BIOL 115 Flashcards
What is human serum albumin?
It is the major protein present in blood plasma (40g/L) (total protein content of blood is 70 g/L)
What is the structure of serum albumin?
Mr of 66500 and pI of 5.67
Entirely alpha-helical in content
a single polypeptide chain with 585 amino acids and 17 intra-chain disulfide bonds
What is unusual about the animo acid sequence of albumin?
it has an unusually high percentage of Cys (amino acid responsible for disulfide bonds)
What is alumins role in drug transport?
A number of hormones and drugs compete for a spot to bind on albumen which is important as small molecules not transported on proteins may be excreted in urine.
What is albumins role in lipid transport?
Albumin contains multiple binding sites for long-chain fatty acids or small heterocyclic or aromatic carboxylic acids (as inside the molecule is hydrophobic)
What is evans blue?
A molecule with high affinity for serum albumin which is easily detected via emission sectroscopy.
It was also used to determine how much blood was in a person by seeing how diluted it became when a known ammount was added.
It is however a carcinogen and no longer used.
What is the EF hand?
It is a protein motif made of 29 residues and binds to calcium.
It has a helix-loop-helix configuration
What is calmodulin?
It is a calcium modulated protein made up of 4 EF hands which after binding to calcium is able to bind to and activated kinases.
When calcium is bound it opens hydrophobic patches allowing it to bind to signalling molecules
It has a vaguely dumbell shape with 2 EF hands on each side
It is very well conserved among vertebrates with minimal changes in the genetic code over a long time.
What enzymes does calmodulin target?
Phosphorylase kinase, myosin light chain kinase and Ca2+ ATP-ase are some examples
It targets enzymes with a mixture of basic and hydrophobic amino acids (which can adopt an aplha helix)
What happens to a red blood cell when dissolved in urea?
It dissolves into two Alpha-Beta dimers
What is the difference between the binding curves for Haemoglobin and Myoglobin?
Myoglobin has a curve wich gets higher % saturation at a lower partial pressure
Haemoglobin has a sigmoidal shape which allows for it to be more cooperative (has a lower affinity for oxygen allowing for easier oxygen delivery)
How do haemoglobin and myoglobin interact?
Haemoglobin does a good job of getting oxygen around the capillaries but myoglobin is more responsible for facilitating diffusion of oxygen to areas of demand.
What are the regulators of haemoglobin and what do they do?
Regulators are H+, CO2 and 2,3-BPG and in significant quantities makes haemoglobin bind less tightly so they are able to release oxygen effectively.
What is the Bohr effect?
The chage of the oxygenn dissociation curve in response increased acidity due to oxygen debt
How would a loack of BPG affect oxygen binding?
It would unload very little oxygen in capillaries.
How does temperature effect haemoglovin affinity?
Higher affinity at lower temps.
How does the binding of an oxygen to haemoglobin affect the distance between iron atoms in beta chains?
The distance decreases (3.99 to 3.34nm)
This also pulls His F8 along with it which in turn pulls along more of the haemoglobin molecule resulting in a change in shape of the molecule
This makes it so that 2,3 BPG can no longer bind as there is not enough space in the central space.
What is responsible for stabilising the T state in haemoglobin?
8 electrostatic bonds involving C-terminal amino acids of each subunit (especially penultimate Tyr)
How does the movement of iron in haemoglobin result in the molecule changing shape?
As it drags His F8 the EF and FG corner follow resulting in the breaking of the 8 electrostatic bonds and the one alpha-beta subunit rotates 15 degrees
This change in shape is what results in the R state where 2,3-BPG can’t bond
What is retinol and why is it important?
One of the active forms of Vitamin A and is used as:
An anti-oxidant
A steroid hormone
A component of night vision
