At pH 7 it's protonated but what does that have to do with basicity?  Lewis base?\nI thought it was a positively charged R group amino acid!
122454
Arginine being an aminoacid has a COOH terminus and an NH3 terminus.\nat Ph 7(also called "isoelectric Ph"),all aminoacids become amphoteric.ie,they have both +ve and -ve charge due to ionization of COOH into COO- and NH3 into NH3+.so,when it is protonated,obviously it's COO- group gets neutralized(since proton is added)and gets converted to COOH and now arginine is left with the +vely charged NH3+ grp.THUS it acts as a base.
406767
This is a tricky question. Perhaps reading: http://www.newton.dep.anl.gov/askasci/chem03/chem03067.htm will help.
389304
a) neutral\nb) basic\nc) basic\nd) acidic\ne) acidic if in solution\nf) basic.\n\npH is a scale ranging from 0-14.  7 is the intermediate and a pH of 7 means that the solution is neutral.  If the pH is below 7, then there are more H+ than OH- in the solution.  Hence the solution becomes acidic.  If the pH however is greater than 7, then there is less H+ than OH- in the solution and the solution is basic.\n\nFor the acid H2SO4, when in solution, it will dissociate to form H+ and SO4-.  The H+ gives the acid its acidic property.  Similarly when Ca(OH)2 is dissolved, it dissociates into Ca2+ and OH-.  The OH- gives the compound its basic property.
126043
The amino and carboxyl protons are very difficult to observe. Using 100% D2O will replace the carboxyl and amino protons with 2H, and you won't see anything. Use a different solvent and you can't be sure you are in the zwitterion form (pH is difficult to control in non-aqueous solutions and you will get different hydrogen bonding)\n\nIf you really want to see those protons your best bet would be to use 90% H2O / 10% D2O with either phosphate buffer or the perdeuterated buffer of your choice (you can get these from Cambridge Isotopes). Make sure the buffer concentration is large compared to your amino acid, and make sure you have adjusted the pH to the zwitterion range. When you aquire the spectrum you will need to use a water suppression sequence. Presat is the easiest, although I much prefer gradient selected 3-9-19. This still may not be enough to see the protons-- if they are exchanging the linewidth may become so broad as to disappear into the baseline.\n\nWhile it's difficult to observe the carboxyl and amino protons (they are *very* sensitive to solvent and pH) you should be able to see changes in the chemical shifts of the remaining protons, particularly the alpha protons.\n\nIf you are really interested, make a sample of your favorite amino acid and take spectra over a range of pH. Plot the chemical shifts of the visible protons as a function of pH and the shape of the curve should allow you to determine the pKa of the amino and carboxyl groups. Here you could get away with just using D2O, which makes the spectroscopy much simpler.\n\nGood luck and have some fun with this!
418761
the amino group of NH2-R, attacks the carbon of -N=C=S group using the lone pair on nitrogen. The amino group acts as nucleophile. \n        -                              +\n-N-C(NH2-R)=S\nThen the N of isothiocyanate will be protonated to give\n(both - and + are on N's)\n-NH-C(NH-R)=S\n\nHere the H of NH2 group is migrated on to the N of the isothiocyanate group\n\nu can go through the following link\n\nAll the best
491345
H      H       H\n         |        |        |\nH --- C --- C --- C --- H\n         |        |        |\n        H      OH    H\n\nsince the functional group is on the 2nd carbon, the answer is (c)
402005
I'm using the Lewis classification of acids and bases, okay? It's pretty much all that works in this case. I'll try to keep it simple.\n\nIt's more acidic than water because water is neutral (it can't accept any more electrons).\n\nIt's more acidic than other alcohols because the carbon chain is the shortest here. The longer the carbon chain is, the more electrons there are, so the chance of another electron being attracted to the molecule is pretty slim. Since there's only one carbon in methanol, the electronegativity of the oxygen atom prevails and attracts electrons to itself.\n\nI hope that was clear enough. Good luck!
357552
1) Bi carbonate buffer system will contain HCO3- ion\n\nwhen a base is added it will liberate the H+ and produce water combining with OH- ion of the base there for reducing the effect of the base\n\nand when an acid is added it will accept the H+ ion and for H2CO3 therefor the effect of the acid will be nullified!!!\n\n2)phosphates are H2O4- or HPO42-\n\nand it will also have the functions as mentioned in the above!!\n\n3)proteins have an NH2 group and well as a COOH group both attached to the same molecule!!!\n\ntherefor when acid is added the NH2 group will neutralize it\n\nand when a base is added COOH group will neutralize it  reducing the alkalinity!\n\nthere for all these chemicals found in the blood and other body tissue will maintain the blood pH level at a constant level acting as natural buffers!!\n\nhope you understood!!!!!\n\ncheers!!
