21 Questions
What is the primary function of myoglobin?
Storing oxygen for limited release
What is the main structural difference between myoglobin and haemoglobin?
Myoglobin is a tetramer while haemoglobin is monomeric
What is the effect of low oxygen concentration on haemoglobin's affinity for oxygen?
Decreases haemoglobin's affinity for oxygen
Why is myoglobin not an effective transporter of oxygen?
It binds to oxygen too tightly
What is the relationship between haemoglobin's affinity for oxygen and higher oxygen concentration?
Haemoglobin becomes saturated at high concentration of oxygen
What is the main reason proline is important for the folding of collagen?
It causes a kink in the chain, allowing it to fold up into its final shape.
What type of membrane protein can have hydrophilic residues in the translocation pore?
Integral membrane protein
What is the primary function of detergents in solubilizing membrane proteins?
To form micelles around the hydrophilic regions of the protein.
What type of algorithm can predict the presence of transmembrane alpha helices?
Hydropathy plots
What characteristic defines most transmembrane proteins?
They are anchored in the membrane by electrostatic interactions.
What is the main cause of sickle cell anaemia?
Substitution of Glu6 with Valine
What effect does the binding of carbon monoxide (CO) have on haemoglobin's affinity for oxygen?
It displaces oxygen, leading to hypoxia
What is the composition of foetal haemoglobin that contributes to its higher oxygen affinity?
Substitution of His143 with a serine residue
What is the structural feature of alpha-keratin that contributes to its stability?
Formation from two left-handed coiled coils of alpha helices
What causes the S-shaped (sigmoid) graph in the oxygen dissociation curve of haemoglobin?
Cooperativity between subunits
Proline is the only amino acid where the side chain bends around and covalently attaches to the amino group. This causes a kink in the chain, allowing it to fold up into its final shape.
True
Glycine has the largest side chain among all amino acids, allowing for tight packing in the center of the coiled coil.
False
Peripheral membrane proteins are only bound by hydrophobic interactions to lipid head groups.
False
Most transmembrane proteins are beta-barrels rather than alpha helical.
False
Hydropathy plots can predict the presence of transmembrane alpha helices using algorithms that detect hydrophilic amino acids.
False
what is the deoxygenated and oxygenated state called?
T & R
Study Notes
- Haemoglobin has an S-shaped (sigmoid) graph due to cooperativity between subunits.
- Oxygen binding induces a conformational change and forms oxyhaemoglobin.
- Haemoglobin exists in two states: T (deoxygenated) and R (oxygenated).
- Cooperativity occurs in multimeric assemblies and affects ligand binding affinities.
- Haemoglobin's affinity for oxygen increases when oxygen binds to one subunit, affecting neighbouring subunits.
- Haemoglobin's purified form has a lower oxygen affinity due to the removal of 2,3-bisphosphoglycerate (BPG), an allosteric effector.
- Foetal haemoglobin has a higher oxygen affinity due to a different composition and a substitution of His143 with a serine residue.
- Sickle cell anaemia is caused by a single nucleotide mutation that results in the substitution of Glu6 with Valine, exposing hydrophobic patches that lead to sickling of RBCs.
- The Bohr effect occurs due to haemoglobin's response to respiring tissues producing CO2 and H+, allowing for better oxygen release.
- Haemoglobin's affinity for oxygen is decreased by the binding of BPG, lower pH, and increased CO2 levels.
- Carbon monoxide (CO) has a higher affinity than oxygen and can displace oxygen, leading to hypoxia.
- Fibrous proteins, such as alpha-keratin and silk fibroin, provide structural support and are insoluble in water.
- Alpha-keratin is formed from two left-handed coiled coils of alpha helices, stabilised by London forces and ionic forces.
- Silk fibroin is predominantly made of beta-sheets, stabilised by hydrogen bonds and London forces, and contains a lot of alanine and glycine residues.
- Collagen is a unique protein with a left-handed helix structure and a right-handed coiled coil, containing a lot of prolines and hydroxylated prolines and lysines.
Test your knowledge about the structure of myoglobin and hemoglobin, their similarities and differences, and the relationship between oxygen concentration and binding. Learn about their helical regions, subunit compositions, and the arrangement of their haem groups.
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