Understanding Nucleotides - Biology

There are two classes of bases in DNA and RNA: purines and pyrimidines. The difference between these classes is the structure of the base. Purines have two rings in their structure, while pyrimidines have only one. Purines will pair with pyrimidines.

The purines are adenine and guanine, and the pyrimidines are thymine, cytosine, and uracil. You can remember that the bases that contain a "y" are pyrimidines (thymine and cytosine).

There are four bases in DNA: adenine, thymine, guanine, and cytosine. Adenine always pairs with thymine, so the number of adenine residues always equals the number of thymine residues. Guanine always pairs with cytosine, which means they are always present in equal amounts as well. If one strand contains three cytosine bases and five thymine bases, then the opposite strand must contain three guanine bases and five adenine bases.

The trick to this problem is remembering that the sum of all four bases by percentage must be 100%.

We know that 30% of the bases are cytosine. Since cytosine pairs with guanine, there is also 30% guanine.

That leave us with 40% of the bases being thymine and adenine.

Since adenine and thymine will be equal, each will represent 20% of the DNA composition.

There are four nitrogenous bases in DNA: adenine, guanine, cytosine, and thymine. A nucleotide is composed of one of these bases bound to a deoxyribose sugar and a phosphate group. Polymers of nucleotides form strands of DNA, which adhere to one another by hydrogen bonding between the bases.

Each strand of DNA is unique and may contain any ratio of the nitrogenous bases, but strands of DNA will always be complementary to one another. The structure of the bases requires that adenine bind to thymine and cytosine bind to guanine to maintain the structural integrity of the DNA molecule. RNA does not contain thymine, and instead uses uracil.

A nucleotide is the building block of nucleic acids (a type of macromolecule). It is made up of three main parts: phosphate group(s), pentose sugar, and a nitrogenous base (adenine, thymine, guanine, cytosine, or uracil). The amount of phosphate groups, the type of pentose sugar, and the type of nitrogenous base varies based on the nucleotide. For example, RNA contains ribose sugar whereas DNA contains deoxyribose sugar.

Arginine is a type of amino acid. Recall that amino acids are found in polypeptide chains that make up proteins (another type of macromolecule); therefore, arginine is found in proteins rather than nucleic acids.

The main difference between a nucleotide and a nucleoside is the presence or absence of phosphate group(s). A nucleotide contains one or more phosphate groups, a pentose sugar, and a nitrogenous base. A nucleoside, on the other hand, contains only a pentose sugar and a nitrogenous base; therefore, a nucleotide always contains more phosphate groups than a nucleoside.

NADH is a coenzyme that functions to carry electrons during metabolism. It is made up of adenine (a nitrogenous base), nicotinamide (a modified nitrogenous base), two phosphate groups, and two pentose sugars. Since it contains nitrogenous bases, phosphate groups, and pentose sugars it is a type of nucleotide.

cAMP, or cyclic adenosine monophosphate, is a second messenger molecule that facilitates signal transduction inside the cell. It is made up of adenine, a phosphate group, and a pentose sugar (ribose); therefore, it is also a type of nucleotide.

Acetylcholine is a type of neurotransmitter that plays a key role in signal transmission between neurons. Acetylcholine does not contain the three essential groups for a nucleotide; therefore, acetylcholine is not a nucleotide.

To answer this question you need to know the difference between a nucleotide and a DNA backbone. A nucleotide is the monomer of nucleic acids and is made up of phosphate group(s), a pentose sugar, and a nitrogenous base. A DNA molecule is a type of nucleic acid and is made up of several nucleotides.

DNA has two different structural divisions: the DNA backbone and the nitrogenous bases. The DNA backbone consists of the phosphate groups and pentose sugars, whereas the bases consist of only the nitrogenous bases. This means that the DNA backbone does not contain any nitrogenous bases; therefore, nucleotide contains more nitrogenous bases than the DNA backbone.

Since the full DNA molecules has several nucleotides, the DNA backbone contains multiple phosphate groups and pentose sugars; therefore, the DNA backbone always contains more phosphate groups and pentose sugars than a nucleotide molecule.

The four nitrogenous bases found in DNA are: thymine, cytosine, adenine, and guanine. Uracil is a nitrogenous base that takes the place of thymine in RNA. Note that uracil only base pairs with adenine, forming two hydrogen bonds.

