2.3.9 - Mode Of Enzyme Action

Question 1

Describe Enzymes ‘Mode Of Action’
(3 Points)

Answer 1

~ Have a unique active site, where specific substrates bind forming an enzyme-substrate complex.

~ Extremes of heat or pH can alter the protein structure and change the shape of the active site, preventing substrate binding, this called denaturation.

~ Substrates collide with the enzymes active site and this must happen at the correct orientation and speed in order for a reaction to occur.

Question 2

Describe Enzymes Specificity
(5 Points)

Answer 2

~ Enzyme specificity is a result of the complementary nature between the shape of the active site and the substrates.

~ Only one specific substrate will fit into one specific active site.

~ Shape of the enzyme is determined by the tertiary structure, which is determined by the primary structure.

~ If the tertiary structure is altered, the shape of the active site will change meaning no enzyme-substrate complexes would be formed and no products will be produced.

~ A change in the primary structure, changes the tertiary structure of the enzyme.

Question 3

Describe The Lock & Key Models Of Enzymes

Answer 3

~ Was suggested that enzymes and substrates were rigid structures that locked into each other very precisely.

~ Was later modified and adapted to our current understanding of enzyme activity.

Question 4

Describe The Induced Fit Hypothesis Of Enzymes
(4 Points)

Answer 4

~ The enzyme and the active site can change shape slightly as the substrate molecules enter the enzyme.

~ These changes in shape are known as conformational changes.

~ The conformational changes ensure an ideal binding arrangement between the enzyme and substrate is achieved.

~ This maximises the ability of the enzyme to catalyse the reaction.