Energy and Metabolism Chapter 6

2 Flow of Energy Energy: the capacity to do work -kinetic energy: the energy of motion -potential energy: stored energy Energy can take many forms: mechanicalelectric current heatlight

3 Flow of Energy Most forms of energy can be converted to heat energy. Heat energy is measured in kilocalories. One calorie = the amount of heat required to raise the temp of water by 1 o C 1 kilocalorie (kcal) = 1000 calories

4 Flow of Energy Potential energy stored in chemical bonds can be transferred from one molecule to another by way of electrons. oxidation: loss of electrons reduction: gain of electrons redox reactions are coupled to each other.

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6 Laws of Thermodynamics First Law of Thermodynamics – energy cannot be created or destroyed -energy can only be converted from one form to another For example: sunlight energy chemical energy photosynthesis

7 Laws of Thermodynamics Second Law of Thermodynamics: disorder is more likely than order entropy: disorder in the universe The 2 nd Law of Thermodynamics states that entropy is always increasing.

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9 Laws of Thermodynamics Free energy: the energy available to do work -denoted by the symbol G (Gibb’s free energy) enthalpy: energy contained in a molecule’s chemical bonds free energy = enthalpy – (entropy x temp.) G = H - TS

10 Laws of Thermodynamics Chemical reactions can create changes in free energy:  G =  H - T  S When products contain more free energy than reactants –  G is positive. When reactants contain more free energy than products –  G is negative.

11 Laws of Thermodynamics Chemical reactions can be described by the transfer of energy that occurs: endergonic reaction: a reaction requiring an input of energy -  G is positive exergonic reaction: a reaction that releases free energy -  G is negative

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13 Laws of Thermodynamics Most reactions require some energy to get started. activation energy: _________________ _________________________________ -destabilizes ____________________ -required ______________________ catalysts: _______________________ _______________________________

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15 Energy Currency of Cells ATP = adenosine triphosphate -the ________ “currency” _____________ ATP structure: - - -

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17 Energy Currency of Cells ATP stores energy ___________________ __________________________________. Phosphates are highly negative, therefore: -the phosphates __________________ -much energy is required ___________ __________________________________ -much energy is released ____________ ___________________________________

18 Energy Currency of Cells When the bond between phosphates is broken: ATP ADP + P i ____________________ ADP = P i = ________________________________.

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20 Energy Currency of Cells The energy released when ATP is broken down to ADP ______________________ __________________________________. The energy released _________________ __________________________________ __________________________________.

21 Enzymes Enzymes: _______________________ ________________________________ -most are __________ -___________ the activation energy required for a reaction -are not __________________________ ________________________________

22 Enzymes Enzymes interact with _____________. substrate: _______________________ _________________________________ active site: _______________________ ______________________________________ Binding of an enzyme to a substrate causes the enzyme to change shape, -_____________ _____________________________________.

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25 Enzymes Multienzyme complexes offer certain advantages: 1._______________________________ ________________________________. 2._________________________________ __________________________________. 3.__________________________________ ___________________________________.

26 Enzymes Not all enzymes are proteins. Certain reactions involving RNA molecules ________________________________. ribozymes:_______________________ For example, the ribosome is a ribozyme.

27 Enzymes Enzyme function is affected___________ ________________________________. Factors that can change an enzyme’s 3- dimensional shape can change its function. -for example, _____________________ ________________________________

28 Enzymes Temperature -enzyme activity may be __________with increasing temp, up to the temp optimum -temperatures too far above the temp optimum_______________________ _______________________________ pH – ___________________________ ________________________________

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30 Enzymes Inhibitors- _______________________ _______________________________. -competitive inhibitors- ______________ ___________________________________ ___________________________________. -noncompetitive inhibitors -___________ __________________________________

31 Enzymes ___________________ exist in either an active or inactive state. -possess a ________________ where molecules other than the substrate bind -______________________bind to the allosteric site to inactivate the enzyme ______________________bind to the allosteric site to activate the enzyme

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33 Metabolism Metabolism:________________________ ___________________________________ Anabolism:__________________________ ___________________________________ Catabolism:_______________________ ______________________________________

34 Metabolism Some enzymes require _______________ for proper enzymatic activity. These molecules could be: -____________: usually metal ions, found in the active site participating in catalysis -___________: nonprotein organic molecules, often used as an electron donor or acceptor in a redox reaction

35 Metabolism ________________________ are a series of reactions in which the product of one reaction becomes the substrate for the next reaction. Biochemical pathways are often regulated by ______________in which the end product of the pathway is an allosteric inhibitor of an earlier enzyme in the pathway.

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