Download Extracting Energy from Food

Extracting Energy from Food
Cost of ion gradients
One ATP is used to 1. Pump3Na+and2K+againstconcentration
gradient
2. Andmove1unitofchargeagainst
concentrationgradient
Low Na+ inside
High Na+ outside
• ProvidesagradientforK+
Energy in a chemical reaction can be calculated
from:
is the energy change when all reactants
are present @1M & STP
for ATP ~ -7.5Kcal/mol
•
•
Electrical and chemical potential energy
• Moleculesdiffusefromhightolow
concentration
• Highconc.differenceshavechemical
potentialenergy
Voltage generates electrical potential energy
Cost of Na+/K+ ATPase
Total cost =42KJ/mol ATP
About 10 Kcal/mol of ATP used
Thermodynamic Limits
Pumps move against the concentration gradient
– if not enough energy they move backwards
(energy from ATP must be greater than sum of
chemical and electrical potential energy)
ADPandPihave~7.5Kcal/mollessenergy
thanATPwhenallareaconcentrationof
1M
REALcellshavemoreATPthanADP
o MovingATP/ADPtowards
equilibriumprovidesenergytomove
otherreactionawayfrom
equilibrium
ATP hydrolysis -> ~12Kcal /mol of ATP
(chemical potential energy)
Glycolysis
- NoO2used,noCO2produced
- 1glucose(6C)in,2pyruvateout(3Ceach)
o gains2molATPperGlucose
- makesNADH(formofenergy)
- pyruvate->lactateandloseNADH
Mitochondria
• glycolysishappensinmitochondria
• pyruvateentersmitochondria(combines
withO2)
o mostATPproductionin
mitochondria
Citric Acid Cycle
Pyruvate -> acetylcoenzyme A (acetyl CoA)
(mitochondria)
• NoO2used–2CO2/perglucose
• O2fromglucose–moreNADHmade:
remaindersenttolactate
• FatmetabolismmakesacetylCoA–fatand
carbohydratesharecommonpathway
NEXT STEP
• 4CO2/glucose
• O2fromfoodorwater
• 2Cin2CleaveasCO2
• 2GTP/glucose
• 6ADH/glucose
• 2FADH
Energy Currency of the Cell
1GTP=1ATP
1 FADH2 = 2 ATP
1 NADH = 3 ATP
Electron Transport Train
• FoodisoxidisedwithNADandFADnotO2
• ReducedNADHandFADH2feedinto
electrontransportchain
o OxidisedNADHandFADH
NADH
Powers 3
H+ pumps
FADH2
enters
ubiquinone – powers 2 pumps
ATP synthesis
H+ produces electrochemical gradient
-140mV potential (inside negative)
• 1.4unitspHdifference
• Largeelectrochemicalgradientpushes
H+ATPasebackwards
o Movestowardsequilibriumdownits
electrochemicalgradient
Oxidative Phosphorylation
ATP synthesis
Glycolysis gives 2mol ATP per mol glucose
- Oxidativephosphorylationgives36molof
ATPpermolGlucose
- EnergyfromC-CandC-Hbonds
- Producesusableenergyina21%O2
atmosphere