potassium channels

the order i think science should be academically taught in

ok so im kinda pissed that im in biology when i havent even touched chemistry once in my life because at the base of all life functions biology IS chemistry and when theres stuff like sodium Na+ and Potassium K+ ion channels in neurons i just don’t know a fucking thing dude. like whats the significance of it being sodium and potassium. i dont know their properties because i havent fucking touched chemistry yet and it’s such a Bad academic order

heres what i think it should be:
1) physics. basic physics like newton’s laws and buoyancy and resistance. sound waves, frequency. physics really needs nothing but math and it is like the basis of everything and knowing this basic level is the first step to go because you dont need much background knowledge besides math

2) chemistry. chemistry comes next because molecular physics involves chemistry (like in temperature where lower temperatures slow the vibration of atoms and higher temperatures speed it up, or even the 4 states of matter (yes im including plasma.)) it’s a good continuation after physics because you can really understand the elements and chemical reactions and with knowledge of physics, doing chemical labs would be easier to grasp

3) geology/astronomy. weather, erosion and gemstone formation has elements from both physics and chemistry, space uses a LOT of both (physics in black holes, gravitational relativity laws on the fabric of space, the chemistry of a star etc)

4) biology could be before or after earth/space science but i’d like it better after, since organisms on earth adapt to its changes, and rely on a lot of the earths natural resources and it’s just nice to know about them beforehand. chemistry is an absolute MUST for biology because every fucking thing and every biological process is chemical. muscles contracting literally produce heat and enzymes have catalysts (although the strength is at a much smaller level than a typical chemical reaction). not knowing chemistry will honestly allow all the lessons to fly over your head and im mad that i havent taken it yet because there is so much i’m missing out on. i’ve taken everything BUT chemistry and it’s that one scientific puzzle piece that is missing and i know will change everything. biology doesnt use too much physics but the gravity on earth is important (this also borrows from space/earth science)

anonymous asked:

Can potassium kill ?

yes ?

if injected (in it’s ionic form) it fucks up all those dang potassium channels so important for muscle function and stops your heart. 

And you probs shouldn’t eat solid potassium metal either. that would defs give you indigestion.

Octopuses living in freezing waters can customize proteins called potassium channels that open when nerve cells fire, allowing ions through and helping transmit electrical signals across the nervous system.

As it gets colder, the channels should shut more slowly, preventing nerve cells from firing again and ultimately bringing movement to a halt. Amino acid changes in the potassium channels of polar octopuses keep their nervous systems working at temperatures that would shut temperate-dwelling creatures down.

  1. The membrane stars in its resting state, polarised, with the inside of the cell being -60mV compared to the outside
  2. Sodium ion channels open when triggered by a change in the external environment (such as pressure). As a result some sodium ions diffuse into the cell
  3. The membrane depolarises, it becomes less negative with respect to the outside and reaches the threshold value of -50mV
  4. Voltage-gated sodium ion channels open and many sodium ions flood in. As more sodium ions enter the cell becomes positively charged compared with the outside
  5. The potential difference across the membrane reaches +40mV. The inside of the cell is more positive than the outside
  6. The sodium ion channels close and potassium ion channels open
  7. Potassium ions diffuse out of the cell down a concentration difference, bringing the potential difference back to negative inside compared with the outside. This is called repolarisation.
  8. The potential difference overshoots slightly, making the cell hyperpolarised.
  9. The original potential difference is restored so that the cell returns to its resting state.
  10. C’est fini!

anonymous asked:

How do some candies/mints/coigh drops make your mouth feel cold? Is it like evaporative cooling?

It’s to do with your perception of temperature rather than a change in temperature its self. There’s over 65 different minty chemicals known as Coolacts - they have differences in structure which affects how they interact with temperature sensing nerve receptors in the skin, but the mechanism for all mints is the same.

External image
External image

Above: stereo-isomers of menthol and the concentration in ppm required to cause the cooling effect.

Mints trick the body into thinking the skin in your mouth is much lower than body temperature. Nerves that sense when the temperature is higher or lower than specific thresholds (ranging between 53 and 18 deg C; body temperature is 37 deg C) are controlled by movement of ions like Calcium, Potassium or Sodium through channels in the cell wall. The nerve fires when the ions in the cell receptor reach a certain concentration; This normally happens when the receptor is exposed to something hot or cold, causing the channel to open, but they can be activated by chemicals too.

Menthol activates the process by transporting these ions through the ion channel in the cell membrane, rapidly changing the concentration which causes the cold temperature sensing nerves to fire. Your brain then interprets this as the sensation that the thing you’re eating is very cold. Chillies do the same thing, but they activate different nerve receptors.

