Biology Chapter 6 Outline
Content
Biology Chapter 6 Outline Introduction: y Cellular respiration ± aerobic harvesting of energy from sugar by muscle cells, yields carbon dioxide, water and ATP 6.1: y Cell uses energy to maintain structure, transport materials, manufacture products, move, grow and reproduce y Cellular respiration has oxygen consumed, glucose broken down into carbon dioxide and water with the energy being released captured in ATP y The products of cellular respiration are used by photosynthesis which has products that are then used by respiration, cycle 6.2: y Breathing and cellular respiration are closely related y Lungs take up oxygen into bloodstream and oxygen then travels to muscle cells where mitochondria uses the oxygen for cellular respiration y The lungs also dispose of the carbon dioxide waste produced from cellular respiration 6.3: y Cells burn many other organic molecules other than glucose during respiration y Cellular respiration is an exergonic process, the chemical energy of the bonds in glucose are broken and stored within the bonds of ATP y Cellular respiration can produce up to 38 ATP for each molecule of glucose with the rest of the energy released as heat 6.4: y Body requires continuous energy for heart pumping, breathing and maintaining body temperature, brain also requires large amount of energy y Kilocalories ± energy units, the quantity of heat required to raise the temperature of one kilogram of water by one Celsius y Average human needs intake of 2,200 kcal of energy per day 6.5: y The energy available to a cell is contained in arrangement of electrons in the chemical bonds that hold organic molecules together y During cellular respiration electrons are transferred to oxygen to form hydrogen-oxygen bonds from the broken carbon-hydrogen bonds y Oxygen strongly attracts electrons, final electron acceptor y Electron loses potential energy when transferred to oxygen y Hydrogen transfer during cellular respiration signifies electron transport y Redox reaction ± movement of electrons from one molecule to another y Oxidation ± loss of electrons, gain in charge y Reduction ± addition of electrons, reduction in charge y Oxidation and reduction always occur together y In cellular respiration glucose is oxidized while oxygen is reduced y Dehydrogenase ± enzyme, removes the hydrogen atoms in oxidation y NAD+ - coenzyme, organic molecule that is made from vitamin niacin and shuttles electrons in the redox reactions, picks up electrons and reduces to NADH
y
y 6.6: y y
Electron transport chain: transfer of electrons from organic molecule to NADH, electron carrier molecules within inner membrane of mitochondrion transfer electrons, oxygen serves as final electron acceptor Electron transport chain involves series of redox reactions that provide enough energy for the formation of ATP The steps of cellular respiration in prokaryotic cells occur in the cytoplasm with electron transport built into plasma membrane Glycolysis ± occurs in cytoplasmic fluid outside organelles, begins respiration by breaking down glucose into two molecules of pyruvate (three-carbon compound), uses no oxygen molecules Citric acid cycle ± within mitochondria, completes breakdown of glucose by decomposing pyruvate to carbon dioxide During first two stages the cell makes 4 ATP, main function to supply electrons for oxidative phosphorylation Oxidative phosphorylation ± involves electron transport chain and chemiosmosis, NADH and FADH2 shuttle electrons to transport chain within inner mitochondrion membrane Most ATP from respiration generated by oxidative phosphorylation which uses the energy released by electron chain to phosphorylate ADP As the electron transport chain passes electrons down staircase it pumps hydrogen ions across inner mitochondria membrane into intermembrane space to form concentration gradient of hydrogen across membrane Chemiosmosis ± potential energy of hydrogen concentration gradient used to make ATP ATP synthases ± protein complexes built into inner mitochondria membrane that synthesize ATP, concentration gradient drives diffusion of hydrogen through these There are nine chemical steps in the change of glucose to pyruvate, each which is catalyzed by its own enzyme As glycolysis occurs two molecules of NAD+ are reduced to form NADH and uses this to form two molecules of ATP Substrate-level phosphorylation ± enzyme transfers phosphate group from substrate molecule directly to ADP to form ATP, glycolysis and citric acid cycle Energy extracted from glucose during