lecture 22. enzymes and chemical reactions

Does delta G indicate anything about the rate of a chemical reaction

the value of delta g does not indicate anything about the rate of a chemical reaction

what does it take for a spontaneous chemical reaction to occur

molecules need to be close and properly oriented depending on the type of reaction, other molecules must be available or excluded

what occurs when hexokinase binds with a glucose molcules

what do enzymes do

speed up biochemical transformations 

more info on enzymes being a biological catalysts

• speed up chemical reactions ( that would occur anyway but at a significantly lower rates)

• No catalysys makes a reaction to occcur that cannot otherwise occur

• Have active sites where specfifc substrates bind( highly specififc)

• Enzymes do not alter the equilibrium point or free energy change in a reaction

• some participate in a reaction ( transfer of electrons or ions) but their participation does not permanently change the enzyme

• they are not consumed by the reactions they catalyze( they end up in the same shape as before reaction)

what is required to initiate exergonic chemical reaction

activation energy (Ea)

transition state

intermediates have higher free energies than either the reactants or the products

enzymes =

effective approach to lower the activation energy of chemical reactions in living systems by bringing molecules together

Enzyme (E) + substrate (s) to enzyme-substrate complex (ES) to enzyme (E) + product (P)

chemcial forces that hold the snzyme- substrate complex

• hydrogen bonding; electrical attraction; temporary covalent bonding

Enzyme = 

bind specific substrates in their active sisters, destabilize the molecule, so water has access to the bond that gets hydrolyzed. draw it

enzyme Oxidoreductases 

catalyze transfer electrons between molecules

Transferases

catalyze the transder of groups of atoms ( functional groups ) between molecules

• aminotransferases transfer amino group (-NH2)

• Kinases transfer a phosphate group

Hydrolases

add water to covalent bonds to break down molecules ( hydrolysis)

isomerases

catalyze transfer of groups from one place to another within the same molecule

Ligases

catalyze joining of 2 molecules together

Lyases

catalyze non-hydrolytic breakage of bonds from proteins

phosphatases

catalyze the remove phosphate group from proteins

phosphodiesrerases

catalyze hydrolysis of cGMP and cAMP

GTPase; ATPase

catalyze hydrolysis of GTP/ATP