Respiration

Cards (45)

  • Structure of ATP
    1. Ribose sugar
    2. Adenine base
    3. 3 phosphate groups
  • Features of ATP that make it suitable as a universal energy currency
    1. Hydrolysis of ATP into ADP + inorganic phosphate (Pi): Add water to release energy
    2. Phosphorylation (condensation) of ADP + inorganic phosphate (Pi) into ATP: release water & catalysed by ATP synthase
    3. Soluble in aqueous environment
  • Role of Nicotinamide Adenine Dinucleotide, NAD and Flavin Adenine Dinucleotide,FAD
    1. Both are coenzymes to dehyrogenases, which oxidises glucose in aerobic respiration
    2. NAD: In glycolysis, link reaction and krebs cycle, protons and electrons are released and transferred to oxidised NAD, NAD+ to form reduced NAD, NADH + H+.
    3. FAD: In krebs cycle, protons and electrons are released and transferred to oxidised FAD, FAD to form reduced FAD, FADH2
  • Location & Overview of Glycolysis
    Cytoplasm; breakdown of one molecule glucose, 6C, to yield 2 molecules of pyruvate, 3C, 2 molecules of reduced nicotinamide adenine dinucleotide, and 2 molecules of ATP from substrate level phosphorylation
  • Energy Investment Phase of Glycolysis, Investment of 2 molecules of ATP
    1. Activation of glucose: 1 molecule of ATP used to phosphorylate glucose, catalysed by hexokinase. Glucose-6-phosphate is formed.
    2. Isomerisation of glucose-6-phosphate to fructose-6-phosphate
    3. 1 molecule of ATP used to phosphorylate fructose-6-phosphate into fructose-1,6-biphosphate, catalysed by phosphofructokinase
    4. Production of 2 molecules of glyceraldehyde-3-phosphate, GALP from 1 molecule of glucose
  • Energy payoff phase of Glycolysis, Production of 4 molecules of ATP from substrate level phosphorylation
    1. 2 molecules of ATP used to convert 1 molecule of glyceraldehyde-3-phosphate into pyruvate via substrate-level phosphorylation.
    2. Release of protons and electrons via dehydrogenation which are transferred to 1 oxidised NAD, NAD+ to form 1 reduced NAD, NADH + H+.
    3. x2 everything since 2 GALP molecules are produced from 1 glucose molecule
  • Mode of action of substrate level phosphorylation
    Synthesis of ATP where ATP synthase transfers a phosphate group (inorganic phosphate, Pi) from a substrate molecule to ADP.
  • Products per glucose molecule for Glycolysis
    1. 2 molecules of ATP
    2. 2 molecules of nicotinamide adenine dinucleotide
    3. 2 molecules of pyruvate
  • Link Reaction ; Oxidative Decarboxylation
    1. Decarboxylation: Pyruvate's, 3C carboxyl group is removed and CO2 is released (forming 2C) by decarboxylase
    2. Oxidation/redox stage/Dehydrogenation: Remaining molecule oxidised via dehydrogenation. Transfer of protons and electrons to oxidised NAD, NAD+ to form reduced NAD, NADH + H+.