glycolysis is placed into ATP and NADH The energy in NADH is used by passing electrons down the transport chain Intermediates ± compounds that form between the initial reactant and the final product, pyruvate serves as intermediate Glycolysis: energy investment phase in which 2 ATP is used to energize a glucose molecule, glucose splits into two smaller sugars that can release energy, energy payoff phase yields energy for cell in which two NADH molecules are produced and four ATP molecules are generated Some yeasts and bacteria can be sustained from energy purely from glycolysis Glycolysis: fuel molecule is energized with cell using 2 ATP molecules, six-carbon intermediate is split into two three-carbon intermediates, redox reaction generates NADH from reduction of NAD+ while oxidation releases energy to attach phosphate group to
y y y y y
y y 6.7: y y y y y y y
y y
substrate, ATP and pyruvate are produced completing pyruvate and forming four molecules of ATP 6.8: y y y Pyruvate is transported from cytoplasm into mitochondria to prep for citric acid cycle Pyruvate does not participate in the citric acid cycle but is changed for the cycle Pyruvate grooming: carboxyl group is removed from pyruvate and used to form CO2, remaining two-carbon compound is oxidized while NAD+ is reduced to NADH, coenzyme A from B vitamin joins with the two-carbon group to form acetyl coenzyme A Acetyl CoA ± high-energy fuel molecule used in citric acid cycle For each molecule of glucose two molecules of acetyl CoA are formed Citric acid cycle/Krebs cycle: acetyl group enters the cycle, acetyl group joins fourcarbon molecule, six-carbon citrate is processed through series of redox reactions as carbon dioxide is produced and the four-carbon molecule is regenerated Only the two-carbon part acetyl part of acetyl CoA participates in the cycle, coenzyme A helps the acetyl group enter the cycle and is then recycled Each turn of the Krebs cycle makes one ATP molecule by substrate-level phosphorylation while also creating three NADH molecules and one molecule of electron carrier FADH2 Overall yield of Krebs cycle from one glucose is 2 ATP, 6 NADH and 2 FADH2, totaling 4 ATP, 10 NADH and 2 FADH2 combined with glycolysis Krebs cycle: acetyl CoA is stripped to form acetyl group at the start of the cycle, acetyl group combines with oxaloacetate (four-carbon) to create citrate, redox reactions produce NADH, ATP and CO2 and four-carbon succinate is formed, enzymes regenerate oxaloacetate and redox reactions reduce FAD and NAD+ to FADH2 and NADH completing one turn of the cycle, accepts another acetyl group to restart cycle
y y 6.9: y
y y
y y
6.10: y Electron carriers built into membrane are spatially placed to have mitochondria use chemical energy released by redox reactions to form hydrogen gradient, energy stored in gradient then drives ATP synthesis through chemiosmosis y The cristae of the inner mitochondria membrane enlarge its surface area to provide for thousands of electron transport chains and ATP synthases y Electrons flow from NADH and FADH2 to oxygen y Each oxygen atom accepts two electrons from the chain and picks up two hydrogen ions from its surroundings to form water, final electron acceptor y Carrier molecules reside in four protein complexes while two mobile carriers transport electrons between each complex, releasing energy through redox reactions with each step y Three protein complexes use energy released from electron transfers/redox to actively transport hydrogen across membrane from less concentrated to more concentrated, resulting hydrogen gradient stores potential energy in intermembrane space y ATP synthases built into inner mitochondrial membranes allow hydrogen ions to diffuse through as the membrane is not permeable to hydrogen y Hydrogen ions going through the ATP synthase spins one if its parts which activates catalytic sites in the synthase that attach phosphate groups to ADP and form ATP, completing the oxidative phosphorylation
