen atoms are combined with coenzymes to carry them so they can later be split into hydrogen ions and electrons to take part in oxidative phosphorylation. Hydrogen reoxidises coenzymes in the cristae so they can recombine with more hydrogen atoms. |
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Background What is the function of NAD? |
NAD is Nicotinamide Adenine Dinucleotide. It -Helps dehydrogenase enzymes carry out oxidation - operates during the link reaction, Krebs cycle, glycolysis and anaerobic pathways |
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Background What is the function of coenzyme a? |
- Carries ethanoate (acetate) groups made from pyruvate in the link reaction onto the Krebs cycle - Can also carry acetate groups made from fatty acids/ amino acids to the Krebs cycle. |
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Background What are mitochondria? |
Organelles found in Eukaryotic cells - they are the site of the aerobic stages of respiration: Link reaction, Krebs Cycle, Glycolysis and Oxidative Phosphorylation. |
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Background Draw and annotate the structure of a mitochondrion |
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Background How long is a mitochondrion? |
2-5 µm |
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Background What is the structure and function of the matrix? |
The matrix is the background material. It is made of lipids and proteins. |
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Background What is the structure and function of the cristae? |
Cristae are folded inner membrane. They provide a large surface area. |
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Background How is the matrix adapted to its function? |
- contains enzymes that catalysse the reactions - contains coenzyme NAD - contains oxaloacetate which accepts acetate in the link reaction - contains mitochondrial DNA which codes for mitochondrial enzymes and proteins |
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Background How is the outer membrane adapted to is function? |
-Contains proteins which form channels or carriers that allow the passage of molecules such as pyruvate - contains enzymes |
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Background How is the inner membrane adapted to its function? |
- It is folded into many critsae to give a large SA - It has electron carriers and ATP synthase enzymes embedded within it - Is impermeable to small ions so protons accumulate in the intermembranal space, building up a proton gradient, |
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Glycolysis Define glycolysis |
The metabolic pathway where each glucose molecule is broken down into two molecules of pyruvate. It occurs in the cytoplasm of licing cells. |
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Glycolysis Where does glycolysis take place? |
In the cytoplasm. |
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Glycolysis What are the four stages of glycolysis? |
1) Phosphorylation of Glucose 2) Splitting of Hexose-1,6,-bisphosphate 3) Oxidation of Triose Phospate 4) Conversion of TP -> Pyruvate |
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Glycolysis Outline what occurs in the first stage of Glycolysis |
- An ATP molecule is hydrolysed and the Phosphate group released attached to Glucose to form Glucose-6-phosphate - It is then converted to Fructose - 6 phosphate - Another ATP molecule is hydrolysed and the Pi attaches to form Fructose-1,6-bisphosphate - The energy from the hydrolysis of ATP activates the hexose sugar and its energy level is raised. It is now called hexose-1,6-bisphosphate. |
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Glycolysis Draw what happens in phosphorylation |
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Glycolysis How many ATP is used in glycolysis? |
2 |
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Glycolysis Outline what happens in step 2: splitting |
Hexose-1,6-bisphosphate is broken down into two molecules of 3C triose phosphate. |
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Glycolysis Draw what happens in step 2. |
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Glycolysis Outline what happens in step 3 - oxidation |
-Two hydrogen atoms are removed from each molecule of triose phosphate - This requires dehydrogenase enzymes and coenzyme NAD which combines with the hydrogen atoms to become reduced - 2 MOLECULES OF ATP ARE PRODUCED FROM SUBSTRATE LEVEL PHOSPHORYLATION. |
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Glycolysis So what is formed so far? |
2 molecules of reduced NAD are produced per glucose 2 ATP are formed by substrate-level phosphorylation (the formation of ATP from ADP +Pi during glycolysis/Krebs cycle) |
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Glycolysis
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Glycolysis Outline what occurs in step 4 + Draw this. |
2 ATP are formed by substrate level phosphorylation as the intermediate is converted to pyruvate. |
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Glycolysis Draw the full reactions for glycolysis. |
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Glycolysis What are the full products of glycolysis? |
2 ATP (2 Used 4 made) 2 Reduced NAD 2 Pyruvate |
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Glycolysis What can happen to the pyruvate now? |
It depends on the availability of oxygen - aerobic respiration active transport is used to move pyruvate to the mitochondrial matrix - this does not occur in anaerobic respiration |
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Link Reaction What is the link reaction? |
A reaction which takes place in the matrix of a mitochondrion in which pyruvate reacts with CoA to from Acetyl CoA and CO2 |
