RespirationBiological process whereby the energy stored in carbohydrates from PS is released in a step-wise, controlled manner.Energy released is coupled to the synthesis of ATP.ATP is essential for plant cell maintenance, growth and development

Carbohydrate ConversionStarchglucose

Sucrose + waterglucose + fructose

Equation for Aerobic Respiration

C6H12O6 + 6O2 + 6H2O 6CO2 + 12H2O + energy (glucose) (ATP)

1 mole glucose 36 ATP

Biological process whereby reduced organic compounds are mobilized and oxidized, energy released is stored in ATP. Glucose considered the direct substrate, but other CHOs are degraded to form glucose

Efficiency of Aerobic RespirationADP-P bond releases -7.6 kcal/mol ATP when bond is brokenTheoretical energy yield from burning 1mol glucose in a calorimeter = -686 kcal/molPractical yield from burning 1mol of glucose in the cell with oxygen = 36ATP

36 ATP X -7.6 kcal/mol = -274 kcal/mol glucose274/686 kcal/mol X 100 = 40% efficiency

Efficiency of Anaerobic RespirationADP-P bond releases -7.6 kcal/mol ATP when bond is brokenTheoretical energy yield from burning 1mol glucose in a calorimeter = -686 kcal/molPractical yield from burning 1mol of glucose in the cell without oxygen = 2 ATP

2 ATP X -7.6 kcal/mol = -15.2 kcal/mol glucose15.2/686 kcal/mol X 100 = 2.2% efficiency

3 Stages of RespirationGlycolysisTCA CycleElectron Transport Chain

GlycolysisOccurs in all living organismsOnly stage which can occur without oxygenOldest stage of respiration

operated for billions of years in anaerobic organismsConverts glucose to 2 pyruvates in cytosol

with O2 goes on to TCA cyclewithout O2 pyruvate is converted to lactate or ethanol (fermentation)Yields 2ATP/mole glucose in the absence of O2

GlycolysisGlucose (6C)

2 Pyruvate (3C)EthanolLactateTCA CycleCO2+O2-O2-O2

TCA cycle

Electron Transport SystemNADH and FADH2e-e-4e- + 4H+ + O22H2Ocyt. oxidaseH+H+ATP

Chemiosmotic modelH+H+H+H+H+H+H+H+H+H+H+H+H+H+H+Ion concentration difference represents a source of free energy

Chemiosmotic modelH+H+H+H+H+H+H+H+H+H+H+H+H+H+H+The energy represented by the H+ gradient is converted to a chemical form (ATP) via the ATP synthase

3 Stages of RespirationGlycolysis

cytoplasmwith or without oxygen presentbreaks glucose (6C) into 2 pyruvates (3C)TCA Cycle

mitochondrial matrixonly if oxygen presentconverts pyruvate via acetyl CoA into CO2; generates NADH and FADH2Electron Transport Chain

mitochondrial membranes = cristaetransfers electrons from NADH and FADH2 to reduce O2 to H2O and generate ATP

MitochondriaSpherical to oval

about 1 micron diameter# mito./cell increases with demand for respiration; 300-1000/root tip cellDouble-membrane bound

outer smoothinner folds forming cristaecontrols movement in/outsite of electron transportmMatrix

soluble phasesite of TCA cycle; DNA, RNA, ribosomesmatrixcristae

Alternate Fates of Glucose CNot all C respired to CO2Intermediates of respiration branch off:

amino acidspentoses for cell wall structurenucleotidesporphyrin biosynthesisfatty acid synthesislignin precursorsprecursors for carotenoid synthesis, hormones

Factors Affecting Resp. Rate[Substrate][ATP][Oxygen]TemperaturePlant typePlant organPlant age

Factors: Substrate AvailabilityResp. higher right after sundown compared to right before sunrise due to [S]Shaded leaves respire slower than lighted leavesStarvation of plant tissue results in utilization of proteinsHigh [ATP] in cell and get negative feedback on resp.

Factors: [Oxygen]No effect until [O2] < 1%

Cyt oxidase not sensitive to O2 until 0.05%O2 diffuses in water 10,000 X slower than in airSome plants have intercellular air system, e.g., aerenchyma in shoots and roots (rice)Very low levels of O2 see accelerated breakdown of sugars to ethanol and CO2 evolved = Pasteur Effect

Factors: TemperatureQ10 for respiration is 2.0 - 2.5 between 5 and 25CQ10 = rate of process at one temperature divided by the rate at 10C lower temp.

Decreases with most plant tissues at 30-35CO2 being used so fast, it cant diffuse fast enough into tissuesTropical regions - 70-80% PS C lost to resp. due to high night temperatures and resp. rates

Factors: Plant Type/Organ/AgeResp. rate tends to increase with age of plant

Young trees lose about 1/3 daily PS C to resp. and doubles with older trees as ratio of PS/Non-PS tissue decreasesGreater metabolic activity = greater resp. rates

Root tips, dev. buds and meristematic regions in general have higher respiration ratesIn veg. tissues, resp. decreases from the tip to the mature regionsSeeds - low resp. rates, dormant, desiccation results in slowdown of respiration

Factors: Plant Type/Organ/Age (cont.)Ripening Fruit

Resp. high when young cells are dividing and growingClimacteric Fruit (apples, tomatoes)

Sharp increase in rate immediately before fruit ripening = climacteric rise in respirationCoincides with full ripeness and flavor and preceded by huge increase in ethylene productionThis leads to senescence and decrease in respirationNon-climacteric Fruit

Citrus, cherries, grapes, pineapple, strawberriesInsensitive to ethylene

Controlled Atmosphere StorageLower O2 (2% - 3%) & raise CO2 (5% - 10%)

slows down resp.No ethylene

high CO2 also inhibits ethylene synthesisTemps. typically about -1 to -0.5CPick apples in Sept./Oct. when green and immature and store in CA

expose to normal air with ethylene when ready to sell fresh apples in March

Cyanide Resistant RespirationAerobic resp. (cyt oxidase) in plants and animals inhibited by CN- and N3- (azide)

bind to Fe in enzyme and halts e- transportAnimals: CN causes resp. to decrease fast, virtually irreversible and fatalPlants: display a 10-25% CN-resistant resp. and alternate pathway for electron flow

electron flow branches off to alternate oxidaseless ATP produced

Cyanide Resistant Respiration (cont.)Metabolic Role?

No clear roleOperates when cyt oxidase poisonedEnergy overflow hypothesisoverflow for electrons when resp. rate exceeds demand for ATP; high with high carbo. levelsSkunk cabbage, Voodoo lily, Stinking lily: CN-res. pathway causes temp. of spadix to increase 10-20C.volatilization of odiferous cmpds which attract pollinators

Biological process whereby reduced organic compounds are mobilized and oxidized, energy released is stored in ATP. Glucose considered the direct substrate, but other CHOs are degraded to form glucose