Enzymes Flashcards
What is the binding curve of haemoglobin?
Sigmoidal
What curve does myoglobin binding show?
Hyperbolic
What is Vmax?
Maximal rate when all enzyme active sites are saturated with substrate
What is Km?
Substrate concentration that gives half maximal velocity
What is the significance of Km?
Km values gives a measure of the affinity of an enzyme for its substrate
What does high Km mean?
Low affinity
Why do you see cooperative binding with Hb?
Hb has 4 subunits- binding of oxygen increases R state making it easier for oxygen to bind to subsequent subunits
What are the two states of Hb and their affinities
T state- low affinity
R state- high affinity
Why is the cooperative binding of Hb important?
Sigmoidal binding curve means that oxygen can be efficiently carried from the lungs to the tissue
Does binding of more oxygen to haemoglobin increase or decrease affinity?
Increases affinity
What effect does 2,3-BPG have on Hb?
Increased BPG decreases affinity and shifts curve to the right (stabilises T state)
What is the Bohr effect?
Binding of H+ and CO2 to Hb lowers its affinity for oxygen- shifts curve to the right
Why is the Bohr effect important?
Metabolically active tissues produce large amounts of H+ and CO2- the Bohr effect ensures the delivery of O2 is coupled to demand
Explain CO poisoning
CO binds to Hb 250x more readily than O2
Fatal when COHb is >50%
It also acts to increase affinity of unaffected subunits
What is the structure of Hb?
2 alpha and 2 beta chains
