Chapter 2 Vocabulary
1. Atom- basic unit of matter.
2. Nucleus- the center of the atom which contains the protons and the neutrons; in
cells, structure that contains the cells genetic material (DNA) and controls the cells
activities.
3. Electron- negatively charged particle; located outside the atomic nucleus.
4. Element- substance consisting entirely of one type of atom.
5. Isotope- atom of an element that has a number of neutrons different from that of
other atoms of the same element.
6. Compound- substance formed by the chemical combination of two or more
elements in definite proportions.
7. Ionic bond- bond formed when one or more electrons are transferred from one
atom to another.
8. Ion- atom that has a positive or negative charge.
9. Covalent bond- bond formed by the sharing of electrons between atoms.
10. Molecule- smallest unit of most compounds.
11. Van der waals forces- a slight attraction that develops between the oppositely
charged regions of nearby molecules.
12. cohesion- attraction between molecules of the same substance
13. adhesion- attraction between molecules of different substances; in plants,
attraction between unlike molecules.
14. mixture- material composed of two or more elements or compounds that are
physically mixed together but not chemically combined.
15. solution- mixture of two or more substances in which the molecules of the
substances are evenly distributed.
16. solute- substance that is dissolved in a solvent to make a solution.
17. solvent- substance in which a solute is dissolved to form a solution.
18. suspension- mixture of water and non-dissolved materials.
19. pH scale- measurement system used to indicate the concentration of hydrogen
ions (H+) in solution; ranges from 0-14.
20. acid- compound that forms hydrogen ions (H+) in solution.
21. base- compound that produces hydroxide ions (OH+) in solution.
22. buffer- weak acid or base that can react with strong acids or bases to help
prevent sharp, sudden changes in pH.
23. monomer- small unit that can join together with other small units to form
polymers.
24. polymer- large compound formed from combinations of many monomers.
25. carbohydrate- compound made up of carbon, hydrogen, and oxygen atoms;
major source of energy for the human body.
26. monosaccharide- single sugar molecule
27. polysaccharide- large macromolecule formed from monosaccharides
28. lipid- macromolecule made mainly from carbon, and hydrogen atoms;
includes, fats, oils, and waxes.
29. nucleic acid- macromolecule containing hydrogen, oxygen, nitrogen, carbon, and
phosphorus.
30. nucleotide- monomer of nucleic acids made up of a 5-carbon sugar, a phosphate
group, and a nitrogenous base.
31. ribonucleic acid (RNA) – single-stranded nucleic acid that contains the sugar
ribose.
32. deoxyribonucleic acid (DNA)- nucleic acid that contains the sugar deoxyribose.
33. protein- macromolecule that contains carbon, hydrogen, oxygen, and nitrogen;
needed by the body for growth and repair and to make up enzymes.
34. amino acid- compound with an amino group (-NH2) on one end and a carboxyl
group (-COOH) on the other end.
35. chemical reaction- process that changes one set of chemicals into another set of
chemicals.
36. reactant- element or compound that enters into a chemical reaction.
37. product- element or compound produced by a chemical reaction.
38. activation energy- energy needed to get a reaction started
39. catalyst- substance that speeds up the rate of a chemical reaction.
40. enzyme- protein that acts as a biological catalyst.
41. substrate- reactant of an enzyme-catalyzed reaction