Nucleation is the process that enables the formation of crystals. Crystals may arise from solutions, liquids or vapors but must undergo the process of nucleation to do so. Essentially, nucleation is to crystals what metamorphosis is to insects.
Nucleation begins with the line up and arrangement of crystal particles. These particles include ions, atoms and molecules, which are established in patterns to enable the conversion to solids. Processes of nucleation may be homogenous or heterogeneous in nature. Heterogeneous nucleation involves the surface of a substance, such as a particle of dust or container wall, which acts as the central location for the orientation of atoms, molecules or ions. The process of homogenous nucleation is much less formal. During this transition, several particles move into their correct positions through random movements. Of the two, heterogeneous nucleation is more common. However, homogenous nucleation is necessitated when the extent of super saturation or super cooling increases. The substances created by nucleation vary widely in color, shape and physical structure. Some may crystallize under stable and predictable conditions, while others undergo transformations in chaotic and volatile environments. Glycerol is one end product of nucleation; this component, like others formed in stable conditions, is prone to super cooling.Learn More
Karyokinesis is the process in which a cell's nucleus is divided by mitosis or meiosis, and cytokinesis is the division of the ctyoplasm in a cell. They are biologically similar processes, with minor differences.Full Answer >
The mesophyll cells in a plant leaf play a vital role in photosynthesis by enabling the gas exchange portion of the process, and through the actions of their specialized chlorophyll-containing organelles, called chloroplasts, in which the primary photosynthetic reactions take place. Because they are surrounded by intercellular air pockets, the mesophyll cells are able to perform a gas exchange when the stomatal pores in the leaf's epidermis open. The Greek term "mesophyll" means "middle leaf," and it reflects the mesophyll cells' location between the leaf's thinner and much stiffer upper and lower epidermal layers.Full Answer >
In plant cells, chloroplasts perform photosynthesis, a process that converts light energy from the sun into chemical energy in the form of glucose. Plants can later use this stored chemical energy to carry out activities integral to life, such as growth and reproduction.Full Answer >
Damaged human brain cells do not regenerate because the process that creates brain cells, neurogenesis, ceases before birth for many brain structures and in all but one brain structure by age two, according to BrainFacts.org. Brain cells only regenerate in the hippocampus.Full Answer >