Energy Transformation Metabolism = total chemical reactions incells. metabole = change Metabolism is concerned with managingthe material and energy resources of the cell -Catabolism -Anabolism
-Catabolism is the degradative processto harvest energy from breaking down themacromolecules to simpler compounds. Cellular respiration is the main processto convert potential energy stored inmacromolecules into available energy forcellular work.
-Anabolism consumes energy to build orsynthesize complicated molecule from simplerones Cells use energy from catabolism todrive reactions in anabolism.
Energy = capacity to do work or capacityto cause specific changes -non biological systems use HEAT toperform work, but -biological systems use CHEMICALENERGY to do work
2 stages of energy -potential energy =stored energy -kinetics energy = theenergy of motion Sliding down convertspotential energy tokinetics energy
In living cells, chemical energy is apotential energy stored in a moleculeresulting from the arrangement of atoms inthat molecules. Catabolic pathways rearrange themolecular structure of nutrients e.g.breaking down glucose to CO2 and water. As a result, the potential energy inthose nutrients is converted to kineticenergy to cause specific changes in cells.
Photosynthesis VS Cellular Respiration In ecosystemenergy flow andchemical recyclingbetween 2 processes:photosynthesis in thechloroplast and cellularrespiration inmitochondria.
ATP, cell’s energy currency, drives cellularworks.
Tracking Atoms through Photosynthesis Hydrogen extracted from water isincorporated into sugar and the oxygenreleased to the atmosphere (where it will beused in respiration).
Summary of KrebsCycle1 Pyruvate yields: -3 CO2 -1 ATP fromsubstrate levelphosphorylation -4 NADH + H+ -1 FADH21 Glucose yields 2pyrvate fromGlycolysis
Electron Transport Chain-inner membrane ofmitochondria-electron is transferred toelectron acceptor with higheraffinity (moreelectronegative)-O2, the mostelectronegative electronacceptor, is the final electronacceptor-free energy was releasedduring electron transfer
Chemiosmosis: The Energy-Coupling Mechanism-innermembrane ofmitochondria is impermeableto proton (H+)-H+ was pumped across themembrane by the freeenergy released by theelectron transfer (frommatrix to the intermembranespace)= generation of protonmotive force ATP synthase
Chemiosmosis: The Energy-Coupling Mechanism -H+ flow back to the matrix by a channel in ATP synthase -free energy released from the H+ flow is used to synthesize ATP=Oxidative Phosphorylation ATP synthase
1 NADH yields ~ 3ATP 8 NADH ~ 24 ATP 1 FADH2 yields ~ 2 ATP 2 FADH2 ~ 4ATP 2 NADH from Glycolysis have to betransported into mitochondria by the electronshuttle system to either FADH or NAD = 2-3ATP/NADH (cytosol)net = 24 + 4 + 6 or 4 = 34 - 32 ATP fromoxidative phosphorylation
Efficiency of Cellular Respiration G for oxidation of glucose to CO2 and H2O = - 686 kcal/mol 38ATP are generated from this process = 38 X 7.3 kcal = 277.4 kcal efficiency = 277.4 X 100 = 40% 68660% of the stored energy was lost as heat -maintain body temperature -dissipated as sweat
Fermentation: anaerobic process-organic compound is an electron acceptor-produce ethanol or lactate
Catabolism of VariousMacromoleculesEvery macromoleculesare broken down intointermediates ofGlycolysis or KrebsCycle.
Energy transformations in biologicalsystems obey 2 fundamental laws ofthermodynamics:The first Law of Thermodynamics: the law ofconservation of energy -the energy of the universe is constant -energy can be transferred andtransformed but it can not be created ordestroyed
The Second Law of Thermodynamics Every energy transfer or transformationmakes the universe more disordered. Entropy is a measure of disorder orrandomness. Thus, every events in the universe havedirection = toward the increase in theentropy of the universe.e.g. -conversion of glucose to CO2 and H2O -sugar cube dissolved in a cup of water
The Organisms Live at the Expense of FreeEnergySpontaneous change/reaction: -occur without input of energy -increase the stability of the systemNonpontaneous change/reaction: -can occur only if energy is added to thesystem -decrease the stability of the system
Free energy = the portion of asystem’s energy that can perform work oris available for work when temperature isuniform throughout the system.
A process can occur spontaneously only if itincrease the disorder (entropy) of the universe. For biological systems the changes in bothsystems and surroundings have to be measures:unpractical.
Enzymes: the biological catalyst (usually = protein)-increase the rate of reaction-are not consumed by the reactions-do not change the free energy change ordirection of the reaction G = -7kcal/molThis reaction can be catalyzed by sucrase.
The reactantsmolecule must absorbenergy fromsurroundings to breaktheir bonds, and energyis released when thenew bonds of theproduct molecules areformed. The energy required to break bonds inreactant molecule = activation energy orfree energy of activation EA.
Enzymes catalyze or speed up thereaction by lower the activation energy. Enzymes cannot make endergonicreaction exergonic or cannot change G ofthe reaction.Q:Why cells do not use heat to speed up the reactions?