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:
The correct answer is "Charles Lyell".
Explanation:
Charles Lyell was a notorious Scottish geologist that associated events of Earth's history with natural events taking place at the same time. In 1830, Charles Lyell published the book "Principles of Geology", associating the formation of the Earth's crust with different small and vast natural events. Charles Darwin's was largely influenced by Lyell's ideas and he took his book during the famous travel trough the Galapagos islands.
Answer;
Semi-permeability means that only certain molecules are allowed to pass through.
Explanation;
-Semi-permeability is one of the features of a cell membrane, which means that the membrane allows selective movement of materials in and out of the cell; that is only certain molecules can enter or leave the cell.
-For example smaller molecules such water and ions such as potassium and sodium ions are able to leave and enter the cell, while other molecules that are large such as protein molecules can not enter or leave the cell.
Answer:
The cell is in a hypertonic solution.
Explanation:
The solution is hypertonic because the amount of solute(s) is higher outside of the cell than it is inside the cell, so the solvent (e.g. water) would move from the cell to the solution in order to obtain equilibrium between the two.
Answer: A semi-permeable membrane is that which only allows certain
substances to pass through.
