Adapted from: faculty.sgc.edu/asafer/BIOL1107/chapt06_lecture.ppt

 Explain the role of catabolic and anabolic pathways in cell metabolism  Distinguish between kinetic and potential energy  Distinguish between open and closed systems  Explain the first and second Laws of Thermodynamics  Distinguish between enthalpy and entropy  Understand the Gibbs equation for free energy change.  Understand how ‘usable’ energy changes with changes in enthalpy, entropy and temperature.  Understand the usefulness of free energy. 2

 Study of how organisms manage their energy resources  Energy is the capacity to do work  Energy exists in multiple forms  Light  Heat  Electricity  Chemical bond energy  Etc.  These various types of energy can be places into two groups  Kinetic energy  Potential energy

 “Energy of motion”  Anything that moves possesses kinetic energy  e.g., Heat, light, balls on a pool table, flowing water, flowing electrons, etc.

 “Energy of location or structure”  “Stored energy”  Resting objects may still possess energy  e.g., A rock at the top of a hill, chemical bond energy

Potential energy stored in chemical bonds can be transferred from one molecule to another by way of electrons. ** the rearrangement of atoms in molecules may results in the potential energy of the molecule being converted into kinetic energy. oxidation: loss of electrons reduction: gain of electrons redox reactions are coupled to each other.

First Law of Thermodynamics  (The Law of Conservation of Energy) “Energy cannot be created or destroyed” “The total amount of energy in the universe is constant”

 Energy cannot be created or destroyed  However, it can be converted from one form to another  What energy transformations are taking place here?

 If energy cannot be created or destroyed, why do living things need continual inputs of energy?

The Second Law of Thermodynamics “Every energy transformation makes the universe more disordered”  Entropy is a measure of this disorder or randomness “Every energy transformation increases the entropy of the universe” “When energy is converted from one form to another, some fraction of the potentially usable energy is lost”  Not destroyed, but converted to entropy

The Second Law of Thermodynamics  Note that we have talked about the universe as a whole, not each individual part of the universe  The universe is a “closed system” No energy enters or leaves In a closed system, entropy increases  The terms of open or closed systems refer to whether or not energy can be transferred between the system and its surroundings (can energy be imported or exported)

The Second Law of Thermodynamics  You, as an individual, can increase in order  You do so at the expense of your environment  Overall, the net change in you and in your environment is an increase in disorder You + environment = a closed system

16 Free energy(G): the portion of energy available to do work under uniform temperature. ie: amount of energy available to break and form other chemical bonds. Enthalpy (H) or work total energy : energy contained in a molecule’s chemical bonds -it is a measure of all the energy in a system free energy = enthalpy – (entropy x temp.) G=H-TS where temperature is measured in K.

17  Chemical reactions can create changes in free energy:  When products contain more free energy than reactants  G is positive.  When reactants contain more free energy than products  G is negative.

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 When  G = 0, no work can be done  When reactions go to equilibrium,  G=0 (therefore metabolic reactions do not usually reach an equilibrium)  Energy needed for Mechanical, Chemical and Transport workings of the cell. 19

 Certain events occur spontaneously, while others do not  Spontaneous processes occur (once initiated) without outside help  e.g., Water flows downhill, not uphill  How can we explain this?

 The free energy released in spontaneous processes can be harnessed to do work

 What energy transformations are occurring here?  What is the spontaneous process?  Is work being done?

 Some chemical reactions release free energy  Spontaneous reactions  Exergonic reaction / Exothermic  (reactants contain more energy)  G is negative  Some chemical reactions require free energy in order to proceed  Non-spontaneous reactions  Endergonic reaction /Endothermic  (products contain more energy)  G is positive  The energy released in exergonic reactions can be used to drive endergonic reactions

 The environment within a cell is highly organized and separate from the external environment  Maintaining this ordered environment costs energy  Many processes within a cell require energy  The requirement for energy is a unifying feature of life  Many organisms extract energy from food via aerobic cellular respiration

Metabolism: the sum of all the anabolic(energy storing) and all the catabolic activities(energy releasing) in the cell Identify each of the following activities as either anabolic or catabolic: (a) protein synthesis (b) digestion (c) DNA synthesis (d) photosynthesis (e) cellular respiration

 Explain the role of ATP in the cell  Describe ATP’s composition and how it performs cellular work  Explain the importance of chemical disequilibrium  Understand the energy profile of a reaction including: activation energy, free energy change & transition state.  Explain how metabolic pathways are regulated. 26

27 Atoms or molecules Energy + Energy Larger molecule The energy that was used to form the bonds is now stored in this molecule.

