Component 1 - Topic 1.3 - Respirqation Releases Chemical Energy in Biological Processes (COMPLETED) Flashcards
(9 cards)
a) What is ‘respiration’?
b) Why is reactions CATABOLIC? Does this mean reactions are exergonic or endergonic?
c) What are the 3 types of phosphorylation? In-depth: Provide location and how ATP stores the energy in the end…
d) What does AEROBIC mean?
e) What does ANAEROBIC mean?
f)
1. What is an OBLIGATE AEROBE?
2. What is a FACULTATIVE ANEROBE?
3. WHat is an OBLGATE ANAEROBE
a) Respiration is a sequence of enzyme CONTROLLED reactions in which the product of one reaction shall be the substrate of the NEXT reaction.
b) Reactions are CATABOLIC - they break apart energy RICH macro-molecules, such as gluecose and fatty acids. Catabolism is the process of breaking down larger molecules into smaller molecules. Catabolic reactions are EXERGONIC (energy is released).
c)
1. Oxidative Phosphorylation = The inner membrane of the mitochondria underogoes aerobic respiration in which energy for making ATP comes from the oxidation-reduction reactions and is released in the transfer of electrons along a chain of electron carrier molecules.
- Photophosphorylation = Occurs on the thylakoid membranes of the chloroplasts in the lght-dependent stage of photosynthesis. The energy for making the ATP comes from LIGHT and is released in the transfer of electrons along a chain of electron carrier molecules. This does NOT happen in respiration.
- Substrate-level phosphorylation, occurs when enough energy is released from a reaction to bind ADP and inorgain Pi to form ATP.
d) Aerobic Respiration = The release of LARGE amounts of energy. This energy is made available in the form of ATP. Oxygen is the terminal electron acceptor.
e) Anerobic Respiration = The breakdown of molecules in the absence of OXYGEN, releasing relatively small amounts of energy, making a small amount of ATP via SUBSTRATE-LEVEL PHOSPHORYLATION.
f)
1. These are organisms NEED oxygen in order to grow.
2. Flexibility to survive in either oxygen or low oxygen conditions.
3. These organisms can’t survive in the presence of oxygen.
AEROBIC RESPIRATION (PART 1 of 4 Stages):
GLYCOLYSIS
a) Glycolysis is the initial stage for BOTH anaerobic and aerobic respiration. It occurs in the CYTOPLASM, this is because gluecose is unable to fit into the MITOCHONDRIAL MEMBRANE. Furthermore, even if it could move into the mitochondria, the enzymes that operate do not exist in the mitochondrial membrane.
1. A gluecose molecules is PHOSPHORYLATED by the addition of 2 phosphate groups, using 2 molecules of ATP. The end result if HEXOSE DIPHOSPHATE. Recall, gluecose is a hexose sugar. Hexose Phosphate formation causes 2 molecules of ATP to form due to substrate-level-phosphorylation.
- Hexosephosphate exhibits 2 qualitites, NO.1, it’s MORE reactive and so LESS EA is required fot the ENZYME-CONTROLLED reactions.
- NO.2 Hexose diphospate is MORE polar than gluecose and so is LESS likely to diffuse OUT of the cell.
- The hexose diphophate is then converted into to two molecules of triose phosphate, a 3 carbon sugar.
- BOTH triose phosphate molecules then get DEHYDROGENATED (this means the removal of 1 or MORE hydrogen atoms from a molecules). This OXIDISES the molecule to PYRUVATE. Two pyruvate molecules are formed in the end. The hydrogen atoms are transferred to NAD, a hydrogen carrier molecules which gets reduced to form reduced NAD. Resulting from this is the formation of 4 ATP molecules of which there is a NET gain of 2.
a) Glycolysis is the initial stage for BOTH anaerobic and aerobic respiration. It occurs in the CYTOPLASM, this is because gluecose is unable to fit into the MITOCHONDRIAL MEMBRANE. Furthermore, even if it could move into the mitochondria, the enzymes that operate do not exist in the mitochondrial membrane.
1. A gluecose molecules is PHOSPHORYLATED by the addition of 2 phosphate groups, using 2 molecules of ATP. The end result if HEXOSE DIPHOSPHATE. Recall, gluecose is a hexose sugar. Hexose Phosphate formation causes 2 molecules of ATP to form due to substrate-level-phosphorylation.
- Hexosephosphate exhibits 2 qualitites, NO.1, it’s MORE reactive and so LESS EA is required fot the ENZYME-CONTROLLED reactions.
- NO.2 Hexose diphospate is MORE polar than gluecose and so is LESS likely to diffuse OUT of the cell.
