Chem 20 Nov Lecture Flashcards
What is the primary function of myoglobin?
Storage of oxygen in muscle tissue
What is the primary function of hemoglobin?
Transport of oxygen from lungs to tissues and carbon dioxide from tissues to lungs
What structural feature is central to the function of heme proteins?
Porphyrin complex with a coordinated iron ion
What is the significance of the Bohr effect?
Explains how pH and temperature affect oxygen binding
How does fetal hemoglobin differ from adult hemoglobin in terms of oxygen affinity?
Fetal hemoglobin has a higher affinity for oxygen
What is the role of 2,3-bisphosphoglycerate (BPG) in hemoglobin function?
It binds to adult hemoglobin and decreases its oxygen affinity
What is cooperative binding?
Binding at one site increases binding at additional sites within the protein structure
What is the Hill coefficient and what does it indicate?
A mathematical tool to quantify cooperative binding; greater than 1 indicates cooperative binding
What is the relationship between myoglobin and hemoglobin regarding their affinity for oxygen?
Myoglobin has a higher affinity for oxygen than hemoglobin
Fill in the blank: Hemoglobin is a _______ protein, while myoglobin is a _______ protein.
tetrameric; monomeric
True or False: Myoglobin participates in cooperative binding.
False
What physiological conditions can affect the ability of oxygen to bind to hemoglobin?
Temperature, pH, and CO2 levels
What is the significance of the sigmoidal curve in the oxygen binding graph of hemoglobin?
Indicates cooperative binding
What are the two main effects discussed in relation to oxygen and carbon dioxide binding?
Bohr effect and Haldane effect
What is carbaminohemoglobin?
Hemoglobin bound to carbon dioxide
How does carbon monoxide affect oxygen transport?
It competes with oxygen for binding to heme, reducing oxygen transport
What is the role of the carbonate buffering system?
Transporting carbon dioxide in the blood and maintaining pH balance
What happens to myoglobin’s oxygen release during exercise?
Releases oxygen as tissue oxygen levels decrease
What is the impact of chloride ions on the carbonate buffering system?
They help maintain balance in transporting carbon dioxide
What type of binding does cyanide exhibit with heme proteins?
Competitive binding
What is the difference in binding site availability between myoglobin and hemoglobin?
Myoglobin has one binding site; hemoglobin has four
What is the Hill coefficient of myoglobin?
1
Myoglobin has a Hill coefficient of one, indicating non-cooperative binding.
What is the Hill coefficient of globin?
2.7
The Hill coefficient of globin suggests cooperative binding.
What does cooperative binding in hemoglobin indicate?
Increased oxygen affinity as more oxygen binds
Cooperative binding allows each subsequent heme group to bind oxygen more easily.
What happens to oxygen affinity as more oxygen is bound to hemoglobin?
It increases
The affinity for oxygen rises from one to four bound oxygens.
What are the two states of hemoglobin?
T state (tense) and R state (relaxed)
T state is rigid, while R state is more flexible and allows for better binding.
What structural change occurs in hemoglobin when oxygen binds?
A shift in protein structure
This shift increases the affinity for additional oxygen binding sites.
What is the difference between fetal hemoglobin and adult hemoglobin in terms of oxygen affinity?
Fetal hemoglobin has a higher affinity for oxygen
This difference is partly due to the presence of gamma domains instead of beta domains in fetal hemoglobin.
What role does 2,3-bisphosphoglycerate (BPG) play in hemoglobin?
It binds to adult hemoglobin and decreases oxygen affinity
BPG stabilizes the T state of hemoglobin, reducing its ability to bind oxygen.
How does BPG interact differently with fetal hemoglobin compared to adult hemoglobin?
BPG binds weakly to fetal hemoglobin
This weak binding allows fetal hemoglobin to maintain a higher affinity for oxygen.
What happens to hemoglobin’s affinity for oxygen when BPG is bound?
It decreases
BPG binding shifts the equilibrium towards the T state, lowering oxygen affinity.
What is the significance of the leftward shift in the dissociation curve for fetal hemoglobin?
Indicates increased affinity for oxygen
A leftward shift means that fetal hemoglobin can bind oxygen more effectively than adult hemoglobin.
What type of interaction does BPG have with the histidine residues in adult hemoglobin?
Ion-ion interactions
These interactions are strong due to the positive charge of histidine and the negative charge of BPG.
What amino acid replaces histidine in fetal hemoglobin, and how does this affect BPG binding?
Serine replaces histidine, reducing BPG binding
The smaller size and lack of charge in serine lead to weaker interactions with BPG.
When hemoglobin is in the R state, what is its binding capability?
It has a higher binding affinity for oxygen
The R state allows for more effective oxygen binding due to structural changes.
