24 Questions
What is the term for the ability of one oxygen binding to an active site to increase the probability of other oxygen binding to other active sites in hemoglobin?
Cooperativity
What is the role of allosteric effectors like 2,3-bisphosphoglycerate (2,3-BPG) in hemoglobin?
To shift the equilibrium towards the T-state
What is the term for the phenomenon where hemoglobin's oxygen binding affinity is inversely related to acidity and carbon dioxide concentration?
Bohr effect
What is the term for the transition of hemoglobin from the T-state to the R-state with oxygen binding?
Concerted model
What is the result of the binding of one oxygen to an active site in hemoglobin?
Increased probability of other oxygen binding to other active sites
What is the role of 2,3-bisphosphoglycerate (2,3-BPG) in hemoglobin?
Allosteric inhibitor
What is the shape of the oxygen binding kinetics curve for hemoglobin?
Sigmoidal
What is the term for the ability of hemoglobin to bind to oxygen more strongly when oxygen levels are high?
Cooperativity
What is the main idea behind the 'induced-fit model' of substrate and enzyme binding?
The shape of the enzyme changes slightly to accommodate the substrate.
What is the primary role of the rest of the protein molecule, excluding the active site?
To stabilize the active site and provide an appropriate environment.
What is a cofactor in the context of enzymes?
A non-protein component necessary for catalytic activity.
What is an example of a type of molecule that can act as a cofactor?
Iron.
What is the effect of molecules that stabilize the protein in its T-state?
They act as allosteric inhibitors
What is the term for the process of generating smaller enzymes that retain activity through laboratory-based directed evolution studies?
Directed evolution.
What is the term for the process by which oxygen binding to one subunit of hemoglobin increases the likelihood of oxygen binding to another subunit?
Cooperative binding
What is the purpose of the 'hand-in-glove' analogy in enzyme-substrate binding?
To illustrate the induced-fit model of substrate and enzyme binding.
What is the name of the scientist who extended Fischer's ideas and presented the 'induced-fit model' of substrate and enzyme binding?
Daniel Koshland.
What is the name of the model used to explain the cooperativity in oxygen binding to hemoglobin?
The Concerted Model
What is the state of hemoglobin in which it is more tense and has a lower affinity for oxygen?
T-state
What topic will be discussed in further detail in Chapter 8?
The regulation of enzyme activity.
What is the effect of molecules that bind to allosteric enzymes and move the protein to its R-state?
They act as allosteric activators
What is the type of protein that myoglobin is?
Monomeric
What is the shape of the oxygen binding curve for myoglobin?
Hyperbolic
What is the difference between deoxyhemoglobin and oxyhemoglobin?
Deoxyhemoglobin has no oxygen bound, while oxyhemoglobin is highly oxygen-bound
Study Notes
Oxygen Binding in Hemoglobin
- Hemoglobin's oxygen binding kinetics exhibit a sigmoidal curve due to cooperative binding.
- The binding of one oxygen molecule to an active site increases the likelihood of oxygen binding to other active sites.
- This cooperative binding is known as cooperativity or allosteric effect.
Allosteric Effectors
- Allosteric effectors, such as 2,3-bisphosphoglycerate (2,3-BPG), function by shifting the equilibrium towards or away from the T-state.
- Allosteric inhibitors stabilize the T-state, while allosteric activators or promoters stabilize the R-state.
The Bohr Effect
- The Bohr effect is a physiological phenomenon where hemoglobin's oxygen binding affinity is inversely related to acidity and carbon dioxide concentration.
- Hemoglobin's oxygen binding affinity decreases with increased acidity and carbon dioxide levels.
Hemoglobin Structure
- Hemoglobin is a tetrameric protein made up of two alpha subunits and two beta subunits.
- It is homologous with the monomeric oxygen-binding protein, myoglobin.
Concerted Model
- The Concerted Model, also known as the symmetry model, explains the cooperativity in oxygen binding and the transitions of proteins made up of identical subunits.
- The model focuses on the two states of hemoglobin: the T-state (tense, deoxyhemoglobin) and the R-state (relaxed, oxyhemoglobin).
Enzyme Structure and Function
- Enzymes are not rigid structures, but are flexible in shape, as demonstrated by X-ray crystallography.
- The induced-fit model of substrate and enzyme binding proposes that the enzyme molecule changes its shape to accommodate the binding of the substrate.
- The active site alone binds to the substrate, while the rest of the protein molecule stabilizes the active site and provides an appropriate environment for interaction.
This quiz explores the concept of cooperative binding in hemoglobin, where the binding of oxygen at one site increases the binding affinity in other active sites, resulting in a sigmoidal curve for oxygen binding kinetics.
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