- The hexose diphophate is then converted into to two molecules of triose phosphate, a 3 carbon sugar.
- BOTH triose phosphate molecules then get DEHYDROGENATED (this means the removal of 1 or MORE hydrogen atoms from a molecules). This OXIDISES the molecule to PYRUVATE. Two pyruvate molecules are formed in the end. The hydrogen atoms are transferred to NAD, a hydrogen carrier molecules which gets reduced to form reduced NAD. Resulting from this is the formation of 4 ATP molecules of which there is a NET gain of 2.
AEROBIC RESPIRATION (PART 2 of 4 Stages):
LINK REACTION:
a) This reaction LINKS together glycolysis and the KREBS CYCLE.
1. BOTH pyruvate molecules synthesised from glycolysis are transported into the mitochondrial matric from the cytoplasm.
2. The pyruvate in the mitochondrial matrix is then DEHYDROGENTATED first, and 2 hydrogen atoms are released and reduced NAD to reduced NAD.
3. Simultaneoulsy, pyruvate is also DECARBOXYLATED, whereby, a molecule of CO2 is removed from it. All that then remains is a 2-carbon ACETATE group. The 2-carbon acetate group then combines with ACETYL COenzyme which enters the KREBS CYCLE.
a) This reaction LINKS together glycolysis and the KREBS CYCLE.
1. BOTH pyruvate molecules synthesised from glycolysis are transported into the mitochondrial matric from the cytoplasm.
2. The pyruvate in the mitochondrial matrix is then DEHYDROGENTATED first, and 2 hydrogen atoms are released and reduced NAD to reduced NAD.
3. Simultaneoulsy, pyruvate is also DECARBOXYLATED, whereby, a molecule of CO2 is removed from it. All that then remains is a 2-carbon ACETATE group. The 2-carbon acetate group then combines with ACETYL COenzyme which enters the KREBS CYCLE.
AEROBIC RESPIRATION (PART 3 of 4 Stages):
KREBS CYCLE:
a) The KREBS cycle means to LIBERATE (i.e FREE) energy from the C-C, C-H and C-OH bonds. It produces ATP, containing the energy which was held in the chemical bonds of the orgional gluecose molecule (substate-level phosphorylation). It also produces ‘reduced NAD’ and ‘reduced FAD’. These two hydrogen carrier molecules transport hydrogen ATOMS to the electron transport chain (the electron-transport chain can be located on the inner mitochondrial membrane. Three molcules of water are used in this reaction and CO2 is released as a WASTE product
1. Acetyl Coenzyme A enters the Krebs cycle by combining with a 4-carbon acid, to form a 6-carbon compound, ctiric acid. The CoA enzyme is regenerated.
2. The 6 carbon acid is then dehdrogenated, to form a reduced NAD and is decarboxylated to form a CO2, making a 5 carbon acid.
3. The 5 carbon acid is then dehydrogenated, to form a reduced NAD AND FAD, and the 5 carbon acid is decarboxylated to form CO2. This re-generates the 4 carbon acid, that can then combine with another Acetyl CoA and repeat the cycle.
The origional GLUECOSE has now been broken DOWN fully…
b) It is key to note that decarboxylation occurs twice. Dehydrogenation meanwhile occurs 4 times and creates 3 reduced NAD and 1 reduced FAD (the reduced FAD is formed on the 3 dehydrogenation).
a) The KREBS cycle means to LIBERATE (i.e FREE) energy from the C-C, C-H and C-OH bonds. It produces ATP, containing the energy which was held in the chemical bonds of the orgional gluecose molecule (substate-level phosphorylation). It also produces ‘reduced NAD’ and ‘reduced FAD’. These two hydrogen carrier molecules transport hydrogen ATOMS to the electron transport chain (the electron-transport chain can be located on the inner mitochondrial membrane. Three molcules of water are used in this reaction and CO2 is released as a WASTE product
1. Acetyl Coenzyme A enters the Krebs cycle by combining with a 4-carbon acid, to form a 6-carbon compound, ctiric acid. The CoA enzyme is regenerated.
2. The 6 carbon acid is then dehdrogenated, to form a reduced NAD and is decarboxylated to form a CO2, making a 5 carbon acid.
3. The 5 carbon acid is then dehydrogenated, to form a reduced NAD AND FAD, and the 5 carbon acid is decarboxylated to form CO2. This re-generates the 4 carbon acid, that can then combine with another Acetyl CoA and repeat the cycle.
The origional GLUECOSE has now been broken DOWN fully…
b) It is key to note that decarboxylation occurs twice. Dehydrogenation meanwhile occurs 4 times and creates 3 reduced NAD and 1 reduced FAD (the reduced FAD is formed on the 3 dehydrogenation).
