Mode of Enzyme Action

Question 1

Enzymes have an active site where specific substrates bind forming an

Answer 1

enzyme-substrate complex

Question 2

The active site of an enzyme has a specific shape to fit a

Answer 2

specific substrate

Question 3

……………. can change the shape of the active site(tertiary structure), preventing substrate binding – this is called denaturation

Answer 3

Extremes of heat or pH

Question 4

Substrates collide with the enzymes …… and must happen at what to allow reaction to occur

Answer 4

active site and this must happen at the correct orientation and speed in order for a reaction to occur

Question 5

The specificity of an enzyme is a result of the ………….nature between the shape of the active site on the enzyme and its substrate(s)

Answer 5

Complementary

Question 6

he shape of the active site (and therefore the specificity of the enzyme) is determined by the complex …………. structure explain further

Answer 6

complex tertiary structure of the protein that makes up the enzyme:

Proteins are formed from chains of amino acids held together by peptide bonds

The order of amino acids determines the shape of an enzyme

If the order is altered, the resulting three-dimensional shape changes

Question 7

An enzyme-substrate complex forms when an

Answer 7

enzyme and its substrate join together

Question 8

The enzyme-substrate complex is only formed temporarily, before the enzyme

Answer 8

catalyses the reaction and the product(s) are released

Question 9

Enzyme reactions can either be

Answer 9

catabolic or anabolic

Question 10

Catabolic reactions involve the breakdown of

Answer 10

complex molecules into simpler products, which happens when a single substrate is drawn into the active site and broken apart into two or more distinct molecules

Examples of catabolic reactions include cellular respiration and hydrolysis reactions

Question 11

Anabolic reactions involve the

Answer 11

e building of more complex molecules from simpler ones by drawing two or more substrates into the active site, forming bonds between them and releasing a single product

Examples of anabolic reactions include protein synthesis and photosynthesis

Question 12

Enzymes work by lowering the

Answer 12

activation energy of a reaction

All chemical reactions are associated with energy changes

For a reaction to proceed there must be enough activation energy

Question 13

Activation energy is the

Answer 13

minimum amount of energy needed by the substrate to become just unstable enough for a reaction to occur and for products to be formed

Enzymes speed up chemical reactions because they influence the stability of bonds in the reactants

The destabilisation of bonds in the substrate makes it more reactive

Question 14

Enzymes work by lowering the activation energy of a reaction and in doing so they provide an

Answer 14

alternative energy pathway