Chapter 8- An Introduction to Metabolism

what is metabolism

al the chemical reactions in an organism

enzymes help regulate the ____ of metabolic pathways

rate/speed

two types of metabolic pathways

catabolic and anabolic

catabolic pathways characteristics

breakdown pathways, complex to simpler, spontaneous, exergonic, energy release, downhill reactions

anabolic pathways characteristics

synthesis pathways, simple to complex, non-spontaneous, endergonic, consume energy, uphill reactions

an organisms metabolism ___ matter and energy

transforms

1st law of thermodynamics

principle of conservation of energy: energy can’t be created or destroyed, total energy of the universe is constant

2nd law of thermodynamics

entropy (disorder): every energy transformation or transfer results in increasing entropy, as energy is transferred, more energy is wasted (unavailable for work)

what is free energy

the portion of a systems energy available to perform work when the systems temperature and pressures are uniform

exergonic reactions

energy outward, spontaneous reaction in which there is a net release of free energy

endergonic reactions

energy inward, non-spontaneous reactions in which free energy is absorbed from the surroundings

reactions in an isolated system will naturally move toward ___

equilibrium

equilibrium and cells

cells are never at equilibrium because of the constant flow of materials in and out of the cell, a cell at equilibrium is a dead cell

energy source used to drive most types of cellular work

ATP

hydrolysis of ATP to ADP

the bond between the final two phosphate groups is broken by hydrolysis, which produces ADP, exergonic reaction

catalyst

a substance that can change the rate of a reaction without being altered in the process

enzyme

a protein catalyst that changes the rate of a reaction without being consumed

bonds are broken and formed in ___

chemical reactions

form bonds to break, ___

reactants must absorb energy from their surroundings

activation energy

energy needed initially to reach transition state, in which bonds can be broken and from which the reaction can proceed

how do enzymes speed up reactions

enzymes lower the activation energy, allowing the reaction to start sooner and proceed quicker

how does temperature effect enzyme activity

each enzyme has an optimal temperature, too much heat breaks enzyme bonds and denatures it

how does pH effect enzyme activity

enzymes have optimal pH between 6 and 8, the enzyme will denature if it goes above or beyond that

cofactors

any non-protein molecule that is required for the proper functioning of an enzyme

coenzyme

a cofactor that is an organic molecule

how is enzyme activity regulated

the cell switches on and off the genes that encode specific enzymes, or the cell regulates their activity once they are made

substrate

the reactant that an enzyme acts on

active site

region on an enzyme where the substrate binds

competitive inhibitors

molecules that resemble the normal substrate and compete to bind to the active site

noncompetitive inhibitors

inhibitors that bind to the other part of the enzyme causing it to change shape so the substrate can’t bind to the active site

feedback inhibition

way in which metabolic pathways are regulated

how does feedback inhibition work

end product shuts down pathways by binding to allosteric site, ATP can act as a feedback inhibitor