1、Energetics,Energy defined as the capacity to do workTwo forms of energy: Potential Energy = Stored Energy Kinetic Energy = Energy that is doing work,Thermodynamics The study of energy transformations,2 Laws 1st law talks about converting energy 2nd law talks about what happens to the energy (Kinetic
2、) during this conversion,Robbing Peter to pay Paul,1st law thermodynamics total energy in universe is constant E to do work cant be generated from nothing it must be obtained from outside the system loses a corresponding amount of E to balance the books,World is going downhill,2nd law thermodynamics
3、 Whenever anything actually happens, the entropy (disorder) of the system (or of the universe) increases (cannot decrease)Entropy is a measure of the amount of energy that becomes unavailable for useful workDisorder may be in the arrangement of matter or energy Heat (thermal energy) is disordered en
4、ergy,How can life exist?,Life is an organization of matterA systematic DECREASE in entropyViolates the 2nd law of thermodynamics!Organizing processes require energySteady input of energy from the sun,Life is a series of energy transfers,Life depends on the fact that energy can be converted from 1 fo
5、rm to anotherCHEMICAL CYCLE Photosynthesis CO2 + H2O C6H12O6 + O2 Respiration Light energy is converted into potential Energy of Glucose (Ps) or this potential Energy is transformed into Kinetic Energy (Respiration) and when some of the energy stored in the glucose molecule is made available for cel
6、lular work),Metabolism,Living cell = chemical factory organic molecules broken down releasing the energy in their bonds & new molecules are synthesizedMetabolism = catabolism + anabolism catabolism - complex molecules broken into simpler onesanabolism - complex molecules constructed out of simpler o
7、nes,Enzymes (ase),Most reactions require initial energy to proceed (ACTIVATION ENERGY)Decrease necessary activation energyCo-factors may be used (changes shape of enzyme excitatory or inhibitory allosteric regulation)Nicotinamide adenine dinucleotide (NAD) - niacinNo loss of enzymeShape critical,Enz
8、ymes, formation of: enzyme-substrate complex substrate optimal position to react (stress on bonds - orientation) After reaction release of enzyme E + S E-S E + P,Substrate,Active Site,Induced Fit,Enzyme Inhibitors,1.Competitive inhibitor resembles substrate and competes with substrate for active sit
9、e2. Noncompetitive inhibitor binds elsewhere (allosteric site) resulting in changing the shape of the enzyme so the active site is no longer functionalReversible inhibitors important regulators of cell metabolism (sometimes inhibitor is product - if ATP demand; ATP acts as noncompetitive inhibitor N
10、EGATIVE FEEDBACK)Pesticide Malathion inhibits nervous system enzyme acetylcholinesterase preventing nerve cells from transmitting signalsPenicillin inhibits enzyme (transpeptidase) bacteria use in making cell walls (enzymes used to form cross-links),Energy Acquiring Pathways,about 40% of glucoses en
11、ergy “banked” 60% lost as heat,Aerobic Respiration The Main Energy Releasing Pathway,1. Energy released from breakdown of organic compounds,2. Released energy transformed to ATP Energy,CO2 & H2O released,O2 required,ATP Adenosine Triphosphate,Energy transfer molecule in living organisms,Metabolic pa
12、thways,Metabolism = the chemical processes of cellsMetabolic Pathway = sequence of reactions by which chemical changes such as cell respiration are carried out in many small stepsCellular respiration using the sugar glucose as fuel takes place in three phases, involving 20 separate reactions, and 20
13、 different enzymes,Cellular Respiration,“Glucose“ converted into form which can be used for cellular work ATP 40% of Glucoses energy banked - 60% lost as “heat”Rearrange electrons in chemical bonds extracting “glucoses” chemical-bond energy and storing it in the chemical bonds of ATPGlucose an elect
