5.1. Molecular Biology: DNA and RNA: Structure of DNA

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Molecular biology is an area of ​​science that studies the structure and function of molecules that are essential for life. In this topic, we will focus on DNA and RNA, two of the main components of molecular biology.

Deoxyribonucleic acid, better known as DNA, is a complex molecule that contains all the information necessary for the development and functioning of an organism. The structure of DNA was discovered in 1953 by scientists James Watson and Francis Crick, and is one of the most important discoveries in biology.

The structure of DNA is made up of two strands of nucleotides, which are twisted together in a double helix fashion. Each nucleotide is composed of a nitrogenous base, a five-carbon sugar (deoxyribose), and a phosphate group. There are four nitrogenous bases in DNA: adenine (A), thymine (T), cytosine (C) and guanine (G). Adenine always pairs with thymine, and cytosine always pairs with guanine. These combinations are known as base pairs.

The sequence of bases in a DNA strand is what determines an organism's genetic information. For example, the ATCGTT base sequence can encode a different protein than the TACGTT base sequence.

On the other hand, ribonucleic acid, or RNA, is similar to DNA but has some important differences. RNA is usually single-stranded, while DNA is double-stranded. Furthermore, RNA contains the sugar ribose instead of deoxyribose and the nitrogenous base uracil (U) instead of thymine.

There are three main types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). Each plays an important role in protein synthesis, which is the process by which cells make new proteins.

The mRNA is the copy of the DNA that is used as a template for protein synthesis. The tRNA transports the amino acids to the ribosome, where they are added to the growing protein chain. rRNA forms the basic structure of ribosomes, which are the cell's protein factories.

In summary, DNA and RNA are vital molecules that play crucial roles in molecular biology. The structure and function of these molecules are fundamental to understanding how living organisms function and evolve. In ENEM, it is important to have a good understanding of these concepts, as they are often tested in the life sciences section.

We hope that this brief summary on molecular biology has been useful and that you are now more prepared to face any question about DNA and RNA that may arise in ENEM. Remember, the key to ENEM success is preparation and continuous study. Good luck!

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155.2. Molecular Biology: DNA and RNA: Structure of RNA