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 (Vmax)