Chem 19 Nov Lecture Flashcards
What are the main functions of hemoglobin?
Transports oxygen from the lungs to tissues
Hemoglobin also picks up carbon dioxide from tissues to return to the lungs.
What is the primary function of myoglobin?
Stores and transports oxygen within muscle tissue
Myoglobin is essential for metabolic pathways like ATP production.
What is the structure of myoglobin?
Monomeric heme protein with one APO protein and one heme complex
Myoglobin’s structure allows it to efficiently store oxygen.
How does hemoglobin differ from myoglobin in terms of structure?
Hemoglobin is a tetramer with four subunits, each with a heme complex
This quaternary structure allows hemoglobin to transport oxygen more effectively.
What is the role of iron in heme proteins?
Binds oxygen in the ferrous state (Fe2+)
Iron forms an octahedral complex with six ligands in heme proteins.
What is the coordination geometry of iron in heme proteins?
Octahedral complex
Six coordination sites are formed by the heme group.
What is the porphyrin system?
A series of heterocyclic rings that form the heme group
Porphyrins are highly conjugated and essential for biological functions.
What are the components required for heme synthesis?
Glycine and succinyl-CoA
These components form protoporphyrin IX, which is then coordinated with iron.
What enzyme coordinates iron into the porphyrin ring during heme synthesis?
Ferrochelatase
This enzyme completes the heme complex.
What happens to the structure of hemoglobin upon oxygen binding?
Iron moves to a more planar position
This change increases hemoglobin’s affinity for additional ligands.
True or False: Myoglobin has a higher affinity for oxygen than hemoglobin.
True
Myoglobin’s higher affinity allows it to effectively store oxygen in muscle tissue.
What is the effect of carbon monoxide on hemoglobin?
Binds to heme complex, better than O2
This can lead to carbon monoxide poisoning due to competitive binding.
Fill in the blank: Myoglobin is found in __________ tissue.
[muscle]
What is the significance of fetal hemoglobin?
Has a higher affinity for oxygen than adult hemoglobin
This is crucial for oxygen transport from mother to fetus.
What biochemical process does myoglobin assist with besides oxygen storage?
Oxidizing nitric oxide into nitrate
This process enhances cellular respiration.
What type of spectroscopy can measure differences between deoxy and oxyhemoglobin?
Absorption spectroscopy
This technique is essential for devices like pulse oximeters.
What happens to myoglobin’s oxygen binding ability as oxygen levels fluctuate?
Releases or binds oxygen based on concentration
Myoglobin adjusts its oxygen storage to meet metabolic demands.
What is the primary function of hemoglobin?
Delivery of oxygen to tissues.
What is the ferrous state of iron?
Iron in the +2 state, which actively binds oxygen.
What type of bonds do ligands form with metals?
Coordination bonds.
What is the role of ligands in coordination with metals?
Ligands stabilize the charge on the metal and help solubilize it.
What types of species can act as ligands?
Simple non-metals (like chlorides) or polyatomic ions.
What is hybridization in the context of bonding?
The mixing of atomic orbitals to create new hybrid orbitals.
What hybridization occurs in carbon to explain its four bonds?
sp3 hybridization.
What types of bonds do s and p orbitals form?
- S orbitals form sigma bonds * P orbitals form pi bonds.
How does iron hybridize when forming coordination complexes?
Iron hybridizes into sp3d2 orbitals.
What is the electron configuration of iron?
Argon, 4s², 3d⁶.
What structure do iron complexes typically form?
Octahedral complex.
What is the coordination number of iron in an octahedral complex?
Six.
True or False: Ligands donate electron density to stabilize the metal’s charge.
True.
What happens to the d electrons during the hybridization of iron?
The d electrons remain in the d orbitals while hybridizing s and p orbitals.
Fill in the blank: The active state of iron that binds oxygen is known as the _______.
ferrous state.
What is the typical coordination geometry of a metal complex with six ligands?
Octahedral.
What keeps the metal-ligand bond from being a full covalent bond?
