Protein Function and Oxygen-binding Proteins Quiz
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Questions and Answers

What is the role of proteins in interacting with other molecules?

  • Preventing the binding of other molecules
  • Acting as a reaction catalyst or enzyme (correct)
  • Stabilizing the chemical configuration of bound molecules
  • Inducing irreversible changes in bound molecules

    • What is the significance of the transient nature of protein-ligand interactions?

  • Stabilizes the protein-ligand complex
  • Allows rapid and reversible responses to changing circumstances (correct)
  • Induces irreversible changes in the protein structure
  • Prevents the discrimination among different molecules

    • What is the term used for a molecule bound reversibly by a protein?

  • Ligand (correct)
  • Substrate
  • Catalyst
  • Enzyme

    • What does a ligand bind to on a protein?

    <p>Binding site complementary in size, shape, charge, and hydrophobic or hydrophilic character</p> Signup and view all the answers

    What allows a protein to selectively bind only one or a few types of molecules from its environment?

    <p>Specificity in protein-ligand interactions</p> Signup and view all the answers

    What is the term for a protein with separate binding sites for several different ligands?

    <p>Multifunctional protein</p> Signup and view all the answers

    What is the major class of antibodies?

    <p>IgG</p> Signup and view all the answers

    Which system is directed at bacterial infections and extracellular viruses?

    <p>Humoral immune system</p> Signup and view all the answers

    How many polypeptide chains make up an antibody?

    <p>4</p> Signup and view all the answers

    What is the primary function of T lymphocytes?

    <p>Recognition of infected cells or parasites</p> Signup and view all the answers

    Which class of immunoglobulins is characterized by the heavy chain δ?

    <p>IgD</p> Signup and view all the answers

    What is the effect of 2,3-bisphosphoglycerate (BPG) on hemoglobin's affinity for oxygen?

    <p>Greatly reduces the affinity of hemoglobin for oxygen</p> Signup and view all the answers

    What type of antibodies are synthesized by a population of identical B cells?

    <p>Monoclonal antibodies</p> Signup and view all the answers

    What is the primary role of helper T cells (TH cells) in the immune response?

    <p>Produce soluble signaling proteins called cytokines</p> Signup and view all the answers

    What are the two major proteins of muscle?

    <p>Actin and Myosin</p> Signup and view all the answers

    What binds to the thin filament and blocks the myosin-binding sites?

    <p>Tropomyosin</p> Signup and view all the answers

    What is the effect of CO2 binding to hemoglobin on the binding of O2?

    <p>Inversely related</p> Signup and view all the answers

    What is the primary function of antibodies (immunoglobulins)?

    <p>Bind bacteria, viruses, or large foreign molecules and target them for destruction</p> Signup and view all the answers

    What is the percentage of oxygen saturation in arterial blood?

    <p>Around 96%</p> Signup and view all the answers

    What stabilizes the T state of hemoglobin?

    <p>Ion pairs at the α1β2 interface</p> Signup and view all the answers

    What is the role of carbonic anhydrase in hemoglobin function?

    <p>Catalyzing the hydration of CO2 to bicarbonate</p> Signup and view all the answers

    What is the primary function of myoglobin's distal His in oxygen transport?

    <p>Enhancing heme's O2 affinity through hydrogen bonding</p> Signup and view all the answers

    How does hemoglobin bind oxygen?

    <p>Cooperatively, with the first O2 molecule binding weakly and subsequent molecules binding with higher affinity</p> Signup and view all the answers

    What acts as an activating homotropic modulator for hemoglobin?

    <p>O2</p> Signup and view all the answers

    Which protein family includes myoglobin, hemoglobin, neuroglobin, and cytoglobin?

    <p>Globins</p> Signup and view all the answers

    What is the coordination number of iron in heme?

    <p>Six</p> Signup and view all the answers

    What does the dissociation constant ($K_d$) represent?

    <p>The equilibrium constant for the release of the ligand</p> Signup and view all the answers

    What is the primary function of myoglobin?

    <p>Oxygen binding</p> Signup and view all the answers

    What prevents the oxidation of Fe$^{2+}$ in heme?

    <p>Heme's organic ring structure</p> Signup and view all the answers

    What affects the binding affinities of carbon monoxide (CO) and oxygen to heme?

