Tutor profile: Nathan M.
What is the difference between covalent and ionic bonds?
A covalent bond can form between two atoms when their nuclei share a pair of electrons, forming a molecule (e.g. the covalent bonds in CH4 occur because C shares its electrons with 4 H atoms). On the other hand, ionic bonds can form between atoms when electrons are transferred from one charged atom to another to form a neutral molecule (e.g. ionic bonds in NaCl occur because Cl- atoms give an electron to Na+ atoms).
Explain the potential mechanism of damage for two separate endocrine disruptors?
Two examples of endocrine disruptors are bisphenol A (BPA) and phthalates. It is possible BPA acts as an endocrine disruptor by binding to estrogen receptors alpha and beta. BPA can both mimic the action of estrogen and antagonize estrogen, blocking the normal function of estrogen. In addition, BPA may act as a endocrine disruptor by binding to estrogen-related receptor gamma (ERRy). BPA has a strong binding affinity for ERRy, a receptor that shows tissue-specific expression in the brain during development and in brain, lung, and other tissues in adults. In this way, BPA may disrupt normal tissue development processes by interfering with ERRy receptors. On the other hand, phthalates may act as an endocrine disruptor through antiandrogenic effects. For example, phthalates are associated with hypospadias and cryptorchidism. It has been proposed that phthalates may affect Leydig cells, causing a decrease in their function. Leydig cells in the testes are responsible for producing the androgen testosterone. Androgen insufficiency can result in hypospadias and cryptorchidism.
The skin possesses a number of amazing protective properties, and one of the most notable is skin coloration as a protection against U.V. irradiation. How does light (U.V.) potentially disrupt cellular function and how is melanin poised to protect against damage?
The skin adapts to U.V. radiation through changes in melanin pigmentation. Melanin is a pigmentation with the capability to absorb harmful UV radiation and protect the genome against the deleterious consequences of UV exposure. Melanin has evolved to form a cap (almost like an umbrella!) on top of the basal keratinocyte, a major skin cell type of the epidermis. This “melanin umbrella” is designed to protect the nucleus of the basal keratinocyte from being exposed to harmful UV exposure that could have deleterious consequences on the genome. Exposure to UV light can rapidly induce DNA damage in the genome of keratinocytes, introducing harmful mutations that could lead to the development of cancerous cells.
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