Chem final Flashcards
What is the diff between myoglobin and hemoglobin
- myoglobin has 1 protein and 1 heme group (tertiary structure)
- hemoglobin is 4 subunits each with a protein and heme (quartenary structure)
Structurally, what are the similarities between Hb and myoglobin
Both are composed of a heme complex that have a coordinated Fe ….
T/F: Heme on its own is soluble
False
What ligands can attach to heme? (4)
- oxygen
- CO
- CO2
- Cyanide (cytochromes)
In regards to oxygen binding, what is the diff between myoglobin and Hb?
- Myoglobin has a higher affinity to oxygen, is monomeric, non cooperative binding
- Hemoglobin is tetrametric (4 domains), cooperative binding,
A rightward shift on an association curve for oxygen binding means?
less affinity for oxygen
When does myoglobin release oxygen?
When levels in muscles are very low
T/F: Hemoglobin can bind to oxygen multiple times
true
The sigmoidal shape of the hemoglobin curve signifies
cooperative binding
When does oxygen affinity increase for Hb?
as more oxygen is bound to heme (saturation increases)
Why do we see an increase in oxygen binding affinity with hemoglogin?
As oxygen binds, there is a shift in the heme and shift in protein structure
(Tense “t” state to Relaxed “r” state)
Binding always leads to ________ and with Hb this causes more _______
confirmational change
oxygen affinity
What is the R state?
4 oxygen have bound to Heme
what is the diff between fetal Hb and adult Hb
fetal has a higher affinity for oxygen
Why is there a higher affinity for oxygen in fetal Hb?
- Structural differences ( adult have 2 alpha and 2 beta)
- 2,3 BPG
Does 2,3 BPG bind to fetal Hg?
No
Why does 2,3 BPG do to adult Hb?
preturbe oxygen from binding to Heme
What charge is on histadine rings in adult Hb?
positive
What charge is on serine residue in fetal Hb?
no charge
Why is there no ion-dipole intermolecular force between 2,3 BPG and fetal hemoglobin
The distance is too great because the serine is small
2,3 BPG which stabalizes the structure of Hb, can also be a
competitive inhibitor
Shifting equilibrium to the left means? Would 2,3 BPG binding to adult Hb cause this?
higher affinity for oxygen
no; there would be a shift to the right
Where does 2,3 BPG come from
our bodies produce it
What does 2,3 BPG essentially do?
prevent conformational change and disallow more oxygen from binding
T/F: Both adult and fetal hemoglobin curves are sigmoidal
true
Shifting equillibrium to the left means oxygen favors the
T state
how can heme overcome binding of 2,3 BPG?
increasing pressure of O2
What are the 3 ways Co2 is transported throughout the blood? Which is primary?
- dissolved gas (10%)
- bicarb (blood buffering system)*
- bound to protein of the Hb
The n terminus of an amino acid is ________ while C is ________
nucleophilic
electrophilic
CO2 bound to Hb is called?
Carbaminohemoglobin
Where does CO2 bind on Hb?
the apoprotein, not the heme
High affinity for CO2 causes a _______ affinity for O2
low
What happens when RBC starts to bind to CO2
localized changes in pH of the environment (Bohr-Haldane Effect)
Oxygen dissociation is increased by (3)
- Increasing temp
- Lowering blood pH
- increasing partial Pco2
What affects does increasing Pco2 have in the blood? (3)
- Increase H concentration
- protonates certain amino acid residues
- leads to conformational change of protein
CO binds _____ times more strongly to heme than O2
200-300
T/F: CO2 binds to the same site as oxygen and CO does not
False
CO binds to the same site as O2 on heme and CO2 does not
CO2 prevents conformational change
Is binding reversible once CO bound to heme? how?
yes; increase the O2 levels or pressure
When does fetal Hb dissipate in children and convert to adult Hb?
around 6 months
What is Myoglobin
Protein that stores and transports oxygen in muscles for metabolic process to convert/product energy
What determines myoglobins ability to bind or release oxygen?
cellular oxygen concentration
Describe the relationship between myoglobin and NO?
The oxygen in myoglobin is used in the conversion of NO
What intercepts free radical oxygen species from causing damage in the body?
Myoglobin
Hemoglobin is ?
Protein that transports oxygen from lungs to tissues in the arterial circulation and transports CO2 from the tissue to lungs in the venous circulation
Hemoglobin has a low affinity for these (4) compounds in the arteries but low in the veins
CO2
Phosphates
hydrogen
chloride
Where does hemoglobin have a low affinity for oxygen?
in the veins
What is the metal that is used to bind to oxygen in myoglobin and hemoglobin
Fe
Which state is the active state for Fe
Fe2+ (ferrous)
What is ferric iron?
Fe3+
Describe the ligands that are attached to the Fe?
Electron rich (nonmetal or polyatomic)
(-) charges or lone pairs
Why are ligands bond to Fe?
to stabalize the charge and to help solubilize
How many coordination sites does Fe have
Six
S orbitals like to form
Sigma bonds (single bonds)
P orbitals like to form
pi bonds (multiple bonds)
1s orbital and 3 p orbitals hybridize to form
sp3 OR (4 single bonds)
sp2 and 2p (3 single and 1 double bond)
sp and 2p (2 single and 2 double bonds)
electron configuration of Fe
(Ar) 4s2 3d6
electron configuration of Fe 2+
(Ar) 4s0 3d6
Fe hybridized orbital
Where do the electrons remain? How many are there?
sp3 d2 3d
in the 3d orbital
6
if all 6 coordination sites are filled on Fe, what is formed?
stable octahedral complex
What are porphyrins?
hetertocyclic macrocycles composed of 4 modified pyrrole subunits connected by carbon bridges
Are porphyrins aromatic?
yes
What are porphyrins attached to heme?
to help with solubility
Macro means
more than 10 atoms
What is the pattern of double bonds on porphyrins?
What is this referred to?
every other carbon has a double bond
conjugation
t/f conjugation makes aromatic compounds more stable
true
t/f only mammals have porphyrin systems
false; mammals, bacteria, plants
Porphyrins are _______ rich
electron
What are the two reactions here?
- substitution
- substitution
Reaction
substitution
Reaction type
Reaction types from right to left
- Elimination
- Elimination and Oxidation
- Redox
The protoporphyrin portion attached to heme is known as
Protoporphryin IX
What enzyme coordinates the Fe molecule to the center of the porphyrin?
Ferrochelatase
Did the N donate electrons to the Fe or the Fe to the N? how many? Describe the position
Each N donates 2 electrons
The N are planar with the Fe
Amino acids have alot of ____ and _____.
Both have alot of _________ and can donate ________
N and O
electrons
electron density
Is heme hydrophobic or hydrophillic?
hydrophobic
unbound inactive protein
apoprotein
On the apoprotein is a ________ residue. What is its function? What does it cause?
- histadine
- bind to the bottom of the heme protein to make it more hydrophillic
- It kind of pulls on the Fe and makes it to where it sits below the plane
Is there another histatine and apoprotein on top of the heme? Does it interact?
Yes
No because its too far away
Where does Oxygen bind on heme?
the top of the structure (6th group)
Differentiate between adult and fetal Hemoglobin. Up until when do babies produce fetal hemoglobin?
2 alpha and 2 beta
2 alpha and 2 gamma
6 months
About how much lower does the Fe sit below the heme group when there is no oxygen bound? (deoxyhemoglobin)
0.4 A
What happens to the structure when Oxygen binds to the Fe?
Fe is more planar with the heme protein