AEROBIC RESPIRATION (PART 3 of 4 Stages):
KREBS CYCLE:
a) The ETC is located on the CRISTAE of the INNER MITOCHODRIAL membranes. The ETC is a series of PROTEIN MOLECULES that act as carriers and PUMPS, which are sometimes called ‘respiratory enzymes’.
The reactions these proteins catalyse RELEASE energy, which is carried by ATP. Hydrogen atoms are carried to the ETC by the CO-ENZYMES NAD and FAD. NAD feeds electrons and protons into the ETC at an EARLIER stage in comparison to the FAD. Each pair of hydrogen atoms carries by reduced NAD provides energy to synthesise THREE molecules of ATP, using 3 protons pumps. Reduced FAD passes the hydrogen atoms directly to the second proton pump so the carrier system involving FAD has two pumps and produces 2 ATP molecules of ATP.
a) The ETC is located on the CRISTAE of the INNER MITOCHODRIAL membranes. The ETC is a series of PROTEIN MOLECULES that act as carriers and PUMPS, which are sometimes called ‘respiratory enzymes’.
The reactions these proteins catalyse RELEASE energy, which is carried by ATP. Hydrogen atoms are carried to the ETC by the CO-ENZYMES NAD and FAD. NAD feeds electrons and protons into the ETC at an EARLIER stage in comparison to the FAD. Each pair of hydrogen atoms carries by reduced NAD provides energy to synthesise THREE molecules of ATP, using 3 protons pumps. Reduced FAD passes the hydrogen atoms directly to the second proton pump so the carrier system involving FAD has two pumps and produces 2 ATP molecules of ATP.
ANAEROBIC RESPIRATION:
a) If there’s NO oxygen in the immediate environement that can remove hydrogen atoms from reduced NAD (recall, oxygen is the termianl electron acceptor) to make WATER, the ETC can NO longer function. There is therefore NO oxidative phosphorylation and so no formation of ATP via this method. Without oxygen, reduced NAD cannot be re-oxidised and NO NAD is regenreated to pick-up hydrogens from glycolysis, the link reaction and the krebs cylcle. ONLY GLYCOLYSIS is possible.
What happens…For glycolysis to continue, pyruvate and hydrogen must be constantly removed and NAD must be regenerated. This is done by pyruvate accepting the hydrogen from reduced NAD forming LACTATE. The only ATP now that can be generated is in the absence of oxygen via substrate-level phosphorylation.
1, In animals, muscle cells may NOT get sufficient supply of oxygen during intense excercise. WHen deprived of oxygen, pyruvate is then the HYDROGEN ACCEPTOR. It’s converted into LACTATE, regenerating the NAD (which becomes oxidised once more, enabling it to accept another hydrogen and become reduced again). If oxygen appears afterwards, the lactate formed, is transported to the liver, and can be converted back into either glycogen or gluecose.
2. In various microorganisms, such as yeast, and in plant cells under certain conditions, such as in the roots in waterlogged soils, PYRUVATE is CONVERTED to CO2 and to ETHANAL by the enzyme decarboxylase. Ethanlal then becomes the hydrogen acceptor molecule which forms ETHANOL, this allows NAD to re-generate (i.e become oxidised once more). This is alcoholic fermentation. It is NOT reversible. A rise in ehtanol can become toxic to the microorganism.
a) If there’s NO oxygen in the immediate environement that can remove hydrogen atoms from reduced NAD (recall, oxygen is the termianl electron acceptor) to make WATER, the ETC can NO longer function. There is therefore NO oxidative phosphorylation and so no formation of ATP via this method. Without oxygen, reduced NAD cannot be re-oxidised and NO NAD is regenreated to pick-up hydrogens from glycolysis, the link reaction and the krebs cylcle. ONLY GLYCOLYSIS is possible.
What happens…For glycolysis to continue, pyruvate and hydrogen must be constantly removed and NAD must be regenerated. This is done by pyruvate accepting the hydrogen from reduced NAD forming LACTATE. The only ATP now that can be generated is in the absence of oxygen via substrate-level phosphorylation.
1, In animals, muscle cells may NOT get sufficient supply of oxygen during intense excercise. WHen deprived of oxygen, pyruvate is then the HYDROGEN ACCEPTOR. It’s converted into LACTATE, regenerating the NAD (which becomes oxidised once more, enabling it to accept another hydrogen and become reduced again). If oxygen appears afterwards, the lactate formed, is transported to the liver, and can be converted back into either glycogen or gluecose.
