Lecture 7.pdf

Lecture 7.pdf - Chemical Reactions one or more substance...

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Unformatted text preview: Chemical Reactions one or more substance Chemical reaction: Process in which _____________________ are changed into other substances. sum total of all the Metabolism: The ____________________ chemical reactions that occur within an organism. break down Includes: catabolism ___________ - metabolic pathways that __________ release energy molecules ____________ into smaller units to ____________. Anabolism construct _____________ - metabolic pathways that ________ larger molecules ___________________ from smaller units. These source of energy reactions require a ____________________. reactants and products Chemical reactions involve both ______________________. 1 A cell’s metabolism involves many intersecting metabolic pathways. Each pathway begins with a specific reactant molecule which is then modified in a series of specific enzyme-catalyzed steps to required product molecule produce the __________________________. Enzyme 1 A B Reaction 1 initial reactant Enzyme 1 Enzyme 1 C Reaction 2 thats three reactant to get D D Reaction 3 final product 2 Energy There are two classes of energy: due to chemical 1)  Potential energy – energy that is stored ________________ structure or to location __________________________. covalent bonds between C-Hs The ______________________________ in organic molecules store potential energy. - cellulose in wood or paper for example. - is chemical potential energy. on one side of Concentrating ions or molecules ___________ a cell membrane ___________________ also represents stored potential energy that can be used to do work in cells. Fig. 4.12 3 with movement, 2) Kinetic energy - energy associated ___________________ active, energy _____________. energy become kinetic - cell can only do work when _____________________. Energy exists in several different forms: - heat, chemical, mechanical, electrical, electromagnetic one of these forms to another Energy can be converted from _________________________. Sunlight to chemical bond energy, for example. making light energy making light energy By Emmanuelm at English Wikipedia, CC BY 3.0, 4 taking outside energy and they break down that energy turn it to heat energy Fig. 3.2 5 open Living systems function as _______ systems within the isolated ___________ system of the universe. Fig. 3.11 energy and matter Open systems bring in ________________ from their surroundings to maintain their highly organized state heat and waste gases And they release ______________________ into their environment entropy increasing the ___________ of their surroundings. island of order A living organisms is an ____________ in sea of increasing disorder. Energy transfers in living systems are subject to the Laws of Thermodynamics 6 First law of thermodynamics: Thermodynamics is the branch of physical science dealing with relations between heat and other forms of energy and relationships between all forms of energy. Energy can be transferred from one type (or form) to another or but energy can not be created from one place to another, _________________________________ or destroyed __________________________. can’t make Means living organisms ______________ the energy they need, so they must get the energy they need from their surroundings. When a plant converts solar energy into chemical bond energy, the energy transformer plant is functioning as an ___________________, not an energy producer. 7 Second Law of Thermodynamics: During a transfer (transformation) of energy: disorder 1)  there is an increase in the degree of ___________ _________________________. (entropy) in the univers - entropy(S) is a measure of disorder. free energy(G) 2) there is a decline in ________________ in the universe useful energy, energy that is actually -  free energy is _________________________________ available to do work __________________________. One of the characteristics of living organisms is their ability to maintain __________________within their bodies (systems). a higher degree of order open systems They can do this by functioning as __________________. 8 They require sources of energy ______________________. rich in free energy flow this energy through reactions Living systems _____________________________ involved in maintaining or increasing order and producing mechanical work, and: - release, as by-products of metabolism, ______________ heat and small energy poor molecular like C02 ________________________________ to their environment, which increases disorder in their surroundings. greater increase As a consequence of growing, organisms cause a _______________ in entropy decrease in entropy ____________ in their environment than the __________________ associated with their growth. 9 free energy (AG) During a chemical reaction, there is a change in ________________. ΔG can be calculated using the formula: ΔG = ΔH - TΔS enthalpy H is _________ is the total potential energy or total heat content of a system. change in the enthalpy ΔH is the ____________________ of a system over the course of a reaction. ΔH = H products – H reactants change in entropy of a system over the course of a reaction ΔS is the _____________ ΔS = S products – S reactants T is the temperature in degrees Kelvin. 