Cooperative Binding in Hemoglobin

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Questions and Answers

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?

T-state transition

Sigmoidal curve

Cooperativity (correct)

Allosteric effect

What is the role of allosteric effectors like 2,3-bisphosphoglycerate (2,3-BPG) in hemoglobin?

To shift the equilibrium towards the T-state (correct)

To shift the equilibrium towards the R-state

To decrease oxygen binding affinity

To increase oxygen binding affinity

What is the term for the phenomenon where hemoglobin's oxygen binding affinity is inversely related to acidity and carbon dioxide concentration?

Sigmoidal curve

Cooperativity

Bohr effect (correct)

Allosteric effect

What is the term for the transition of hemoglobin from the T-state to the R-state with oxygen binding?

Concerted model Signup and view all the answers

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 Signup and view all the answers

What is the role of 2,3-bisphosphoglycerate (2,3-BPG) in hemoglobin?

Allosteric inhibitor Signup and view all the answers

What is the shape of the oxygen binding kinetics curve for hemoglobin?

Sigmoidal Signup and view all the answers

What is the term for the ability of hemoglobin to bind to oxygen more strongly when oxygen levels are high?

Cooperativity Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

What is a cofactor in the context of enzymes?

A non-protein component necessary for catalytic activity. Signup and view all the answers

What is an example of a type of molecule that can act as a cofactor?

Iron. Signup and view all the answers

What is the effect of molecules that stabilize the protein in its T-state?

They act as allosteric inhibitors Signup and view all the answers

What is the term for the process of generating smaller enzymes that retain activity through laboratory-based directed evolution studies?

Directed evolution. Signup and view all the answers

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 Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

What is the name of the model used to explain the cooperativity in oxygen binding to hemoglobin?

The Concerted Model Signup and view all the answers

What is the state of hemoglobin in which it is more tense and has a lower affinity for oxygen?

T-state Signup and view all the answers

What topic will be discussed in further detail in Chapter 8?

The regulation of enzyme activity. Signup and view all the answers

What is the effect of molecules that bind to allosteric enzymes and move the protein to its R-state?

They act as allosteric activators Signup and view all the answers

What is the type of protein that myoglobin is?

Monomeric Signup and view all the answers

What is the shape of the oxygen binding curve for myoglobin?

Hyperbolic Signup and view all the answers

What is the difference between deoxyhemoglobin and oxyhemoglobin?

Deoxyhemoglobin has no oxygen bound, while oxyhemoglobin is highly oxygen-bound Signup and view all the answers

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.

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Description

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.