Biological molecules- enzymes

Question 1

What is an enzyme?

Answer 1

a biological catalyst (substance that speeds up the rate of reaction without being
used up – lowers activation energy)

Question 2

What makes an enzyme specific?

Answer 2

? has a specific active site shape, only complementary substrates
can bind to the active site to form enzyme-substrate complexes

Question 3

Lock and Key Model

Answer 3

active site shape is rigid, only exactly complementary substrates can bind to form ES complexes

Question 4

Induced Fit Model

Answer 4

active site changes shape, the substrate binds to the active site – the active site changes shape so the
substrate fits exactly forming an ES complex

Question 5

Affect of substrate concentration on enzyme activity?

Answer 5

 increase substrate concentration, increases chance of successful collisions, increase chance of forming an
ES complex, increase rate of reaction
 this continues until all the enzyme’s active sites are full/saturated = maximum rate of reaction

Question 6

Affect of enzyme concentration on enzyme activity?

Answer 6

 increase enzyme concentration, increases chance of successful collisions, increase chance of forming an
ES complex, increase rate of reaction
 this continues until all the substrates are used up = maximum rate of reaction

Question 7

Affect of temperature on enzyme activity?

Answer 7

 as temperature increases
 the kinetic energy increases
 the molecules move faster
 increase chance of successful collisions
 increase chance of forming ES complex
 increase rate of reaction
 carries on till optimum
 after optimum
 bonds in tertiary structure break (hydrogen and ionic bonds)
 lose active site shape
 substrate no longer complementary
 cant form ES complexes
 enzyme denatured

Question 8

Affect of pH on enzyme activity?

Answer 8

if change pH away from optimum, bonds in tertiary structure
break, lose active site shape, no longer form ES complex,
enzyme denatured

Question 9

Competitive Inhibitor

Answer 9

a substance with a similar shape to the substrate and a complementary shape to the
enzyme’s active site, binds to the active site, blocking it, preventing ES complexes from forming

Question 10

Non-Competitive Inhibitors

Answer 10

a substance that binds to another site on the enzyme other then the active site, causes
the active site to change shape, so less ES complexes can form