BIOL 112 Lecture : 10 - Enzymes.docx

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17 Apr 2012

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BIOL 112 Full Course Notes

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Substrates bind to specific site on the enzymes surface called the active site, where catalysis occurs. 3 possibilities: bind in a correct orientation to speed up. promote reaction, cause strain, slightly change conformation, making reaction more likely, charge transfer, molecule is given charge to induce reaction and charge is returned. Some enzymes require them to function, examples: metal ions (zn, cu, small organic molecules that are permanently or temporarily bound to help catalysis. Enzymes are saturated when all active sites have a substrate, thus theres a maximal reaction rate. Maximum rate = (turnover from 1 molecule/sec for lysosome all the way to 40 million molecules/sec for catalase) Feedback inhibition - stops formation of final product so that it is not created in excess. Multiple feedback - allows cells to adjust ratio of different compounds (such as amino acids) Irreversible inhibition occurs when inhibitor destroys enzymes ability to interact with its normal substrate - such as covalently bonding to active site.

Related Questions

28. Which of the following statements about enzymes is false?

An enzyme changes shape when it binds to a substrate.

Enzymes lower the activation energy.

Enzymes are highly specific.

An enzyme may orient substrates, induce strain, or temporarily add chemical groups.

Most enzymes are much smaller than their substrates.

29. What is a transition state?

The place where a substrate molecule binds to an enzyme

A reactant with high potential energy

The combination of a substrate and an enzyme

The state at which the bonds of reactants are unstable

The active site where reactants are oriented

39. Which of the following statements about enzymes is true?

Enzymes are proteins.

Enzymes have a specific amino acid sequence.

enzymes are highly specific.

Enzymes lower the energy barrier.

All of the above

orangepug991

Explain how the following mechanisms regulate enzyme activity.

Part A

Covalent modification

a)The product of a series of reactions acts as an inhibitor for an earlier reaction.

b)Hormones control the synthesis of enzymes.

c)A regulator binds to the enzyme at a site other than the active site. This binding changes the shape of the enzyme and alters the catalytic ability of the enzyme.

d)An inhibitor binds reversibly to the enzymesubstrate complex, blocking the binding of the second substrate to the active site.

e)The activity of an enzyme is influenced by the addition or removal of a group that is covalently bonded to the enzyme.

f)An inhibitor forms covalent bonds to the active site, permanently blocking it.

Part B

Genetic control

a)The product of a series of reactions acts as an inhibitor for an earlier reaction.

b)Hormones control the synthesis of enzymes.

c)A regulator binds to the enzyme at a site other than the active site. This binding changes the shape of the enzyme and alters the catalytic ability of the enzyme.

d)An inhibitor binds reversibly to the enzymesubstrate complex, blocking the binding of the second substrate to the active site.

e)The activity of an enzyme is influenced by the addition or removal of a group that is covalently bonded to the enzyme.

f)An inhibitor forms covalent bonds to the active site, permanently blocking it

Part C

Allosteric regulation

a)The product of a series of reactions acts as an inhibitor for an earlier reaction.

b)Hormones control the synthesis of enzymes.

c)A regulator binds to the enzyme at a site other than the active site. This binding changes the shape of the enzyme and alters the catalytic ability of the enzyme.

d)An inhibitor binds reversibly to the enzymesubstrate complex, blocking the binding of the second substrate to the active site.

e)The activity of an enzyme is influenced by the addition or removal of a group that is covalently bonded to the enzyme.

f)An inhibitor forms covalent bonds to the active site, permanently blocking it.

Part D

Feedback inhibition

a)The product of a series of reactions acts as an inhibitor for an earlier reaction.

b)Hormones control the synthesis of enzymes.

c)A regulator binds to the enzyme at a site other than the active site. This binding changes the shape of the enzyme and alters the catalytic ability of the enzyme.

d)An inhibitor binds reversibly to the enzymesubstrate complex, blocking the binding of the second substrate to the active site.

e)The activity of an enzyme is influenced by the addition or removal of a group that is covalently bonded to the enzyme.

f)An inhibitor forms covalent bonds to the active site, permanently blocking it

Which statement is FALSE concerning feedback inhibition and allosteric sites?

	1.	An allosteric activator causes the active site to be functional.
	2.	Feedback inhibition usually occurs with metabolic pathways.
	3.	Enzyme allosteric sites are not used in feedback inhibition.
	4.	Allosteric inhibitors can keep an enzyme in an inactive shape.
	5.	Allosteric sites can bind molecules other than the substrate.

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BIOL 112 Lecture : 10 - Enzymes.docx

BIOL 112 Full Course Notes

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