Following are the types of sales people in organizations: 1  The Diplomat As the name suggests, a diplomat is one who always tries to play a safe game. 2  The Rejection Dreader Such sales professionals fear rejections and failures at work.
A phosphodiester bond occurs when exactly two of the hydroxyl groups in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. Phosphodiester bonds are central to all life on Earth, as they make up the backbone of the strands of nucleic acid. In DNA and RNA, the phosphodiester bond is the linkage between the 3' carbon atom of one sugar molecule and the 5' carbon atom of another, deoxyribose in DNA and ribose in RNA. Strong covalent bonds form between the phosphate group and two 5-carbon ring carbohydrates (pentoses) over two ester bonds. The phosphate groups in the phosphodiester bond are negatively charged. Because the phosphate groups have a pKa near 0, they are negatively charged at pH 7.
The DNA double helix is held together by hydrogen bonds and the nucleotide bases Adenine, Guanine, Cytosine, or Thymine. Check out the source I provided. There's a great diagram of the double helix. Hydrogen bonds hold the two helices together to form a double helix. I also remember somethign called base stacking, which if i recall was hydrogen bonding of the same strand, which promoted the helical nature and enforced rigidity of the structure. Proteins have nothing to do with holding the DNA together, btw; it is due to simple chemistry.