10 anabolic So, in an _____________ reaction, ΔH increases in value while ^G having a +ve value ΔS decreases, which will result in ________________________. - because this type of reaction is an endergonic reaction or energy storing ______________ reaction. catabolic And, in a _________ reaction, ΔH decreases while ΔS increases a-ve value which will result in ΔG having a ______________. - because this type of reaction is an exergonic reaction or energy releasing ______________ reaction. 11 Exergonic Reactions exergonic ( exothermic) reaction Energy releasing reactions are _______________________________. negative Exergonic reactions have a ___________ ΔG because products of the reaction will have ____________________ than the _________ of the reactants less free energy reaction. spontaneous Exergonic reactions are ______________ because they do not require outside source of energy to take place. an _____________________ Fig. 3.7 ΔG =-ve value 12 Endergonic Reactions energy storing Endergonic reactions are _____________ reactions and their ΔG positive value is always a _______________ more free Positive because the products of the reaction have ____________ energy than ________________ the reactants of the reaction. not spontaneous Are _________________ reactions because they require an outside source of energy to proceed. Fig. 3.7 ΔG = + ve value 13 ΔG indicates which reactions are exergonic and spontaneous and which reactions are endergonic and thus requiring an input of energy. not possible to have a An implication of the second law is that it is ___________________ complete transfer of free energy _____________________________ from one molecule to another during a reaction. heat which can not be used by living There is energy released as _____ organisms to do work. to exergonic reaction or process in cell to get the Endergonic reactions are coupled __________________________ input of energy they require to proceed. Many endergonic reactions in cells are coupled to the conversion ATP to ADP _____________, the latter reaction being an exergonic reaction. 14 hexokinase 1. Glucose + phosphate + energy Glucose-phosphate + H2O 7.3 kcal/mole ΔG = ____ 2. ATP ADP + Pi + energy 7.3 kcal/mole ΔG = ____ Pi transferred to gluoce 4 ΔG = ____ kcal/mole heat ATP is adenosine triphosphate bond to get enegry out Pi bond ADP is adenosine diphosphate Pi is an inorganic phosphate molecule. decrease in entropy Note that there is a ________________ in reaction 1. Fig. 3.14 15 ~ Example illustrates: couples 1)  Enzyme hexokinase) _____________ two reactions. - thermodynamically favorable reaction is used to unfavorable one - drive the thermodynamically ________________. 2) Whenever energy is transformed, there is always an increase added to in entropy (decrease in free energy) as energy is __________ the surrounding _______________________. 16 resynthesized ATP used to drive endergonic processes must be ________________. photsphorylation reaction Resynthesis of ATP from ADP is a _______________________. endergonic reaction It is also an ____________________ so it has to be coupled to an exergonic reaction. ADP + Pi +energy The ATP/ADP Cycle ATP exergonic Energy from one of the ____________ reaction _____ in respiration or in photosynthesis heat like a vaucum Fig. 3.16 17 75g of ATP There is roughly __________________ in the average human. 75kg A reasonably active person turns over about __________ of ATP per day, so a typical ATP molecule is broken down and 1000 times resynthesized ___________________ each day. In rapidly metabolizing tissues the lifetime of each ATP molecule A FEW seconds is only ____________________ . 18 Enzymes slowly at Reactions proceed _____________ physiological temperatures. energy barriers prevent reactions from At these temperatures, _____________ proceeding at a reasonable rate. Energy required to overcome this energy barrier is called activation energy )Ea) __________________. Fig. 3.17 19 Activation energy makes critical bond(s) in the reactants _________________. less stable transition Enough molecules must gain enough Ea to occupy a ___________ _______ where critical bonds are unstable and ______________. can be broken state Reaction rates can be sped up by the application of high heat or pressure, but these options kill living organisms. Living organisms, instead, speed up reaction rates using globular proteins called ___________________. enzymes as catalysts speed up the rate of reaction Catalysts are chemical agents that _______________________ but are, themselves, not modified during the reaction. 20 Fig. 3.19 substrates Don’t need a lot of enzyme to speed up a reaction because enzymes _____________________. can be repeatedly reused - reaction rate sped up without need for an increase of heat. not change the ^G Note the enzyme does _____________________for a reaction. Reactants in enzyme catalyzed reactions are called ____________. substrates 21 lowering the required Ea Enzymes speed up reactions by ________________________. very little energy needed substrates 22 substrance(s) Each enzyme has a particular location into which the __________ ______________________________. can fit, called the active site - it is the site of _______________. catalysis The active site for each enzyme has a __________________ and unique 3-D shape unique chemistry ______________________. β-galactosidase specific as to which subtrate(S) Thus, each enzyme is ______________________________ it can interact with. exhibit specificity - enzymes _______________________. 