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.
The answer is : linea aspera
Answer:
Water vapor is a greenhouse gas, which absorbs the heat radiated from the earth's surface. It allows less heat to escape back to space by trapping the heat energy in the lower atmosphere and keeps the atmosphere warm.
Explanation:
Water vapor is formed through a process called evaporation. In this process, water from the ocean, rivers, and lakes evaporates to become water vapor using the energy from the sun. Water vapor also moves into the atmosphere by transpiration (plants) and sublimation (snow and ice).
The water vapor cools down and transforms into water droplets by a process called condensation, as it rises high in the atmosphere where the air is cooler. This water droplets that formed by condensation make up clouds.
When the earth’s surface get heated by the sunlight, some of the heat radiates back into the atmosphere and most of this heat is absorbed by gases in the atmosphere called green house gases. This process is called greenhouse effect, which keeps the earth warm. The green house gases mainly consists of carbon dioxide and water vapor. Water vapor absorbs the heat radiated from the earth's surface. It allows less heat to escape back to space by trapping the heat energy in the lower atmosphere and keeps the atmosphere warm.
The amount of water vapor in the atmosphere is directly proportional to the temperature. When addition of the other greenhouse gases causes a temperature increase (such as extra CO2 from fossil fuels), more water evaporates and this leads to an increase in water vapor which further increases the atmospheric temperature since water vapor is a greenhouse gas. So, water vapor is part of a positive feedback system.