Protein function Flashcards
Why are O2 carrier proteins nessercary?
Oxygen dissolves poorly in blood
What are Haemoglobin and Myoglobing?
Oxygen transporting proteins
What is a haem group?
Fe, surrounded by four N’s and two O atoms with a porphyrin ring attached
What is the Quaternary structure of haemoglobin?
4 polypeptide chains, 2 A 2B with 4 haem groups.Each chain similar in structure to Myoglobin.
What type of binding curve will you see with haemoglobin?
Sigmoidal
What is cooperativity in haemoglobin?
binding of one oxygen molecule promotes binding of subsequent molecules
Why is cooperativity an advantage in Haemoglobin
Carrier protein more sensitive to small changes in O2.
What is structure of myoglobin?
Compact, 75% a helix. Oxygen binding causes small change in conformation.One haem group.
What type of binding curve does myoglobin give?
Hyperbolic
Describe the major structural differences between oxygenated and deoxygenated haemoglobin
Exists in T state when at lower affinity, R state when at higher affinity.Rotates from T to R, making haem more available. Oxygen binding stabilises R state.
What effect does BPG have on haemoglobin?
decreases affinity to O2. 1 per haemoglobin. Increases at high altitudes.
What effect does CO2 and H+ have on haemoglobin?
Binds to it, lowering affinity for O2. Called bohr shift.
What effect does CO have on haemoglobin?
Binds 250x more readily that O2. O2 can no longer bind.
What amino acids mutate in Sickle Cell anaemia?
Glutamate to Valine in B globin
Why is the amino acid change bad?
Val hydrophobic, bonds with vals in other haemoglobin creating “sickle” shaped red blood cell
What are the ill effects of the sickle shaped blood cells?
More prone to lysesMore rigid
When do sickle cell suffer’s blood cells join?
When they are not carrying oxygen
What is alpha thalassemia?
Decreased or absent a chain in haemoglobinDifferent levels of severityb chains form. Stable tetramers with high affinity for O2.Onset before birth.
What is beta thalssaemia?
decreased or absent B chain productionalpha chains unable to form stable tetramerssymptoms appear after birth
why is it important that HBf has a higher binding affinity with O2 than HbA (mothers)
allows transfer of O2 to foetal blood supply from mother