23 The substrate(s) enters the active site and ___________ the enzyme binds onto for a brief period of time, to form an ____________________. enzyme- substrate complex An enzyme-substrate complex is a temporary molecule formed perfect contact when an enzyme comes into ______________ with its substrate. alters Just before the substrate(s) binds to the enzyme, the enzyme _______ its shape ____________ such that it will more precisely binds to the substrate induced fit - called ________________. 24 Induced Fit: Example - Enzyme Hexokinase glucose ATP enzyme’s shape The _________________ is actually modified during the interaction between the enzyme and its substrate. induced fit occurring A change in shape of the enzyme induced fit occurs called _______________. Only the proper substrate is capable proper alignment of of inducing the _______________ the active site. pull them together in the middle enzyme-substrate complex established reaction happens after induced fit Hexokinase has a large induced fit motion that closes over adenosine triphosphate and the substrate glucose. 25 broke apart and water is brought in Fig. 3.21 Binding of the substrate to the enzyme causes changes in the distribution of electrons ____________________ in the chemical bonds of the substrate(s), ultimately causing reactions to take place that lead to the formation of the products. 26 factors that lower Ea and thus, speed up of the reaction rate close Enzymes bring substrate molecules ________ together ______________ and in an orientation that facilitates the reaction. Fig. 4.23 charge environment Enzyme has a unique _____________________ in the active site which promotes catalysis. The enzyme may also stretch a critical bond on the substrate(s) causing it to reach a _ transition state _ _________________ which makes the bond _ easier _to break _____________________. _ _ _ _ _ _ _ speed up lower Ea It’s these factors that ____________ and, thus, ___________ of the reaction rate. 27 The reaction proceeds and the substrate(s) are converted to product)s) ___________________. released The product(s) are _____________ and the enzyme returns to its shape opening up the active site so that it is ready to catalyze another reaction ________________________. 25 Catalytic Cycle of an Enzyme substrate enzyme-substrate complex products released Fig. 3.21 hydrolysis This is a _________ reaction 29 Some enzymes require that a non-protein functional group or cofactor molecule called a _________ to associate with the enzyme for the enzyme to function. Cofactor Types Metal ions 1) _________ that bind to a specific location in the enzyme, usually within the active site. - include ions of iron, copper, zinc or manganese Metals are known to be involved in over 40% of enzymatic reactions. metallome the life-supporting metals These metals are part of the ________, that have biological functions. 30 coenzymes are organic cofactors which 2) ______________________________________ are intermediate carriers that transfer functional groups or electrons from one organic molecule to another. They are required by certain enzymes to carry out their catalysis. They bind into the active site of the enzyme, participating considered to be substrates in catalysis, but they are _______________________________ of the reaction. phosphate group ____________________, that as ADP, picks up a ______________ ATP is coenzyme in one reaction, becoming ATP, and then delivering the phosphate group to another protein involved in a different reaction. 31 Conditions Affecting Enzyme Activity I. Effects of Temperature and pH on Enzyme Activity maximal activity narrow ranges Enzymes reach their ________________ within ______________ of pH and temperature. Activity of enzymes subjected to pH or temperature on either side be reduced of their optimum can __________ because the chemical structure of the enzyme is altered. Activity of an enzyme can drop dramatically when environmental suboptimal conditions are ____________ for the enzyme. 32 I. A. pH Most cytosolic enzymes have a pH optima close to cellular contents neutrality (pH7) ________________, the pH found within the _________________. lysosomes However, hydrolytic enzymes in ____________ have their highest acidic pHs activity in _________________. Fig. 4.28 human stomach is most active at Pepsin secreted into the _______________________________ low small intestine (acidic) pHs, whereas trypsin secreted into the ______________ is moderate basic pHs most at _______________________. 33 I. B. Temperature more quickly As temperatures rise, chemical reactions proceed _____________. kinetic motion Because the _________________ of molecules increases at higher temperatures. number _________ of collisions and strength of collisions increase between enzymes and their substrates at higher temperatures. At cooler than optimum temperatures, the substrate molecules enough kinetic energy do not have ____________________ to interact with the enzyme and enzyme activity drops off dramatically. 34 Peak activity for most enzymes, is between 40-50oC. Moderate disruption of structure and function Fig. 4.29 still with slight function enzyme denatured u need to boil food to kill the enzyme but if temperature get to high, the protein begins to unfold losing its 3-D globular structure, resulting in significant reduction in function and finally complete loss of function at very high temperatures. we say enzyme has become denature. 35 ...
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