Nucleic acids (article) | Khan Academy
The Nucleic Acids Research Database Issue and the online Molecular .. online database of protein-binding microarray data on protein–DNA interactions a database for the global exploration of virus–host evolutionary relationships. Different types of proteins. The structure and properties of amino acids. Formation of peptide bonds. Genetic information is stored in the sequence of bases along a nucleic acid Genes specify the kinds of proteins that are made by cells, but DNA is not the Most Eukaryotic Genes Are Mosaics of Introns and Exons; Summary; Problems.
Structural model of a DNA double helix.
This is referred to as antiparallel orientation and is important for the copying of DNA. So, can any two bases decide to get together and form a pair in the double helix? The answer is a definite no. Because of the sizes and functional groups of the bases, base pairing is highly specific: A can only pair with T, and G can only pair with C, as shown below.Protein Structure and guiadeayuntamientos.info4
This means that the two strands of a DNA double helix have a very predictable relationship to each other. This allows each base to match up with its partner: The A-T pairs are connected by two hydrogen bonds, while the G-C pairs are connected by three hydrogen bonds.
When two DNA sequences match in this way, such that they can stick to each other in an antiparallel fashion and form a helix, they are said to be complementary. Hydrogen bonding between complementary bases holds DNA strands together in a double helix of antiparallel strands.
Thymine forms two hydrogen bonds with adenine, and guanine forms three hydrogen bonds with cytosine.
Volume 46 Issue 7 | Nucleic Acids Research | Oxford Academic
Image modified from OpenStax Biology. A nucleotide in an RNA chain will contain ribose the five-carbon sugarone of the four nitrogenous bases A, U, G, or Cand a phosphate group.
Here, we'll take a look at four major types of RNA: These exquisitely specific enzymes copy sequences from nucleic acid templates with an error rate of less than 1 in million nucleotides. Genes specify the kinds of proteins that are made by cells, but DNA is not the direct template for protein synthesis. Rather, the templates for protein synthesis are RNA ribonucleic acid molecules.
This process of transcription is followed by translation, the synthesis of proteins according to instructions given by mRNA templates.
Introduction to proteins and amino acids
Thus, the flow of genetic information, or gene expression, in normal cells is: This flow of information is dependent on the genetic code, which defines the relation between the sequence of bases in DNA or its mRNA transcript and the sequence of amino acids in a protein. The code is nearly the same in all organisms: During protein synthesisthe carboxyl group of the amino acid at the end of the growing polypeptide chain chain reacts with the amino group of an incoming amino acid, releasing a molecule of water.
The resulting bond between amino acids is a peptide bond Peptide bond formation between two amino acids. In a peptide bond, the carbonyl C of one amino acid is connected to the amino N of another. Image modified from OpenStax Biology.
Because of the structure of the amino acids, a polypeptide chain has directionality, meaning that it has two ends that are chemically distinct from one another. At one end, the polypeptide has a free amino group, and this end is called the amino terminus or N-terminus. The other end, which has a free carboxyl group, is known as the carboxyl terminus or C-terminus.
How Are Protein & Nucleic Acids Related?
The N-terminus is on the left and the C-terminus is on the right for the very short polypeptide shown above. How do we go from the amino acid sequence of a polypeptide to the three-dimensional structure of a mature, functional protein? To learn how interactions between amino acids cause a protein to fold into its mature shape, I highly recommend the video on orders of protein structure.