Aerobic Respiration

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Aerobic Respiration. SBI4U1. Aerobic Respiration : catabolic pathway that requires oxygen C 6 H 12 O 6 (s) + 6O 2 (g)  6CO 2 (g) + 6H 2 O (l) + energy Plants and animals rely on it to form ATP Obligate anaerobes (organisms that must have oxygen) - PowerPoint PPT Presentation

Text of Aerobic Respiration

Aerobic Respiration

Aerobic RespirationSBI4U1

Aerobic Respiration: catabolic pathway that requires oxygen

C6H12O6 (s) + 6O2 (g) 6CO2 (g) + 6H2O (l) + energy

Plants and animals rely on it to form ATPObligate anaerobes (organisms that must have oxygen)Energy from food molecules is transferred to ATPCells use ATP to power endergonic rxnsGoals of Cellular RespirationBreak bonds b/t C-atoms in glucose to form 6CO2

Move H atom electrons from glucose to oxygen, to form 6H2O

Trap free energy released in the process in form of ATP

C6H12O6 (s) + 6O2 (g) 6CO2 (g) + 6H2O (l) + energy

Cellular respiration decreases potential energy and increases entropy

Yields 2870kJ of free energy per mol of glucose

G = -2870 kJ per mol of glucose4 Steps in Cellular RespirationGlycolysis (cytoplasm, 10 steps)

Pyruvate Oxidation (mitochondrial matrix, 1 step)

Krebs Cycle (mitochondrial matrix, 8 steps)

Oxidative Phosphorylation/Electron Transport Chain (cristae, most ATP generation)

#1#2#3#4Glycolysisglykos = sweet, lysis = splittingBreaks down glucose into 2 molecules of pyruvate There are two stages (each w/ 5 steps, 10 total)Does not require oxygen (essential anaerobic)

Animation: 1st Stage: Glucose Split into TwoPhosphorylation of glucose by ATP2-3. Molecule is rearranged and 2nd ATP phosphorylation4-5. 6-C molecule split into two 3-C moleculesOne glyceraldehyde 3-phosphate (G3P) and one that will be converted later

2nd Stage: Forms Pyruvate6. Oxidation then phosphorylation to produce NADH to 2 BPG (NAD+ reduced)7. 2 ADP removes high energy phosphates, leaving 2 3PG molecules8-9. H2O removed leaving 2 PEP molecules10. 2 ADP removes high energy phosphates, leaving 2 pyruvate moleculesReactantsC6H12O62 NAD+2 ADP2 Pi

Products2 C3H4O3 (pyruvate) 2 NADH + H+2 ATP (net)2 H2ONet Reaction for Glycolysis:

Glucose + 2 NAD+ + 2 ADP + 2Pi 2 pyruvate + 2H2O + 2NADH + 2ATP

Animation (one more time!): Pyruvate OxidationCarboxyl group removed from pyruvate as CO2C2 fragment is oxidized into acetic acid (as NAD+ is reduced to NADH)Coenzyme A (a sulfur containing vitamin B derivative) forms an unstable bond with acetic acidTwo molecules of Acetly-CoA and NADH produced

Acetyl CoAAcetyl CoA is a pivotal molecule in cellular metabolism

Most molecules used to provide an organism with energy are converted to acetyl CoA(reversible)

Krebs CycleA.k.a. Citric Acid CycleCyclic metabolic pathwayAcetyl CoA is oxidized to CO2Regenerates compound that picks up more acetyl CoAConverts released energy to ATP, NADH, and FADH2

For each turn of the cycle:2 C atoms enter as acetyl group and 2 C leave as CO2

much of acetyl groups energy is transferred as high energy electrons to reduce 3NAD+ 3NADH and 1 FAD 1 FADH2

some of acetyl groups energy is used in the substrate level phosphorylation of 1 ADP 1ATP

for each glucose molecule oxidized 2 acetyl CoA are produced

there are 2 turns of the Krebs cycle for each 1 glucose

Reactants2 acetyl CoA2 oxaloacetate6 NAD+2 ADP2 FAD2 Pi

Products2 CoA4 CO22 oxaloacetate6 NADH 6 H+2 FADH22 ATP (net)Reactants and Products of the Krebs Cycle:Animation: Oxidative PhosphorylationDuring glycolysis and 2 rounds of the Krebs cycle carbon from glucose CO2Very few ATP molecules have been produced at this pointEnergy is in NADH and FADH2Oxygen is used here to produce majority of ATP


Electron Transport Chain (ETC)System of enzymes (with cofactors) embedded in the inner mitochondrial membrane

Enzymes pass electrons from NADH and FADH2 to O2 in a series of redox reactions

Each component of the ETC is more electronegative than the previous

Final electron acceptor, O2, is one of the most electronegative substances on earth

Electron transfer from NADH to O2 is highly exergonicIntermediate steps help release the energy in manageable amounts to accommodate the change in energy form

FADH2 enters the ETC after the first part of the multi-enzyme complexTherefore yields 1/3 less energy

NADH from cytosol cannot move into the mitochondrial matrixElectrons must be shuttled, usually via an FADH2 Therefore usually yields 1/3 less energy then NADH produced in the mitochondrial matrix

ETC Animation (one more time!):

ChemiosmosisH+ ions pumped using energy released in the electron cascade through the ETC Creates a high [H+] in the inner membrane spaceThis gradient drives phosphorylation of ADP ATP

ATP Synthase

ATP is formed (oxidative phosphorylation)As the H+ re-enter the matrix through special protein channels that are coupled with ATP synthase

Yield of ATP from Aerobic RespirationIt is possible to generate 36 or 38 molecules of ATP from one glucose molecule38 for prokaryotes b/c they do not need to use 2 ATP transport NADH from glycolysis across mitochondrial membrane

These #s are theoreticalExperimental yields are lower. Why? (read text for reasons to account for lower values)

Interconnections of Metabolic PathwaysHumans eat more than just glucose. So what happens to the other molecules?

Compounds from all nutrients can be broken downThey can enter glycolysis and the Krebs cycleE.g. Glycerol from fatty acids can be converted to G3PE.g. Amino acid alanine is directly converted to pyruvate

Things You Should Know...Aerobic respiration4 stages in respirationKnow where they occurKnow the basic steps (not all intermediates, but major molecules)Know electron carriers (NAD+ and FAD)Reactants/products for each (esp. ATP)Examples of common intermediates between fat, carbohydrates, protein and stages in respiration.