2. In various microorganisms, such as yeast, and in plant cells under certain conditions, such as in the roots in waterlogged soils, PYRUVATE is CONVERTED to CO2 and to ETHANAL by the enzyme decarboxylase. Ethanlal then becomes the hydrogen acceptor molecule which forms ETHANOL, this allows NAD to re-generate (i.e become oxidised once more). This is alcoholic fermentation. It is NOT reversible. A rise in ehtanol can become toxic to the microorganism.
a) Why isn’t 38 the real number of ATP produced per gluecose?
a) In reality 38 aren’t formed, this is a theoretical value, this is because in reality, ATP are used to move pyruvate, ADP, reduced NAD and FAD across the mitochondrial membrane.
Alternative Respiratory Pathways:
a) The KREBS cycle is also called the metabolic hub because the metabolic pathways of carbohydrates, lipids and proteins feed into the KREBS cycle, in some instances fats and proetins can even be used as respiratory substrates…
b) Lipids: Fats provide an energy store and is used as a respiratory substrate when carbohydrtae levels in the body, such as glycogen and BLOOD gluecose are VERY low. First, fat is hydrolysed into its constituents, glycerol and fatty acids. Then the glycerol is phosphorylated with ATP, dehydrogenated with NAD and converted into 3-carbon sugar, triose phosphate, which enters the glycolysis pathway. The long chain fatty acid molecules are split into 2 carbon fragments that enter the Krebs cycle as acetyl CoA. Hydrogen is released, picked up by NAD and FAD and fed into the ETC. Precise no. of ATP fomed can vary depending on the length of the hydrocarbon chain of the fatty acid.
- More carbon atoms = more CO2 produced. Muscles have limited blood supply and if they respire FAT, rather than gluecose, they would produce MORE CO2 that could be removed quickly.
- More hydrogen atoms = more FAD and NAD are reduced, so more ATP is formed. This explains why tissues with a rich blood supply, such as liver, respire FAT: the large amount of ATP they produce is transported around the body.
- More hydrogen atoms mean more water is produced. This ‘metabolic water’ is very imporatnt for desert animals in particular!
a) The KREBS cycle is also called the metabolic hub because the metabolic pathways of carbohydrates, lipids and proteins feed into the KREBS cycle, in some instances fats and proetins can even be used as respiratory substrates…
b) Lipids: Fats provide an energy store and is used as a respiratory substrate when carbohydrtae levels in the body, such as glycogen and BLOOD gluecose are VERY low. First, fat is hydrolysed into its constituents, glycerol and fatty acids. Then the glycerol is phosphorylated with ATP, dehydrogenated with NAD and converted into 3-carbon sugar, triose phosphate, which enters the glycolysis pathway. The long chain fatty acid molecules are split into 2 carbon fragments that enter the Krebs cycle as acetyl CoA. Hydrogen is released, picked up by NAD and FAD and fed into the ETC. Precise no. of ATP fomed can vary depending on the length of the hydrocarbon chain of the fatty acid.
- More carbon atoms = more CO2 produced. Muscles have limited blood supply and if they respire FAT, rather than gluecose, they would produce MORE CO2 that could be removed quickly.
- More hydrogen atoms = more FAD and NAD are reduced, so more ATP is formed. This explains why tissues with a rich blood supply, such as liver, respire FAT: the large amount of ATP they produce is transported around the body.
- More hydrogen atoms mean more water is produced. This ‘metabolic water’ is very imporatnt for desert animals in particular!
Alternative Respiratory Pathways:
a) Protiens can be used as a respiratory substrate whenever dietary supplies are inadequate; the protein component of the food is diverted for energy purposes if carbohydrates and fat are alcking diet. in prolonged starvation, tissue protein is MOBILISED to supply energy. HEART muscle and kedney are among the first the body breaks to release protein. Protien gets hydrolysed into its constituent amino acids, which get De-aminated in the liver. The amino group is converted into urea as we already know and gets excreted. The residue after de-amination is converted into Acetyl CoA, pyruvate or some other KREBS cycle intermediate and gets oxidised.
a) Protiens can be used as a respiratory substrate whenever dietary supplies are inadequate; the protein component of the food is diverted for energy purposes if carbohydrates and fat are alcking diet. in prolonged starvation, tissue protein is MOBILISED to supply energy. HEART muscle and kedney are among the first the body breaks to release protein. Protien gets hydrolysed into its constituent amino acids, which get De-aminated in the liver. The amino group is converted into urea as we already know and gets excreted. The residue after de-amination is converted into Acetyl CoA, pyruvate or some other KREBS cycle intermediate and gets oxidised.