6.11: y One type of poison blocks the electron transport chain y Rotenone can bind to electron carrier molecules in the first protein complex and prevent electrons from moving on, prevents ATP synthesis y Cyanide and carbon monoxide bind with electron carrier in forth protein complex and cut off electrons to oxygen, blocking formation of hydrogen gradient and ATP y Another respiratory poison inhibits ATP synthase y Oligomycin blocks passage of hydrogen through ATP synthase y Uncouplers make the membrane of mitochondria permeable to hydrogen and prevents the creation of ATP by destroying the concentration gradient, all cellular respiration continues to run and take oxygen but chemiosmosis does not occur 6.12: y 38 ATP is considered the maximum yield from one glucose molecule as factors such as electron shuttles or energy of the hydrogen gradient limit the amount actually created y ATP yield depends heavily on supply of oxygen to cell y Muscle cells can continue to function for a while without oxygen 6.13: y Fermentation has same metabolic pathway as glycolysis y Fermentation provides anaerobic path to recycle NADH into NAD+ for electron acceptor y Lactic acid fermentation ± muscle cells and some bacteria, NADH is oxidized to NAD+ as pyruvate is reduced to lactate y Lactate builds up in muscle cells during strenuous exercise and is carried in blood to liver where it once more forms pyruvate y More oxygen intake after exercise indicates return of muscles to aerobic respiration and lactate back into pyruvate y Alcohol fermentation ± brewing/baking, yeasts and some bacteria recycle NADH back to NAD+ while converting pyruvate to carbon dioxide and ethanol y The carbon dioxide provides the carbonation for beer and the rise for bread dough y Ethanol is toxic to the yeasts and they release the alcohol wastes into surroundings y Obligate anaerobes ± prokaryotes that live in stagnant ponds and deep soil, require anaerobic conditions, poisoned by oxygen y Facultative anaerobe ± make ATP by fermentation or by oxidative phosphorylation depending on the availability of oxygen, yeasts/bacteria/muscles 6.14: y Glycolysis is universal for energy-harvesting, present in almost all living cells y Ancient prokaryotes used glycolysis to make ATP before oxygen was present, evolved very early in ancestors to all domains of life y Glycolysis does not require any membrane-bound organelles 6.15: y Wide range of carbohydrates can be funneled into glycolysis, enzymes in digestive tract hydrolyze starch to glucose which then goes through cellular respiration y Proteins are first digested into amino acids and then used to create own proteins while excess amino acids are used as intermediates in glycolysis or Krebs cycle y During conversion of amino acids by enzymes the amino groups are stripped and disposed of through urine
y y
Fats are excellent cellular fuel because they contain many hydrogen atoms and many energy-rich electrons Cell hydrolyzes fats to glycerol and fatty acids, glycerol is converted to intermediate in glycolysis and fatty acids are broken into two-carbon fragments that enter Krebs cycle as acetyl CoA, yields more ATP than starch
6.16: y Biosynthesis ± production of organic molecules using energy-requiring metabolic pathways, food molecules are used for this y Amino acids can be incorporated directly into macromolecules for organism y Cells can make molecules not present in food by using intermediates of respiration y Feedback inhibition regulates the biosynthetic pathways to create macromolecules, inhibits enzyme early on, controls cellular respiration by inhibiting enzyme early in glycolysis if ATP accumulates in cell to conserve resources, same enzyme is activated by buildup of ADP y Plant cells can produce organic molecules from inorganic ones y Citric acid cycle uses amino groups to form amino acids to form proteins y Acetyl CoA turns to fatty acids combined with glycerol to form fats y Pyruvate is converted to G3P to glucose to form sugars which form carbohydrates y ATP drives all biosynthesis and all biosynthesis results in cells/tissues/organs
y
y 6.6: y y
Electron transport chain: transfer of electrons from organic molecule to NADH, electron carrier molecules within inner membrane of mitochondrion transfer electrons, oxygen serves as final electron acceptor Electron transport chain involves series of redox reactions that provide enough energy for the formation of ATP The steps of cellular respiration in prokaryotic cells occur in the cytoplasm with electron transport built into plasma membrane Glycolysis ± occurs in cytoplasmic fluid outside organelles, begins respiration by breaking down glucose into two molecules of pyruvate (three-carbon compound), uses no oxygen molecules Citric acid cycle ± within mitochondria, completes breakdown of glucose by decomposing pyruvate to carbon dioxide During first two stages the cell makes 4 ATP, main function to supply electrons for oxidative phosphorylation Oxidative phosphorylation ± involves electron transport chain and chemiosmosis, NADH and FADH2 shuttle electrons to transport chain within inner