Respiration! Chapter 9~ Cellular Respiration: Harvesting Chemical Energy Great Animation (show at end too)

Essential idea: Energy is converted to a usable form in cell respiration. Big Picture: Organic molecules (esp. glucose) have Stored Energy, but Cells must Convert it to ATP (an immediate source of energy for the cell) This happens through a series of energy releasing redox reactions. Overall Equation for aerobic cellular respiration: C6H12O6 + 6O2 ---> 6CO2 + 6H2O + E (ATP + heat)

Redox reactions Oxidation-reduction reactions (involve the transfer of electrons) Oxidation (i.e. to be oxidized) is e- loss; Or oxygen gain Reduction (i.e. to be reduced) is e- gain; Or hydrogen atom gain LEO GER Redox reactions release energy!!!

Cellular respiration Cell Respiration = the controlled release of energy from organic compounds in cells to form ATP STAGES of Aerobic Respiration: Glycolysis: location: cytoplasm Link Reaction: location mitochondrial matrix Krebs Cycle: location mitochondrial matrix Electron Transport Chain location: inner membrane of mitochondrion Note: Must know substrates and final waste products for these stages

Glycolysis Overall: 1 Glucose (6C)2 pyruvate molecules (3C each) Guidance: • The names of the intermediate compounds in glycolysis and the Krebs cycle are not required. Overall: 1 Glucose (6C)2 pyruvate molecules (3C each) We will focus on 4 stages: Phosphorylation cell uses ATP to phosphorylate hexose sugar (glucose) making Hexose biphosphate Phosphorylation of molecules makes them less stable (more likely to react!) Lysis Hexose is split in half to make two triose sugars Oxidation Each triose loses electrons and hydrogens These are transferred to NAD+ to make NADH and H+ ATP formation ATP is produced by substrate-level phosphorylation 2 Pyruvates are made. 2 inorganic phosphates Animation http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_glycolysis_works.html

Glycolysis continued Net energy yield per glucose molecule: 2 ATP plus 2 NADH + H+; Note: Does not require oxygen; also no CO2 is released

For Reference: The 10 steps of Glycolysis

The link reaction Each pyruvate is converted into acetyl CoA How? pyruvate is decarboxylated (CO2 is released); Pyruvate is oxidized: NAD+ gets reduced as follows: NAD+  NADH + H+ NADH is an electron carrier

Krebs/Citric Acid Cycle Guidance: • The names of the intermediate compounds in glycolysis and the Krebs cycle are not required. Krebs/Citric Acid Cycle From this point, for each turn, 2 C atoms enter (acetyl CoA) and 2 exit (carbon dioxide) Oxaloacetate is regenerated (the “cycle”) For each acetyl CoA that enters: 3 NAD+ reduced to 3 NADH; 1 FAD reduced to FADH2 1 ATP molecule produced

IB Understanding: This is how IB phrases what happens during the Krebs cycle: “In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.”

Big Idea so far Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD.

Electron transport chain The ETC carries electrons from carrier molecules (NADH & FADH2) down to oxygen (the final electron acceptor!) The ETC pumps H+ into the intermembrane space! Chemiosmosis: The production of ATP when protons diffuse through ATP synthase This whole process of making ATP is also called oxidative phosphorylation (b/c it uses oxygen as the final electron acceptor) OXYGEN is the final electron acceptor. It gets reduced to make H2O Note: this helps maintain the hydrogen gradient

Electron Transport NADHFMN iron sulfur protein (FeS) a lipid called ubiquinone (Q) cytochromes O2 FADH2 starts donating its electrons to the iron sulfur protein. Therefore it is able to make less ATP than NADH. http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter9/animations.html# ATP synthase animation ATP

Review: Aerobic Respiration Glycolysis 2 ATP (substrate-level phosphorylation) Kreb’s Cycle: 2 ATP (substrate-level phosphorylation) Electron transport & oxidative phosphorylation: 32-34 ATP as follows: 38 TOTAL ATP/glucose Great Animation

Mitochondria (Structure and function) Cristae Small space between inner and outer membranes Fluid matrix

Skill: Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.

What if there’s no oxygen? (Anaerobic respiration) Anaerobic cell respiration gives a small yield of ATP from glucose. Consists of: Glycolysis (yield =2 ATP) Fermentation: alcohol~ pyruvate is converted to ethanol and CO2 (in yeast and bacteria) lactic acid~ pyruvate is converted to lactate (in animals)

Application: Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.

Application: Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions.

Why Fermentation? *Fermentation allows glycolysis to continue It recycles NAD+ (a necessary oxidizing agent required for the continuation of glycolysis) see next slide for review of glycolysis…

2 inorganic phosphates

Aerobic vs. Anaerobic Respiration Pathways Glycolysis can occur aerobically or anaerobically Aerobic Respiration= Requires oxygen Occurs in mitochondrion Pyruvate broken down into CO2 and H2O Large yield of ATP Anaerobic Respiration= No oxygen Occurs in cytoplasm Pyruvate converted to either lactate OR ethanol and CO2 No further yield of ATP

Skill: Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur.

Skill: Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer. There are many simple respirometers which could be used. Students are expected to know that an alkali is used to absorb CO2, so reductions in volume are due to oxygen use. Temperature should be kept constant to avoid volume changes due to temperature fluctuations. Note: we can do similar experiments with LabQuests and probes. See page 127 for more explanation and page 128 for sample data questions

Application: Electron tomography used to produce images of active mitochondria. Electron tomography can be used to obtain 3D images of active mitochondria. Has shown cristae to be dynamic Images of mitochondria Three-dimensional model was reconstructed by electron tomography. The outer membrane and cristae are shown in purple and yellow, respectively.  [work by T. Frey (SDSU) and G. Perkins (UCSD); with the permission of Professor Frey]

Nature of Science and Theory of knowledge : Read and discuss: Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics. (2.3) • Peter Mitchell’s chemiosmotic theory encountered years of opposition before it was finally accepted. For what reasons does falsification not always result in an immediate acceptance of new theories or a paradigm shift?

End of IB The next slides are interesting but not in the syllabus

What if there’s no Glucose? Respiration still can continue Beta-oxidation: lipid catabolism to acetyl CoA. Amino acids Converted to intermediates in glycolysis and Krebs cycle

Control of Respiration Feedback Inhibition Examples Phosphofructokinase (Enzyme 3 in Glycolysis) allosterically inhibited by ATP Allosterically activated by AMP (derived from ADP) Why?

Oxidizing agents in respiration NAD+ (nicotinamide adenine dinucleotide)= initial electron acceptor (oxidizing agent) NAD + is reduced to NADH Oxygen is the eventual e- acceptor (The ULTIMATE Oxidizing Agent)

Facultative anaerobes don’t require oxygen but can live with it Facultative anaerobes don’t require oxygen but can live with it. (yeast/bacteria) Obligate anaerobes Can’t live with oxygen Clostridium botulinum (botulism bacterium)

The Next Slides deal with Aerobic Respiration … Aerobic Respiration Steps: Link Reaction Krebs Cycle (Citric Acid Cycle) Electron Transport Chain (ETC)