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Link Reaction Draw the reaction for the link reaction |
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Link Reaction Explain what happens in the Link Reaction |
- Pyruvate is decarboxylated - a C atom is removed in the form of CO2 by pyruvate decarboxylase - Hydrogen atom is removed from pyruvate by pyruvate dehydrogenase. These hydrogens are accepted by NAD. Pyruvate is now acetate. - Acetate combines with CoA to form Acetyl CoA |
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Link Reaction What is the function of CoA? |
Carries acetate to Krebs cycle |
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Krebs Cycle Where does the Krebs cycle take place? |
Mitochondrial matrix |
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Krebs Cycle What is the Krebs cycle? |
A cycle of reactions that takes place in the mitochondrial matrix in which pyruvate is oxidised to oxaloacetate; ATP, reduced NAD and reduced FAD are produced and CO2 is released |
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Krebs Cycle
Draw the Krebs cycle |
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Krebs Cycle Outline what happens in the Krebs Cycle |
1) Acetyl CoA made in the link reaction combines with 4C oxaloacetate to form 6C Citrate. 2) CoA goes back into the Link reaction 3) Citrate is carboxylated and dehydrogenated to form a 5C compound. NAD accepts the hydrogen to become reduced and CO2 is released. 4) The 5C compound is decarboxylated and dehydrogenated to produce a 4C compound, CO2 and reduced NAD 5) The 4C compound is converted to another 4C compound. A molecule of ATP is generated by substrate-level phosphorylation 6) The second 4C compound is converted to another 4C compound by dehydrogenation: a molecule of FAD becomes reduced 7) The 4C compound is dehydrogenated further to form oxaloacetate and another reduced NAD. |
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Krebs Cycle How many cycles of the Krebs cycle occur for each molecule of glucose? |
2 cycles (2 acetate are produced from the 2 pyruvate) |
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Krebs Cycle How many __ is produced in the Link Reaction a) reduced NAD b) reduced FAD c) ATP d) CO2 |
a) 2 b) 0 c) 0 d) 2 |
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Krebs Cycle How many __ is produced in the Krebs cycle a) reduced NAD b) reduced FAD c) ATP d) CO2 |
a) 6 b) 2 c) 2 d) 4 |
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Krebs Cycle What are other sources of things for respiration to occur? |
- other food sources can be respired instead of glucose - fatty acids can be broken down to acetate and enter the Krebs cycle by CoA - Amino acids can be deaminated (-NH2) and enter the Krebs cycle or it might need to be changed to pyruvate or acetate first |
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Krebs Cycle Do these stages require oxygen? |
YES. Even though oxygen is not used, the reactions won't occur in the absence of oxygen |
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Oxidative Phosphorylation What is oxidative phosphorylation? |
The production of ATP via the electron transport chain in a mitochondrion |
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Oxidative Phosphorylation Where do the electrons and protons for chemiosmosis come from/? |
Reduced NAD and Reduced FAD become reoxidised when they release hydrogen atoms. These hydrogen atoms then split into H+ and e-. |
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Oxidative Phosphorylation What does Oxidative Phosphorylation involve? |
The use of electron carriers embedded in the mitochonrdrial membranes which are folded into cristae to give a large surface area for electron carriers and ATP synthase enzymes. |
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Oxidative Phosphorylation Outline what happens in Oxidative Phosphorylation |
1) Hydrogen atoms released from reduced NAD and reduced FAD from the Krebs cycle split into H+ and e-. 2) The electrons move along a series of electron carriers in the electron transport chain and energy is released. 3) This energy is used to pump protons into the intermembranal space, building up a proton gradient (electrochemical gradient) 4) The build up of potential energy causes protons to flow down their electrochemical gradient by ATP synthase 5) This movement drives the formation of ATP from ADP + Pi (this is chemiosmosis) 6) Electrons are passed to the final electron acceptor, O2, where they combine with protons to form H20. |
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Draw the full aerobic respiration. include site of each stage. |
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Evidence for Chemiosmosis Outline how a pH gradient provides evidence for chemiosmosis. |
- There is a pH gradient across the membranes involved in ATP production -The pH is higher on the side of the membrane that contains the ETC than the other -This indicated that H+ ions are being actively moved across the membrane (=chemisomosis) |
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Evidence for Chemiosmosis Outline how uncouplers provide evidence for chemiosmosis |
-Uncouplers are substances that destroy the proton gradient across the inner mitochondrial membrane - When added to mitochondria with reduced NAD, ADP and Pi, no ATP was produced - Thus, indicating that a proton gradient is required for ATP synthesis |
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Evidence for Chemiosmosis Outline how the isolation of thylakoids provides evidence for chemiosmosis |
-Kept in the dark, isolated thylakoids were placed in a pH 4 Buffer solution -They were left long enough for H+ ions to become equal inside and outside the thylakoids -When given ADP+Pi, no ATP was produced -But, when put in a fresh pH 8 buffer, ATP was produced = proton gradient required. |