mitochondrion membrane Most ATP from respiration generated by oxidative phosphorylation which uses the energy released by electron chain to phosphorylate ADP As the electron transport chain passes electrons down staircase it pumps hydrogen ions across inner mitochondria membrane into intermembrane space to form concentration gradient of hydrogen across membrane Chemiosmosis ± potential energy of hydrogen concentration gradient used to make ATP ATP synthases ± protein complexes built into inner mitochondria membrane that synthesize ATP, concentration gradient drives diffusion of hydrogen through these There are nine chemical steps in the change of glucose to pyruvate, each which is catalyzed by its own enzyme As glycolysis occurs two molecules of NAD+ are reduced to form NADH and uses this to form two molecules of ATP Substrate-level phosphorylation ± enzyme transfers phosphate group from substrate molecule directly to ADP to form ATP, glycolysis and citric acid cycle Energy extracted from glucose during glycolysis is placed into ATP and NADH The energy in NADH is used by passing electrons down the transport chain Intermediates ± compounds that form between the initial reactant and the final product, pyruvate serves as intermediate Glycolysis: energy investment phase in which 2 ATP is used to energize a glucose molecule, glucose splits into two smaller sugars that can release energy, energy payoff phase yields energy for cell in which two NADH molecules are produced and four ATP molecules are generated Some yeasts and bacteria can be sustained from energy purely from glycolysis Glycolysis: fuel molecule is energized with cell using 2 ATP molecules, six-carbon intermediate is split into two three-carbon intermediates, redox reaction generates NADH from reduction of NAD+ while oxidation releases energy to attach phosphate group to
y y y y y
y y 6.7: y y y y y y y
y y
substrate, ATP and pyruvate are produced completing pyruvate and forming four molecules of ATP 6.8: y y y Pyruvate is transported from cytoplasm into mitochondria to prep for citric acid cycle Pyruvate does not participate in the citric acid cycle but is changed for the cycle Pyruvate grooming: carboxyl group is removed from pyruvate and used to form CO2, remaining two-carbon compound is oxidized while NAD+ is reduced to NADH, coenzyme A from B vitamin joins with the two-carbon group to form acetyl coenzyme A Acetyl CoA ± high-energy fuel molecule used in citric acid cycle For each molecule of glucose two molecules of acetyl CoA are formed Citric acid cycle/Krebs cycle: acetyl group enters the cycle, acetyl group joins fourcarbon molecule, six-carbon citrate is processed through series of redox reactions as carbon dioxide is produced and the four-carbon molecule is regenerated Only the two-carbon part acetyl part of acetyl CoA participates in the cycle, coenzyme A helps the acetyl group enter the cycle and is then recycled Each turn of the Krebs cycle makes one ATP molecule by substrate-level phosphorylation while also creating three NADH molecules and one molecule of electron carrier FADH2 Overall yield of Krebs cycle from one glucose is 2 ATP, 6 NADH and 2 FADH2, totaling 4 ATP, 10 NADH and 2 FADH2 combined with glycolysis Krebs cycle: acetyl CoA is stripped to form acetyl group at the start of the cycle, acetyl group combines with oxaloacetate (four-carbon) to create citrate, redox reactions produce NADH, ATP and CO2 and four-carbon succinate is formed, enzymes regenerate oxaloacetate and redox reactions reduce FAD and NAD+ to FADH2 and NADH completing one turn of the cycle, accepts another acetyl group to restart cycle
y y 6.9: y
y y
y y
6.10: y Electron carriers built into membrane are spatially placed to have mitochondria use chemical energy released by redox reactions to form hydrogen gradient, energy stored in gradient then drives ATP synthesis through chemiosmosis y The cristae of the inner mitochondria membrane enlarge its surface area to provide for thousands of electron transport chains and ATP synthases y Electrons flow from NADH and FADH2 to oxygen y Each oxygen atom accepts two electrons from the chain and picks up two hydrogen ions from its surroundings to form water, final electron acceptor y Carrier molecules reside in four protein complexes while two mobile carriers transport electrons between each complex, releasing energy through redox reactions with each step y Three protein complexes use energy released from electron transfers/redox to actively transport hydrogen across membrane from less concentrated to more concentrated, resulting hydrogen gradient stores potential energy in intermembrane space y ATP synthases built into inner mitochondrial membranes allow hydrogen ions to diffuse through as the membrane is not permeable to hydrogen y Hydrogen ions going through the ATP synthase spins one if its parts which activates catalytic sites in the synthase that attach phosphate groups to ADP and form ATP, completing the oxidative phosphorylation
