bio mod 3
are the structures of deoxyhemoglobin and oxyhemoglobin the same or differentq
noticeably different oxygen binding causes a slight rotation that decreases the size of the central cavity between the 4 subunits and alters some of the contacts and distance between them
Addition of ______________________alters the shape of the iron-heme complex, and therefore its absorption of light as indicated by its color change from dark purple (the color of hemoglobin in venous blood) to brilliant scarlet (the color of hemoglobin in arterial blood). Select one: a. iron b. oxygen c. porphyrin d. globin subunit
oxygen Correct!
what is hemoglobin structure exquisitely sensitive to
oxygen binding and the entire conformation of the protein changes as a result of oxygen binding or release
explain what happens to the shape of hemoglobin and heme when binding oxygen
oxygen binds to iron in the heme group and causes the heme to change from a bent to planar state, the change tugs on the protein chain holding the heme group causing a conformational shift, this shift influences the conformation of the neighboring subunits such that oxygen binding occurs
what does it mean to bind reversibly
oxygen can bind reversibly to iron, meaning it will bind to iron when oxygen concentraions are relatively high and release from the iron when oxygen concentrations are low
what does the R state corresponds with
oxyhemoglobin
what is the carbon and nitrogen ring system known as in the heme
porphyrin meaning bright colors
what is myoglobin
protein consisting of a single subunit that contains a heme group with an iron atom bond.
hemoglobin has what kind of structure
quaternary structure myoglobin is only tertiary because it has only one subunit
hemoglobins relatively low oxygen affinity and its cooperative binding behavior are the result of its ______ structure
quaternary structure as well as the keys to the physiolocial function
the oxygenated form is referred to as the
relaxed or R state
what is the Fe atom held in place by
the four porphyrin N atoms and one N from a histidine (His) side chain a molecule of oxygen 02 can act as a sixth binding partner to the iron atom
what does the iron atom bind
the iron atom binds one molecule of oxygen
what is the crucial element of hemoglobins oxygen binding behavior
the structural rearrangement (the T and R)
a persons genes dictate the amino acid sequence of
their protein proteins then fold into 3 dimensional functional proteins based on interactions between the amino acid R groups
what must the four heme groups of hemoglobin be able to do so they can bind or release oxygen
they must sense one anothers oxygen binding status so they can release or bind oxygen at the same time
fatal exposure to carbon monoxide
60-70% death
where is sickle cell more common
common in regions of the world where malaria is endemic
in the lungs, where oxygen concentration is high, O2 binding by hemoglobin changes the _____
conformation to the R state, thereby releasing the protons (H+) bound to hemoglobin, which recombine with bicarbonate to form CO2, which is then exhaled by the lungs.
the Bohr Effect - what does that do
conformational changes in hemoglobin that occur upon oxygen binding or release are also impacted by pH. T state is favored by low pH and induces the release of oxygen R state is favored by higher pH and stimulates hemoglobin to bin more oxygen by increasing the affinity
when every other bond is a double bond the system is known as a
conjugated systems and absorb colored light well
Where is myoglobin found?
inside vertebrale muscle cells
hemoglobin is a tetramer protein containing
2 alpha and 2 beta globin units
what binds to deoxygenated hemoglobin and stablizes the T state of the protein
2,3-BPG
extreme exposure to carbon monoxide
30-40% droozy lethargic coma
the Fe (iron) atom at the center of heme has a charge of
+2
medium exposure to carbon monoxide
10-15% dizzy confused achy
average life span of sickle red blood cell
10-20 days causes the anemia
average life span of normal red blood cells
120 days
Why is the hemoglobin binding curve sigmoidal in shape?
At low O2 concentrations, hemoglobin appears to be reluctant to bind the first O2, but as the O2 concentration increases, O2 binding increases sharply, until hemoglobin is almost fully saturated. A look at the binding curve in reverse shows that at high O2 concentrations, oxygenated hemoglobin is reluctant to give up its first O2, but as the O2 concentration decreases, all the O2molecules are easily given up. This behavior suggests that the binding of the first O2 increases the affinity of the remaining O2-binding sites. In fact, the fourth O2 taken up by hemoglobin binds with about 100 times greater affinity than the first. Apparently, hemoglobin's four heme groups are not independent but communicate with each other in order to work in a unified fashion. This is known ascooperative binding behavior.
Hemoglobin acts as a buffer and controls the pH of the blood by binding to __________. Select one: a. bicarbonate ion b. oxygen c. H+ ions d. carbon dioxide
H+ ions Correct! A high concentration of H+ ions, if left unbound, will result in an acidic environment (low pH value). Hemoglobin by binding H+ ions contribute to the acidity of blood. By binding to these ions, hemoglobin is able to act as a buffer and maintain the pH at an appropriate range.