Guanine always binds to cytosine in DNA and RNA. Thymine always bonds to adenine in DNA. Uracil replaces thymine in RNA, and uracil bonds to adenine.

Adenine and guanine are the purines that bond to the pyrimidines. Cytosine and thymine are the pyrimidines. The purines consist of two carbon rings, and the pyrimidines consist of one carbon ring.

DNA contains four nitrogen bases: adenine, thiamine, guanine and cytosine. Adenine and thymine pair, and guanine and cytosine pair. Adenine and thiamine form two hydrogen bonds, and guanine and cytosine form three hydrogen bonds. In RNA, uracil takes thiamine's and binds with adenine.

Bonds between A-T (adenine and thymine) are held together by 2 hydrogen bonds, while G-C (guanine and cytosine) are held together by 3 hydrogen bonds. Therefore, A-T bonds are weaker, and will separate first when exposed to heat stress. DNA does not contain uracil.

DNA is the hereditary material found in virtually all organisms; however, some viruses use RNA. DNA consists of several components. It has a phosphate-sugar (deoxyribose) backbone and is composed of two strands made from purine-pyrimidine hydrogen bonds in a double helix confirmation. The purines associated with DNA include adenine and guanine and the pyrimidines include cytosine and thymine. Adenine bonds with thymine and cytosine bonds with guanine.

Each base pair (adenine - thymine and cytosine - guanine) are held together with hydrogen bonds. These bases form the 'ladder steps' part of a DNA molecule. Hydrogen bonds are much weaker than the covalent bonds that hold all the other parts of the molecule together, so when DNA needs to be replicated, its easy for an enzyme to 'unzip' the DNA molecule and expose those bases for replication.

Guanine - cytosine and adenine - thymine form "complimentary base pairs." Guanine can only form hydrogen bonds with cytosine and adenine can only form hydrogen bonds with thymine (and vice versa). With that in mind, any base pairing other than those two can be excluded from this answer. Furthermore, cytosine and guanine form a total of three hydrogen bonds together while adenine and thymine only form two. The extra bond between guanine and cytosine makes the pairing about 50% stronger.

Purines are one of the two families of nitrogenous bases, the other being pyrimidines. Purines consist of a double ring structure, while pyrimidines contain only a single ring making them smaller than purines. Adenine and guanine are purines, while their complimentary base pairs (thymine and cytosine) are pyrimidines. If two purines were to pair together, there would be an unstable bulge in the DNA due to a purine-purine pair being slightly larger than purine-pyrimidine complimentary base pairs. If two pyrimidines were to create a pair, there would be a slight pinch in the DNA for the same reasons. The backbone of DNA consists of deoxyribose and phosphate, not the nitrogenous bases.

For DNA: A nucleotide contains a nitrogenous base (adenine, thymine, cytosine, or guanine), a pentose (five-carbon) sugar (in this case, deoxyribose), and a phosphate group. A nucleo_side_ is simply a nitrogenous base and a sugar. You could also say that a nucleo_tide_ is a nucleo_side_ with an attached phosphate group.

We will assume this is the "perfect" DNA molecule and there are no anomalies or mutations.

That being said, we know that the amount of adenine (A) is equal to the amount of thymine (T), and the amount of guanine (G) is equal to the amount of cytosine (C) due to the complementarity of DNA; A=T and C=G. We are dealing with percentages, so the total amount of each 4 nucleotides will equal 100.

The amount for adenine is given; A = 23%. Because A=T, the amount of thymine must be 23% as well. Add these two values together to get the total amount of A and T : 23 + 23= 46.

Again, since we are dealing with percents, we subtract the total amount of A and T from 100: 100 - 46 = 54. Now we know the total amount of C and G is 54. Since the amount of C=G, we can divide 54 by 2 = 27.

The amount of Cytosine in the molecule is 27%, and the amount of Guanine is 27%.

There are two types of nucleotides in DNA, pyrimidines and purines. The purines are Adenine and Guanine. Pyrimidines are Thymine and Cytosine. In RNA, Thymine is replaced with Uracil. Purines pair with pyrimidines in a specific order, therefore Adenine pairs with Thymine, and Cytosine pairs with Guanine. Adenine pairs with Uracil only in RNA, not DNA.