Protein structure is the three-dimensional arrangement of atoms in a protein molecule. Proteins are polymers — specifically polypeptides — formed from sequences of amino acids, the monomers of the polymer. A single amino acid monomer may also be called a residue (chemistry) indicating a repeating unit of a polymer. Proteins form by amino acids undergoing condensation reactions, in which the amino acids lose one water molecule per reaction in order to attach to one another with a peptide bond. By convention, a chain under 30 amino acids is often identified as a peptide, rather than a protein.[1] To be able to perform their biological function, proteins fold into one or more specific spatial conformations driven by a number of non-covalent interactions such as hydrogen bonding, ionic interactions, Van der Waals forces, and hydrophobic packing. To understand the functions of proteins at a molecular level, it is often necessary to determine their three-dimensional structure. This is the topic of the scientific field of structural biology, which employs techniques such as X-ray crystallography, NMR spectroscopy, and dual polarisation interferometry to determine the structure of proteins.
Protein structures range in size from tens to several thousand amino acids.[2] By physical size, proteins are classified as nanoparticles, between 1–100 nm. Very large aggregates can be formed from protein subunits. For example, many thousands of actin molecules assemble into a microfilament.
A protein may undergo reversible structural changes in performing its biological function. The alternative structures of the same protein are referred to as different conformational isomers, or simply, conformations, and transitions between them are called conformational changes.
Answer:
Semi-permeable membrane
Explanation:
In semi-permeable membranes, only some substances can pass through. Sometimes, some can also pass through the channel protein molecules or transport proteins on the cell membrane.
Answer:
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Codon
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Explanation:
The sequence of DNA is transcribed into mRNA, containing the sequence for protein synthesis, protein is synthesized according to the codons in mRNA. This sequence of nucleotide on DNA/ RNA is divided into a series of three nucleotide units, and one unit of three nucleotide is known as codons.
There are overall 64 codons, 61 codons out of 64 codons, codes for overall 20 amino acids, and the remaining three are stop codons.
These there codon do not code for any amino acid.
And these 61 codons, they code for total 20 amino acids. So one amino acid can be coded by one or more than one codons.
Answer:
Stabilizing selection results in a decrease of a population 's genetic variance when natural selection favors an average phenotype and selects against extreme variations. In directional selection, a population's genetic variance shifts toward a new phenotype when exposed to environmental changes.
Explanation:
I don't bite, don't worry
