Chemistry (including Biochemistry)/Chemical Reactions

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Expert: - 12/2/2011


Question
What are some examples of precipitate forming in everday life? Is snow or rain an example, I'm not sure.
Thanks

Answer
Hi Erin!

You've hit on three cool concepts with one question, and largely this is to do with how scientists define words. Scientists are very choosy when they use a word, because they prefer to be very specific. So confusion is easy to come by.

So in the science of meteorology and the weather, precipitation is water falling from the sky as rain or snow. You can read more about how this process works here.  (http://en.wikipedia.org/wiki/Precipitation_(meteorology))

In the science of chemistry, precipitation refers to a solid forming in a solution as the result of a chemical reaction . Much of the time in the laboratory this is a very deliberate, controlled process, at specific heating conditions or strong (non-7) pH. The best 'Everyday' example of a precipitation reaction I could find is what happens when you boil my tap water here in Texas. We have very 'hard' water; i.e. there are a lot of dissolved calcium ions in the water. When we boil it, the calcium carbonate gives up its carbonate ion and becomes solid Ca2.  (http://en.wikipedia.org/wiki/Precipitate)

CaCO3 + CO2 + H2O ⇋ Ca2+ + 2HCO3-

This results in a gross coffee pot with either white powder on the surface of the coffee, or calcium crystals forming on the sides of the container. (To remove the precipitates easily, use dilute vinegar.) Most homeowners in San Antonio, Texas have to drain their hot water heaters every six months to keep too much calcium from forming on the sides of the tank. (http://en.wikipedia.org/wiki/Hard_water)

What we most often encounter in everyday life related to chemistry solutions and crystals forming are questions of solubility. Solubility is a property of a compound that describes how much of that compound (a solute) dissolves in another compound (the solvent) at a particular temperature and pressure.  For example, table sugar has higher solubility in water than table salt. Try the experiment of having two cups of water at the same temperature. Label one sugar and the other salt. Add one teaspoon of solute to each, and stir until you no longer see crystals. You'll notice that you can add many more spoonfuls of sugar than salt before the crystals no longer dissolve in the bottom of the cup. When a solute can no longer be dissolved, we say that the solution is saturated.

If you change the conditions of the solution - most typically by chilling it, though changes in pH can do this too - a solution can no longer support as much solute. Typically then crystals of solid will form in the the bottom of the solution container. Oftentimes crystal formation is accelerated when there is a flaw or seed in the bottom of the container. This solid formation may not be the result of a chemical reaction, so it's not technically precipitation, even though we get similar pretty crystals out of solution. (http://en.wikipedia.org/wiki/Solubility)

Two handy examples of manipulating solubility are detergents and drug development. A soap typically is used to increase the solubility of oil or grease in solution so you can get those burnt bits off your dishes. How well an experimental drug dissolves in water has great impact on whether it is developed for sale... because if you can't dissolve it at a strong enough dose, it's useless in your body.

Good luck! :)

Chemistry (including Biochemistry)

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Trista Robichaud, PhD

Expertise

No homework questions, especially ones copied and pasted from textbooks. I will answer questions about principles or give hints, but I do not do other's homework. I'm comfortable answering basic biochemistry, chemistry, and biology questions up to and including an undergraduate level of understanding. This includes molecular biology, protein purification, and genetics. My training/inclination is primarily in structural biology, or how the shapes of things affect their function. Other interests include protein design, protein engineering, enzyme kinetics, and metabolic diseases such as cancer, atherosclerosis, and diabetes. My chemistry weaknesses are that I do not know organic or inorganic synthesis well, nor am I familiar with advanced inorganic reactions. I will attempt quantum mechanics and thermodynamics questions, but primarily as they relate to biological systems. Furthermore, I cannot tell you if a skin photograph is cancerous, or otherwise diagnose any disease. I can tell you how we currently understand the basic science behind a disease state, but I cannot recommend treatment in any way. Please direct such questions to your medical professional.

