1. Cell Respiration Part 5 Anaerobic Respiration, Respiratory Quotient, and Rice Adaptations

2. Anaerobic Respiration No free oxygen = nothing pulling electrons and hydrogen ions into the mitochondria Remember, reduced NAD from glycolysis are supposed to head into mitochondria for ETC No oxygen = no mitochondria for those electron carriers ETC stops working No large supply of ATP from oxidative phosphorylation 1 glucose  4 ATP (2 net ATP) and 2 reduced NAD 2 anaerobic pathways solve problem of “dumping” hydrogen from reduced NAD Lactic Fermentation Alcohol Fermentation

4. Anaerobic Respiration “Fermentation” Lactic Fermentation and Alcohol Fermentation Both: Occurs in absence of oxygen Take place in Cytoplasm Begin with glycolysis Regenerate NAD Enable glycolysis to occur again to produce more ATP “Buy time” by making small amounts of ATP Both products (lactate and ethanol) are toxic to organism Reactions cannot continue indefinitely

5. Alcohol Fermentation Def: Conversion of glucose to ethanol Microorganism (yeast) and some plant tissue Hydrogen from reduced NAD is passed to ethanal (CH 3 CHO) NAD is then made available for glycolysis to occur again Steps: Pyruvate (3C) is decarboxylated to ethanal (CO2 removed) Ethanal (2C) is reduced to ethanol (C 2 H 5 OH) By enzyme alcohol dehydrogenase Pathway is IRREVERSIBLE Carbon dioxide is lost Remaining potential energy in ethanol is wasted

6. Lactic Fermentation Def: Conversion of glucose to lactic acid Microorganisms and mammalian tissue Pyruvate (3C) acts as a hydrogen acceptor Reduced NAD drops of hydrogen to pyruvate, yielding a lactate molecule (3C) By enzyme Lactate dehydrogenase Named after reverse reaction (which it also catalyzes) NAD is then made available for glycolysis to occur again in anaerobic conditions Pathway REVERSIBLE

7. Lactic Fermentation Pathway REVERSIBLE Lactate carried by blood plasma to liver Lactate converted back to pyruvate in liver Liver oxidizes 20% of incoming lactate to carbon dioxide and water via aerobic respiration (when oxygen is available again) 80% remaining lactate is converted by liver into glycogen

8. Figure to the left shows what happens to oxygen uptake of a person before, during, and after strenuous exercise At Rest = absorbing oxygen at less than 1000 mL min -1 Beginning exercise = more oxygen needed to support aerobic respiration in muscles A.Demand for oxygen begins increasing B.Takes heart & lungs 2 minutes to meet demand C.Lactic acid fermentation occurs in the mean time D.Person builds up oxygen deficit E.Next few minutes, enough oxygen is supplied Exercise ends = person breathing deeply, absorbing oxygen at higher rate than at rest Extra oxygen uptake after work out is to pay that oxygen deficit established at the beginning of working out Oxygen debt  post-exercise uptake of extra oxygen Oxygen needed for: Conversion of lactate to glycogen in liver Reoxygenation of hemoglobin in blood A high metabolic rate Lactic Fermentation E

9. Respiratory Substrates Cells require substrates to breakdown for energy Glucose not the only substrate used for energy Neurons, RBCs, and lymphocytes  can oxidize glucose Brain neurons can ONLY respire Glucose Other cells  can oxidize lipids and amino acids Lipids as a substrate Carbon atoms removed in pairs (acetyl coenzyme A) from fatty acid chains of triglycerides These pairs enter Krebs cycle Amino Acids as a substrate Carbon-hydrogen skeleton converted into pyruvate or acetyl coenzyme A

10. Energy Values of Respiratory Substrates Where does most energy come from in aerobic respiration? Oxidation of hydrogen to water when reduced NAD and reduced FAD get to the ETC Main Idea: The greater the number of the hydrogens in the substrate molecule = the greater the energy value “Energy Density”  energy value per unit mass (aka amount of energy packed into a substrate molecule) Fatty acids have more hydrogens than carbohydrates Therefore, fatty acids have greater energy density

11. Measuring Energy of Substrates How to determine energy in s substance Burn know mass of substance in a calorimeter Calorimeter  measures the energy value of a respiratory substrate Energy released by burning (oxidizing) substrate will cause the a known mass of water’s temperature to rise Measuring the change in water temperature will determine energy value of substrate oxidized

12. Respiratory Substrates Respiratory SubstrateEnergy Released/kJ g -1 Carbohydrate16 Lipid39 protein17 Lipids provide TWICE as much energy per gram as carbs or proteins Lipids contain more carbon- hydrogen bonds (more H atoms) H atoms used to generate the most ATP is oxidative phosphorylation Brain cells  only use glucose Heart muscle  prefers fatty acids Other cells  carbs, lipids, or fats Respiratory SubstrateRQ Carbohydrate1.0 Lipid0.7 protein0.9

15. Determining Respiratory Quotient Two ways: Look at Carbon Dioxide produced Look at Oxygen used Use: Volume (if given volume/data table/graph) Moles (if given equation)

16. Alcohol Fermentation: No oxygen is used… Dividing carbon dioxide produce by 0 RQ = infinity Yeast use some aerobic respiration so small amounts of oxygen are used…. High values of RQ indicate alcohol fermentation is occurring Lactic Fermentation No oxygen is used… No carbon dioxide produced…. No respiratory quotient can be determined Determining Respiratory Quotient Anaerobic

17. Practice problems 1.During 30 minutes of steady-state exercise a subject averages an oxygen consumption of 3.22 L/min with a CO 2 production of 2.78 L/min. Determine RQ 2.Determine respiratory quotient of complete oxidation of oleic acid (C 18 H 34 O 2 ) from olive oil. Hint: balance equation first….oxygen can be half a molecule.

18. Answers 1.RQ or RER = 2.78 / 3.22 = 0.86 2.RQ= 18/25.5= 0.7 (C 18 H 34 O 2 ) + 25.5O 2  18 CO 2 + 17H 2 O + energy