    3. Addition of Coenzyme A, CoA: Coenzyme A is attached to acetate to form acetyl-CoA.
  • Products per glucose molecule for Link Reaction
    1. 2 molecules of CO2
    2. 2 molecules of reduced nicotinamide adenine dinucleotide, NADH + H+
    3. 2 molecules of Acetyl-CoA
  • Location of Link Reaction
    Mitochondrial Matrix
  • Location of Krebs Cycle
    Mitochondrial Matrix
  • Krebs Cycle

    1. Acetyl-Co, 2C combines with oxaloacetate, 4C to form citrate, 6C
    2. Decarboxylation to remove carboxyl group from 6C citrate to release 1 molecule of CO2
    3. Dehydrogenation, transferring protons and electrons to oxidised NAD, NAD+, to form reduced NAD, NADH + H+
    4. Substrate-level phosphorylation occurs, where 1 ATP is produced
    5. Dehydrogenation occurs, transferring protons and electrons to oxidised FAD, FAD, to form reduced FAD, FADH2
    6. Dehydrogenation occurs, transferring protons and electrons to oxidised NAD, NAD+, to form reduced NAD, NADH + H+
    7. Oxoacetate regenerated
  • Products per actetyl-CoA molecule for Krebs Cycle, glucose x2
    1. 2 molecules of CO2
    2. 3 molecules of reduced nicotinamide adenine dinucleotide
    3. 1 molecule of reduced flavin adenine dinucleotide
    4. 1 ATP
  • Location of Oxidative phosphorylation
    Inner mitochondrial membrane
  • Structure of mitochondira in relation to electron transport chain
    1. Electron carriers embedded in inner mitochondiral membrane
    2. Inner mitochondrial membrane extensively folded to increase surface area for embedding of more electron carrier
  • Oxidative phosphorylation: Electron transport chain
    1. Reduced NAD and reduced FAD transfer high energy protons and electrons to ETC
    2. Electrons are passed along electron transport chain from one electron carrier to the next, each with an energy level lower than the one preceding it.
    3. Oxygen, a final proton and electron acceptor, accepts an electron and forms water, catalyzed by cytochrome oxidase
    4. Oxidised NAD and FAD are regenerated in the process
  • Chemiosmosis of oxidative phosphorylation
    1. Energy released from electron transport chain is used to actively pump protons, H+ from mitochondria matrix into intermembrane space
    2. High concentration of H+ in the intermembrane space generates a steep electrochemical proton gradient, giving rise to proton motive force
    3. H+ diffuse through Stalked particles containing ATP synthase embedded on inner mitochondrial membrane, down the electrochemical proton gradient, back into matrix
    4. This provides energy to synthesize ATP by phosphorylation of ADP with inorganic phosphate, Pi
  • Total yield of reduced NAD and FAD per glucose molecule
    1. 2 molecules of reduced NAD during glycolysis
    2. 2 molecules of reduced NAD during Link Reaction
    3. 6 molecules of reduced NAD during Krebs Cycle
    4. 2 molecules of reduced FAD during Krebs Cycle
  • Total yield of ATP by S.L.P
    1. 2 molecules of ATP during Glycolysis
    2. 2 molecules of ATP from Krebs cycle
  • Total yield of ATP from O.P
    1. 5 molecules of ATP from Glycolysis
    2. 5 molecules of ATP from Link Reaction
    3. 15 + 3 molecules of ATP from Krebs Cycle, 3 molecules NAD x 2.5 x2 + 1 molecule FAD x 1.5 x 2
  • Total ATP per glucose molecule
    1. Glycolysis: 2, SLP + 5
    2. Link Reaction: 5
    3. Krebs Cycle: 2, SLP + 18
  • Anaerobic respiration
    1. Absence of oxygen
    2. Glycolysis occurs, producing pyruvate and small yield of ATP
    3. Fermentation regenerates oxidised NAD
  • Alcoholic Fermentation in yeast, conversion of pyruvate into ethanol
    1. Decarboxylation of pyruvate, 3C to acetaldehyde/ethanal, catalysed by decarboxylase. Carbon dioxide released.
    2. Oxidation of reduced NAD, regenerating oxidised NAD, when acetaldehyde/ethanal is reduced to ethanol by reduced NAD. Reaction is catalysed by alcohol dehydrogenase.
  • Lactate fermentation, reduction of pyruvate into lactate, SINGLE STEP, catalysed by lactate dehydrogenase
    1. Lactate reconverted to pyruvate in liver
  • To
    tal yield of ATP in anaerobic respiration is 2 molecules of ATP in substrate level phosphorylation
  • Role of oxygen in aerobic respiration
    1. Final proton and electron acceptor at end of electron transport chain, combining electrons and protons forming water, catalysed by cytochrome oxidase
    2. Oxygen re-oxidises ETC for reduced NAD and FAD to continuously donate electrons, allowing oxidative phosphorylation to continue to regenerate ATP
    3. Regeneration of oxidised NAD and FAD allowing them to pick up more electrons from Glycolysis, Link Reaction and Krebs cycle
  • Why is less glucose required in aerobic respiration than anaerobic respiration, in yeast cells?
