Enzymes

Question 1

What is a co-factor

Answer 1

A co-factor is a chemical that binds to the active site to change its
shape, allowing it to bind to the substrate. Ex. zinc, vitamins, etc.

Question 2

What is an inhibitor

Answer 2

Inhibitors stop the enzyme from binding with its substrate by changing
the shape of / binding to its active site. This would therefore slow or
stop biological reactions. Inhibitor examples: lead, antibiotics, heavy metals, etc.

Question 3

What is a competitive inhibitor

Answer 3

A competitive inhibitor binds to the active site and physically blocks the substrate from binding at all. An example is cyanide

Question 4

What are noncompetitive inhibitors

Answer 4

Noncompetitive inhibitors bind to a different site on the enzyme, but forces enzyme to change
the shape of the active site. No enzyme/substrate complex can be formed. An example is a heavy metal ion such as lead

Question 5

Will a competitive inhibitor block the active site

Answer 5

Yes, A competitive
inhibitor will block
the active site, but
eventually they will
be “beaten out” by
the increasing
substrate. Since the
enzyme’s active site
hasn’t changed, it
can still bind to the
substrate

Question 6

What will a non-competitive inhibitor do the active site

Answer 6

A non-competitive
inhibitor will attach
somewhere else but
CHANGE the active site
shape. This renders the
enzyme non-functional
and it cannot bind to
the substrate no
matter how much is
present

Question 7

How does temperature affect the enzyme

Answer 7

• Activity increases as
  temperature increases, due to
  more kinetic energy for the
  particle collisions
• Enzymes have an optimum
  temperature at which they have
  the highest activity
• If temperature increases past
  this point, activity quickly reduces
  to a stop

Question 8

How does pH affect the enzyme activity

Answer 8

• Enzymes have an optimum pH level at which activity is highest
• Different enzymes have different optimum pH levels, depending on
  their environment
• When out of the optimum range, enzyme activity reduces and stops

Question 9

What happens if we go past the optimum

Answer 9

• If the optimum temperature or pH
  value is exceeded, activity ceases
  immediately
• This occurs because the shape of the
  enzyme’s active site changes
  permanently = DENATURATION
• Changed shape of active site means
  that the substrate cannot fit = reaction
  cannot be catalysed and will not
  proceed

Question 10

Explain substrate surface area

Answer 10

• Reaction rate increases as surface area
  of the substrate increases
• This is why animals chew food - to
  increase surface area of the food, which
  increases the efficiency and speed of
  digestion. There will be a levelling off
  effect once enzymes become “full”

Question 11

Explain what happens when reaction rates are levelling off

Answer 11

At some point, the concentration of
the “other” molecule will become a
limiting factor (stops the rate from
increasing further) This is because all the enzyme’s
active sites will be filled if substrate
concentration keeps increasing or all
the substrate will already be reacting
with available enzymes / no more
substrate remains if enzyme
concentration keeps increasing