Respiration

• Name the four main stages in aerobic respiration and where they occur

  ~ Glycolysis: cytoplasm

  ~ Link reaction: mitochondrial matrix

  ~ Krebs cycle: mitochondrial matrix

  ~ Oxidative phosphorylation via electron transport chain: membrane of cristae
• Outline the stages of glycolysis

  ~ Glucose is phosphorylated to glucose phosphate by 2x ATP

  ~ Glucose phosphate splits into 2x triose phosphate

  ~ 2x TP is oxidised to 2x pyruvate

  ~ Net gain of 2x reduced NAD and 2x ATP per glucose
• How does pyruvate from glycolysis enter the mitochondria


  Via active transport
• What happens during the link reaction

  ~ Oxidation of pyruvate to acetate

  ~ Per pyruvate molecules: net gain 1x CO2 (decarboxylation) and 2H atoms

  ~ Acetate combines with coenzyme A (CoA) to form acetylcoenzyme A
• What happens in the Krebs cycle


  ~ Series of redox reactions produces:

  ~ ATP by substrate - level phosphorylation

  ~ Reduced coenzymes

  ~ CO2 from decarboxylation
• What is the electron transfer chain

  ~ Series of carrier proteins embedded in membrane of the cristae of mitochondria

  ~ Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration
• What happens in the electron transfer chain

  ~ Electrons released from the reduced NAD and FAD undergo successive redox reactions

  ~ The energy released is coupled to maintaining proton gradient or released as heat

  ~ Oxygen acts as final electron acceptor
• How is a proton concentration gradient established during chemiosmosis in aerobic respiration


  Some energy released from the ETC is coupled to the active transport of h+ ions from the mitochondrial matrix into the intermembrane space
• How does chemiosmosis produce ATP during aerobic respiration

  ~ H+ ions move down their concentration gradient from the intermembrane space into the mitochondrial matrix via the channel protein ATP synthase

  ~ ATP synthase catalyses ADP + Pi = ATP
• State the role of oxygen in aerobic respiration

  Final electron acceptor in electron transfer chain
• What is the benefit of an electron transfer chain rather than a single reaction

  ~ Energy is released gradually

  ~ Less energy is released as heat
• Name two types of molecule that can be used as alternative respiratory substrates

  ~ Amino acids from proteins

  ~ Glycerol and fatty acids from lipids
• How can lipids act as an alternative respiratory substrate

  ~Phosphorylation of glycerol = TP for glycolysis

  ~Fatty acid = acetate

  ~Acetate enters link reaction

  ~H atoms produced for oxidative phosphorylation
• How can amino acids act as an alternative respiratory substrate

  ~Deamination produces

  ~3C compound = pyruvate for link reaction

  ~4C/5C compounds = intermediates in krebs cycle
• Name the stages in respiration that produce ATP by substrate level phosphorylation

  ~Glycolysis

  ~Krebs cycle
• What happens during anaerobic respiration in animals

  ~Only glycolysis continues

  ~Reduced NAD + pyruvate = oxidised NAD + lactate
• What happens to the lactate produced in anaerobic respiration

  ~Transported to liver via bloodstream, where it is oxidised to pyruvate

  ~Can enter link reaction in liver cells or be converted to glycogen
• What happens during anearobic respiration in some microorganisms

  ~Only glycolysis continues

  ~Pyruvate is decarboxylated to form ethanal

  ~Ethanal is reduced to ethanol using reduced NAD to prduce oxidised NAD for further glycolysis
• What is the advantage of producing ethanol/lactate during anaerobic respiration

  Converts reduced NAD back into NAD so glycolysis can continue
• What is the advantage of producing ethanol during anaerobic respiration

  ~Cells die when ethanol concentration is above 12%

  ~Ethanol dissolves cell membranes
• What is the disadvantage of producing lactate during anaerobic respiration

  ~Acidic, so decreases pH

  ~Result in muscle fatigue
• Compare aerobic and anaerobic respiration


  ~Both involve glycolysis

  ~Both require NAD

  ~Both produce ATP
• Contrast aerobic and anaerobic respiration

  Aerobic

  ~Produces ATP by substrate level phosphorylation and oxidative phosphorylation

  ~Produces much more ATP

  ~Does not produce ethanol or lactate

  Anaerobic

  ~Substrate level phosphorylation only

  ~Produces fewer ATP

  ~Produces ethanol or lactate
• Suggest how a student could investigate the effect of names variable on the reate of respiration of a single celled organism

  ~Use respirometer

  ~Use a dye as the terminal electron acceptor for the ETC
• What is the purpose of sodium hydroxide solution in respirometer set up to measure the rate of aerobic respiration

  Absorbs CO2 so that there is a net decrease in pressure as O2 is consumed
• How could a student calculate the rate of respiration using a respirometer

  ~Volume of O2 produces or CO2 consumes/time x mass of sample