TLDR;
This lecture provides an introduction to nucleic acids, focusing on DNA and RNA as carriers of genetic information. It covers the structure and components of DNA, including nucleotides, sugars, and nitrogenous bases (purines and pyrimidines). The lecture also explains the functions of nucleotides and nucleic acids, the concept of base pairing (Watson-Crick model), and the primary structure of nucleic acids, including phosphodiester bonds.
- DNA and RNA are the primary carriers of genetic information.
- Nucleotides are the building blocks of nucleic acids, consisting of a sugar, a phosphate group, and a nitrogenous base.
- DNA has a double helix structure with specific base pairing (adenine with thymine, guanine with cytosine).
Introduction to Nucleic Acids [0:04]
The lecture introduces nucleic acids, specifically DNA and RNA, as molecules that carry genetic information. DNA is found in almost every living cell and contains biological instructions that make each organism unique. It aids in protein synthesis and reproduction, featuring a twisted helical, double-stranded structure. DNA comprises nucleotides, each containing a sugar (deoxyribose), a phosphate group, and a nitrogenous base (adenine, thymine, guanine, or cytosine). Adenine pairs with thymine via two hydrogen bonds, while guanine pairs with cytosine via three hydrogen bonds.
DNA: Structure and Function [1:04]
DNA, or deoxyribonucleic acid, is a chemical substance present in the nucleus of all cells in living organisms. It controls chemical changes within the cell. Different cells, such as myocytes (muscle cells), erythrocytes (red blood cells), and nerve cells, are controlled by DNA. The DNA molecule is a large, long chain of subunits called nucleotides. Each nucleotide consists of a five-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base.
Nucleotides: Building Blocks of Nucleic Acids [5:27]
Nucleic acids, including DNA and RNA, are biological polymers made up of nucleotides. These nucleotides contain pentose sugars linked to purine or pyrimidine bases and a phosphate group. Purines include adenine (A) and guanine (G), while pyrimidines include cytosine (C), thymine (T), and uracil (U). In DNA, adenine pairs with thymine, guanine pairs with cytosine, represented as A, C, T, and G. In RNA, uracil replaces thymine. Nucleosides consist of a sugar and a nitrogenous base, while nucleotides include a phosphate group attached to the sugar.
Deoxyribonucleotides and Hydrogen Bonding [11:20]
Deoxyribonucleotides found in DNA include deoxyadenosine, deoxyguanosine, deoxycytidine, and deoxythymidine, each with specific symbols and representations. Hydrogen bonding occurs between base pairs, with adenine pairing with thymine via two hydrogen bonds and cytosine pairing with guanine via three hydrogen bonds. These base pairs are fundamental to the double-stranded DNA structure.
Functions of Nucleotides and Nucleic Acids [15:43]
Nucleotides function in energy metabolism, with ATP serving as the universal energy currency. They are also found in enzyme cofactors like nicotinamide adenine dinucleotide and in signal transduction. Nucleic acids store genetic information in DNA, transmit genetic information via messenger RNA, and process genetic information through ribosomes and transfer RNA in protein synthesis. The linkage between molecules occurs via phosphodiester bonds.
Watson-Crick Model and Base Pairing [17:18]
The Watson-Crick model (1953) describes DNA as consisting of two polynucleotide strands running in opposite directions, coiling around each other in a double helix. The strands are held together by hydrogen bonds between specific base pairs: adenine with thymine (two hydrogen bonds) and cytosine with guanine (three hydrogen bonds). The strands are complementary, meaning wherever guanine occurs in one strand, cytosine occurs in the opposite strand, and vice versa.
Primary Structure of Nucleic Acids [20:25]
The primary structure of nucleic acids involves nucleotides (phosphate group, sugar, and nitrogenous base) linking together via phosphodiester bonds. The 3' OH of one nucleotide forms an ester bond with the phosphate group on the 5' carbon of the next nucleotide. A nucleic acid polymer has a free 5' phosphate group at one end and a free 3' OH group at the other end. The sequence is read from the 5' end to the 3' end using the letters of the bases (A, C, G, T).
DNA Properties and Structure [26:06]
DNA exhibits a double helical structure with antiparallel strands, meaning one strand runs 5' to 3' while the other runs 3' to 5'. Guanine pairs with cytosine via three hydrogen bonds, and adenine pairs with thymine via two hydrogen bonds. The strands are complementary, with the number of guanines equalling the number of cytosines and the number of adenines equalling the number of thymines. There are base stacking interactions and approximately 10 base pairs per turn in the helix.