Myoglobin and Hemoglobin Flashcards
majority of cell proteins, soluble in water
globular proteins
Hydrogen bonding acts to _________ the highly polar N-H bonds and C=O of the secondary structure
neutralize
Globular protein structure is stabilized by what three things?
Hydrogen bonds, ionic interactions, and disulfide bonds (least common)
What are some functions of globular proteins?
storage of ions (myoglobin which stores the majority of the body’s iron in ferritin), transport (hemoglobin and oxygen), antibodies, muscle contraction (actin/myosin), enzymes
T/F. Ligands or globular proteins are held irreversibly.
False
If a protein has multiple subunits, and a ligand binds leading to a conformational change in the other subunits, this is _______________.
cooperativity (can be positive or negative)
What quality of proteins make myoglobin and hemoglobin unique?
Unlike other protein side chains which lack an affinity for oxygen, myoglobin and hemoglobin evolved to contain organometallic compounds that can carry oxygen
What makes iron suitable for oxygen carrying?
Easily oxidized but doesn’t form free radicals like other transition metals
What is the purpose of having a globular protein surround the heme?
The protein protects the iron from becoming oxidized early
How do myoglobin and hemoglobin compare in relation to oxygen binding affinity?
Myoglobin binds oxygen with higher affinity so even at low pO2 levels
Although myoglobin and hemoglobin have similar functions, their ______ _______ are completely different.
primary structures
What is the missense mutation that leads to sickle cell anemia?
E6V
Mutation of glutamate to valine at the sixth amino acid position
Protoporphyrin IX containing a bound iron atom is called a _____.
heme
With oxygen binding, does the iron shift closer to the proximal or distal His?
proximal
The _____ His forms a coordination complex with the iron.
proximal
Why are there hydrophobic amino acids (Val and Phe) surround the heme group?
Prevent polar molecules from entering and oxidizing the Fe
- What are the two states hemoglobin can be found in?
2. Which state forms in low pH and why?
- T and R state
- T state forms in low pH. High concentration of hydrogen ions leads to the protonation of the His 1446 at the C term of beta. The His-H forms a salt bridge with an Asp 94 residue. This makes the hemoglobin have a lower oxygen affinity.
Salt bridges and 2,3- BPG stabilize _____ state.
T
Positive cooperativity is recognized by a ______ binding curve when graphed.
sigmoidal
What can you add to patient blood to encourage release of oxygen?
2,3- BPG
How does the pH difference between the lungs and the tissues make oxygen transport more effective?
Tissues have lower pH because actively metabolizing tissues releasing hydrogens and carbon dioxide. Lungs have higher pH. In lungs, the R state is more common allowing Hb to pick up oxygen. Once Hb travels throughout the body, comes into contact with acidic tissues. Protonation of His occurs, forcing Hb into T state and leading to dropping off oxygen.
How does 2,3- BPG stabilize the T state?
binds to positive residues in Hb
CO wants to bond as a triple bond, but the ________ histidine group blocks the linear fashion in the pocket
E7
Heme can also bind this molecule, which stimulates tissues to relax and blood to flow
nitric oxide
