Why Ethylene Can Make A Fast Fruit Ripe?

To discuss how it works, we should mention that there are two types of fruit: climacteric and non-climacteric. Climacteric fruits continue ripening after being picked (which will be accelerated by ethylene gas). Climacteric fruits include: apples, apricots, avocados, bananas, cantaloupes, figs, guava, kiwis, mangoes, nectarines, peaches, pears, plums, and tomatoes. Non-climacteric fruits ripen only while still attached to the plant. Their shelf life is diminished if harvested at peak ripeness. Non-climacteric fruits include: cherries, grapes, limes, oranges, pineapples, and berries (blue-, black-, rasp-, straw-, etc.). Essentially all parts of higher plants produce ethylene (stems, roots, flowers, tubers, and seedlings). Ethylene production is induced at several key stages of the plant’s life. Notable for us, ethylene production is promoted during fruit ripening and abscission (dropping) of leaves. However, it is now known that ethylene production can be artificially increased by external factors: wounding of the fruit, environmental stress, and exposure to certain chemicals. The biosynthesis of ethylene starts with the amino acid methionine. The enzyme met adenosyltransferase converts methionine into S-adenosyl-L-methionine (SAM). The enzyme ACC synthase (ACS) converts SAM into 1-aminocyclopropane-1-carboxylate (ACC). The last step in ethylene biosynthesis involves molecular oxygen. The enzyme ACC-oxidase (ACO, which used to be called Ethylene Forming Enzyme, EFE) converts ACC into ethylene, as well as carbon dioxide, hydrogen cyanide, and water. Ethylene Biosynthesis Ethylene Biosynthesis The rate of ethylene production is regulated by ACC synthase converting SAM into ACC. Thus, regulation of this enzyme is key for the biosynthesis of ethylene. Manipulation of this enzyme by biotechnology delays fruit ripening. The Flavr Savr tomatoes used this biotechnology. On the other hand, in a sort of positive feedback loop, the biosynthesis of ethylene is upregulated by either endogenous or exogenous ethylene. Producing ethylene causes more ethylene to be produced. In 1993, the genes involved in the fruit ripening response were identified. The ETR1 and CTR1 genes are turned on until ethylene is produced. Then ETR1 and CTR1 turn off. This initiates a cascade ultimately turning other genes on. These other genes make the various enzymes mentioned earlier (amylases, hydrolases, kinases, and pectinases) needed to ripen the fruit. ince ethylene controls the ripening process, if we can control the ethylene, we can control the fruit. While ethylene is synthesized by plants, it is also prepared commercially. Ethylene is the most produced organic compound in the world (>107 million metric tons in 2005). The petrochemical industry produces ethylene through steam cracking of gaseous or light liquid hydrocarbons by heating to 750-950 °C. Compression and distillation purifies the ethylene. Ethylene is then used for a variety of applications, including the synthesis of PVC and polyethylene plastics. The picking of unripe fruit and artificial ripening later is not uncommon. In parts of Asia, a plastic cover is placed over unripe harvested mangoes. Calcium carbide is placed in open containers in strategic positions inside the bag. Moisture from the air converts the calcium carbide into acetylene which has the same fruit-ripening effect as ethylene. However, industrial-grade calcium carbide is sometimes contaminated with trace arsenic and phosphorous. The use of calcium carbide to stimulate fruit ripening is illegal in most countries. Catalytic Ethylene Generator An ethylene generator More commonly, however, catalytic generators are used to produce the ethylene gas necessary for fruit ripening. The generators allow for control of the overall ethylene concentration in the room. Typically, between 500-2000 ppm of ethylene is administered for 24-48 hours to successfully ripen the fruit. On the other side of the spectrum, after the unripe fruit is picked, we want it to remain unripe until after shipment. Scientists have researched ways to inhibit ethylene biosynthesis and inhibit ethylene perception. Aminoethoxyvinylglycine (AVG), aminooxyacetic acid (AOA), and silver ions inhibit ethylene synthesis, but this is not always effective because exogenous ethylene can still be perceived by the fruit and stimulate ripening. 1-methylcyclopropene 1-MCP

solution and solid

How can an unsaturated solution of a solid in a liquid become saturated? How can a saturated solution of a solid in a liquid become supersaturated?

