Ribosome

The ribosome is a large and complex molecular machine, found within all living cells, that serves as the primary site of biological protein synthesis(translation). Ribosomes linkamino acidstogether in the order specified bymessenger RNA(mRNA) molecules. Ribosomes consist of two major components — the small ribosomal subunit which reads the RNA, and the large subunit which joins amino acids to form apolypeptidechain. Each subunit is composed of one or moreribosomal RNA(rRNA) molecules and a variety of proteins. The ribosomes and associated molecules are also known as thetranslational apparatus.

The sequence of DNAencoding for a protein may be copied many times intomessenger RNA(mRNA) chains of a similar sequence. Ribosomes can bind to an mRNA chain and use it as a template for determining the correct sequence of amino acids in a particular protein. Amino acids are selected, collected and carried to the ribosome bytransfer RNA(tRNA molecules), which enter one part of the ribosome and bind to the messenger RNA chain. The attached amino acids are then linked together by another part of the ribosome. Once the protein is produced, it can then'fold'to produce a specific functional three-dimensional structure.

A ribosome is made from complexesof RNAs and proteins and is therefore aribonucleoprotein. Each ribosome is divided into two subunits: a smaller subunit which binds to the mRNA pattern, and a larger subunit which binds to the tRNA and the amino acids. When a ribosome finishes reading an mRNA molecule, these two subunits split apart. Ribosomes areribozymes, because thecatalyticpeptidyl transferaseactivity that links amino acids together is performed by theribosomal RNA.

Ribosomes from bacteria,archaeaandeukaryotes(the three domains oflife on Earth) differ in their size, sequence, structure, and the ratio of protein to RNA. The differences in structure allow someantibioticsto kill bacteria by inhibiting their ribosomes, while leaving human ribosomes unaffected. In bacteria and archaea, more than one ribosome may move along a single mRNA chain at one time, each "reading" its sequence and producing a corresponding protein molecule. The ribosomes in themitochondriaof eukaryotic cells functionally resemble many features of those in bacteria, reflecting the likely evolutionary origin of mitochondria.

ULTRAFINE PARTICLE

Ultrafine particles (UFPs) are particulate matterofnanoscalesize (less than 100nanometresin diameter). Regulations do not exist for this size class of ambient air pollution particles, which are far smaller than the regulatedPM₁₀ and PM_2.5 particle classes and are believed to have several more aggressive health implications than those classes of larger particulates. There are two main divisions that categorize types of UFPs. UFPs can either be carbon-based or metallic, and then can be further subdivided by their magnetic properties. Electron microscopy and special physical lab conditions allow scientists to observe UFP morphology. Airborne UFPs can be measured using a condensation particle counter, in which particles are mixed with alcohol vapor and then cooled allowing the vapor to condense around them which are then counted using a light scanner. UFPs are both manufactured and naturally occurring. UFPs are the main constituent of airborne particulate matter. Due to their numerous quantity and ability to penetrate deep within the lung, UFPs are a major concern for respiratory exposure and health.

Sources and applications

UFPs are both manufactured and naturally occurring. Hot volcanic lava, ocean spray, and smoke are common natural UFPs sources. UFPs can be intentionally fabricated as are fine particlesto serve a vast range of applications in both medicine and technology. Other UFPs are byproducts, like emissions, from specific processes, combustion reactions, or equipment such as printer toner and automobile exhaust. In 2014, anair qualitystudy found harmfulultrafine particlesfrom the takeoffs and landings at Los Angeles International Airport to be of much greater magnitude than previously thought. There are a multitude of indoor sources that include but are not limited to laser printers, fax machines, photocopiers, the peeling of citrus fruits, cooking, tobacco smoke, penetration of contaminated outdoor air, chimney cracks and vacuum cleaners.

UFPs have a variety of applications in the medical and technology fields. They are used in diagnostic imagining, and novel drug delivery systems that include targeting the circulatory system, and or passage of the blood brain barrier to name just a few. Certain UFPs like silver based nanostructures have antimicrobial properties that are exploited in wound healing and internal instrumental coatings among other uses, in order to prevent infections.In the area of technology, carbon based UFPs have a plethora of applications in computers. This includes the use of grapheneandcarbon nanotubesin electronic as well as other computer and circuitry components. Some UFPs have characteristics similar to gas or liquid and are useful in powders or lubricants.