14、ron bank and NAD+ / FAD and dehydrogenase enzymes efficient system for extracting electrons,Three main steps in Cellular Respiration,Glycolysis occurs in cytosol fluid of the cell breaks glucose into 2 molecules of Pyruvate / pyruvate supplies third stage with electrons small amount of ATP producedC
15、itric Acid (=Krebs) Cycle occurs in matrix of mitochondria completes breakdown of glucose to carbon dioxide supplies third stage with electrons small amount of ATP producedElectron Transport Chain Uses the downhill flow of electrons to pump H+ ions across a membrane - storing energy that ATP synthas
16、e uses to make most of the cells ATP,Mitochondrion,http:/www.imtech.res.in/raghava/rslpred/mitochondria.jpg,Glycolysis,Energy investment (uses 2 ATP) molecule energized by addition of 2 phosphates 6-carbon molecule split into two 3-carbon molecules,Energy yielding 2 NADH + 2 H+ (not shown) 2 H2O pro
17、duced 4 molecules of ATP per glucose (NET of 2 ATP) ( 2% energy recovery) NO O2 used - encountered in cytoplasm of all living cells whatever mode of life,Problem,NAD+ functions as electron carrierCell has limited supply of NAD+ that must be used 50 Kcal/mole of free energy is stored in 2 NADH To har
18、vest energy electron must be transferred (usually ultimately to O2)If oxygen Citric Acid Cycle Electron Transport ChainIf no oxygen Lactic Acid or Alcohol Fermentation,Transition Reaction,NAD+ NADH + H+ Coenzyme A (from vitamin B complex Pantothenic acid vitamin B5 1 molecule glucose 2 molecules of
19、acetyl CoANo ATP,Citric Acid Cycle,2 “turns”Coenzyme A recycledMost important function: Generation of electron carriers (NADH & FADH2),The Electron Transport System,Array of enzymes & coenzymes sequentially transfer electronsFound in membranes of chloroplasts and mitochondriaElectrons at higher ener
20、gy levels released at lower energy levels like a staircaseAs electrons drop down each step small amounts of energy releasedSome energy used to do work move ions and setup concentration and electric gradients across membraneFinal electron acceptor oxygen combines with H+ to form water (low energy pro
21、duct most energy extracted),Electron Transport Chain,Inner membrane of mitochondria thylakoid membrane in PsUses electrons and H+ from previous steps to produce most of ATPO2 final electron acceptor,No O2 Available (Anaerobic Metabolism),Pyruvate + NADH + H+ Lactic Acid + NAD+2 ATP extracted from Gl
22、ucoseReformation of NAD+Lactic Acid carried to Liver and reconverted to Pyruvate,No O2 Available (Anaerobic Metabolism),Pyruvate Acetaldehyde + CO2Acetaldehyde + NADH + H+ Ethanol + NAD+2 ATP extracted from GlucoseReformation of NAD+Waste products: ETOH and CO2,Metabolism of Fats and Proteins,Fats,F
23、atty acids,glycerol,Glycolysis,Pyruvate,Acetyl-CoA,Citric Acid Cycle,Proteins,Amino acids,“carbon backbone”,-NH3,urine,Energy Acquiring Pathways,O2 released,Sunlight Energy drives reactions,Photosynthesis The Main Energy Acquiring Pathway,1. Sun Energy transformed to ATP Energy,2. ATP Energy glucose
24、 synthesis,CO2 & H2O required,Chloroplast,http:/www.ualr.edu/botany/chloroplast.jpg,Photosynthesis,2 main reactions each with multiple steps Light dependent- thylakoid membrane (light E ATP) Light independent- in stroma (sugars assembled),NOTE WELL: Plant cells use the food they make in the same way
25、 that animal cells do - by cellular respiration,http:/hawaii.hawaii.edu/laurab/generalbotany/images/Plant%20Cell.gif,Energy Flow,SUNLIGHT,GLUCOSE,ATP,CELL WORK,Carbon Dioxide,+,Water,ADP,+,Inorganic Phosphate,(Photosynthesis),(Cellular Respiration),+ O2,-Active transport,-Movement,-Bio-synthesis,heat,heat,heat,(Splitting ATP),