6.11: y One type of poison blocks the electron transport chain y Rotenone can bind to electron carrier molecules in the first protein complex and prevent electrons from moving on, prevents ATP synthesis y Cyanide and carbon monoxide bind with electron carrier in forth protein complex and cut off electrons to oxygen, blocking formation of hydrogen gradient and ATP y Another respiratory poison inhibits ATP synthase y Oligomycin blocks passage of hydrogen through ATP synthase y Uncouplers make the membrane of mitochondria permeable to hydrogen and prevents the creation of ATP by destroying the concentration gradient, all cellular respiration continues to run and take oxygen but chemiosmosis does not occur 6.12: y 38 ATP is considered the maximum yield from one glucose molecule as factors such as electron shuttles or energy of the hydrogen gradient limit the amount actually created y ATP yield depends heavily on supply of oxygen to cell y Muscle cells can continue to function for a while without oxygen 6.13: y Fermentation has same metabolic pathway as glycolysis y Fermentation provides anaerobic path to recycle NADH into NAD+ for electron acceptor y Lactic acid fermentation ± muscle cells and some bacteria, NADH is oxidized to NAD+ as pyruvate is reduced to lactate y Lactate builds up in muscle cells during strenuous exercise and is carried in blood to liver where it once more forms pyruvate y More oxygen intake after exercise indicates return of muscles to aerobic respiration and lactate back into pyruvate y Alcohol fermentation ± brewing/baking, yeasts and some bacteria recycle NADH back to NAD+ while converting pyruvate to carbon dioxide and ethanol y The carbon dioxide provides the carbonation for beer and the rise for bread dough y Ethanol is toxic to the yeasts and they release the alcohol wastes into surroundings y Obligate anaerobes ± prokaryotes that live in stagnant ponds and deep soil, require anaerobic conditions, poisoned by oxygen y Facultative anaerobe ± make ATP by fermentation or by oxidative phosphorylation depending on the availability of oxygen, yeasts/bacteria/muscles 6.14: y Glycolysis is universal for energy-harvesting, present in almost all living cells y Ancient prokaryotes used glycolysis to make ATP before oxygen was present, evolved very early in ancestors to all domains of life y Glycolysis does not require any membrane-bound organelles 6.15: y Wide range of carbohydrates can be funneled into glycolysis, enzymes in digestive tract hydrolyze starch to glucose which then goes through cellular respiration y Proteins are first digested into amino acids and then used to create own proteins while excess amino acids are used as intermediates in glycolysis or Krebs cycle y During conversion of amino acids by enzymes the amino groups are stripped and disposed of through urine
y y
Fats are excellent cellular fuel because they contain many hydrogen atoms and many energy-rich electrons Cell hydrolyzes fats to glycerol and fatty acids, glycerol is converted to intermediate in glycolysis and fatty acids are broken into two-carbon fragments that enter Krebs cycle as acetyl CoA, yields more ATP than starch
6.16: y Biosynthesis ± production of organic molecules using energy-requiring metabolic pathways, food molecules are used for this y Amino acids can be incorporated directly into macromolecules for organism y Cells can make molecules not present in food by using intermediates of respiration y Feedback inhibition regulates the biosynthetic pathways to create macromolecules, inhibits enzyme early on, controls cellular respiration by inhibiting enzyme early in glycolysis if ATP accumulates in cell to conserve resources, same enzyme is activated by buildup of ADP y Plant cells can produce organic molecules from inorganic ones y Citric acid cycle uses amino groups to form amino acids to form proteins y Acetyl CoA turns to fatty acids combined with glycerol to form fats y Pyruvate is converted to G3P to glucose to form sugars which form carbohydrates y ATP drives all biosynthesis and all biosynthesis results in cells/tissues/organs
