protein function Flashcards
Every third residue in the protein collagen is ___________.
glycine
In haemoglobin what is the transition from a low-affinity state to high-affinity state triggered by?
oxygen binding
In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as:
hyperbolic
hyperbolic meaning
At low oxygen concentrations, even small changes in oxygen concentration lead to significant changes in the fraction of occupied binding sites. As the concentration of oxygen increases, myoglobin quickly becomes saturated, reaching a point where further increases in oxygen concentration have minimal effect on binding.
Myoglobin and the subunits of haemoglobin have:
very similar tertiary structures, but different primary structures.
The amino acid substitution of valine for glutamate in Haemoglobin S results in aggregation of the protein because of ___________ interactions between molecules.
hydrophobic
The fundamental cause of sickle-cell disease is a change in the structure of:
haemoglobin
What is the Bohr effect?
the regulation of haemoglobin-binding by hydrogen ions and carbon dioxide
What type of binding is indicated by a sigmoidal-shaped binding curve?
cooperative
what’s the difference between haemoglobin and myoglobin?
Haemoglobin exhibits cooperative binding of O2 while myoglobin does not.
Why is the sickle-cell haemoglobin mutation so prevalent in Africa and other tropical regions?
people with the sickle-cell trait are resistant to malaria, increasing the prevalence of the sickle-cell haemoglobin allele.
what is the major fibrous protein present in skin, bone, tendon, cartilage, and teeth.
collagen
what is the fibrous protein and is the primary component of wool and hair.
α-Keratin
what does the globin chain of myoglobin have
an extensive α-helix structure.
what happens to the diameter of the iron ion in myoglobin when oxygen binds
decreases
what state is the iron of the haem group in myoglobin
Fe2+ oxidation state.
what’s the function of myoglobin
oxygen storage in muscle.
what binds the haem group to the globin chain in myoglobin
coordinated interactions
attachment of the heme iron to a histidine residue within the globin chain
myoglobin structure
- single polypeptide chain of 154 amino acids
- eight α-helices assigned the letters A–H chain
- contains a heme prosthetic group, which includes a porphyrin ring iron ion.
- heme-bound Fe cation can exist in the 2+ (reduced) or 3+ (oxidized) state.
why is lower oxygen binding better
function as a better oxygen-transport protein
When oxygen binds to a haem-containing protein what are the two open coordination bonds of Fe2+ are occupied by?
one oxygen molecule and one amino acid atom.
