Chapter 7: Protein Function: Myoglobin and Hemoglobin, Muscle Contraction, and Antibodies Flashcards
Compare and contrast myoglobin and hemoglobins
similarities: bind to oxygen molecules by using prosthetic groups called heme groups.
differences: myoglobin has a single (monomeric) polypeptide, single heme group, more simple
hemoglobin is a tetramer consisting of 4 polypeptides, more complex, contains four heme groups. delivers oxygen to tissues throughout the body
myoglobin has how many a helices
small intracellular protein in vertebrate muscle with 8 helices
Describe heme group structure
Each heme group consists of an organic component called porphyrin and an inorganic component that consists of a single iron atom. The iron atom is located at the center of the organic component and is bound to four different nitrogen atoms
. This oxygen is brought to the cells by what two proteins and how?
myoglobin and hemoglobin. Both of these proteins have the ability to bind to oxygen molecules by using prosthetic groups called heme groups.
Myoglobin binds O2 to facilitate what
Oxygens diffusion
major role of myolglobin
its major physiological role is to facilitate oxygen diffusion in muscle also oxygen storage protein
heme group is responsible for what
the actual binding to the oxygen
which can bind more oxygen
hemoglobin cause of 4 subunits need 4 hemes hemes each give one oxygen
why is myoglobin oxygen binding curve hyperbolic
hyperbolic due to the high affinity myoglobin with oxygen.
p50 for myoglobin is?
2.8 torr
name another oxygen transport protein
hemocyanin
Hemocyanins, which are exclusively extracellular, in invertebrates, transport O 2 in mollusks and arthropods. e large multimeric proteins that differ in their primary through quaternary structures. However, their oxygen-binding sites are highly similar, consisting of a pair of copper atoms, each liganded by three His residues.
what kind of curve does hemoglobin form and why?
sigmoidal (s) curve because it has a lot smaller binding affinity to oxygen/cooperative interactions
what are hemoglobins 2 conformations
T-state (tense, lacks oxygen) deoxyhemoglobin and the R-state (relaxed, fully oxygenated) oxyhemoglobin
what are hemoglobins 2 conformations
goes from T to R with the addition of oxygen
T-state (tense, lacks oxygen) deoxyhemoglobin and the R-state (relaxed, fully oxygenated) oxyhemoglobin
name the equations used for hemoglobin
hill equation
hemoglobin has a p50 of?
26 torr
what kind of subunits does hemoglobin consist of?
2β 2tetramer (a dimer of α β protomers)
2 idenical ab dimers
definitions of saturation and partial pressure?
Saturatution-how much of protein is bound to oxygen
Partial pressure-concentraion of oxygen
how does myoglobin help facilitate diffusion
-quicker diffusion
The rate at which O 2 can diffuse from the capillaries to the tissues is limited by its low solubility in aqueous solution (∼10 −4 M in blood). Myoglobin increases the effective solubility of O 2 in muscle cells, acting as a kind of molecular bucket brigade to boost the O 2 diffusion rate.
The oxygen-storage function of myoglobin is probably significant only in?
The oxygen-storage function of myoglobin is probably significant only in aquatic mammals such as seals and whales, need it to dive deeper
Myoglobin’s Oxygen-Binding Curve Is ?
Hyperbolic
the mb equation describes its?
hyperbola
describe myoglobin’s hyperbola in terms of pO2,YO2 and O2
At low pO2, very little O 2 binds to myoglobin (Y O 2 is very small). As the pO 2 increases, more O2 binds to myoglobin. At very high pO2 , virtually all the O2 -binding sites are occupied and myoglobin is said to be saturated with O2.
K=?
P50
Myoglobin, a single polypeptide chain with one heme group and hence one oxygen-binding site, is a useful model for?
other binding proteins
Even proteins with multiple binding sites for the same small molecule, or ligand, may generate hyperbolic binding curves like myoglobin’s. A hyperbolic binding curve occurs when ligands interact independently with their binding sites.
Myoglobin is half-saturated with O 2(Y O2= 0.5) at an oxygen partial pressure (pO2) of ?
2.8 torr
Hemoglobin gives blood its?
color
Hemoglobin gives blood its? and where is it contained?
color
erythrocytes (RBC)
Idek
The α β protomers of hemoglobin are symmetrically related by a 2-fold rotation (i.e., a rotation of 180° brings the protomers into coincidence). In addition, hemoglobin’s structurally similar α and β subunits are related by an approximate 2-fold rotation (pseudosymmetry) whose axis is perpendicular to that of the exact 2-fold rotation.
what happens when oxygen binds to hemoglobin
alters the structure of the entire hemoglobin tetramer to form the 2 conformations
When oxygen binds to hemoglobin, the α1 – β 2 (and α2 – β 1 ) contacts shift, producing a change in quaternary structure.
what happens to iron during oxygen binding?
changes its position. so because of the electronegative character of oxygen when ditomic oxygen shown here actually
binds on to this heme group more
specifically onto the iron of that heme
group, it pulls away some of that
electron density from that heme group. it
pulls away some of that electron density
from that iron atom, and because some of
the electrons move away from that iron
atom it decreases the electron density
and the size of that iron atom, and now
because the iron atom is smaller it is
able to move into the
center of the plane of that
protoporphyrin
what causes cooperative behavior in hemoglobin?
In any binding system, a sigmoidal curve is diagnostic of a cooperative interaction between binding sites.This means that the binding of a ligand to one site affects the binding of additional ligands to the other sites. In the case of hemoglobin, O 2 binding to one subunit increases the O 2affinity of the remaining subunits.
differrence between deoxyhemoglobin and oxyhemoglobin
Deoxy -no heme groups are present, very constrained because few interactions
Oxy- when oxygen binds, causes interactions between surfac3es of polypeptide
Lifts restraints
s curve implies?
cooperative interactions
In the hills equations for hills constant n, what does it mean if n=1, n>1, and n<1
If n = 1, noncooperative.
If n > 1, the reaction is described as being positively cooperative,
if n < 1, the reaction is said to be negatively cooperative,
binding of oxygen to one submit increases or decreases the oxygen binding affinity ?
increases
this is positive cooperatively
binding of oxygen to one submit increases or decreases the oxygen binding affinity ?
increases
this is positive cooperatively
oxygen binding shifts the state from T to R and the Fe ion into where?
the porphyrin plane
which has a low affinity for oxygen T or R
T
in the Bohr effect the O2 affinity of hemoglobin increases with?
increasing pH/removing protons
shif of the binding curve to the left or right means what?
left=low oxygen affinity T state
right=high oxygen affinity R state