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Misc What can you use to measure the rate of respiration? |
A respirometer to measure the uptake of Oxygen |
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Misc What is the theoretical yield of ATP from one molecule of glucose? |
32 |
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Misc Why can this theoretical yield not be achieved? |
-Some ATP is used in the active transport of pyruvate into the matrix -Some ATP is used for the active transport of reduced NAD from glycolysis into the inner membrane -Some protons leak through the inner membrane and into the matrix, so the proton gradient is decreased |
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Anaerobic Respiration Why does aerobic respiration require oxygen? |
To act as the final electron acceptor
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Anaerobic Respiration What happens therefore, when there is no oxygen? |
The electron transport chain cannot function so the link reaction and the Krebs cycle stop, leaving only glycolysis as a source of ATP. |
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Anaerobic Respiration What is the problem with only having glycolysis? |
The Reduced NAD produced needs to be reoxidised for glycolysis to keep happening. |
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Anaerobic Respiration What are the two ways in which reduced NAD can be reoxidised? |
- Alcoholic fermentation - Lactate fermentation |
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Anaerobic Respiration Draw and explain what happens in alcoholic fermentation. |
1) Pyruvate is decarboxylated by pyruvate decarboxylase to form Ethanal 2) Ethanal accepts hydrogen from reduced NAD to form Ethanol and oxidised NAD. 3) NAD can now accept more hydrogen atoms in glycolysis. |
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Anaerobic Respiration What uses alcoholic fermentation? |
Yeast |
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Anaerobic Respiration What uses lactate fermentation ? |
Mammals |
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Anaerobic Respiration Draw and explain what happens in lactate fermentation |
1) Pyruvate accepts hydrogen from reduced NAD to form Lactate and oxidised NAD. It is catalysed by lactate dehydrogenase. |
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Anaerobic Respiration How does lactate build up in muscle cells? |
- The lactate pathway is most likely to occur in skeletal muscle cells - When exercising vigorously, they need more oxygen than can be supplied to them from the blood. -So, they keep using whatever oxygen they can in aerobic respiration and also top up their ATP by the lactate pathway. THUS lactate builds up. |
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Anaerobic Respiration Where does the lactate go? |
1) Lactate diffuses into the blood where is dissolves in blood plasma and is passed around the body 2) Once it reaches the liver, it is absorbed by hepatocytes. They first convert it to pyruvate. 3) When exercise stops and oxygen is plentiful, pyruvate is oxidised using the link reaction and the Krebs cycle 4) Some lactate is converted to glycogen for an energy store. |
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Anaerobic Respiration What is oxygen debt? |
The removal of lactate by hepatocytes requires oxygen: hence why you keep breathing heavily after exercise to build up extra oxygen for the metabolism of lactate. THis is oxygen debt. |
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Anaerobic Respiration What are the effects of a high concentration of lactate? |
- Nausea
- Stops muscle contraction |
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Anaerobic Respiration Which pathway produces a higher ATP yield? Why? |
Aerobic respiration because anaerobic respiration only involves one energy producing step: glycolysis. Krebs and Oxidative phosphorylation cannot occur without oxygen. |
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Respiratory Substrates What is a respiratory substrate? |
An organic compound that is respired to produce ATP |
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Respiratory Substrates
How does the hydrogen content of a respiratory substrate affect ATP yield? |
More hydrogen atoms per mole of respiratory substrate means that there are more protons so more ATP can be produced by oxidative phosphorylation. |
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Respiratory Substrates What is the energy yield of carbohydrates and proteins? |
17 kJ g-1
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Respiratory Substrates What is the energy yield of fats/lipids? Why is this higher than carbohydrates of proteins? |
39kJg-1 Because it contains more H in comparison to C and O |
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Respiratory Substrates How can proteins be used as respiratory substrates? |
- Excess amino acids can be deaminated to produce urea -It can then be converted to glycogen or fats - These can be stored and later respired to release energy |
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Respiratory Substrates What else can be done to the glycogen/fats made from amino acids? |
-They can be converted to pyruvate and be carried to the krebs cycle -Can directly enter Krebs cycle. |
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Respiratory Substrates What can triglycerides be hydroysed to ? |
Glycerol and fatty acids (by lipase) |
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Respiratory Substrates What can then happen? |
- Glycerol can be converted to glucose- fatty acids cannot. -Fatty acids are long chain hydrocarbons with COOH, so have a lot of hydrogen atoms which can be used as a source of protons for oxidative phosphorylation. |
