cellular respiration

• External respiration


  • Pulmonary ventilation, alveoli, respiratory membrane
• Internal respiration


  • Oxygen and carbon dioxide exchange at tissue beds
• Cellular respiration


  Making ATP in the mitochondria of a cell, energy-yielding oxidative reactions in living matter, involves transfer of electrons, usually involves oxygen
• Biochemical respiration


  Cellular respiration is the breakdown of nutrients to produce ATP, ATP is the cells energy molecule, ATP fuels most reactions/activity in cells
• Adult human female requires 6300–7500 kJ metabolic energy per day
• Corresponds to free energy released from breaking of 200 moles ATP per day
• 1 mole of ATP is 507.18 g (has 6.0221 x 10^23 molecules of ATP)
• Generally less than 0.1 mole of ATP in body at any point
• Weight of 200 moles = 200 x 507.18 g = 101436 g = 101.44 kg
• Cellular respiration


  Aerobic means, Anaerobic means, Metabolism is, Catabolism is, Anabolism is
• Cellular metabolism


  • Provides energy (ATP), reducing power, biosynthetic intermediates
• Redox reactions


  Oxidation is the addition of oxygen or dehydrogenation, loss/removal of electrons, Reduction is the gain of hydrogen, gain/addition of electrons
• Energy released from redox reactions

  Temporarily stored in the form of ATP, used for energy requiring processes like synthesis of macromolecules and active transport
• Electron carriers


  Carry electrons around the cell, can be oxidised or reduced, carry energy from energy rich molecules like fats and carbohydrates
• Coenzymes


  • NAD+/NADH, NADP+, FAD+/FADH2, catalyse redox reactions
• Basic respiration equation


  Oxygen is present - this is aerobic respiration
• Respiration in absence of oxygen

  This is anaerobic respiration, can produce either lactate or ethanol
• Cellular respiration


  Is the formation of ATP
• Mitochondria


  • Powerhouses of the cell
• ATP


  Serves as an energy currency in cells, hydrolysis of ATP releases a relatively large amount of free energy
• ATP production


  Minor portion by substrate level phosphorylation, major portion by oxidative phosphorylation in mitochondria
• Phosphorylation


  Substrate level phosphorylation is direct transfer of phosphate group, oxidative phosphorylation uses electron transport chain and chemiosmosis, oxygen is essential
• 3 processes to produce ATP

  Glycolysis, Krebs cycle, Oxidative phosphorylation
• Glycolysis


  10 steps, 1 glucose molecule -> 2 pyruvate molecules, 2 ATP used, 4 ATP produced, net 2 ATP and 2 NADH
• Pyruvate oxidation


  Reaction links glycolysis and citric acid cycle, pyruvate converted to acetyl-CoA, occurs in mitochondrial matrix, yields 1 NADH
• Citric acid cycle


  Also known as Kreb's cycle, occurs in mitochondrial matrix, 1 acetyl-CoA used per turn, produces 3 NADH, 1 FADH2, 1 GTP
• Oxidative phosphorylation


  Occurs across mitochondrial inner membrane, 2 linked stages: electron transport chain creates proton gradient, chemiosmosis uses proton gradient to make ATP
• Electron transport chain


  • 4 protein complexes in/on inner mitochondrial membrane, high energy molecules feed electrons into these, electrons flow to oxygen which binds with H+ to form H2O, energy released pushes protons across membrane
• Chemiosmosis


  High proton concentration in intermembrane space, low proton concentration in matrix, proton flow down gradient drives ATP synthase to make ATP, 1 NADH allows 2.5 ATP to be made
• Anaerobic metabolism


  Glycolysis can still happen, then pyruvate enters fermentation pathway - mammals/animals generate lactate, some microbes generate ethanol
• Lactate fermentation


  Lactate dehydrogenase converts pyruvate to lactate, regenerates NAD+ to re-enter glycolysis, often occurs in muscle cells after strenuous activity
• Alcoholic fermentation


  1. step reaction converts pyruvate to ethanol and CO2, regenerates NAD+ to re-enter glycolysis, used by yeasts to produce alcohol and CO2
• Aerobic vs anaerobic respiration

  Aerobic 1 glucose -> 32 ATP, anaerobic 1 glucose -> 2 ATP, oxidative phosphorylation much more efficient, but anaerobic glycolysis can be 100x faster
• Catabolism of glucose makes most ATP (approx. 95%)
• Other sugars are broken down to glucose or fructose
• Metabolism of fats and proteins will give intermediates that can enter the citric acid cycle
• In starvation, body breaks down protein then fat to maintain ATP production