Structure and Function of Protein Flashcards
What do red blood cells do?
- Transfer Oxygen from lungs to tissue
- Transfer Carbon Dioxide from tissue to lungs
Haemoglobin and Myoglobin were the first proteins to:
- Be crystallised - 1849
- Have mass accurately measured
- Be studied by ultracentrifugation
- Be associated with a physiological condition
- Show that a point mutation can relate to disease
- Have X-ray structures determined (myoglobin in 1959 -Perutz; Haemoglobin in 1968)
- Theories of cooperativity and control explain haemoglobin function
Where can the the Backbone structure of Myoglobin be found ?
Found in skeletal and heart muscle of vertebrates
What does Myoglobin facilitate ?
Myoglobin facilitates rapidly respiring muscle tissue
The rate of O2 diffusion from capillaries to tissue is slow because ?
Of the solubility of oxygen
What does Myoglobin increase and facilitates what ?
Myoglobin increases the solubility of oxygen. Myoglobin facilitates oxygen diffusion
Explain the Haem complex in myoglobin ?
TWO histidine residues anchor the haem (distal and proximal)
What do Globin genes encode ?
Haemoglobin
In adults, haemoglobin =
Iron containing haem molecules in each of 4 globin proteins: 2 α globins and 2 β globins
During development, different globin genes are expressed which alter ?
The oxygen affinity of embryonic and fetal haemoglobin
Where is Haem and Globin synthesis ?
- Haem in mitochondria
- Globin in polyribosomes
What does the mature red blood cell not contain?
Mitochondria
Different globins combine with haem to form ?
Different haemoglobins
Explain the Eight functional globin chains, arranged in two clusters :
- β- cluster on the short arm of chromosome 11
2. α - cluster on the short arm of chromosome 16
In order to bind to Oxygen the iron must be ?
The iron must be in the Fe(II) for or reduced
What is Fe(III) ?
Methemoglobin - can not bind oxygen
Protoporphyrin binds O2 to?
6th ligand of Fe(II) out of the plane of the haem
What is the fifth ligand ?
The fifth ligand is a Histidine, F8 on the side across the haem plane.
His F8 binds to ?
The proximal side
What binds to the distal side?
Oxygen
When haemoglobin is deoxygenated, the heme group adopts a ?
Domed configuration
When haemoglobin is oxygenated, the haem group adopts a ?
Planar configuration
The conformational change in the haem group causes?
The protein to change its conformation, as well
What do butchers use to make the meat look fresh?
Ascorbic acid to reduce methemoglobin. There is an enzyme methemoglobin reductase that converts methemoglobin to regular haemoglobin
What percentage of haemoglobin is methemoglobin ?
1-2%
What happens if there is more 10% of methemoglobin?
It causes symptoms (headache to seizures)
What happens if there is more than 70% ?
Death
Increased Methemoglobin can be caused by ?
Drugs (eg. Benzocaine) and environmental agents (nitrites, arsine etc)
Hb subunits independently compete for O2 for ?
The first oxygen molecule to bind
When the YO2 is close to 1 i.e. 3 subunits are occupied by O2 ?
O2 binding to the last site is independent of the other sites
However by extrapolating slopes: the 4th O2 binds to haemoglobin 100 fold greater affinity than ?
The first Oxygen
When one molecule binds, what happens ? and when one is released, what happens ?
When one molecule binds, the rest bind and when one is released, the rest are released
D-2,3-Bisphosphoglycerate (BPG) binds to ?
Haemoglobin
What is meant by “stripped” haemoglobin ?
It means BPG has been removed from the solution. This is done by adding concentrated NaCl
Explain a right shift (easy oxygen delivery) in Hb-oxygen dissociation curve ?
- High BPG
- High H+
- High CO2
- HbS
Explain a left shift (give up oxygen less readily) in Hb-oxygen dissociation curve ?
- Low BPG
- HbF
