Exam 2: Fundamentals of Chemistry

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Electrons can have different levels of energy. Electrons with the least energy are located nearest the nucleus and those with more energy are located farther away from the nucleus (and are most likely to interact to form bonds with other atoms).
Energy associated with chemical bonds hold the atoms together forming molecules. It is the energy from sharing the electrons that allows two atoms to form chemical bonds.
The cell uses fats,sugars,proteins and nucleic acids for energy and energy storage. The cell releases this energy by breaking down complex molecules (macromolecules)into simple molecules,for example polysaccharides into monosaccharides,proteins into amino acids,etc. Or the cell releases this energy by breaking down high energy bonds (which have more energy than covalent bonds)that form within these chemicals- these bonds are found in nucleic acids (ie ATP),sugars,amino acids and lipids.

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A hydrogen bond is a special type of bond that forms between a hydrogen atom that has a partial positive charge because of a bond to atoms that strongly attract electrons (ie oxygen or nitrogen)and another atom that has a partial negative charge. This type of bond always involves a hydrogen atom. The hydrogen bond is important because it is found between water molecules or because it contributes to the structure of large molecules such as proteins or nucleic acids.
Water is essential to life because water can act as a dissolving medium or solvent. Water is a good solvent because the polar water molecules surround ions. Or stated differently because many different kinds of ions can be distributed evenly throughout water because water is polar.
Water plays the following roles in cells: it keeps them moist by forming a thin film of water (surface tension),it is the medium for most chemical reactions,it allows many different ions to be dissolved in cells,it contributes to the structure of large molecules such as proteins or nucleic acids,it participates in dehydration and hydrolysis reactions.