    <p>Protein structure</p> Signup and view all the answers

    Which of the following is true about the Bohr effect?

    <p>It describes the effect of pH and [CO2] on the binding and release of O2 by hemoglobin</p> Signup and view all the answers

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

    <p>It greatly reduces the affinity of hemoglobin for oxygen</p> Signup and view all the answers

    What is the primary function of fetal hemoglobin?

    <p>It has a higher affinity for O2 than normal adult hemoglobin</p> Signup and view all the answers

    What is the primary function of T lymphocytes in the immune response?

    <p>Recognition of infected cells or parasites</p> Signup and view all the answers

    What is the role of haptens in the immune response?

    <p>They can elicit an immune response when covalently attached to large proteins</p> Signup and view all the answers

    What is the primary function of vaccines in the immune system?

    <p>To stimulate the production of memory cells</p> Signup and view all the answers

    What is the coordination number of iron in heme?

    <p>6</p> Signup and view all the answers

    What is the primary function of monoclonal antibodies?

    <p>Used in analytical procedures and diagnostic tests for their specificity</p> Signup and view all the answers

    What is the structure of IgM antibodies?

    <p>Cross-linked pentamer</p> Signup and view all the answers

    What is the role of tropomyosin in muscle contraction?

    <p>Prevents binding of the myosin head to actin</p> Signup and view all the answers

    What is the major function of the sarcoplasmic reticulum in muscle cells?

    <p>Stores and releases Ca$^{2+}$ for muscle contraction</p> Signup and view all the answers

    What is the primary function of the immunoglobulin fold structural motif?

    <p>Is a well-conserved structural motif in the all-β class of proteins</p> Signup and view all the answers

    What is the coordination number of iron in heme?

    <p>6</p> Signup and view all the answers

    What is the primary function of myoglobin's distal His in oxygen transport?

    <p>Facilitating the release of oxygen to tissues</p> Signup and view all the answers

    What does the dissociation constant ($K_d$) represent?

    <p>Equilibrium constant for the release of the ligand</p> Signup and view all the answers

    What is the effect of 2,3-bisphosphoglycerate (BPG) on hemoglobin's affinity for oxygen?

    <p>Decreases its affinity for oxygen</p> Signup and view all the answers

    What is the significance of the transient nature of protein-ligand interactions?

    <p>It enables rapid association and dissociation of the ligand</p> Signup and view all the answers

    What is the role of carbonic anhydrase in hemoglobin function?

    <p>Converts CO2 into bicarbonate for transport in the blood</p> Signup and view all the answers

    What is the primary function of hemoglobin's selective enhancement of O2 affinity?

    <p>Preventing CO poisoning from metabolism and industrial sources</p> Signup and view all the answers

    What stabilizes the T state of hemoglobin?

    <p>Ion pairs at the α1β2 interface</p> Signup and view all the answers

    What is the coordination number of iron in heme?

    <p>6</p> Signup and view all the answers

    What is the effect of pH and CO2 concentration on the binding of oxygen by hemoglobin?

    <p>They regulate oxygen binding and release in the blood</p> Signup and view all the answers

    What is the primary function of myoglobin's distal His in oxygen transport?

    <p>Enhancing heme's O2 affinity through hydrogen bonding</p> Signup and view all the answers

    What is the percentage of oxygen saturation in arterial blood?

    <p>~96%</p> Signup and view all the answers

    What does a ligand bind to on a protein?

    <p>The binding site that is complementary to the ligand in size, shape, charge, and hydrophobic or hydrophilic character</p> Signup and view all the answers

    What is the term used for a molecule bound reversibly by a protein?

    <p>Ligand</p> Signup and view all the answers

    What is the significance of the transient nature of protein-ligand interactions?

    <p>It allows an organism to respond rapidly and reversibly to changing environmental and metabolic circumstances</p> Signup and view all the answers

    What stabilizes the T state of hemoglobin?

    <p>2,3-bisphosphoglycerate (BPG)</p> Signup and view all the answers

    What is the coordination number of iron in heme?

    <p>6</p> Signup and view all the answers

    What is the primary function of vaccines in the immune system?

    <p>To stimulate the immune system to produce antibodies</p> Signup and view all the answers

    What is the term for a molecule bound reversibly by a protein?

