BIO Exam 2: Enzymes (2)

Question 1

Enzymology

Answer 1

Enzymes lower activation energy to increase rate.

No effect on DGo’ or Keq

Vmax reflects catalysis rate

Km reflects substrate binding

Question 2

Specific Activity

Answer 2

Comparing enzymes: Grow cultures, lyse cells, measure vi

Usually, compare the specific activity

Normalize to the total amount of protein present

Question 3

Controlling Enzyme Activity

Answer 3

Many enzymes can be regulated by a post-translational modification

Question 4

Competitive Inhibition

Answer 4

Many enzymes can be regulated by a other small molecules

Competitive Inhibitors bind to the active site

No catalysis

Compete with the substrate for binding

No effect on Vmax

Km is increased

Question 5

Noncompetitive Inhibitors

Answer 5

Not all inhibitors bind the active site

Some bind to an allosteric site. Binding changes enzyme conformation.

Noncompetitive (or allosteric) inhibitors

Question 6

How will an allosteric inhibitor affect Vmax and Km?

Answer 6

Two subclasses:
Pure noncompetitive inhibitors
Lowers Vmax; No effect on Km

Mixed noncompetitive inhibitors
Lowers Vmax; Raises Km

Question 7

Enzyme Activators

Answer 7

Some small molecules do the opposite: activators

Always allosteric
May be pure (raises Vmax, no effect on Km)or mixed (raises Vmax, lowers Km

Question 8

Enzymes and pH: How would the pH affect the an enzyme’s function?

Answer 8

Non-ideal pH denatures some of the enzymes

each enzyme has its own optimal pH

Each enzyme has a different optimum

Question 9

Hess’ Law

Answer 9

Enzymes can’t change a DGo’ but can help overcome it

Energetic coupling of two reactions together. Hess’ Law