chapter 5 enzymes, coenzyme and energy biology 100 spring 2009
TRANSCRIPT
Chapter 5Chapter 5Enzymes, Coenzyme and Enzymes, Coenzyme and
EnergyEnergy
Biology 100
Spring 2009
EnergyEnergyAll living things require energy.
◦Nutrients are one source of energy, as well as being molecules organisms require to grow, reproduce or repair
Biochemical reactions are the processes used for the formation, breakdown and rearrangement of molecules to provide organisms with energy
Activation EnergyActivation EnergyActivation Energy is the required
input of energy to make a reaction start
CatalystCatalystA catalyst is a chemical that
speeds up the reaction but is not used up in the reaction◦Lowers the activation energy needed
to start a reaction◦Is not used up during the reaction◦Is unchanged after a reaction
EnzymesEnzymesEnzymes act as catalysts.
Enzymes are proteins that speed up a rate of reaction◦Found in cells throughout the body◦Lowers activation energy◦Enzymes will end in –ase◦SPECIFIC!
EnzymesEnzymes
How Enzymes WorkHow Enzymes WorkEach enzyme has a specific size
and 3-D shape◦Each enzyme is going to fit with a
certain substrate (molecule enzyme connects to)
How Enzymes WorkHow Enzymes WorkWhen the enzyme and substrate
are connected, it is known as enzyme-substrate complex
The binding site is where the enzyme physically attaches itself to the substrate
The active site is where the enzyme will cause a specific part of the substrate to change
Cofactors/CoenzynesCofactors/CoenzynesSome enzymes need an
additional molecule to carry out the process◦Cofactors are inorganic ions or
organic molecules that serve an enzyme helpers
◦Coenzymes are organic molecules that function as a cofactor May be certain amino acids, nitrogenous
bases, and vitamins
CofactorsCofactors
Turnover NumberTurnover NumberThe number of molecules of
substrate with which a single enzyme can react at a given time (ex. reactions/minute) is known as the turnover number◦ Can be quite large compared to
uncatalyzed reeactions◦Can depend on the environment
EnvironmentEnvironmentTemperature can have a huge
impact on turnover rate◦a higher temperate will increase the
rate of molecular motion, to a certain extent
◦Too high of temperatures may cause the enzyme to change its shape, this is known as denaturing, where a protein structure is permanently changed
EnvironmentEnvironmentOptimum temperature is when
the rate of formation of the enzyme-substrate complex is fastest
EnvironmentEnvironmentpH also affects the rate of
enzyme-substrate complexes◦Most enzymes have an optimum pH
of around 7 (neutral) However, some prefer acidic or basic
conditions
CompetitionCompetitionEnzymatic competition is where there
are several kinds of enzymes available to combine with the same kind of substrate molecule◦ The substrate acetyl can be acted upon by
three different enzymes: citrate synthetase, fatty acid synthetase, and malate synthetase
Fig. 5.7,
pg.103
Gene Regulator ProteinsGene Regulator Proteins are
chemical messengers that inform the genes of the cell’s need for enzymes◦Gene-repressor proteins decrease
protein production◦Gene-activator proteins will increase
protein production
Fig. 5.7, pg.103
InhibitorInhibitor is a molecule that
attaches itself to an enzyme and interferes with the enzymes ability to form an enzyme-substrate complex◦Competitive Inhibition◦Negative-Feedback Inhibition
Competitive InhibitionCompetitive InhibitionIn competitive inhibition an
inhibitor has a shape that is closely resembling the normal substrate of an enzyme◦Enzyme becomes ineffective
Negative-Feedback Negative-Feedback InhibitionInhibitionIn negative-feedback inhibition is a process where the output of a system acts to oppose changes to the input of the system
Allosteric Regulation is the regulation of an enzyme or other protein by binding an effector molecule at the protein's allosteric site (a site other than the active site)
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