Biology: Unit 2-The Chemistry of Life exam study guide questions and answers

Atom The basic unit of all matter that consits of three subatomic particles-neutrons, protons, and electrons. Nucleus The center of an atom which contains the protons and neutrons; in cells, structure that contains the cell's genetic material (DNA) and controls the cell's activities. Electron Negatively charged particle that is located outside the atom's nucleus. Element Pure substance that consists entirely of one type of atom. Isotope Atoms of the same element that has the same number of protons but different number of neutrons. Compound Substance formed by the chemical combination of two or more elements in definite proportions. These substances are formed by bonds (meaning the electrons). Chemical Bond Force of attraction between the electrons in two or more atoms in their outer energy levels which forms a molecule. Ionic Bond A bond formed when one or more electrons are transferred from one atom to another. This makes the atom's outer energy levels become full, and it gives the atom a positive or negative charge. Ion An atom that has a positive or negative charge. Covalent Bond A bond formed by the sharing of electrons between atoms. This bond produces a stron bond between the atoms, and their outer energy levels will NOT be filled. Molecule The smallest unit of most compounds which is created from a combination of atoms. van der Waals Forces A very weak bonding between atoms that causes a slight attraction that develops between the oppositely charged regions of nearby molecules. The rapid movement of electrons creates regions on a molecule that have a tiny positive or negative charge. Cohesion An attraction between molecules of the same substance. Adhesion An attraction between molecules of different substances. Polarity The attraction between two atoms that have opposite charges. Surface Tension Ability of water molecules at the surface to resist external force. Mixture Material composed of two or more elements or compounds that are physically put in together but not chemically combined. Solution Mixture of two or more substances in which the molecules of the substances are evenly distributed. Solute Substance that is dissolved in a solvent to make a solution (breaks apart). Solvent Substance in which a solute is dissolved to form the solution (does the dissolving). pH scale Measurement system used to indicate the concentration of hydrogen ions (H+) in solution; ranges from 0-14. Determines if something is an acid or base. Acid Compound that forms hydrogen ions (H+) in a solution. Base Compound that forms hydroxide ions (OH+) in a solution. Buffer Weak acid or base that can react with strong acids or bases to help prevent sharp, sudden changes in pH. Monomer Small unit that can join together with other small units to form polymers. Polymer Large compound formed from combinations of many monomers. Carbohydrate Compound made up of carbon, hydrogen, and oxygen atoms; major source of energy for the human body. Monosaccharide Single sugar molecule. Polysaccharide Large macromolecule formed from monosaccharides. Lipid Macromolecule made mainly from carbon and hydrogen atoms; includes fats, oils, and waxes. Nucleic Acid Macromolecule containing hydrogen, oxygen, nitrogen, carbon, and phosphorus. Nucleotide Monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base. Ribonucleic Acid (RNA) Single-stranded nucleic acid that contains the sugar ribose. Deoxyribonucleic Acid (DNA) Nucleic acid that contains the sugar deoxyribose. Protein Macromolecule that contains carbon, hydrogen, oxygen, and nitrogen; needed by the body for growth and repair and to make up enzymes. Amino Acid Compound with an amino group (-NH2) on one end and a carboxyl group (-COOH) on the other end. Chemical Reaction Process that changes one set of chemicals into another set of chemicals. Reactant Element or compound that enters into a chemical reaction. Product Element or compound produced by a chemical reaction. Activation Energy Energy needed to get a reaction started. Catalyst Substance that speeds up the rate of a chemical reaction. Enzyme Protein that acts as a biological catalyst. Substrate Reactant of an enzyme-catalyzed reaction.