Now we're back onto the topic of nucleic acids! Hopefully this should be a lot more straightforward than the other topics I've covered so far. After all, I've learned more about nucleic acids previously than about proteins, carbohydrates or lipids.
What are the chemical properties of phosphate, ribose and bases?
What is a purine - give 2 examples?
What is a pyrimidine - give 2 examples?
Phosphate groups have a phosphate atom in the middle covalently bonded to four oxygen groups. One of the oxygen atoms is double-bonded to the phosphate and has a neutral charge. The other three are singly bonded and have negative charges at neutral pH.
Ribose is a pentose sugar (that is, it has five carbons). (I wrote more about sugars in my posts about carbohydrates.) As a sugar, it has many -OH groups, making it water-soluble. These -OH groups are also capable of being hydrolysed to form bonds with other molecules.
Bases come in two categories: purines and pyrimidines. Purines are single-ringed bases roughly based off a benzene ring (i.e. it's kinda like benzene but has some Ns in place of Cs). Pyrimidines have two rings: a six-membered ring roughly based off a benzene ring and a five-membered ring. Two common purines are adenine and guanine (I remember this as being "pure gold"- the symbol for gold is Ag) and three common pyrimidines are cytosine, thymine and uracil. Thymine is only seen in DNA whereas uracil is only seen in RNA.
What are the differences and components of
nucleosides and nucleotides?
What are the essential repeat units of nucleic acids?
A nucleoside is a combination of a sugar and a base. A nucleotide, on the other hand, also includes the phosphate group(s) bound to the nucleoside. Nucleotides are the "essential repeat units" of nucleic acids as nucleic acids are essentially just made up of long chains of nucleotides.
What is a phosphodiester bond?
A phosphodiester bond is the bond between two nucleotides. In a phosphodiester bond, the phosphate group esterified to the 5' carbon of the ribose or deoxyribose sugar is also esterified to the 3' carbon of the preceding nucleotide.
What is the significance of double bonds in bases?
All of the bases have double bonds. These have a resonance character to them (a topic I might cover in a later post), which provide the bases with greater stability. It also makes the bases planar or nearly planar, allowing for easier "stacking" of bases.
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