Chemistry and Molecules of Life Definitions Homeostasis the maintenance of a relatively constant internal environment Energy the ability to do work Living organisms obtain energy from food which they either make using energy of sunlight or consume from the environment Metabolism all the chemical reactions taking place in the cells of a living organism that allow it to obtain and use energy Element a chemically pure substance that cannot be chemically broken down each element is made up of and defined by a single type of atom Matter anything that takes up space and has mass Atom the smallest unit of an element that cannot be chemically broken down into smaller units Proton a positively charged subatomic particle found in the nucleus of an atom Electron a negatively charged subatomic particle with negligible mass Neutron an electrically uncharged subatomic particle found in the nucleus of an atom Nucleus the dense core of an atom Covalent Bond a strong chemical bond resulting from the sharing of a pair of electrons between two atoms Molecule atoms linked by covalent bonds Organic Molecule a molecule with a carbon based backbone and at least one carbonhydrogen bond Inorganic Molecule A molecule that lacks a carbon based backbone and carbonhydrogen bonds Carbohydrate an organic molecule made up of one or more sugars A one sugar carbohydrate is called a monosaccharide a carbohydrate with multiple linked sugars is called a polysaccharide Protein an organic molecule made up of linked amino acid subunits Lipids organic molecules that generally repel water Nucleic Acids organic molecules made up of linked nucleotide subunits DNA and RNA are examples of Nucleic Acids Macromolecules large organic molecules that make up living organisms they include carbohydrates proteins and nucleic acids Amino acids the building block or monomer of a protein Nucleotide the building block or monomer of a nucleic acid Cell the basic structural unit of living organisms Phospholipid a type of lipid that forms the cell membrane Phospholipid Bilayer a double layer of lipid molecules that characterizes all biological membranes Hydrophobic water fearing hydrophobic molecules will not dissolve in water Hydrophilic water loving hydrophilic molecules dissolve in water Solvent a substance in which other substances can dissolve fro example water Solute a dissolved substance Solution a mixture of solutes dissolved in a solvent Polar molecule a molecule in which electrons are not shared equally between atoms causing a partial negative charge at one end and a partial positive charge at the other for example water Ionic Bond a strong electrical attraction between oppositely charged ions Ion an electrically charged atom the charge resulting from the loss or gain of electrons Hydrogen Bond a weak electrical attraction between a partially positive hydrogen atom and another atom with a partial negative charge pH a measure of the concentration of positive hydrogen in a solution Acid a substance that increases the hydrogen ion concentration of solutions making them more acidic Base a substance that reduces the hydrogen ion concentration of solutions making them more basic Virus an infectious agent made up of a protein shell that encloses genetic information Prion a protein only infectious agent
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