Enzymes

Question 1

Explain how a competitive inhibitor decreases the rate of an enzyme controlled reaction

Answer 1

• Has a similar shape to the substrate which is specific to the enzyme’s active site
• The inhibitor is able to bind to the active site
• This prevents the enzyme from binding to the intended substrate - reducing the number of enzyme-substrate complexes formed

Question 2

What is an enzyme?

Answer 2

a protein that acts as a biological catalyst, reducing the activation energy of a reaction, without being used up itself

Question 3

How will an enzyme reduce the activation energy of a condensation reaction?

Answer 3

Holding the 2 reactants close together, minimising repulsion and allowing bonds to form

Question 4

How will an enzyme reduce the activation energy of a hydrolysis reaction?

Answer 4

it will put strain on bonds making them easier to break

Question 5

Describe the induced fit model of enzyme action

Answer 5

• An enzyme will bind to a substrate that has a shape complementary to that specific active site
• forming an enzyme-substrate complex
• the active site will change shape slightly to better fit the substrate molecule

Question 6

Why can an enzyme only bind to one substrate?

Answer 6

• each enzyme has a different primary structure
• therefore they have different tertiary structures
• this means that the shape of the active site is different for each enzyme
• this active site is only complementary to 1 substrate, therefore any other substrate will not be able to form enzyme-substrate complexes as it would be unable to bind

Question 7

Describe the lock and key model of enzyme action

Answer 7

The shape of the substrate is an exact fit the shape of the enzyme’s active site allowing it to fit into the active site

Question 8

How could you measure the rate of enzyme action?

Answer 8

time taken for reactant to be used up OR for a product to form

Question 9

How does increasing temperature impact enzyme activity?

Answer 9

• increased kinetic energy
• more frequent and successful collisions
• more E-S complexes
• further increases break bonds
• denatures enzyme by changing shape of active site

Question 10

How does changing pH impact enzyme activity?

Answer 10

• each enzyme has optimum pH
• deviation will slow the rate of reaction as charges of amino acids are disturbed
• extremities will result in broken bonds and the enzyme becoming denatured

Question 11

How does enzyme concentration impact enzyme activity?

Answer 11

• excess substrate, as enzyme concentration increases
• more enzyme molecules collide with substrate molecules
• rate of reaction increases.
• Once substrate concentration becomes limiting the rate of reaction with cease to increase further

Question 12

How does substrate concentration impact enzyme activity?

Answer 12

• as substrate concentration increases rate of reaction increases
• more substrate available to fill the active sites.
  Once the enzymes are working at maximum capacity the rate of reaction cannot increase further

Question 13

What is one difference between the lock and key theory and the induced fit model of enzyme action?

Answer 13

in the induced fit model, the active site changes shape, but does not change in lock and key

Question 14

What is one similarity between the lock and key theory and the induced fit model of enzyme action?

Answer 14

both form enzyme substrate complexes