Chapter 2.3

Question 1

Can the Km value be changed by altering the concentration of the substrate or enzyme

Answer 1

• no

- >it is an intrinsic property

Question 2

What do enzymes with no cooperativity look like on a graph

Answer 2

-they have the shape of a hyperbola

Question 3

What do enzymes with cooperativity look like on a graph

Answer 3

• they have a sigmoidal shape

- >multiple subunits and active sites

Question 4

What two states do cooperative enzymes exist in? What does binding of substrate do to these states?

Answer 4

• they exist in T states and R states
• binding of substrate transitions enzyme from T state to R state
• > increases the likelihood of substrate binding to other subunits
• loss of substrate promotes transition of enzyme from R to T state
• > promotes dissociation of substrate from the remaining subunits

Question 5

What role do cooperative enzymes play

Answer 5

• cooperative enzymes are often regulatory enzymes in pathways
• > they are also subject to activation and inhibition

Question 6

What does the Hill coefficient indicate about the binding of substrates to the enzymes

Answer 6

• if Hill coefficient is>1
• > positively cooperative binding occurs
• if Hill coefficient is<1
• > negatively cooperative binding occurs
• > one ligand binding decreases the affinity for other ligands binding
• if Hill coefficient=1
• > enzyme does not exhibit cooperative binding