Hemoglobin's ability to bind or release oxygen depends on the pH of the environment. This behavior is known as the Bohr effect. Considering this, which of the following statements is true? Select one: a. Hemoglobin binds to the oxygen at high pH and releases oxygen at low pH. b. Hemoglobin binds to the oxygen at low pH and releases oxygen at high pH. c. At low pH hemoglobin is able to bind and release oxygen. d. At high pH hemoglobin is able to bind and release oxygen.
Hemoglobin binds to the oxygen at high pH and releases oxygen at low pH. Correct! pH is a measure of H+ ion concentration. High pH indicates a more basic environment in which the H+ ion concentration is low, as seen in the lungs. Under these conditions, hemoglobin binds more oxygen. Low pH indicates an acidic environment in which the H+ ion concentration is high. Such conditions encourage the binding of H+ ions to hemoglobin and stabilizing a form of hemoglobin which decreases the affinity for oxygen, resulting in release of oxygen.
Hemoglobin consists of four protein subunits. Each subunit contains ______ that holds ______ , which can bind to _____
Hemoglobin consists of four protein A HEME GROUP. Each subunit contains AN IRON ATOM that holds AN OXYGEN MOLECULE , which can bind to blank .
In locations where the pH is low, hemoglobin will be in the ______ state, allowing it to ______oxygen more effectively.
In locations where the pH is low, hemoglobin will be in the T state, allowing it to RELEASE oxygen more effectively.
Increased levels of 2,3-BPG will ______ the affinity for oxygen by binding to and stabilizing the _______ state of hemoglobin. The action of 2,3-BPG allows hemoglobin to _______ oxygen more effectively, which is similar to the effect of ______ pH on the action of hemoglobin.
Increased levels of 2,3-BPG will DECREASE the affinity for oxygen by binding to and stabilizing the T state of hemoglobin. The action of 2,3-BPG allows hemoglobin to RELEASE oxygen more effectively, which is similar to the effect of LOW pH on the action of hemoglobin. The molecule 2,3-BPG is produced by RBCs, binds to the deoxygenated form of hemoglobin and stabilizes the T state of the protein. This causes a decrease in hemoglobin's affinity for oxygen, which allows it to release more oxygen to the tissues. In this way, 2,3-BPG has a similar effect to low pH on the action of hemoglobin.
mammalian hemoglobin is an _____tetramer
Mammalian hemoglobin is an α2β2 tetramer, meaning it has two α (alpha) and two β (beta) subunits. (Note that these alpha/beta designations are in reference to the subunits, not the secondary structures inside these subunits.). The α and β subunits are structurally related to each other and to myoglobin; there are only small differences between the monomer of myoglobin and the α/β subunits of hemoglobin.
Myoglobin and hemoglobin each have different numbers of subunits and this affects their respective oxygen storage and delivery capabilities. How many subunits do myoglobin and hemoglobin each have? Select one: a. Four, One b. One, Four c. One, Two d. Two, Three
One, Four Correct! Myoglobin consist of one and hemoglobin consists of four subunits. The number of subunits affects their respective oxygen storage and delivery capabilities.
When binding hemoglobin or myoglobin, CO binds in place of _________. Select one: a. Histidine b. Iron c. Heme d. Oxygen
Oxygen Correct! CO binds in place of oxygen.
Hemoglobin's cooperative binding behavior is key to its physiological function. The binding of which of the following molecules influences this behavior? Select one: a. Iron b. Heme c. Oxygen d. None of these
Oxygen Correct! Binding of the first oxygen molecule to a hemoglobin subunit greatly enhances binding of the remaining oxygen molecules. All subunits communicate with each other and work in a unified fashion. This property is referred to as cooperativity.
Oxygen binding alters the structure of an entire hemoglobin tetramer, so the structures of oxyhemoglobin and deoxyhemoglobin are noticeably different. The oxyhemoglobin conformation is specifically referred to as the __________ state, whereas the deoxyhemoglobin conformation is referred to as the __________ state. Select one: a. O and D b. Relaxed or R and Tense or T c. There is no difference between the two states d. Oxygenated and Deoxygenated
Relaxed or R and Tense or T Correct! Oxygen binding causes a marked change in hemoglobin structure. In the presence of oxygen, hemoglobin is in the Relaxed state or R state. In the absence of oxygen, hemoglobin is in the Tense state or T state.
