As today was the first time we had seen the sun in a few days, we decided to have this meeting outside. On our way we discussed aspects of the biophysics course, such as the prerequisites, the textbook, etc. We came back to this topic briefly a number of times during the meeting, but I didn’t think it was necessary to record these digressions.
The main topic of chapter 11, and thus our discussions, was ion channels. Much of the maths derived for topics that we have studied in previous chapters, which deal with bulk solutions and continuums, breaks down when applied to ion channel physics. Before the structures of the ion channels were known, many models were suggested, but were not able to reflect reality. This is because ion channels often allow transmission of single molecules at a time, and statistical assumptions like those made for the Boltzmann distribution break down at this level.
We briefly discussed voltage gated ion channels, and how a potential can be stored in a cell membrane. This discussion moved on to how electric eels generate charge, and how the charge hurts/kills prey. They have thousands of cells in series called electroplaques which generate and store potential, like a capacitor.
The sodium anomaly was discussed, which lead to the concept of the anion gap. This is where a coma patient’s electrolyte count is measured, to indicate how the coma was induced. Brain injury patients are at risk of low electrolyte concentrations, as brain swelling increases the amount of water in the brain.
The unusual features of the chlorine channels were mentioned. These channels come in pairs, and have inward curving channel walls, and have a glutamate residue gating the channel, which only allows chlorine ions to pass through in one direction. KcsA channels were also brought up and the way that the protein mimics the hydration sphere of the potassium ion, to allow only potassium ions to pass through, rather than sodium ions, which as smaller. The concept of the potential mean force on an ion as it passes thorough a channel was introduced. Ligand gated ion channels were also mentioned.
The nature of torque was discussed, and how it relates to the ATP synthase motor experiment in section 11.3.4. The mitochondrial role in glycolysis was touched upon, as well as the molecule pyruvate, but most of us were happy with this area.
How some toxins work as ion channel blockers, and how lethal they can be was also discussed. We then moved into Megan’s lab to view some videos illustrating how detergents can affect crystallised protein structures and how ions travel through ion channels.