    1. In anaerobic respiration, glucose is incompletely oxidised. Alcoholic fermentation occurs in yeast cells to regenerate oxidised NAD, to keep glycolysis going to produce 2 ATP via substrate-level phosphorylation per glucose
    2. In aerobic respiration, 32 ATP is produced per glucose molecule, which is completely oxidised
  • How does ATP control rate of glycolysis
    1. Negative feedback; end-product inhibition on phosphofructokinase in glycolysis
    2. In high rate of respiration, ratio of ATP:ADP increases
    3. Phosphfructokinase is an allosteric enzyme which is inhibited by high ATP:ADP ratio
  • Why anaerobic respiration, lactate fermentation cannot be continued for long periods of time
    1. In anaerobic respiration, only glycolysis occurs, incompletely oxidising glucose to produce only net of 2 ATP
    2. Pyruvate converted to lactate/lactic acid which accumulates
    3. Lactic acid is acidic and lowers pH of cells, until it is lower than optimal pH cellular enzymes function in
  • Why fatty acids are not used in place of glucose
    1. Fatty acids bigger than glucose hence less easily transported from blood into muscle cells
    2. Fatty acids need to be converted into a form that can enter krebs cycle for use as respiratory substrate
  • Why only small amount of reduced NAD in cell at any time
    1. Reduced NAD can be regenerated by oxidation very quickly, when reduced NAD donates and electron to ETC during oxidative phosphorylation in presence of oxygen
  • Role of NAD/FAD in Krebs Cycle
    1. Co-enzyme to dehydrogenase
    2. Removes protons and electrons from Krebs cycle to form reduced NAD/FAD
    3. Reduced NAD/FAD transfers high energy protons and electrons to electron transport chain, allowing for oxidative phosphorylation in the inner mitochondrial matrix to occur
    4. Regeneration of oxidised NAD and FAD for subsequent glycolysis, link reaction and krebs cycle
  • Respiratory Quotient
    Variation in ratio of CO2 given out to O2 when different respiratory substrates are used
  • Significance of different RQ values
    1. When glucose is used, RQ exactly 1 as exactly same number of molecules of CO2 given out and O2 taken in.
    2. Other respiratory substrates RQ less than 1
  • Why inner membrane of mitochondrion remains intact when organelle is placed in pure water
    1. Inner membrane of membrane has H+ ions pumped from mitochondrial matrix into intermembrane space, increasing water potential inside matrix
    2. Less water enters by osmosis in intermembrane space
    3. OR Cristae is highly folded which let inner membrane to expand when water enters by osmosis
    4. OR Inner membrane impermeable to water so water does not enter by osmosis
  • Molecules found in mitochondrial matrix and role in respiration
    1. Pyruvate (2C, initially 3C) joins with acetate (2C) when coenzymeA binds to form acetyl-coA in link reaction
    2. Pyruvate makes reduced NAD when it is dehydrogenated
    3. Oxaloacetate (4C) binds to acetyl-coA (2C) to form citrate (6C)
    4. Citrate makes reduced NAD by dehydrogenation
    5. Enzymes catalyse link reaction and Krebs Cycle
    6. Oxygen accepts electrons and protons to form water
  • Why inner membrane must be impermeable to ions
    1. So H+ ions must pass though ATP synthase to provide energy for synthesis of ATP
    2. AND To maintain proton gradient
  • How inorganic phosphate is transported across inner mitochondrial membrane into matrix
    1. By facilitated diffusion via channel proteins
    2. Inorganic phosphate and H+ ions move together
    3. As H+ ions move through ATP synthase into matrix
  • Advantage of linking ATP transport to ADP transport across inner membrane of the mitochondrion
    1. Such that inorganic phosphate and ADP substrate is always present
    2. ATP can continue to be produced