Information:  - Trimethylglycine (TMG) is an that occurs in plants. Trimethylglycine was the first betaine discovered; originally it was simply called betaine because, in the 19th century, it was discovered in sugar beets. Since then, many other betaines have been discovered, and the more specific name "glycine betaine" distinguishes this one.  - Protein folding is the physical process by which a protein chain acquires its native 3-dimensional structure, a conformation that is usually biologically functional, in an expeditious and reproducible manner. It is the physical process by which a polypeptide folds into its characteristic and functional three-dimensional structure from random coil. Each protein exists as an unfolded polypeptide or random coil when translated from a sequence of mRNA to a linear chain of amino acids. This polypeptide lacks any stable (long-lasting) three-dimensional structure (the left hand side of the first figure). As the polypeptide chain is being synthesized by the ribosome, the linear chain begins to fold into its three dimensional structure. Folding begins to occur even during translation of the polypeptide chain. Amino acids interact with each other to produce a well-defined three-dimensional structure, the folded protein (the right hand side of the figure), known as the native state. The resulting three-dimensional structure is determined by the amino acid sequence or primary structure (Anfinsen's dogma). The energy landscape describes the folding pathways in which the unfolded protein is able to assume its native state. Experiments  beginning in the 1980s indicate the codon for an amino acid can also influence protein structure.  - The renal medulla is the innermost part of the kidney. The renal medulla is split up into a number of sections, known as the renal pyramids. Blood enters into the kidney via the renal artery, which then splits up to form the interlobar arteries. The interlobar arteries each in turn branch into arcuate arteries, which in turn branch to form interlobular arteries, and these finally reach the glomeruli. At the glomerulus the blood reaches a highly disfavourable pressure gradient and a large exchange surface area, which forces the serum portion of the blood out of the vessel and into the renal tubules. Flow continues through the renal tubules, including the proximal tubule, the Loop of Henle, through the distal tubule and finally leaves the kidney by means of the collecting duct, leading to the renal pelvis, the dilated portion of the ureter.  - Ectoine ( 1,4,5,6 - tetrahydro - 2 - methyl - 4 - pyrimidinecarboxylic acid ) is a natural compound found in several species of bacteria . It is a compatible solute which serves as a protective substance by acting as an osmolyte and thus helps organisms survive extreme osmotic stress . Ectoine is found in high concentrations in halophilic microorganisms and confers resistance towards salt and temperature stress . Ectoine was first identified in the microorganism Ectothiorhodospira halochloris , but has since been found in a wide range of Gram - negative and Gram - positive bacteria . Other species of ectoine were found in Brevibacterium linens Halomonas elongata Marinococcus halophilus Pseudomonas stutzeri  - Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane. It is also defined as the measure of the tendency of a solution to take in water by osmosis. Potential osmotic pressure is the maximum osmotic pressure that could develop in a solution if it were separated from distilled water by a selectively permeable membrane. The phenomenon of osmosis arises from the propensity of a pure solvent to move through a semi-permeable membrane and into a solution containing a solute to which the membrane is impermeable. This process is of vital importance in biology as the cell's membrane is semipermeable.  - Osmolytes are compounds affecting osmosis. They are soluble in the solution within a cell, or in the surrounding fluid, e.g. as plasma osmolytes. They play a role in maintaining cell volume and fluid balance. For example, when a cell swells due to external osmotic pressure, membrane channels open and allow efflux of osmolytes which carry water with them, restoring normal cell volume. Osmolytes also contribute to protein folding.  Natural osmolytes that can act as osmoprotectants include trimethylamine "N"-oxide (TMAO), dimethylsulfoniopropionate, trimethylglycine, sarcosine, betaine, glycerophosphorylcholine, myo-inositol, taurine, glycine, and others. Bacteria accumulate osmolytes for protection against a high osmotic environment. The osmolytes will be neutral non-electrolytes, except in bacteria that can tolerate salts. In humans, osmolytes are of particular importance in the renal medulla. Current understanding of osmolytes have been used to calculate the maximum depth where a fish can survive: 26,900 feet (8,200 meters).  - Sarcosine, also known as "N"-methylglycine, is an intermediate and byproduct in glycine synthesis and degradation. Sarcosine is metabolized to glycine by the enzyme sarcosine dehydrogenase, while glycine-"N"-methyl transferase generates sarcosine from glycine. Sarcosine is an amino acid derivative that is naturally found in muscles and other body tissues. In the laboratory, it may be synthesized from chloroacetic acid and methylamine. Sarcosine is found naturally as an intermediate in the metabolism of choline to glycine. Sarcosine is sweet to the taste and dissolves in water. It is used in manufacturing biodegradable surfactants and toothpastes as well as in other applications.  - Glycine (abbreviated as Gly or G) is the amino acid that has a single hydrogen atom as its side chain. It is the simplest possible amino acid. The chemical formula of glycine is NHCHCOOH. Glycine is one of the proteinogenic amino acids. Its codons are GGU, GGC, GGA, GGG of the genetic code.  - Dimethylsulfoniopropionate (DMSP), is an organosulfur compound with the formula (CH)SCHCHCOO. This zwitterionic metabolite can be found in marine phytoplankton, seaweeds, and some species of terrestrial and aquatic vascular plants. It functions as an osmolyte as well as several other physiological and environmental roles have also been identified. DMSP was first identified in the marine red alga "Polysiphonia fastigiata" by Frederick Challenger and Margaret Simpson (later Dr. Whitaker)   - Fluid balance is an aspect of the homeostasis of living organisms in which the amount of water in the organism needs to be controlled, via osmoregulation and behavior, such that the concentrations of electrolytes (salts in solution) in the various body fluids are kept within healthy ranges. The core principle of fluid balance is that the amount of water lost from the body must equal the amount of water taken in; for example, in human homeostasis, the output (via respiration, perspiration, urination, defecation, and expectoration) must equal the input (via eating, drinking, and parenteral intake). Euvolemia is the state of normal body fluid volume, including blood volume, interstitial fluid volume, and intracellular fluid volume; hypovolemia and hypervolemia are imbalances. Water is necessary for all life on Earth. Humans can survive for 4 to 6 weeks without food but only for a few days without water.  - Osmosis is the spontaneous net movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves across a semipermeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Osmosis can be made to do work.  - Taurine, or 2-aminoethanesulfonic acid, is an organic compound that is widely distributed in animal tissues. It is a major constituent of bile and can be found in the large intestine, and accounts for up to 0.1% of total human body weight. Taurine has many fundamental biological roles, such as conjugation of bile acids, antioxidation, osmoregulation, membrane stabilization, and modulation of calcium signaling. It is essential for cardiovascular function, and development and function of skeletal muscle, the retina, and the central nervous system. Taurine is unusual among biological molecules in being a sulfonic acid, while the vast majority of biologically occurring acids contain the more weakly acidic carboxyl group. While taurine is sometimes called an amino acid, and indeed is an acid containing an amino group, it is not an amino acid in the usual biochemical meaning of the term, which refers to compounds containing both an amino and a carboxyl group.  - Osmoprotectants or compatible solutes are small molecules that act as osmolytes and help organisms survive extreme osmotic stress. In plants, their accumulation can increase survival during stresses such as drought. Examples of compatible solutes include betaines, amino acids, and the sugar trehalose. These molecules accumulate in cells and balance the osmotic difference between the cell's surroundings and the cytosol. In extreme cases, such as in bdelloid rotifers, tardigrades, brine shrimp, and nematodes, these molecules can allow cells to survive being completely dried out and let them enter a state of suspended animation called cryptobiosis. In this state the cytosol and osmoprotectants become a glass-like solid that helps stabilize proteins and cell membranes from the damaging effects of desiccation.  - A betaine (BEET-ah-een) in chemistry is any neutral chemical compound with a positively charged cationic functional group such as a quaternary ammonium or phosphonium cation (generally: onium ions) which bears no hydrogen atom and with a negatively charged functional group such as a carboxylate group which may not be adjacent to the cationic site. A betaine thus may be a specific type of zwitterion. Historically the term was reserved for TMG (trimethylglycine) only. Biologically, betaine is involved in methylation reactions and detoxification of homocysteine.    After reading the paragraphs above, we are interested in knowing the entity with which 'ectoine' exhibits the relationship of 'instance of'. Find the answer from the choices below.  Choices: - 1  - acid  - amino acid  - animal  - artery  - aspect  - bacteria  - behavior  - branch  - cell  - century  - chemical compound  - code  - degradation  - derivative  - dogma  - drought  - energy  - enzyme  - fish  - fluid  - formula  - function  - human  - hydrogen  - inositol  - loop  - may  - membrane  - metabolite  - number  - onium  - organic compound  - part  - principle  - protein  - region  - role  - semipermeable membrane  - sequence  - single  - solution  - solvent  - species  - state  - surface  - three  - understanding  - water  - work
A:
chemical compound