28 Energy The energy is now released. It may be in a form such as heat or light or it may be transferred to another molecule. Menu

29 ATP = adenosine triphosphate -the energy “currency” of cells -energy molecule used to couple exergonic and endergonic -has a high  G ATP structure: -ribose, a 5-carbon sugar -adenine -three phosphates

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31 A Base (adenine) Sugar (ribose) 3 phosphate groups

32 A ATP The phosphate bonds are high-energy bonds. A Energy ADP + P i + Energy Breaking the bonds releases the energy. What type of reaction is this?

33 Phosphates are highly negative, therefore: -the phosphates repel each other -much energy is required to keep the phosphates bound to each other -much energy is released when the bond between two phosphates is broken Remember  ATP has a high  G

34 When the bond between phosphates is broken: ATP ADP + P i energy is released (  G=-7.3Kcal/mol in the lab, -13 Kcal/mol in the cell) ADP = adenosine diphosphate P i = inorganic phosphate Is this reaction catabolic or anabolic? This reaction is reversible.

35  The energy used to produce ATP comes from glucose or other high- energy compounds.  ATP is continuously produced and consumed as illustrated below.

 Hydrolysis of ATP produces inorganic phosphate that is attached to a molecule involved in an endergonic process.  Phosphorylation is the process of ATP transferring phosphate to a molecule.  Results in a phosphorylated intermediate that can complete the intended reaction.

What type of reaction is the recycling of ATP?

38  Two kinds of phosphorylation are illustrated on the next several slides. –Substrate-Level Phosphorylation –Chemiosmotic Phosphorylation

39 ADPHigh-energy molecule A high-energy molecule (substrate) is used to transfer a phosphate group to ADP to form ATP. This bond will be broken, releasing energy.The energy released will be used to bond the phosphate group to ADP, forming ATP. Enzyme An enzyme is needed.

41 Low-energy moleculeATP The energy has been transferred from the high- energy molecule to ADP to produce ATP.

 Use of ATP  ATP is a good energy source because: It can participate in many different kinds of reactions within the cell. Usually is directly involved in reactions Little wasted energy during phosphorylation of an intermediate.  Use of enzymes  Decrease randomness of reactions  Regulation of enzymes and thus, reactions

44 Biochemical pathways 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 feedback inhibition in which the end product of the pathway is an allosteric inhibitor of an earlier enzyme in the pathway.

 Allosteric Regulation: enzyme function may be stimulated or inhibited by attachment of molecules to an allosteric site.  Feedback Inhibition: end product of metabolic pathway may serve as allosteric inhibitor  Cooperativity: Single substrate molecule primes multiple active sites increasing activity.

IS THERE ENOUGH ENERGY TO RUN ALL METABOLIC PROCESSES IN A CELL?? WHAT HAPPENS TO THE ENTROPY PRODUCED IN ALL THE CHEMICAL CONVERSIONS IN A CELL?? IN A BODY??

The laws of thermodynamics define which reactions are spontaneous and which are not… Some reactions are spontaneous but occur at nearly imperceptibly slow rates  Too slow to sustain life Enzymes can increase the rate of chemical reactions by more than x

 Cellular Respiration is the controlled breakdown of glucose -catabolic  CR involves a series of chemical reactions that release free energy  Exergonic reactions/Exothermic  spontaneous  This free energy is used for cellular work

 Cellular respiration is also known as the “ Oxidation of Glucose ”  Oxidation is a chemical reaction in which an atom loses one or more electrons.  Lost electrons must have somewhere to go  Reduction is a chemical reaction in which an atom gains one or more electrons.  A redox reaction - oxidation coupled with reduction!