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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