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Biology chapter2

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atom
basic unit of matter.
nucleus
the center of the atom which contains the protons and neutrons; in cells, structure that contains the cell's activities.
electron
negatively charged particle;located outside the atomic nucleus.
element
substance consisting entirely of one type of atom.
isotope
atom of an element that has a number of neutrons different from that of other atoms of the same element.
compound
substance formed by the chemical combination of two or more elements in definite proportions.
ionic bond
bond formed when one or more electrons are transferred from one atom to another.
ion
atom that has a positive or negative charge.
covalent bond
bond formed by the sharing of electrons between atoms.
molecule
smallest unit of most compounds.
van der Waals forces
a slight attraction that develops between the oppositely charged regions of nearby molecules.
cohesion
attraction between molecules of the same substance.
adhesion
attraction between molecules of different substances; in plants, attraction between unlike molecules.
mixture
material composed of two or more elements or compounds that are physically mixed together but not chemically combined.
solution
mixture of two or more substances in which the molecules of the substances are evenly distributed.
solvent
substance in which a solute is dissolved to form a solution.
suspension
mixture of water and nondissovled materials.
pH scale
measurement system used to indicate the concentration of hydrogen ions (H+) in solution; ranges from 0 to 14
acid
compound that forms hydrogen ions (H+) in solution.
base
compound that produces hydroxide ions (OH+) in solution.
buffer
weak acid or base that cna 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.
polysoccharide
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.
solute
substance that is dissovled in a solvent to make a sollution.