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Nucleic Acids (DNA and RNA) are the key biomolecules that enable cells to transfer genetic information from one generation to another. They also direct protein synthesis and determine an organism’s inherited traits.
DNA is a long polymer of ribose sugar and the nitrogenous bases adenine, guanine, cytosine, and thymine. RNA is also a long polymer of ribose and the nitrogenous bases uracil and cytosine.
DNA
DNA is a molecule that carries genetic information inside the cells of your body. The genes in your DNA tell your cells how to make proteins, the complex molecules that help your body function.
A DNA molecule is made of a long chain of monomer nucleotides, each with a deoxyribose sugar and a phosphate group attached to it. There are four different types of nitrogen bases: two purines (adenine and guanine) and two pyrimidines (cytosine and thymine).
These nitrogen bases combine in specific sequences to form the instructions that make up the genes in your DNA. These genes tell your cell how to make proteins, which are important for growing and surviving.
RNA
RNA is an essential part of every cell, where it serves as both a storage device and catalyzing agent. It stores genetic information and can also shape-shift to create proteins.
It is made from ribose nucleotides (nitrogenous bases appended to a ribose sugar) attached to phosphodiester bonds and forms strands of different lengths. Bases on one strand link up to complementary ones on the opposite strand.
In RNA, this is done by linking up pairs of nitrogenous bases: C to G in RNA and A to T in DNA. Unlike DNA, which has the iconic double-helix structure of two strands that spiral around each other like a twisted ladder, RNA has the flat and flexible form of a single molecule.
RNA is used in a wide range of biochemical processes including protein synthesis, gene regulation and RNA interference. It is also a key component of vaccines and plays a role in immunity.
Proteins
Proteins are large, complex molecules that play many important roles in the body. They carry in vital supplies, clean up waste, and send messages to help cells do their work.
Each protein contains long chains of amino acids, each linked to its neighbors through peptide bonds. Each amino acid in a polypeptide chain is chemically distinct and can occur at any position in the protein.
Because amino acids are so closely arranged, there is a vast number of possible polypeptide chains. For example, a typical protein with 300 amino acids could have more than 10390 different polypeptide chains.
These polypeptide chains are stabilized by hydrogen bonds (Figure 3-1), which create regular repeating local structures. These include a-helices, b-sheets, and turns.
Viruses
Viruses are tiny infectious particles that can only reproduce inside the cells of their host organism. They are essentially bags of genetic material (RNA or DNA) and protein, packed into a shell called a capsid. Some viruses also have a membrane surrounding the capsid called an envelope.
Almost all viruses have an RNA or DNA genome, a genetic material that contains instructions for making proteins. Viruses can vary in size and complexity, from the smallest, which have just four genes to huge, complex viruses with hundreds of genes.
In order to infect a cell, viruses need to bind to cellular surface receptors. These receptors are proteins that stick on the surface of the cell, like interlocking puzzle pieces. Once the viral genome binds to these receptors, the cell’s obedient molecular assembly line will produce proteins that will form a new virus capsid. The new capsid will carry the viral genome to a new host cell.