Principle of Bioenergetics

what is bioenergetics

it is the quantitative study of energy transductions that occur in living cells and of the nature and function of the chemical processes underlying these transductions

what are the 3 major types of energy transformation

photosynthesis, cellular respiration, biological work

what is the first law of thermodynamics

the total energy of the universe does not change and remains contsant

what is the second law of thermodynamics

all spontaneous processes increase the entropy or the randomness of the universe

what is entropy

it is the quantitative expression of the degree of the randomness or disorder of the system

when does something have a gain in entropy

it has a gain when the products of the reaction are less complex and more disordered than the reactants

what happens when delta S is negative, positive?

when negative the disorder of the system has decreased, when positive the disorder of the system has increased

what is enthalpy

it is the heat content of the system and it reflects the number and kinds of chemical bonds in the reactants and products

what happens when enthalpy (delta H) is negative, positive?

when negative, the chemical reaction produces heat and is exothermic, so the heat content of the products is less than that of the reactants. when positive, the reaction system absorbs heat from their surroundings and is endothermic

what is Gibbs free energy

it is the amount of energy capable of doing work during a reaction at constant temperature and pressure

what does Gibbs free energy determine

it will determine if a reaction will proceed spontaneously or require energy investment from an external source to proceed. it will also determine the direction of the chemical reaction and the equilibrium position of the reaction

what happens when free energy change (delta G) is negative

the reaction will be favorable and move forward, the products contain less free energy than the reactant and will proceed spontaneously, they are exergonic

what happens when free energy change (delta G) is negative

the reaction will be unfavorable and move backwards, the products contain more free energy than the reactants and will proceed non spontaneously. they are endergonic

what happens to free energy change when the reaction is at equilibrium

at equilibrium there will be no net change in the amount of reactant or product so free energy change will equal zero

what is chemical equilibrium

it is the point in a reaction where the rates of the forward and reverse reactions proceeding at equal rated

why does relatively small changes in standard free energy change (delta G’) correspond to large changes inn the equilibrium constant (K’eq)

because their relationship is exponential

how can a thermodynamically unfavorable (endergonic) reaction be driven in the forward direction

it can be driven forward by coupling it to a highly exergonic reaction through a common intermediate

what is the structure for ATP

nitrogenous base (adenine), ribose sugar, 3 phosphate groups bonded in series. the first bone is bonded via phosphoester and the last two are bonded by phosphoanhydride

what type of reaction is the hydrolysis of the bond between the two outermost phosphate groups in the formation of ADP and Pi

it is a highly exergonic reaction, delta G is negative and the reaction is negative

where is the energy to reform ATP derived from

it is derived from food in heterotrophs (cellular respiration) and light energy in autotrophs (photosynthesis)

What is a minor role of ATP

direct hydrolysis of it is the source of energy for some endergonic conformational changes

what is the major role of ATP

the transfer of phosphoryl, pyrophosphoryl or adenyl group to a substrate or enzyme that couples the energy of ATP will breakdown to the endergonic transformation of substances- a group transfer reaction

for the overall reaction, what does K’ eq equal

it equals the product of the individual values for the two reactions

what are the results of a low (-) K’eq

a positive delta G’ and there will be more reactants than products

what are the results of a high (+) K’eq

a negative delta G’ and there will be more products than reactants

what do hexokinases do

they are enzymes that can regulate the rate at which glucose is used in glycolysis, and they can also help regulate the amount of glucose free in the body

what are mutations interfering with the function of glucokinase linked to

they are linked to specific forms of diabetes

what are the two step process of an ATP reaction

a phosphoryl group is transferred from ATP to glutamate then the phosphoryl group is displaced by ammonia NH3 and released as Pi

what synthesizes most of the ATO

the ETC synthesizes most of it

what are redox reactions

they are chemical reactions that involve electron transfer

when is an atom or molecule oxidized

when it loses an electron, often loses and H+

when is an atom or molecule reduced

when it gains an electron, often gains an H+

how can electrons be transferred in a redox reaction

they can be transferred completely from one atom to another or can shift their position in covalent bond

what do reduced organic compounds serve as

they serve as fuels from which electrons can be stripped off during oxidation

what happens when a carbon is more reduced

it will have more free energy released upon oxidation

what do carbohydrates do

they store energy in their bonds, they have more energy than CO2, but less energy than fatty acids

where is potential energy stored

they are stored in bonds. electrons in C-O bonds are held more tightly and have low potential energy while elections in C-H and C-C bonds are shared more equally and have higher potential energy

what do electron carriers/cofactors do

they can temporarily store energy in the form of electrons during cellular respiration and readily cycle between oxidized and reduced forms

what is the flow of electrons like in the ETC

it may proceed spontaneously depending on the relative affinity of the electron accept of each redox pair for electrons and it functions biologically because they are energetically favorable and the reduction potential (E) is a measure (volts) of this affinity

what does reduction potential determine

it determines the affinity for electrons (higher E=higher affinity) and electrons transferred from lower to higher E

what type of delta E do we need for a negative delta G

we will need a positive delta E

when are reactions favorable

they are favorable when the free energy of products in much lower than the free energy of reactants

when are biochemical phosphoryl transfer reactions favorable

they are favorable when the phosphate donors are destabilized by electrostatic repulsion of when the reaction products are stabilized by resonance

when can unfavorable reactions be made possible

they can be made possible by chemically coupling a highly favorable reaction to the unfavorable reaction

what do oxidation-reduction reactions commonly involve

they commonly involve the transfer of electrons from reduced organic compounds to specialized redox cofactors

what can reduced cofactors be used in

they can be used in biosynthesis, or may serve as a source of energy for ATP synthesis