The interaction is more akin to a coordination bond where electron density is donated.
What is the importance of having empty orbitals in transition metals?
Empty orbitals are required to accept electron density from ligands.
What are the two types of tornado groups mentioned?
Equatorial and axial (E and F) tornado groups
What is the role of iron in the heme complex?
Iron is where oxygen binds
What is ligand E in the heme complex?
Oxygen, which typically sits above the iron
What must happen for iron to effectively bind oxygen?
Other components are needed due to solubility issues
What is a porphyrin?
A series of heterocyclic rings tied together, forming a macrocycle
What defines a macrocyclic structure?
Contains more than 10 atoms
How many pyrrole rings are in a porphyrin?
Four pyrrole rings
What is conjugation in organic compounds?
The overlapping of p orbitals that allows electrons to move freely
True or False: Conjugation is important for biological functions.
True
What enzyme in the eye is related to the concept of conjugation?
Merdopsin
What is the significance of conjugation in vision?
It allows electrons to travel and release a protein essential for vision
What is aromaticity based on?
The concept of conjugation
Where can porphyrin systems be found besides humans?
In plants (chlorophyll) and bacteria
What is the porphyrin in hemoglobin and myoglobin called?
Protoporphyrin IX
What is required to synthesize heme from protoporphyrin?
Iron must coordinate with the porphyrin
What type of enzyme is ferrochelatase?
An enzyme that coordinates iron into the porphyrin
What is an APO protein?
An unbound protein that is inactive
How does a protein become functional in relation to heme?
It coordinates with heme to increase solubility and functionality
What makes heme hydrophobic?
The electron density donated to iron by the coordinated nitrogens
What type of reactions are involved in heme synthesis?
Substitution, elimination, and redox reactions
Fill in the blank: Conjugation allows for _______ movement of electrons.
free
What happens to heme when it coordinates with a protein?
It becomes soluble and functional
How many coordination sites does iron have in the heme complex?
Six coordination sites
What is the role of the histidine residue in the heme complex?
The histidine residue binds to the iron, acting as the fifth ligand
What are the two types of protein structures compared in myoglobin and hemoglobin?
Myoglobin is a monomeric heme protein (tertiary structure), while hemoglobin is a tetramer (quaternary structure)
What is the difference between adult hemoglobin and fetal hemoglobin?
Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin
True or False: Hemoglobin has four subunits.
True
Fill in the blank: Myoglobin has a ______ structure.
tertiary
What happens to the iron position in the heme complex when oxygen binds?
The iron is pulled back up into a more planar position
What is the difference in binding affinity between carbon monoxide and oxygen?
Carbon monoxide is a better binder than oxygen
What is the significance of measuring the absorbance of deoxyhemoglobin versus oxyhemoglobin?
It allows determination of the relative amounts of oxyhemoglobin and deoxyhemoglobin
What type of spectroscopy is used to measure differences in hemoglobin states?
Absorbance spectroscopy
What does the presence of multiple peaks in the absorbance spectrum indicate?
The presence of oxyhemoglobin
Fill in the blank: Hemoglobin contains two ______ subunits and two ______ subunits in its adult form.
alpha; beta
What can affect the ability of heme to bind oxygen?
Environmental factors such as pH and salt concentration
What happens to the affinity of hemoglobin for oxygen after the first oxygen is bound?
The affinity for the remaining heme groups increases
What is the structural characteristic of myoglobin that differentiates it from hemoglobin?
Myoglobin consists of a single heme group
Fill in the blank: The histidine that binds to the iron is known as ______.
histidine eight
What is the consequence of a histidine being too far away from the iron in the heme complex?
It cannot form an interaction with the iron
What happens to fetal hemoglobin production after six months of age?
It begins to diminish
What is the primary function of hemoglobin?
Transport oxygen from the lungs to tissues
True or False: The heme complex can bind cyanide.
True
How does the presence of oxygen change the heme structure?
It alters the heme structure to allow all six binding sites to be occupied
What type of model is used to represent myoglobin in structural biology?
Tertiary structure model