what causes sickle cell anemia
Sickle cell anemia is caused by the mutation of the beta hemoglobin gene that changes the charged amino acid glutamate (Glu) located at position 6 in the primary structure to the hydrophobic amino acid valine (Val). This amino acid is positioned on the outer surface of the protein, so the mutation to Val results in a hydrophobic amino acid anxious for opportunities to make hydrophobic interactions to escape the water that surrounds it. In normal hemoglobin, the switch from the oxy to the deoxy conformation exposes a hydrophobic patch on the protein surface between two of the alpha helices. The hydrophobic Val residues on hemoglobin S are optimally positioned to bind to this patch. This association between the Val of one Hb S and the hydrophobic patch of another Hb S leads to the rapid aggregation of hemoglobin S molecules to form long, rigid fibers.
what are the 2 conformational states of hemoglobin
T for tense R for relaxed
the heme group photo
The image on the left shows the central Fe(II) atom bound to the four N atoms of the porphyrin ring. The Fe(II) is also liganded to a His side chain and to O2. The image on the right shows the heme in green, oxygen in orange, and His in blue. The planar (flat) shape of the heme is more apparent in this image, with the Fe(II) in the center of the plane, the oxygen above the plane, and the His below the plane of the heme.
what are some benefits of sickle cell
They are protected against malaria, a parasitic disease
what does each subunit contain of a hemoglobin
a heme molecule and an iron atom allowing each hemoglobin protein to bind four molecules of oxygen
what does the myoglobin structure consist of
a monomer (single polypeptide chain with no quaternary structure) with 8 alpha helices that are arranged to form a globular protein
Myoglobin contains
a single heme group heme is tightly wedged in a hydrophobic pocket between 2 alpha helices
tertiary struccture of myoglobin is
almost identical to each of the globin subunits of hemoglobin, though thier amino acid sequences are quite different
why is deoxyhemoglobin reluctant to bind the first oxygen molecule
because the protein in in the deoxy (T) conformation which is unfavorable to oxygen binding (the Fe lies out of the heme plane) once one binds the entire tetramer switches to the oxy (R) conformation bringing Fe and heme into a planar conformation for optimal oxygen binding
how does hemoglobin bind with oxygen
binds oxygen cooperatively due to structural communication between the four subunits. allows the protein to coordinate oxygen binding and release to support its function in oxygen delivery
what does carbon monoxide bind to and what does it stabilize
binds to the iron atoms in hemoglobin and stabilizes the R state of the protein
how do you assess the oxygen carrying capacity of the blood
by measuring the hematocrit percentage of the blood volume occupied by red blood cells, which ranges from about 40% (in women) to 45% (in men). Individuals with anemia (too few red blood cells) can sometimes be treated to increase red blood cell production.
besides oxygen what else can bind to heme groups
carbon monoxide CO, and nitric oxide NO bind more tightly accounts for the toxicity CO will bind before oxygen
what does the T state correspond with
deoxyhemoglobin
CO2 by respiring tissues diffuses from the tissues to capillaries what happens to CO2
enzyme carbonic anhydrase in the RBD accelerates the reaction to turn CO2 into bicarbonate HCO3-
Carbonic anhydrase is an important __________ present in the red blood cells that aids in efficient transportation of carbon dioxide in the form of _________, from tissues to lungs. Select one: a. chemical, carbon monoxide b. substrate, bicarbonate ions c. enzyme, bicarbonate ions d. enzyme, carbon dioxide
enzyme, bicarbonate ions Correct! Carbonic anhydrase is an enzyme which catalyzes the conversion of carbon dioxide to bicarbonate ions. This mechanism enables efficient transport of carbon dioxide by warding off bubble formation in the blood.
what does the shift in protein conformation from the T to the R state result in
from the change in heme shape that takes place when oxygen binds to the Fe
explain the graph of myoglobins oxygen binding
graph of myoglobin's oxygen binding has a hyperbolic shape (increases rapidly and then levels off), indicating its sensitivity to low oxygen concentrations
What gives blood its red color?
hemoglobin
explain the hemoglobin overall oxygen affinity to that of myoglobin
hemoglobin's overall oxygen affinity is lower than that of myoglobin: hemoglobin is half-saturated (50% of all hemoglobin is full of oxygen) at an oxygen pressure of 26 torr, whereas myoglobin is half-saturated at 2.8 torr. Thus, it takes a much higher concentration of oxygen to fill hemoglobin than it does myoglobin, despite the structural similarity of their individual subunits.
what is the heme
heterocyclic (contains both carbon and nitrogen)
Patients with sickle cell anemia have atypical hemoglobin, which will distort the red blood cells into sickle shape during oxygen delivery. The substitution of a hydrophilic amino acid with a ____________amino acid in hemoglobin subunits results in the polymerization of hemoglobin, leading to the sickling of red blood cells. Select one: a. hydrophobic b. polar c. hydrophilic d. cysteine
hydrophobic Correct! In case of sickle cell anemia, a hydrophilic amino acid-glutamate is replaced by a non polar-hydrophobic amino acid-valine, leading to polymerization of hemoglobin, fibril formation and eventually sickling of the red blood cells.