Experience

I hold a PhD in Biomedical Science from the University of Massachusetts Medical School in Worcester. I specialize in Biochemistry, with a focus on protein chemistry. My thesis work involved the structure and functions of the human glucose transporter 1. (hGLUT1) Currently I am a postdoc working in peptide (mini-protein) design and enzymology at the University of Texas Health Science Center in San Antonio, Texas. I am in Bjorn Steffensen's lab (PhD, DDS), studying gelatinase A and oral carcinoma.

Organizations
2001 American Association for the Advancement of Science
2007 American Chemical Society
2007 Protein Society
2011 UTHSCSA Women’s Faculty Association


Publications
Levine KB, Robichaud TK, Hamill S, Sultzman LA, Carruthers A. Properties of the human erythrocyte glucose transport protein are determined by cellular context. Biochemistry 44(15):5606-16, 2005. (PMID 15823019)
Robichaud TK, Appleyard AN, Herbert RB, Henderson PJ, Carruthers A “Determinants of ligand binding affinity and cooperativity at the GLUT1 endofacial site” Biochemistry 50(15):3137-48, 2011. (PMID 21384913)
Xu X, Mikhailova M, Chen Z, Pal S, Robichaud TK, Lafer EM, Baber S, Steffensen B. “Peptide from the C-terminal domain of tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) inhibits membrane activation of matrix metalloproteinase-2 (MMP-2)” Matrix Biol. 2011 Sep;30(7-8):404-12. (PMID: 21839835)
Robichaud TK, Steffensen B, Fields GB. Exosite interactions impact matrix metalloproteinase collagen specificities. J Biol Chem. 2011 Oct 28;286(43):37535-42 (PMID: 21896477)

Poster Abstracts:
Robichaud TK, Carruthers. A "Mutagenesis of the Human type 1 glucose transporter exit site: A functional study." ACS 234th Meeting, Boston MA. Division of Biological Chemistry, 2007
Robichaud TK, Bhowmick M, Tokmina-Roszyk D, Fields GB “Synthesis and Analysis of MT1-MMP Peptide Inhibitors” Biological Chemistry Division of the Protein Society Meeting, San Diego CA 2010
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Catalytic Domain Exosites Contribute to Determining Matrix Metalloproteinase Triple Helical Collagen Specificities” Dental Science Symposium. UTHSCSA 2011
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Exosite Interactions Determine Matrix Metalloproteinase Specificities” Gordon Research Conference on Matrix Metalloproteinase Biology, Bristol RI 2011


Education/Credentials
Oakland University, Auburn Hills MI BS, Biochemistry 1998
University of Massachusetts Medical School, Worcester MA PhD, Biochemistry & Molecular Pharmacology 2001-2008
University of Texas Health Science Center, San Antonio TX Postdoc, Biochemistry 2009-Present


Awards and Honors
1998 Honors College Graduate, Oakland University
2009 Institutional National Research Service Award, Pathobiology of Occlusive Vascular Disease T32 HL07446
2011 1st Place, Best Postdoctoral Poster, Dental Science Symposium, UTHSCSA, April 2011


Past/Present Clients
Invited Seminars:
Robichaud TK, Fields GB. “Synthesis and Analysis of MTI-MMP Triple Helical Peptide Inhibitors” Pathology Research Conference, University of Texas Health Science Center San Antonio Pathology Department (June 18th, 2010)
Robichaud TK & Hill, B “How To Give A Great Scientific Talk” Invited Lecture, Pathobiology of Occlusive Vascular Disease Seminars, UTHSCSA (Nov 11th 2010), Cardiology Seminar Series, Texas Research Park (Feb 21st, 2011)
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Exosite Interactions Determine Matrix Metalloproteinase Specificities” Gordon-Keenan Research Seminar “Everything You Wanted to Know About Matrix Metalloproteinases But Were Afraid to Ask” Bristol, RI (Aug 6th, 2011)

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