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Across 1. carbon, hydrogen, and oxygen atoms, usually in a 1:2:1 ratio—that is, one carbon to two hydrogen and one oxygen atom. Used to store and release energy as well as for structural support and protection 3. a small chemical unit that makes up a polymer 5. principal pigment of plants and other photosynthetic organisms 7. compound that releases hydrogen (H+) ions into a solution 9. molecules of life that contain carbon 10. a well-tested explanation that unifies a broad range of observations and hypotheses, and enables scientists to make accurate predictions about new situations 13. the group(s) of an experiment that receive special treatment, the subjects of the tested variable. 15. compound used by cells to store and release energy 16. Single sugar molecules include glucose, galactose, and fructose. Galactose is found in milk; fructose is found in fruits. Also is used as a monomer to build larger carbohydrate molecules. 21. the component of the experiment that is observed or measured. 22. molecules composed of many monomers; makes up macromolecules 23. a compound that produces hydroxide (OH-) ions in a solution. 28. genetic material that organisms inherit from their parents 29. chemical bond formed when one or more electrons are transferred from one atom to another 30. process used by plants and other autotrophs to capture light energy and use it to power chemical reactions that convert carbon dioxide and water into oxygen and energy-rich carbohydrates such as sugars and starches 32. type of bond between aotms in which the electrons are shared 33. subunit (monomer) of which nucleic acids are composed; made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base 37. the sum of protons and neutrons in the nucleus of an atom 42. a procedure where a hypothesis is tested and all variables, except one, are kept unchanged and data is collected 43. The reactants in an enzyme-catalyzed reaction. these bind to a part of the enzyme called the active site. They have complementary shapes, which fit together like a lock and key. 44. a pure substance that consists entirely of one type of atom. 45. macromolecule that contains carbon, hydrogen, oxygen, and nitrogen; needed by the body for growth and repair 46. substance that can dissolve other substances in a solution 47. light-absorbing molecules used by plants to gather the sun’s energy

Down 1. process that releases energy from food in the presence of oxygen 2. organism whose cells contain a nucleus 4. macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus 6. many lipids are formed by combining a glycerol with this molecule. Several versions exist, depending on the number of bonds: saturated, unsaturated, and polyunsaturated 8. compound with an amino group on one end and a carboxyl group on the other end, used to build proteins 11. a negatively charged particle of an atom 12. a weak attraction between a hydrogen atom of one molecule, and an atom of another molecule. 14. Complex carbohydrates are polysaccharides formed by joining together many monosaccharides. Many animals store excess sugar as a polysaccharide called glycogen. Glycogen is broken down into glucose when glucose levels are low or when needed for muscle contraction. 17. n cells, structure that contains the cell's genetic material in the form of DNA 18. biological catalysts, and most are proteins. The role of enzymes is to speed up chemical reactions that take place in cells 19. macromolecule made mostly from carbon and hydrogen atoms; includes fats, oils, and waxes 20. the process of obtaining information by using the senses 24. the group in an experiment that is exposed to the same conditions as the experimental group except for changes in the independent variable 25. a logical interpretation based on prior knowledge and experience 26. a possible explanation for a set of observations or a possible answer to a scientific question 27. the number of protons in the nucleus of an atom 31. unicellular organism that lacks a nucleus 34. values from 0-14, used to measure the concentration of H+ ions in a solution; 35. A molecule in which the charges are unevenly distributed, resulting in oppositely charged poles. 36. The elements or compounds produced by a chemical reaction 38. evidence; information gathered from observations 39. a positively charged particle of an atom 40. a neutrally charged particle of an atom 41. single stranded nucleic acid that contains the sugar ribose