Chapter 2—The Chemical Composition of Cells Key
1. The mass number of an atom is determined by
2. Atoms that have the same number of protons but different numbers of neutrons are called…
3. When two atoms share a pair of electrons, a(n) ____ bond is formed.
4. When ions are attracted to one another by opposite electrical charges, a(n) ____ bond is formed.
5. A special covalent bond, called a(n) ____ bond, links two amino acids together.
6. Which of the following properties is exhibited by water?
7. The large and complex carbon-containing molecules found in living things are called…
8. The smallest general kind of carbohydrate is called ____.
9. ____ is an example of a structural carbohydrate found in plants.
10. Fats and oils are structurally made of one, two or three fatty acid molecules connected to a single
“backbone” molecule of ____.
11. Proteins are large compounds made up of smaller units called
12. A nucleotide, the repeating subunit that makes up a nucleic acid, is composed of which three smaller
building blocks?
13. A(n) ____ is a long molecule of repeating subunits called nucleotides.
14. The most common atoms in living things are hydrogen and oxygen, bonded together in molecules of
15. The second law of thermodynamics implies that in every energy conversion, some energy is lost, usually as
____.
16. The ____ is the location on an enzyme where the substrate attaches.
17. The ____ is the energy required to get a reaction started.
18. An atom’s ability to combine with other atoms is determined by the number of electrons in its inner energy
level.
19. When an atom absorbs energy, one or more of its electrons move from a lower to a higher energy level.
20. Since hydrogen bonds are weak compared to covalent bonds, they really are not very important in biological
systems.
21. The pH of a plant cell can change a great deal, and the chemical reactions within will still take place.
22. Few organisms can digest cellulose.
23. Gram for gram, fats contain more than twice as much energy as carbohydrates.
24. A single enzyme can control a variety of different reactions.
25. The order of amino acids in a protein determines its structure and function.
26. The energy present in the universe decreases over time.
27. Proteins are important structural molecules in cells.
28. The ____________________ of water is the primary characteristic that causes it to be a good solvent.
29. A substance when added to pure water dissociates and results in a solution with a pH of 4.9. The general
name for that kind of substance is ____________________.
30. A substance when added to pure water dissociates and results in a solution with a pH of 8.9. The general
name for that kind of substance is ____________________.
31. The basic units of carbohydrates are made up of the atoms C, H and 0, in the ratio ____________________.
32. The first energy level of an atom can hold a maximum of ____________________ electrons.
33. ____________________ are carbohydrates made up of two monosaccharides linked together.
34. ____________________ are carbohydrates made up of many monosaccharides linked together.
35. When a fatty acid contains one or more double bonds in its hydrocarbon chain, it is said to be
____________________.
36. Lipids all share the characteristic that they are not soluble in ____________________.
37. The first law of thermodynamics states that energy cannot be created or destroyed, but only
____________________ in form.
38. Energy is defined as the capacity to ____________________.
39. The second law of thermodynamics implies that in every system the ____________________ is increasing.
40. What is the biological importance of the evaporation of water?
41. What does “essential amino acids” mean?
42. How are nucleic acids used in the cell?
43. What do we mean when we call ATP the “energy currency” of cells?