Problem 69 - Chemistry: An Atoms-Focused Approach

Question

Draw the structure of adenosine \(5^{\prime}\) -monophosphate, one of the four ribonucleotides in a strand of RNA.

Step-by-Step Solution

Answer

Answer: The structure of adenosine 5'-monophosphate (AMP) consists of three components: the adenine nitrogenous base, the ribose pentose sugar, and the phosphate group. Adenine is connected to ribose's C1' atom, and the O5' atom of ribose is connected to the central phosphorus atom of the phosphate group.

Step 1: Draw the structure of adenine

Adenine is a purine nitrogenous base. Its structure consists of a pyrimidine ring fused to an imidazole ring. The pyrimidine ring contains two nitrogen atoms at positions 1 and 3, while the imidazole ring has three nitrogen atoms at positions 3, 7, and 9. Here is the structure of adenine: ``` N9 || C8---C7 | || N1-----C5---C6---N || | || C2 C4 C3 | N ```

Step 2: Draw the structure of ribose

Ribose is a 5-carbon pentose sugar, with a hydroxyl group (-OH) attached to each carbon except for the first carbon. The carbons in ribose should be numbered with a prime (') to differentiate them from the carbons in the nitrogenous base. The structure of ribose is as follows: ``` HO--C2'--OH || O3'H---C1'--OH | HO-C3'--OH | C4'--OH | CH2OH ```

Step 3: Draw the structure of a phosphate group

A phosphate group is formed by a central phosphorus (P) atom bound to four oxygen (O) atoms. One of the oxygen atoms has a negative charge and is referred to as a single-bonded terminal oxygen (O−). The three other oxygen atoms are double-bonded to the phosphorus atom. Here is the phosphate group structure: ``` O || P \\ O- ```

Step 4: Combine the structures

To form adenosine 5'-monophosphate (AMP), we need to: 1. Connect the N9 atom of adenine to the C1' atom of ribose. 2. Connect the O5' atom (which is the oxygen atom bonded to the C5' carbon) of ribose to the central phosphorus atom of the phosphate group. Here is the final structure of adenosine 5'-monophosphate (AMP): ``` N9 || C8---C7 | || N1-----C5---C6---N HO--C2'--OH || | || || C2 C4 C3 O5'C1'--OH | | | N HO-C3'--OH C4'--OH | | C5'--O CH2OH || P \\ O- ```

Key Concepts

Purine Nitrogenous Base

A purine nitrogenous base is a type of organic molecule that forms an important part of nucleic acids like DNA and RNA. Nitrogenous bases are crucial because they contribute to the structure of the genetic code.
Purine bases, like adenine, have a double-ring structure:

• The first ring is known as the pyrimidine ring, which has nitrogen atoms at specific positions.
• The second ring is called the imidazole ring, which has additional nitrogen atoms.

The double-ring structure is important because it allows purines to pair with complementary pyrimidine bases through hydrogen bonds.
Adenine, a specific purine base found in adenosine 5'-monophosphate (AMP), can pair with uracil in RNA, forming a vital part of the genetic message.

Ribose Sugar

Ribose sugar is a simple sugar that plays a critical role in the structure of RNA nucleotides. Unlike deoxyribose, found in DNA, ribose has a hydroxyl group (-OH) on its 2' carbon, which makes RNA more reactive and less stable compared to DNA.
Key features of ribose include:

• It is a five-carbon pentose sugar.
• Each carbon (except the first) binds with a hydroxyl group.
• The carbons are numbered with a prime (') to distinguish them from the nitrogenous base carbons.

This hydroxyl group on the 2' position makes ribose crucial for the formation of RNA, enabling the sugar to easily engage in additional reactions.

Phosphate Group

A phosphate group is essential in the formation of nucleotides and carries a negative charge due to its chemical structure. It consists of a phosphorus atom at the center, connected to four oxygen atoms—three of which are bonded through double bonds, while the fourth bears a negative charge.
What sets a phosphate group apart?

• It participates in forming high-energy bonds, like those found in ATP.
• When bonded with the ribose sugar, it helps form the backbone of the RNA strand.
• The negative charge plays a role in the solubility and function of nucleotides within biological systems.

In adenosine 5'-monophosphate, the phosphate connects to the ribose's 5' position, integrating it into the nucleotide's structure.

RNA Nucleotide Structure

An RNA nucleotide consists of a purine or pyrimidine nitrogenous base, a ribose sugar, and a phosphate group. Together, these components create the unique architecture of RNA, making it crucial for a variety of biological processes.
The structure is built by connecting:

• The nitrogenous base binds to the ribose sugar at the 1' carbon.
• The phosphate group connects to the 5' carbon of the ribose.

This combination forms a monomer of RNA, playing a key role in synthesizing proteins and transmitting genetic information.
In the specific case of adenosine 5'-monophosphate, the adenine base is attached to the ribose sugar, and then the ribose is linked to a phosphate group, creating an integral component of RNA strands.