Fill in the blank: The T state of hemoglobin is also known as the _______.
tense state
True or False: BPG binding increases the binding affinity of oxygen to hemoglobin.
False
BPG binding decreases oxygen affinity by stabilizing the T state.
What happens to hemoglobin affinity when BPG binds?
It shifts the curve to the right, lowering oxygen affinity.
BPG (2,3-bisphosphoglycerate) stabilizes the T state of hemoglobin, making it less likely to bind oxygen.
How does fetal hemoglobin differ from adult hemoglobin in terms of BPG binding?
Fetal hemoglobin has a higher affinity for oxygen and does not bind BPG effectively.
This allows fetal hemoglobin to absorb oxygen more readily from maternal blood.
What is the role of BPG in hemoglobin function?
BPG stabilizes the T structure of hemoglobin, preventing conformational changes necessary for higher oxygen affinity.
This rigidity affects the ability of hemoglobin to release oxygen.
True or False: Binding of oxygen to hemoglobin increases the affinity for BPG.
False.
Binding oxygen causes conformational changes that can displace BPG.
What is the primary way carbon dioxide is transported in the blood?
As bicarbonate, through the blood buffering system.
About 70% of CO2 is converted to bicarbonate, with 10% dissolved in plasma and 20% bound to hemoglobin.
What is carbaminohemoglobin?
Hemoglobin that has CO2 bound to its N-terminal groups, forming carbamate.
This binding lowers hemoglobin’s affinity for oxygen.
What effect does increased temperature have on oxygen dissociation?
Increased temperature causes oxygen to dissociate more rapidly.
Higher temperatures promote oxygen release, which is crucial during metabolic activity.
Fill in the blank: The Bohr effect describes how increased _______ lowers the affinity of hemoglobin for oxygen.
CO2 levels.
Increased CO2 leads to lower pH, affecting hemoglobin’s structure and function.
What happens to hemoglobin affinity for oxygen when pH decreases?
The affinity for oxygen decreases.
This is due to protonation of amino acid residues, affecting conformational changes.
What is the relationship between the Haldane effect and carbon dioxide affinity?
The Haldane effect states that decreased oxygen affinity increases carbon dioxide affinity.
This reflects the competitive binding interactions between oxygen and carbon dioxide.
True or False: A decrease in temperature increases the ability of hemoglobin to release oxygen.
False.
Lower temperatures decrease the dissociation of oxygen, making it harder for tissues to receive oxygen.
What does the term ‘cooperative binding’ refer to in the context of hemoglobin?
The phenomenon where binding of one oxygen molecule increases the affinity for subsequent oxygen molecules.
This characteristic is crucial for efficient oxygen uptake and release.
How does BPG affect the T state and R state of hemoglobin?
BPG favors the T state, which is the deoxygenated form, over the R state, which is oxygenated.
This shift is essential for the release of oxygen in tissues.
What is the primary difference between affinity and dissociation in the context of binding?
Affinity looks at the desire to bind, while dissociation looks at the desire to release.
How does temperature affect the release of oxygen?
Increasing temperature increases the ability to release oxygen; decreasing temperature decreases it.
Which gas has a higher affinity for heme than oxygen?
Carbon monoxide (CO).
Why is carbon monoxide considered toxic?
It binds to heme with a higher affinity than oxygen and does not release it, interrupting oxygen exchange.
What happens to oxygen transport when carbon monoxide binds to heme?
It prevents oxygen from binding due to competitive binding at the same site.
What is the role of carbon dioxide (CO2) when binding to hemoglobin?
CO2 binds at a different site and allows conformational shifts to occur for oxygen binding.
What can be done to overcome carbon monoxide binding to hemoglobin?
Increase oxygen saturation levels to kick out CO and allow O2 to bind.
Does myoglobin have a similar binding issue with carbon monoxide as hemoglobin?
Not significantly, as myoglobin is stored in muscles and has a strong affinity for oxygen.
What prevents carbon monoxide from binding to myoglobin when oxygen is already bound?
If oxygen is bound, CO cannot bind unless CO levels are extremely high.
Where does carbamate bind in the hemoglobin structure?
To the N terminus of the protein, not to the heme portion.
What is the Haldane effect?
It describes how CO2 affects the dissociation of oxygen in the blood.
What is the Hamburger phenomenon?
It deals with chloride movement in the carbonate buffering system during CO2 exchange.
How many ways can carbon dioxide be transported in the body?
Three ways.
What happens to CO2 when it enters the blood?
It converts to bicarbonate and is transported back to the lungs.
What occurs when bicarbonate reaches the lungs?
It converts back to CO2, which then crosses the lung membrane.
