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Chpt. 8 An Intro to Metabolism Metabolismtotality of an organism’s chemical reactions Metabolismtotality of an organism’s chemical reactions molecules are altered molecules are atered molecules are ateed Metabolismmolecules are altered molecules are atered molecules are ateed Enzymes catalyze each step Metabolic Reactions: Types: Catabolicbreak down molecules •release energy ex. cellular respiration Metabolic Reactions: Types: Anabolicbuild molecules consume energy ex. making proteins from amino acids Examples • dehydration synthesis (synthesis) + enzyme H2O • hydrolysis (digestion) enzyme H2O + Examples • dehydration synthesis (synthesis) enzyme • hydrolysis (digestion) enzyme HOW ORGANISMS MANAGE THEIR ENERGY capacity to do work: change in the state or motion of matter Cells obtain chemical energy when molecules are rearranged: Therefore, a basic knowledge of ENERGY is necessary to understand how cells work… Potential Energy •stored in molecules in the chem. bonds …is converted to Kinetic Energy Potential Energy - where is it in this picture? Kinetic Energy •(energy of motion) • energy that “powers” the cell. ex. cell respiration, releases energy stored in the bonds of sugar molecules. Kinetic Energy Where is it here??? This one is easy to see! energy transformatio n 1st Law of Thermodynamics chemical energy was not created, and will not be destroyed… but it can change forms B A C Flow of energy through life • Life is built on chemical reactions transforming energy from one form to another organic molecules ATP & organic molecules sun solar energy ATP & organic molecules organic molecules ATP & organic molecules 2nd Law of Thermodynamics Every energy transfer or transformation, increases entropy (disorder) in the Universe Christian Right Lobbies To Overturn Second Law Of Thermodynamics September 6, 2000 | Issue 36•31 TOPEKA, KS–The second law of thermodynamics, a fundamental scientific principle stating that entropy increases over time as organized forms decay into greater states of randomness, has come under fire from conservative Christian groups, who are demanding that the law be repealed. "What do these scientists want us teaching our children? That the universe will continue to expand until it reaches eventual heat death?" asked Christian Coalition president Ralph Reed, speaking at a rally protesting a recent Kansas Board Of Education decision upholding the law. "That's hardly an optimistic view of a world the Lord created for mankind. The American people are sending a strong message here: We don't like the implications of this law, and we will not rest until it has been reversed in the courts." The controversial law of nature, which asserts that matter continually breaks down as disorder increases and heat is lost, has long been decried by Christian fundamentalists as running counter to their religion's doctrine of Divine grace and eternal salvation. "Why can't disorder decrease over time instead of everything decaying?" HEAT is a very DISORDERED form of energy 2nd Law of Thermodynamics Every energy transfer or transformation increases entropy (disorder) in the Universe Chemical reactions & energy • Some chemical reactions release energy – exergonic – breaking polymers – hydrolysis = catabolism digesting molecules= LESS organization= lower energy state • Some chemical reactions require input of energy building molecules= MORE organization= higher energy state – endergonic – building polymers – dehydration synthesis = anabolism QuickTime™ and a decompressor are needed to see this picture. Living cells, unavoidable, convert organized forms of energy to heat Get it… convert to HEAT QuickTime™ and a decompressor are needed to see this picture. Now, THAT’s some disordered HEAT!! changes that occur on their own… •When spontaneous processes occur in a system (an organism), stability increases~ but in terms of the •Unstable systems tend to become more stable spontaneously. How can we predict which changes occur spontaneously, and which require input of E. from the outside? ENERGY, in a system, THAT CAN PERFORM measure of this free energy Yale scientist featured in stamp series Gibbs received the first Ph.D. in engineering in the U.S. from Yale in 1863 He later became a member of the Yale faculty. G=H-TS free energy = total energy - temp*entropy change Entropy = measure of disorder G=H-TS free total = energy potential amount energy~ of useable total E. to do bond work energy enthalpy - entropy unuseable energy Not all of the energy in a system is available for We can use this to predict which changes occur spontaneously, and which require input of E. from the outside? G=H-TS free energy = total energy - entropy spontaneous changes, decrease free energy Unstable Systems change spontaneously, becoming stable systems, and Free Energy Decreases Endergonic vs. exergonic reactions exergonic endergonic - energy released - digestion - energy invested - synthesis +G -G G = change in free energy = ability to do work Chemical Reactions (2 types): Exergonic- proceeds with a net release of free E. G is negative spontaneous Endergonic- proceeds with a net gain of Energy/ absorbs it G is positive nonspontaneous Chemical Reactions (2 types): Exergonic- proceeds with a net release