Questions

The stability of the ions is determined by the energy of the lone pairs. Carbon has the least effective nuclear charge (Zeff) and so the lone pair on the CH3− ion has the highest energy, making it the least stable ion and so the strongest base. The Zeff increases as we move across the period until we get to fluorine which has the greatest Zeff and so its lone pairs have the lowest energy, making F− the least basic ion.

In order of decreasing basicity they are ranked LiCH3 > LiNH2 > LiOH > LiF. We are dealing with the ions F−, OH−, NH2− and CH3− and so the factor which influences their basicity is the stability of the ion compared to its conjugate acid.

Golden Rice (Oryza sativa) denotes a genetically modified rice capable of biosynthesizing and accumulating β-carotene (provitamin A) in the endosperm, yielding a characteristic yellow color in the polished grains. Golden rice was developed to help cope with vitamin A deficiency, a problem that prevails in developing countries, affecting millions (Underwood, 2000; UNICEF, 2000). Vitamin A deficiency causes mortality and growth retardation in children and frequently impairs vision, leading to blindness. It also contributes indirectly to anemia by interfering with iron bioavailability.

The endosperm of Golden Rice (Oryza sativa) is yellow due to the accumulation of β-carotene (provitamin A) and xanthophylls. The product of the two carotenoid biosynthesis transgenes used in Golden Rice results in Pale Yellow color.