Bio Ch. 8

the totality of an organisms chemical reactions. An emergent property of life that arises from orderly interactions between molecules

a series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule to a simpler molecule (catabolic pathway)

breakdown pathways. release energy by breaking down complex molecules to simpler compounds eg. cellular respiration

consume energy to build complicated molecules from simpler ones; sometimes called biosynthetic pathways. e.g.. synthesis of amino acids into proteins

the study of how energy flows through living organisms

the capacity to cause change. Energy can be used to do work- to move matter against opposing forces such as gravity and friction. Energy is also the ability to rearrange a collection of matter.

energy of motion

kinetic energy associated with the random movement of atoms or molecules

thermal energy in transfer from one object to another

another tupe of energy that can be harnessed to perform work, such as powering photosynthesis in green plants

energy that matter possesses because of its location or structure

potential energy available for release in a chemical reaction

the study of energy transformations that occur in a collection of matter

unable to exchange wither energy or matter with its surroundings

energy and matter can be transferred between the system and its surroundings

they absorb energy- for instance light energy or chemical energy in the form of organic molecules- and release heat and metabolic waste products such as carbon dioxide to the surroundings

the energy of the universe is constant— energy can be transferred and transformed but it cannot be created or destroyed. ie. the principle of conservation of energy

measure of disorder or randomness

every energy transfer or transformation increases the entropy of the universe.

a given process leads to an increase in entropy, the process can proceed without requiring an input of energy. energetically favorable

a process that leads to a decrease in entropy

the portion of a systems energy that can preform work when temperature and pressure are uniform throughout the system ΔG = ΔH - TΔS ie. change in free energy equals the change in the systems enthalpy minus the absolute temperature in kelvin times the change in the systems entropy. A measure of a systems instability- its tendency to move to a more stable state.

in biological system, equivalent to total energy

processes with a negative ΔG are spontaneous. processes that have a positive or zero ΔG are never spontaneous

Gfinal state - G initial state thus ΔG can only be negative when the process invokes a loss of free energy during the change from initial state to final state. because it has less free energy the system in its final state is less likely to change and is therefore more stable than it was previously

equilibrium. as a reaction proceeds towards equilibrium, the free energy of the mixture of reactants and products decreases. free energy increases when the reaction is pushed away from equilibrium

MOVING TOWARDS EQUILIBRIUM

"energy outward." Proceeds with a net release of free energy. because the chemical mixture loses free energy (G decreases) ΔG is negative for exergonic reactions. occur spontaneously The magnitude of ΔG for an exergonic reaction represents the maximum amount of work the reaction can perform

absorbs free energy from its surroundings. This kind of reaction essential stores free energy in molecules (G increases), ΔG is positive. Such reactions are non-spontaneous and the magnitude of the ΔG is the quantity of energy required to drive the reaction.

the pushing of energetic reactions that would not occur spontaneously, such as the synthesis of polymers from monomers

The pumping of substances across membranes against the direction of spontaneous movement

such as the beating of cilia, the contraction of muscle cells and the movement of chromosomes during cellular reproduction

the use of an exergonic process to drive an endergonic one. ATp is responsible for mediating most energy coupling in cells

contains a sugar ribose, with the nitrogenous base adenine and a change of three phosphate groups bonded to it. In addition to its role in energy coupling, ATP is also one of the nucleoside triphosphates used to make RNA. When ATP is hydrolyzed it realizes a terminal phosphate group and releases energy. because the hydrolysis releases energy, the phosphate bonds of ATP are sometimes referred to as high energy phosphate bonds meaning the reactants have high energy compared to the products but the bonds of ATP are not unusually strong. the energy ATP release on losing a phosphate group is somewhat greater than the energy most other molecules could deliver.

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when an ATP hydrolyzed couples with another reaction to form an exergonic reaction usually involving phosphorylation, the transfer of a phosphate group from ATP to some other molecule such as the reactant. the recipient molecule with the phosphate group covalently bonded to it is called the phosphorylated intermediate. The key to coupling exergonic and endergonic reactions is the formation of the phosphorylated intermediate, which is more reactive than the original unphosphorylated molecule

the transfer of a phosphate group from ATP to some other molecule such as the reactant

opposite of phosphorylation

energy released by breakdown reactions (catabolism) in the cell is used to phosphorylate AD O, regenerating ATP. regeneration of ATP is endergonic

a macromolecule that acts as a catalyst

a chemical agent that speeds up a reaction without being consumed by the reaction. Without regulation by enzymes, chemical traffic through the pathways of metabolism would become terribly congested because many chemical reactions would take such a long time

contorting the starting molecule (by inputting energy) into a highly unstable state before the reaction can proceed. When the new bonds of the product molecules form, energy is released as heat and the molecules return to stable shapes with lower energy than the contorted state

the initial investment of energy for starting a reaction- the energy required to contort the reactant molecule so the bonds can break. often supplied as heat in the form of thermal energy

the reactant molecules so they collide more often and more forcefully it also agitates the atoms within the molecules, making the breakage of bonds more likely. determines rate of the reaction.

when the molecules have absorbed enough energy for the bonds to break

because heat denatures proteins and kills cells and it would speed up all reaction not just those that are needed

by lower the activation energy barrier

the reactant an enzyme acts on

the enzyme bound to the substrate.

the restricted region of the enzyme molecule that actually binds to the substrate. the specificity of an enzyme is attributed to a complementary fit between the shape of its active site and the shape of the substrate

caused by entry of substrate. the change in shape of the active site of an enzyme so that it binds more snugly to the substrate.

weak interactions such as hydrogen and ionic bonds.

1. when there are two or more substrates, the active site provides a template on which the substrate can come together in proper orientation for reaction to occur between them 2. the enzyme distorts the substrate. Because the activation energy is proportional to the difficulty of breaking the bonds, distorting the substrate helps it approach the transition state and thus reduces the amount of free energy that must be absorbed to achieve that state 3. the active site may provide a microenvironment that is more conducive to a particular type of reaction than the solution itself would be without the enzyme 4. amino acids in the active site directly participate in the chemical reaction

as soon as a product exits an active site another substrate molecule enters

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non protein helpers for catalytic activity that many enzymes require. may be permanent or reversibly

a cofactor that is an organic molecule

reversible inhibitors that resemble the normal substrate molecule and compete for admission into the active site. They reduce the productivity of enzymes by blocking substrates from entering the active site. Can be overcome by increasing the concentration of substrate molecules so that as the active site becomes available, more substrate molecules than inhibitor molecules are bound to gain entry to the sites

Do not directly compete with the substrate to bind to the enzyme at the active site. Instead, they impede enzymatic reactions by binding to another part of the enzyme. This interaction causes the enzyme molecule to change it shape in such a way that the active site becomes less effective at catalyzing the conversion of substrate to product

term used to describe any case in which a proteins function at one site is affected by the binding of a regulatory molecule to a separate site. It may result in either inhibition or stimulation of an enzymes activity

the shape that has functional active sites, whereas the binding of an inhibitor stabilizes the inactive form of the enzyme.

a substrate molecule binding to one active site in a multisubunit enzyme triggrs a shape change in all subunits, thereby increasing catalytic activity at the other sites. amplifies the response of enzymes to substrates one substrate molecule primes an enzyme to act on an additional substrate molecule more readily

when ATP allosterically inhibits an enzyme in an ATP generation pathway, the result is feedback inhibition, a common mode of metabolic control. A metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway