Chapter 7: Protein Function: Myoglobin and Hemoglobin, Muscle Contraction, and Antibodies Flashcards
exhibits a hyperbolic O2-binding curve.
Myoglobin
can adopt the deoxy (T) or oxy (R) conformation
Hemoglobin
triggers conformational changes in hemoglobin
oxygen binding
why does oxygen binding trigger conformational changes in hemoglobin
so that oxygen binds to the protein cooperatively, yielding a sigmoidal binding curve.
alter hemoglobin’s O2-binding affinity.
Bohr effect and BPG
has low affinity for oxygen
hemoglobin
has high affinity for oxygen
myoglobin
what has better oxygen delivery hemoglobin or myoglobin
hemoglobin
prevents this oxidation and makes it possible for O2 to bind reversibly to the heme group
The protein portion of myoglobin and hemoglobin
CO has what affinity for hemoglobin than does O2.
200-fold greater
its major physiological role is to facilitate oxygen diffusion in muscle.
myoglobin
The rate at which O2 can diffuse from the capillaries to the tissues is limited by its what
low solubility in aqueous solution
which is present mainly in brain, retina, and endocrine tissues
neuroglobin
which occurs in most tissues.
cytoglobin
occurs when ligands interact independently with their binding sites.
hyperbolic binding curve
Animals that are too large (>1 mm thick) for simple diffusion to deliver sufficient oxygen to their tissues have circulatory systems containing what
hemoglobin
what makes hemoglobin a better O2 carrier
high concentration of BPG
High P50
what happens to the BPG concentration in low O2 environments such as in high altitudes
increases
O2 binding to hemoglobin is described by a
sigmoidal (S-shaped) curve
This permits the blood to deliver much more O2 to the tissues
sigmoidal (S-shaped) curve
increases with the degree of cooperativity of a reaction
quantity n, the Hill constant
For normal human hemoglobin, the Hill constant is between
2.8 - 3.0
Oxygen Binding to Hemoglobin Triggers a Conformational Change from what to what
T to R
are conformations of deoxyhemoglobin & oxyhemoglobin respectively
T & R states
has low O2 affinity
T state of hemoglobin
tears away the ion pairs formed by C-
terminal residues of each subunit in a process that is driven by the energy of formation of the Fe—O2 bonds.
T —> R transition
Increasing the pH stimulates hemoglobin to bind more O2 at lower O2 pressures.
The Bohr Effect Enhances Oxygen Transport
has important physiological functions in transporting O2 from the lungs to respiring tissue and in transporting the CO2 produced by respiration back to the lungs.
The Bohr effect
CO2 also modulates O2 binding to hemoglobin by combining reversibly with the N-terminal amino groups of blood proteins to form
carbamates
binds more CO2 and transport it to lung.
The T (deoxy) form of hemoglobin
decreases hemoglobin’s oxygen affinity by keeping it in the deoxy conformation.
BPG
can be adjusted more rapidly than hemoglobin can be synthesized for example increases as a result of high-altitude adaptation.
BPG concentration
Fetal hemoglobin has low what?
BPG Affinity
a molecule that binds to hemoglobin in red blood cells, affecting its oxygen affinity
BPG
is an oligomer of symmetrically related subunits.
allosteric protein
Each oligomer can exist in two conformational states called what
designated R and T
Only the what alters the affinity for the ligand.
conformational change
The molecular symmetry of the protein is what during the conformational change
conserved
The subunits must therefore change conformation in a what manner
concerted
ligand binding induces a conformational change in the subunit to which it binds, and cooperative interactions arise through the influence of those conformational changes on neighboring subunits.
sequential model
deoxyhemoglobin S forms insoluble filaments that deform erythrocytes.
sickle-cell hemoglobin (hemoglobin S)
The immune response is triggered by the presence of a foreign macromolecule, often a protein or carbohydrate, known as an
antigen
B cells display what on their surfaces.
immunoglobulins (antibodies)
the most common immunoglobulin
IgG
The ability for the basic immunoglobulin structure to recognize a variety of antigens resides in three loops in the variable domain called
hypervariable
divalent molecules meaning they can bind two identical antigens simultaneously
immunoglobulins
allows antibodies to cross-link antigens to form an extended lattice, which hastens the removal of the antigen and triggers B cell proliferation.
Divalent binding
Loses Its Tolerance in Autoimmune Diseases.
Immune System
