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Across 4. a term for substances an enzyme acts on, including carbohydrates, lipids, nucleic acids and proteins and their monomers 6. water channel proteins 10. when the concentration of solutes is greater inside the cell; water will enter the cell 12. atoms joined together by a covalent bond 13. when the cell uses energy to move materials across the membrane (protein pumps, endocytosis and exocytosis are examples) 15. a substance that speeds up chemical reactions by lowering the required activation energy 16. a bond formed when atoms share electrons 19. when the concentration of solutes is greater outside the cell; water will leave the cell 20. they include fats and oils; source of long-term energy; make up membranes 22. maintaining constant internal conditions 23. the chemicals going in to a chemical reaction 26. the amount of energy needed to begin a reaction 27. these molecules have many functions, including speeding up chemical reactions, sending signals, and forming parts of the cell membrane 28. single units of a polymer 29. when the concentration of water and solutes is the same on both sides of a membrane 30. movement of molecules from high to low concentration

Down 1. diffusion through channel proteins 2. the dense center of an atom 3. usually proteins; they are catalysts in living things 5. a pure substance made of only one type of atom 7. these include DNA and RNA, made of monomers called nucleotides 8. these compounds include sugar, starch and cellulose; source of quick energy 9. the force of water moving into or out of a cell 11. the movement of materials without the use of energy from the cell (diffusion, facilitated diffusion and osmosis are examples) 14. the basic unit of matter 17. negatively charged particles in an atom 18. the chemicals produced in a chemical reaction 21. a bond formed when one or more electrons transfer from one atom to another 24. two or more elements chemically combined 25. a positively or negatively charged atom