Answer:
There are 20 different standard L-α-amino acids used by cells for protein construction. Amino acids, as their name indicates, contain both a basic amino group and an acidic carboxyl group. This difunctionality allows the individual amino acids to join in long chains by forming peptide bonds: amide bonds between the -NH2 of one amino acid and the -COOH of another. Sequences with fewer than 50 amino acids are generally referred to as peptides, while the terms, protein and polypeptide, are used for longer sequences. A protein can be made up of one or more polypeptide molecules. The end of the peptide or protein sequence with a free carboxyl group is called the carboxy-terminus or C-terminus. The terms, amino-terminus and N-terminus, describe the end of the sequence with a free α-amino group.
The amino acids differ in structure by the substituent on their side chains. These side chains confer different chemical, physical, and structural properties to the final peptide or protein. The structures of the 20 amino acids commonly found in proteins are shown in Figure 1. Each amino acid has both a one-letter and three-letter abbreviation. These abbreviations are commonly used to simplify the written sequence of a peptide or protein.
figure1-Protein-Structure
Depending on the side-chain substituent, an amino acid can be classified as being acidic, basic or neutral. Although 20 amino acids are required for synthesis of various proteins found in humans, we can synthesize only ten. The remaining 10 are called essential amino acids and must be obtained in the diet.
The amino acid sequence of a protein is encoded in DNA. Proteins are synthesized by a series of steps called transcription (the use of a DNA strand to make a complimentary messenger RNA strand – mRNA) and translation (the mRNA sequence is used as a template to guide the synthesis of the chain of amino acids which make up the protein). Often, post-translational modifications, such as glycosylation or phosphorylation, occur which are necessary for the biological function of the protein. While the amino acid sequence makes up the primary structure of the protein, the chemical/biological properties of the protein are very much dependent on the three-dimensional or tertiary structure.
Evolution. As climate and environment change over time, populations change over time
Answer:Chromatography is actually a way of separating out a mixture of chemicals, which are in liquid or gas form, by letting them flow slowly past another substance, which is either a solid or a liquid. It consist of a stationary phase and a mobile phase.
Explanation: All chromatographic systems rely on the fact that a substance placed in contact with two unmixable phases, one movable phase and one stationary phase, will equilibrate between them. A selectivity (or separation) factor (α) is used to 'chemically' distinguish between sample components. It is usually measured as a ratio of the retention (capacity) factors (k) of the two peaks in question and can be visualized as the distance between the apices of the two peaks. reproducible fraction will partition into each phase, depending on the relative affinity of the substance for each phase. A substance which has affinity for the moving or mobile phase will be moved rapidly through the system. A material which has a stronger affinity for the stationary phase, on the other hand, will spend more time immobilized in that phase, and will take a longer time to pass through the system. Therefore, it will be separated from the first substance. By definition, chromatography is a separation technique in which a sample is equilibrated between a mobile and a stationary phase. A theoritical plate or tray is used to produces the best possible difference between the liquid and vapour phases in equilibrium with it
Chromatographic separations are best done with a small amount of analyte (substance to be separated during analysis), which keeps either phase from becoming saturated with analyte, so that the concentrations in the two phases are directly proportional. Overloading the column with sample causes one of the phases to become saturated, leading to a loss of column efficiency, and poorly shaped peak profiles.
The retention volume in chromatographic separation (Vr) is the volume of the mobile phase required to carry the solute through the column to elution, is related to the column flow (Fc) and the retention time (tr). Likewise, the volume of the mobile phase(Vm), is related to the flow and the time the void volume takes to pass through the column.
Band broadening using the kinetic model is a phenomenon that reduces the efficiency of the separation being carried out, leading to poor resolution and chromatographic performance. This is problematical in terms of both the quality of the separation obtained and the accuracy with which sample components can be quantified.The wider band results in a dilution effect that produces a decrease in peak height accompanied by a loss in sensitivity and resolution. The eddy dispersion, accounts for the source of band broadening related to any flow unevenness in the column.
True that should be the answer