454726
There are two possibilities. Follow this link for a picture of the first possibility. http://img175.imageshack.us/img175/8223/ncssh2.jpg\n\nBasically, all 3 of these elements follow the octet rule (they want 8 electrons in their outermost shell), and as you can see, they all have 8. Now, S is carrying the - sign because it's formal charge is -1. Formal charge is calculated by Formal Charge=# of electrons the element has (S brings in 6) - the # of electrons it "owns" within the bond. Sulfur "owns" 7 in this case (3 lone pairs and one in a shared covalent bond--thus (3*2)+1=7.\n\nTherefore Formal Charge of Sulfur (in this case): is -1 because\n\n6-7=-1\n\nI probably made it sound more confusing than it is. Sorry about that.\n\nBut other than that, you know that Carbon should be the central atom here because it's coming in with only 4 electrons in it's valence shell, so it's more needy than Nitrogen with it's 5 and Sulfur with it's 6. So you stick it in the middle and then pretty much trial and error. \n\nThe other possibility is here.\nhttp://img175.imageshack.us/img175/6659/ncs2wf4.jpg\n\nThis time Nitrogen is carrying the -1 formal charge, because it comes into the bond with 5 electrons in it's valence shell, but it "owns" 6 in this case (2 lone pairs and 2 electrons out of the 4 in the N=C double bond..(2*2)+2=6. So...Formal charge of -1 comes from \n\n-1=5-6\n\nEven though these two molecules look different, they are in fact the same. This is a concept called resonance. \n\nI hope this wasn't too confusing.
364975
An acid and its conjugate base differs by a hydrogen cation (or proton) H+, so:\n\na. H2SO4 and HSO4-\nd. HCl and Cl-\ne. HF and F-\n\nare conjugate acid-base pairs
378623
acids are proton donors ^^ the guy above is dead wrong bases produce hydroxide ions, acids produce hydronium ions, but that depends on the solvent so ur answer is proton donors
261939
Answer is B.\n\nPart A is half true, half false.  The shape *and* function are affected by the sequence.\nParts B and D go together.  The HYDROPHILIC molecules -- usually translated as "water-loving" -- will remain outside while the HYDROPHOBIC molecules (these fats/lipids are "water-fearing") will remain inside.  The shape of the protein is formed in part by this association and disassociation with water.\nPart C is incorrect.  The linking of amino acids is part of the same amine-alkyl-carboxylic acid backbone.  There is no molecule separating each amino acid.\n\nHope this helps!
224573
The weaker the acid, the stronger the conjugate base.  The stronger the acid, the weaker the conjugate base.\n\nBy "strong", we are refering to its ability to dissassociate in water and break into ions.\n\nIt might help if you convert all your pKa values to Ka, or all your Ka values to pKa to make it easier to compare.\nWhat does a high Ka value mean?  What does a low Ka value mean?  How does this compare to your definition of a "Strong" acid/base or a "strong" conjugate acid/conjugate base?
406738
If the molecule has O,N,F,or Cl then most likely it is polar.  Look at the periodic chart and remember that the elements in the upper right are the most electronegative, so they want electrons.  When these elements are in a compound with other atoms such as C and H they will pull electrons closer making a dipole moment.  \n\nThe only real trick is looking at the geometry of the molecule, if there is more than one electronegative atom pulling in opposite directions then the dipole is canceld.  Such as O=C=O which is liniar.\n\nLook at an electronegativity chart you will see what I mean
421776
i think an ion makes up a molecule. i am taking physical science and i went over it a few weeks ago.
407490
sokay....\n\n\nStrong electrolyes are the STRONG ACIDS (limited to 8: sulfuric, nitric, hydrochloric, hydroiodic, hyrdobromic, periodic, chloric, and perchloric), STRONG BASES (limited to the OH-s of  alkali (grp. 1 metals) and heavy grp 2 metals....from Ca and down), ALL IONIC Compounds....\n\nWeak electrolytes are NH3, weak acids, and weak bases\n\nNonelectrolytes are limited to the molecular compounds
510260
1. Bronsted-Lowry and Lewis\n\n2. Water pH=7 (neutral) neither acid nor base\n\n3. pH scale is the scale to determine the acidity or the basicity of a solution.\n\n4. Søren Peter Lauritz Sørensen, a Danish Biochemist.