MID TEST BASIC CHEMISTRY LECTURE:Dr.Syamsurizal 1.Explain where is the key point of the similarities and diffrences between matter waves and electromagnetic waves.Give at least two examples. 2.Do atoms in excited states emit radiation randomly, at any wavelength?why? what does it mean to say that the hydrogen atom has only certain discrete energy levels available?how do we know this?why was the quantization of energy levels suprising to scientists when it was first discovered? 3.You have much studied some things related to the modern atomic theory.Do you think electrons are more like baseballs or guitar strings.explain your reason. 4.Describe the relationship between stability and potential energy.give at least two examples. 5.You have carried out an experiment about the water surface tension properties in the paper,plastic,and glass.write down your observations.comparing the cohesive and adhesive forces on all three materials,why is that?

why of the dipole, dispersion, and induction can be interaction in the van der waals force? the ability of polarization or molecular polarizabilities is expressed by the simbol alpha.in the molecules with the same shape the increased mass of the molecule would lead to increas in the number of electrons.this causes the nuclei to the influence of the electron could is getting weaker ,so it will easily polarized and london style that occurs will be stronger.London style is more powerfull cause melting and boiling the molecules.Involved in this style requires a great energy to enlarge the non polar intermolecular distances... interaction induced dipole is dependent on two factors, namely: 1. the number of electrons in atoms or molecules the more electrons that possess the greater the molecular interaction 2.molecular shape molecules are elangated or not round more easily be compared with the molecular dipoles are rounded so that their interactions will also be great. compound that have a dipole commonly referred to as polar compound, polar compounds are formed through a polar covalent bond.it shoud be noted that in contrast to ion dipole.owned electric dipole strength is weaker than the ion electric power .we must remember that the ion present ionic compounds where the molecule is divided positive or cation and negative or anion. When the dipole is misguided happens, there will be also the style of london (blue line putis-break). When the dipole is lost, is lost london style. London force strength depends on various factors: A. Complexity of the molecular more complicated molecules (Mr greater), then the force is getting stronger london. 2. Molecular size the larger molecular size, style london also intensified. this is because the large molecules more easily polarized, so that the dipole moment is more apt to occur. Van der Waals forces that occur between the dipole - dipole arranged on a regular basis. Substances that have the style of van der Waals forces in a regular arrangement is usually are solid. The substances which have van der Waals force in disorganized arrangement (random) is usually liquid. Van der Waals forces do not cause spikes in the boiling point. This is due to inter-molecular forces are weak. The dipole-dipole attraction is a bit compared to the dispersion forces, and their effects can only be seen if we compare the two atoms with the same number of electrons of the same size. Appeal that there is electrical in nature. At the symmetric molecules such as hydrogen, does not look distorted to produce the electrically positive and negative parts. Electrons are constantly moving, and at one time the electron is found possible for the end of the molecule. On the other end while the shortage of electrons. At the end of the condition of the right electron will move to the other end. In doing this, the electrons in the electron will be the only one left. Of all the forces that occur in the bonds between molecules called Van der Walls forces no doubt is the weakest force even the most universal. Associated with energy around 0.4 to 40 kJ / mol, this style bias is offset by the stronger covalent forces within the molecule whose energy is about 400 kJ / mol. His role is important only to explain the interaction between neighbor molecules or atomic orbitals fellow saturated. Unlike covalent bonds within the core work in close and connected with the overlap or electron transfer, and result in higher energy, then the Van der Waals bonding can work at a distance which can not cause squeezing or transfer of electrons that are usually associated with energy smaller.

EXAMPLE emission of energy by atom Parrots, which are renowned for their vibrant colors, apparently have a secret weapon that enhances their colorful appearance—a phenomenon called fluorescence. Fluorescence occurs when a substance absorbs ultraviolet (UV) light, which is invisible to the human eye, and converts it to visible light. This phenomenon is widely used in interior lighting in which long tubes are coated with a fluorescent substance. The fluorescent coating absorbs UV light (produced in the interior of the tube) and emits intense white light, which consists of all wavelengths of visible light. Interestingly, scientists have shown that parrots have fluorescent feathers that are used to attract the opposite sex. Note in the accompanying photos that a budgerigar parrot has certain feathers that produce fluorescence. Kathryn E. Arnold of the University of Glasgow in Scotland examined the skins of 700 Australian parrots from museum collections and found that the feathers that showed fluorescence were always display feathers—ones that were fluffed or waggled during courtship. To test her theory that fluorescence is a significant aspect of parrot romance, Arnold studied the behavior of a parrot toward birds of the opposite sex. In some cases, the potential mate had a UV-blocking substance applied to its feathers, blocking its fluorescence. Arnold’s study revealed that parrots always preferred partners that showed fluorescence over those in which the fluorescence was blocked.