what is sickle cell anemia
inherited recessive disorder that results in the changes in hemoglobin structure
what happens when Fe binds to the heme complex
it changes the chemical properties of the ring such that it changes how it absorbs light dark purple -no oxygen bound to brilliant scarlet -oxygen bound if Fe2 becomes oxidized to Fe3 it will be brown (responsible for the brown color of meat)
what does the Bohr effect describe
it describes the influence that ph has on oxygen binding by hemoglobin at high ph hemoglobin has a high affinity for oxygen, at low ph it has a low affinity for oxygen and tends to release it
light exposure of carbon monoxide
minutes headache soree eyes runny nose
n the lungs, the CO2 concentration is ______and the pH is _____ , while in the tissues, the CO2 concentration is _____ and the pH is ____
n the lungs, the CO2 concentration is LOW and the pH is HIGH , while in the tissues, the CO2 concentration is HIGH and the pH is LOW In the lungs, CO2 concentration are low, resulting in decreased carbonic acid and higher pH. This creates a more basic (or alkaline) environment that promotes oxygen binding.In the tissues, CO2 concentration tends to be high, resulting in increased carbonic acid which lowers the pH. This creates an acidic environment that promotes oxygen release.
explain deoxyhemoglobin
reluctant to bind oxygen at low O2 concentrations, oxyhemoglobin tends to retain its bound O2 molecules until the oxygen pressure drops significantly. Once one or two subunits release O2 it triggers the protein to change to the deoxy (T) conformation. This decreases the affinity of the remaining bound O2 molecules, making it easier for hemoglobin to unload its bound oxygen. The essential feature of hemoglobin's T → R or R → T transition is that its subunits are so tightly coupled that large tertiary structural changes within one subunit cannot occur without quaternary structural changes involving all four subunits of the protein.
how does hemoglobin bind with oxygen
reversibly but not as simple as myoglobin plot of the fraction of hemoglobin with oxygen bound versus oxygen concentration is sigmoidal (S-shaped) rather than hyperbolic
how does myoglobin bind to oxygen
reversibly in response to oxygen concentration
measuring myoglobin in the blood can provide evidence of what
rhabdomyolysis, mild heart attack or muscular degenerative disease While myoglobin is normally contained only in the muscles, it can be released into the bloodstream if there is muscle damage. For this reason, measuring the levels of myoglobin in the blood can provide evidence of rhabdomyolysis, a mild heart attack, or a muscular degenerative disease.
the deoxygenated form is known as the
tense or T state of the protein
Myoglobin is a small protein with relatively simple oxygen-binding behavior. Hemoglobin a _______________ is a more complicated protein that functions as a sophisticated system for delivering oxygen to the tissues throught the body
tetramer (four subunits)
what happens to cause the deoxygenated hemoglobin its color of deep purple
the absence of oxygen the histidine residue that binds to the Fe atom will pull on the Fe and slightly bend (dome) the heme plane. The distoration alters the light absorption of the porphyrin ring giving the deoxygenated state T state its characteristic of deep purple or color of venous blood
what is the function of myoglobin
to bind and store oxygen for the muscles to use when blood oxygen is low like when you sprint -breathing may not keep up with oxygen demand but the oxygen in the muscle allows you to keep sprinting
how does the Bohr effect become an important physiological functions
transporting oxygen from lungs to respiring tissue in transporting the CO2 produced by respiration back to the lungs
Sickle Cell Anemia: A Problem with Hemoglobin Structure
well-known hemoglobin variant is sickle cell hemoglobin (known as hemoglobin S or Hb S). Individuals with two copies of the defective gene develop sickle cell anemia, a debilitating disease that affects predominantly those of African descent.
how does the blood gets it red color of arterial blood
when oxygen binds it brings the Fe and heme group back inot the planar position and the color changes to the characteristic scarlet color of arterial blood
when does sickling tend to occure
when the red blood cells pass through oxygen-poor capillaries. The misshapen cells often get stuck in the capillaries and obstruct blood flow, leading to intense pain and sometimes tissue damage due to impaired oxygen delivery. rigidity of the sickle red blood cells also causes them to be more fragile and die more quickly.
how doe bicarbonate change the pH
where oxygen concentration is low, the H+ generated by bicarbonate formation is taken up by hemoglobin by binding to negatively charged side chains. This binding alters some of the ionic bonds between subunits and favors a conformational change to the T state, thereby inducing hemoglobin to unload its bound O2. This H+ uptake also facilitates CO2 transport by stimulating bicarbonate formation (too much H+ will slow the conversion of CO2 to bicarbonate by carbonic anhydrase).