of free E. exergonic - energy released - digestion -G Chemical reactions & energy • Some chemical reactions release energy – exergonic – breaking polymers – hydrolysis = catabolism digesting molecules= LESS organization= lower energy state • Some chemical reactions require input of energy building molecules= MORE organization= higher energy state – endergonic – building polymers – dehydration synthesis = anabolism Cells “work” three ways: •Mechanical work •Transport work •Chemical work = muscle contraction = pumping across membranes = making polymers ENERGY SOURCE for the work is ATP Adenine Phosphates Ribose sugar ATP •Adenine (Nitrogen-base) •Ribose (sugar) Phosphate chain (3) ATP •Ribose (sugar) •Phosphate chain (3) ATP •Phosphate chain (3) Bond hold potential energy!!! ATP •Phosphate chain (3) Bond can be broken via. hydrolysis ATP •Phosphate chain (3) Unstable b/c three negative charges Label the three parts of the ATP molecule below: ATP + H2O ---> ADP + P + ENERGY release the “P” flew off!!!! -G ATP + H2O ---> ADP + P + ENERGY B/C moving to a more stable condition -G ATP, when hydrolysized, releases free energy (energy that is able be used) broken to ATP, when hydrolysized, releases free E. Cell takes the energy and transfers the Phosphate to another molecule. ATP, when hydrolysized, releases free E. Cell takes the E. and transfers the Phosphate to another molecule. Phosphorylation! QuickTime™ and a decompressor are needed to see this picture. Cell takes the E. and transfers the Phosphate to another molecule. This molecule is less stable than the original molecule. WHAT DOES A graph HAVE TO DO WITH BIOLOGY ??????? A chemical reaction will occur spontaneously if it releases free energy , but the process may be too slow to be effective, in living cells… A chemical reaction will occur spontaneously if it releases free energy , but the process may be too slow to be effective, in living cells… ex. hydrolysis of sucrose: Does occur spontaneously…. But it would take way too long…. ex. hydrolysis of sucrose: Energy of Activation energy required to break bonds (EA) barrier is EXTREMELY high - the reaction will occur only if reactants are heated: ex. hydrolysis of sucrose: Energy of Activation EA barrier is EXTREMELY high - the reaction will occur only if reactants are heated: Enzymes lower EABut do not change G Energy o Energy released Enzymes don’t change G Energy o Substrate Active Site Conformational Change Energy released Energy released Energy released Energy released Enzymes are substrate specific Enzym e Enzymes are effected by environmental factors: Enzymes are affected by environmental factors: TOO MUCH Heat disrupts H-bonds in the protein …remember, enzymes are PROTEIN However: Heat does increase rate of rx…. TO A POINT …remember, enzymes are PROTEIN Beyond that temp, speed of reaction drops: WHAT about pH changes???? pH disrupts H-bonds in the protein …remember, enzymes are PROTEIN paperose A B substrate paperase Sometimes enzymes have “hitch hiker” chemicals/molecules that INHIBIT their effectiveness Sometimes enzymes have “hitch hiker” chemicals/molecules that INHIBIT their effectiveness Competitive Inhibitors Molecules that are bound to the active site “normal” QuickTime™ and a decompressor are needed to see this picture. “competative” WHAT does this to to the RX. RT??? QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. How can we “get around” the lower RX RATE??? QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. How can we “get around” the lower RX RATE??? ADD more substrate paperose A B substrate inhibitor A paperase B see the differ ence QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. IMPLICATIONS?? Turns out, the pesticide DDT is a noncompetitive inhibitor QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. paperose A B substrate inhibitor A paperase B “A cell is not just a bag of chemicals with thousands of different kinds of enzymes and substrates wandering about randomly.” Chaos would result if all of a cell’s metabolic pathways were open at the same time… must be regulated Allosteric Regulation QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Allosteric Regulation • The control of an enzyme complex by the binding of a regulatory molecule. • Regulatory molecule may stimulate or inhibit the enzyme complex. Allosteric Regulation enzyme complex Allosteric Regulation regulatory molecule may stimulate or inhibit the complex Allosteric Regulation•allosteric enzymes have 2 or more polypeptides. •Oscillates between active and inactive. •activator keeps it “on” - active •inhibitor keeps it “off” - inactive Cooperativity•Enzyme having many subunits •Binding of one substrate to the active site causes all active sites to “run” Feedback Inhibition•pathways are switched on and off by the end product. •the end product acts as an inhibitor of an enzyme within the pathway. QuickTime™ and a decompressor are needed to see this picture. Sometimes enzymes require nonprotein “helpers” Molecules that are bound to the active site CoEnzymes QuickTime™ and a decompressor are needed to see this picture. Summary of chpt. 8 • Recognize that Life must follow the Laws of Thermodynamics. • The role of ATP in cell energy. • How enzymes work & all senarios in which they can be placed… what is the result?