    <p>Ligand</p> Signup and view all the answers

    What is the primary function of a ligand in protein function?

    <p>Binding to a protein at a complementary binding site</p> Signup and view all the answers

    What allows a protein to selectively bind only one or a few types of molecules from its environment?

    <p>Specificity of the protein's binding site</p> Signup and view all the answers

    What is the significance of the transient nature of protein-ligand interactions?

    <p>Enables rapid and reversible organism response</p> Signup and view all the answers

    What is the term for a protein with separate binding sites for several different ligands?

    <p>Allosteric protein</p> Signup and view all the answers

    What type of interactions do proteins engage in with other molecules?

    <p>Reversible interactions</p> Signup and view all the answers

    Study Notes

    Protein Function and Oxygen-Binding Proteins

    • Proteins exhibit reversible interactions and flexibility in binding to ligands, often undergoing conformational changes for tighter binding.
    • Multisubunit proteins can undergo conformational changes in one subunit that affect the others, and interactions between ligands and proteins may be regulated.
    • Myoglobin and hemoglobin are well-studied oxygen-binding proteins, crucial for the evolution of larger, multicellular animals.
    • Heme, a protein-bound prosthetic group, consists of a complex organic ring structure with a bound Fe2+ atom and prevents the oxidation of Fe2+.
    • The coordination bonds of iron in heme include six bonds, with two being perpendicular to the porphyrin and one being the binding site for molecular oxygen (O2).
    • Globins, a widespread protein family, include myoglobin, hemoglobin, neuroglobin, and cytoglobin, each with specific functions related to oxygen binding.
    • Myoglobin has a single binding site for oxygen and consists of 153 residues with eight α helices typical of the globin fold.
    • Protein-ligand interactions can be quantitatively described by an equilibrium expression, with an association constant (ka) providing a measure of ligand affinity.
    • The dissociation constant (kd) is the reciprocal of ka and represents the equilibrium constant for the release of the ligand, with lower Kd indicating higher affinity.
    • Protein structure affects how ligands bind, as seen in the significantly different binding affinities of carbon monoxide (CO) and oxygen to heme.
    • CO binds free heme much better than O2, but the difference in affinity is mediated by the globin structure, affecting the binding geometries of CO and O2 to heme.
    • The change in relative affinity of CO and O2 for heme when bound to a globin is influenced by differences in their orbital structures and the binding conformation readily accommodated by myoglobin.

    Hemoglobin's Role in Oxygen Transport and Allosteric Regulation

    • Myoglobin's distal His enhances heme's O2 affinity through hydrogen bonding, increasing stability of the Fe-O2 complex
    • Hemoglobin's selective enhancement of O2 affinity prevents CO poisoning from metabolism and industrial sources
    • Hemoglobin is formed from hemocytoblasts and carries oxygen in erythrocytes, with arterial blood being ~96% saturated with O2
    • Hemoglobin subunits are structurally similar to myoglobin, with interactions causing conformational changes for oxygen storage and transport
    • Hemoglobin undergoes a structural change on binding oxygen, transitioning between the R state (O2-affine) and T state (deoxyhemoglobin)
    • The T state is stabilized by ion pairs at the α1β2 interface, and O2 binding triggers a conformational change to the R state
    • Hemoglobin binds oxygen cooperatively, with the first O2 molecule binding weakly and subsequent molecules binding with higher affinity
    • Hemoglobin is an allosteric protein, with O2 acting as an activating homotropic modulator, inducing conformational changes
    • Hemoglobin also transports H+ and CO2, with carbonic anhydrase catalyzing the hydration of CO2 to bicarbonate
    • Hemoglobin transports around 40% of total H+ and 15-20% of formed CO2 in tissues to the lungs and kidneys
    • The binding of oxygen by hemoglobin is influenced by pH and CO2 concentration, with CO2 and bicarbonate interconversion regulating oxygen binding and release in the blood

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    Week 4 - Protein Function PDF

    Description

    Test your knowledge of protein function and oxygen-binding proteins with this quiz. Explore topics such as reversible interactions, multisubunit proteins, myoglobin, hemoglobin, heme, globins, protein-ligand interactions, and the binding affinities of carbon monoxide and oxygen to heme.

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