Source: Everything you could possibly want to know about menthol is in this PDF.

A touch of biochem in morning rounds

Intern V doing a short presentation on sulfonylurea drugs: sulfonylureas block ATP sensitive potassium channels in pancreatic Beta cells … blahty blah…which then affects the Krebs cycle… blahty blah

Attending Dr. B: Ok, too much detail!

External image

Sassy Wayfaring, now post-24 hour call: I’m sorry Dr. B but I’m going to need a detailed refresher on the Krebs Cycle from V if I’m going to be able to prescribe sulfonylureas properly in the future.  Now V, from what I remember, the Krebs Cycle is circular, correct? 


Atomic-level view provides new insight into translation of touch into nerve signals

Whether stubbing a toe or stroking a cat, the sensation of touch starts out as a mechanical force that is then transformed into an electrical signal conveying pain or other sensations. Tiny channels in neurons act as translators by helping to formulate that signal to the brain. However, scientists know little about the fine details of how these channels work.

(Image caption: Molecular roadblock: The TRAAK channel (purple and orange) dampens sensations by letting potassium ions escape from a neuron. Researchers found the channel uses a never-before-seen system for blocking that flow of ions when it closes: A lipid (yellow) from the neuron membrane (gray) protrudes into the channel.)

New work at Rockefeller University has revealed that one such channel in humans responds to mechanical force using a never-before-seen mechanism. Researchers led by Roderick MacKinnon, John D. Rockefeller Jr. Professor and head of the Laboratory of Molecular Neurobiology and Biophysics examined the TRAAK channel, which is involved in painful touch sensation, at the molecular and atomic levels, finding that it works by reducing the flow of potassium ions that create an electrical signal. The researchers’ findings were released today (December 3) in Nature.

”It is fascinating to wonder how living cells evolved molecules capable of turning small mechanical forces, such as those associated with touch, into electrical signals in the nervous system. That question served as the impetus for this work,” MacKinnon says.

The channels that act as gates in the membranes that envelop neurons, including TRAAK, allow electrically charged atoms, called ions, to move in or out. It’s this movement that is the basis for an electrical signal that carries information. TRAAK channels are one of 78 types of channels in the human body that transport potassium ions; there are other devoted to other ion types. By allowing potassium to trickle out of the neuron, TRAAK normally quiets the neurons, balancing out other channels, which would otherwise create a strong electrical signal for pain.

“TRAAK acts kind of like the brakes on a painful touch sensation, while other channels act as the gas. If you take away the brakes, innocuous touch becomes painful,” says first author Stephen Brohawn, a postdoc in the lab.

Prior work in the lab has shown TRAAK responds to membrane tension – that is stretching caused by a physical force. However, it wasn’t clear how this force caused the channel to open. In fact, scientists had previously only explained the workings of two mechanical-force sensing channels, both of which are found in bacteria.

After purifying the protein that makes up TRAAK, the team crystallized it and determined its structure using X-ray diffraction analysis. Based on the pattern produced by X-rays bounced off the crystallized protein, scientists can infer the structure of the molecule. But because it is difficult to get high-quality crystals from TRAAK, the researchers used antibodies that targeted it to create a sort of scaffold to help guide the formation of crystals.

In the structural images revealed by this work, the researchers found a unique system is responsible for holding off the flow of ions. TRAAK’s central cavity, through which the ions must pass, is flanked by two spiral-shaped chains called helices. When both of these chains are kinked upward, the channel is open so potassium can leave the cell. But when one of these two chains relaxes downward, it uncovers a sort of side door into the center of the neuron membrane.

Neuron membranes, like all cell membranes, consist of two layers of molecules called lipids that have heads facing outward and greasy chains extending inward. When TRAAK’s side door is open, one of those greasy chains, called an acyl chain, pokes into TRAAK’s central cavity, blocking it so no potassium can pass. No known channel uses a mechanism like this.

“This is the first time anyone has seen, at a molecular level, how mechanical force can open a channel in animals, including humans,” Brohawn says. “When the membrane stretches, TRAAK widens, sort of like a dot on a balloon that expands as it is inflated. That wider conformation pulls the helices upward, preventing an acyl chain from blocking the channel, and so leaving it open for potassium ions.”

“The direct involvement of lipid molecules in the gating mechanism begins to explain another well-known property of TRAAK channels – that their gating is sensitive to general anesthetics and other molecules known to enter the lipid membrane where they insert themselves between its acyl chains. By doing so, it appears these anesthetics can shut down pain sensations by locking TRAAK in an open position,” MacKinnon says.