![]() Some of the friends are super greedy so they’ll take even if the jar’s really low. Then you have the opposite type of friends – those that come cookie-less (or at least cookie-deficient). Some acids are multiprotic – this means they come with more than one cookie they can share – often times they’ll give up the first most willingly then have a harder time giving up the other(s) Some common weak acids are sulfurous acid (H2SO3) & phosphoric acid (H3PO4). Other friends would rather keep the cookies for themselves but they also want to be a good friend so they keep an eye on the jar and if it gets too low they’ll pitch in. The 6 strong acids are hydrochloric acid, nitric acid, sulfuric acid, hydrobromic acid, hydroiodic acid, perchloric acid, and chloric acid. These are like strong acids, which deprotonate fully when you dissolve them in water. Some friends really want to give away those cookies, regardless of how full the jar is. Some of the friends come with cookie(s) (have the potential to act as acids). These are like “always neutral” molecules. They don’t have any cookies to give and they don’t have any desire to take any. How full will that cookie jar be at the end of the night? Depends on what type of friends you invite!Ī lot of the friends don’t care whether or not there are cookies in the jar. The pH is a property of the solution that comes from the properties of the things in it, which can include proton-donors ( acids) and proton-takers (bases).īack to our protons as cookies analogy – Say you have a partially-filled cookie jar and you invite over some friends. When there are lots of H⁺ (pH 7) we call it BASIC or ALKALINE. ![]() It’s on a negative log scale, so MORE H⁺ means LOWER pH & vice versa. ![]() PH is a measurement of “how full” the cookie jar is. The ions are spread out throughout the solution, but for the sake of visualization you can think of all the protons as being in a jar, and for the sake of fun analogy-ness you can think of these protons as cookies! So, water is just cookies waiting to be made! Protons can easily find a water to latch onto (forming hydronium ion (H3O+) because the vast vast majority of water is in water form (not ionized). Or they can come from other molecules, including proteins. These protons can come from water itself, which is MOSTLY H2O, but also OH- & H⁺. Hydrogen atoms only have 1 proton & 1 electron & they often leave that electron behind when they go, so all they’re left with is a H⁺, so we often call H⁺ a proton. Just how easily depends on what they’re attached to. H’s are really small & don’t offer much latchbility so they’re relatively easily removed. If you need a review of pH, check out yesterday’s post: īut here’s the gist: Even though they’re attached by covalent bonds, bonds to H are weaker than bonds to other atoms. And we can take advantage of this charge for things like ION EXCHANGE CHROMATOGRAPHY which separates proteins by charge by getting them to bind oppositely-charged resin. How many of these friends a protein has and how greedy or generous they are under their current conditions will determine how charged the protein is under those conditions. Protons are positively-charged, so giving & taking them alters the protein’s charge. If you think about acids and bases as “cookie monsters” donating (in the case of acids) or taking (in the case of bases) proton “cookies” from a “proton cookie jar,” proteins are like a big linked-up group of friends where some of them are cookie monsters. And understanding *why* is a great way to explore WEAK ACIDS & BASES in general. Is your protein proton-greedy? Do you want to find out? Call up a pI to see what they’ll charge! Instead of “private investigator” pI in the protein investigator world stands for the ISOLECTRIC point, and it is the pH at which a protein is charge-neutral (overall).
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