Enzyme Kinetics Flashcards
What are kinetics?
The rate of a reaction
Will enzyme activity increase when more substrate is added?
Yes, until it reaches saturation
What is Vmax?
The reaction rate at saturation, when every active site is filled
What type of curve will an enzyme with cooperativity have?
Sigmoidal
What is Km?
The Michaelis constant. Indicates affinity of the enzyme
What is the relationship between Km and substrate affinity?
High Km = low affinity
Low Km = high affinity
Why is it hard to determine Vmax from an MM graph?
Asymptotic relationship, not linear
What is the Y-intercept in an LB graph?
1/Vmax
What is the X-intercept in an LB graph?
-1/Km
What is the slope in an LB graph?
Km/Vmax
Where does a competitive inhibitor bind?
Active site. It looks very similar to the substrate and actively competes with it for the active site
How does a competitive inhibitor affect Vmax and Km?
Vmax doesn’t change, but Km will increase
What happens to enzyme activity when an allosteric modifier binds?
Activity can either increase or decrease, depends on what the molecule is
Where does a non-competitive inhibitor bind?
Allosteric site. It changes the conformation of the active site so the substrate will bind but can’t react
How does a non-competitive inhibitor affect Vmax and Km?
Vmax changes, but Km doesn’t
What is feedback inhibition?
Buildup of a downstream product will slow down upstream reactions
How do we predict which metabolic pathway a substrate will go into?
Calculate Vmax and Km
What determines if pyruvate will enter fermentation or CAC?
Presence of oxygen
What are allosteric activators of glycolysis?
CoA, AMP, ADP, NAD+
What are allosteric inhibitors of glycolysis?
Acetyl-CoA, Citrate, ATP, NADH
What are the 3 metabolic pathways that oxaloacetate can go into?
CAC, aspartate biosynthesis, gluconeogenesis
What enzyme uses oxaloacetate in the CAC?
Citrate synthase
What are the allosteric inhibitors of the CAC?
ATP, acetyl-CoA, succinyl-CoA, NADH
What enzyme uses oxaloacetate in gluconeogenesis?
Carboxykinase
What is the allosteric inhibitor of gluconeogenesis?
DPNH
What enzyme uses oxaloacetate in aspartate biosynthesis?
Aspartate amino transferase
What determines if oxaloacetate will go into the CAC, gluconeogenesis, or Asp biosynthesis?
Km, which will change depending on what the cell needs
