# Chapter 2 Exercises

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## Review Questions for Chapter 2:

### Multiple Choice

1) If xenon has an atomic number of 54 and a mass number of 108, how many neutrons does it have?

1. 54
2. 27
3. 100
4. 108

2) Atoms that vary in the number of neutrons found in their nuclei are called ________.

1. ions
2. neutrons
3. neutral atoms
4. isotopes

3) Potassium has an atomic number of 19. What is its electron configuration?

1. shells 1 and 2 are full, and shell 3 has nine electrons
2. shells 1, 2 and 3 are full and shell 4 has three electrons
3. shells 1, 2 and 3 are full and shell 4 has one electron
4. shells 1, 2 and 3 are full and no other electrons are present

4) Which type of bond represents a weak chemical bond?

1. hydrogen bond
2. atomic bond
3. covalent bond
4. nonpolar covalent bond

5) Which of the following statements is not true?

1. Water is polar.
2. Water stabilizes temperature.
3. Water is essential for life.
4. Water is the most abundant molecule in the Earth’s atmosphere.

6) When acids are added to a solution, the pH should ________.

1. decrease
2. increase
3. stay the same
4. cannot tell without testing

7) We call a molecule that binds up excess hydrogen ions in a solution a(n) ________.

1. acid
2. isotope
3. base
4. donator

8) Which of the following statements is true?

1. Acids and bases cannot mix together.
2. Acids and bases will neutralize each other.
3. Acids, but not bases, can change the pH of a solution.
4. Acids donate hydroxide ions (OH); bases donate hydrogen ions (H+).

9) Each carbon molecule can bond with as many as________ other atom(s) or molecule(s).

1. one
2. two
3. six
4. four

10) Which of the following is not a functional group that can bond with carbon?

1. sodium
2. hydroxyl
3. phosphate
4. carbonyl

11) Which of the following is the name for molecules whose structures are nonsuperimposable mirror images?

1. structural isomers
2. monomers
3. polymers
4. enantiomers

12) By definition, carbohydrates contain which elements?

1. carbon and hydrogen
2. carbon, hydrogen, and nitrogen
3. carbon, hydrogen, and oxygen
4. carbon and oxygen

13) Monosaccharides may link together to form polysaccharides by forming which type of bond?

1. hydrogen
2. peptide
3. ionic
4. glycosidic

14) Which of the following describes lipids?

1. a source of nutrients for organisms
2. energy-storage molecules
3. molecules having structural role in membranes
4. molecules that are part of hormones and pigments
5. all of the above

15) Molecules bearing both polar and nonpolar groups are said to be which of the following?

1. hydrophilic
2. amphipathic
3. hydrophobic
4. polyfunctional

16) Which of the following groups varies among different amino acids?

1. hydrogen atom
2. carboxyl group
3. R group
4. amino group

17) The amino acids present in proteins differ in which of the following?

1. size
2. shape
3. side groups
4. all of the above

18) Which of the following bonds are not involved in tertiary structure?

1. peptide bonds
2. ionic bonds
3. hydrophobic interactions
4. hydrogen bonds

19) Which of the following characteristics/compounds is not considered to be a phenotypic biochemical characteristic used of microbial identification?

1. poly-β-hydroxybutyrate
2. small-subunit (16S) rRNA gene
3. carbon utilization
4. lipid composition

20) Proteomic analysis is a methodology that deals with which of the following?

1. the analysis of proteins functioning as enzymes within the cell
2. analysis of transport proteins in the cell
3. the analysis of integral proteins of the cell membrane
4. the study of all accumulated proteins of an organism

### Fill-in-the-Blanks

21) Waxes contain esters formed from long-chain __________ and saturated __________, and they may also contain substituted hydrocarbons.

22) Cholesterol is the most common member of the __________ group, found in animal tissues; it has a tetracyclic carbon ring system with a __________ bond in one of the rings and one free __________group.

23) The sequence of amino acids in a protein is called its __________.

24) Denaturation implies the loss of the __________ and __________ structures without the loss of the __________ structure.

25) What makes ionic bonds different from covalent bonds?

26) Why are hydrogen bonds and van der Waals interactions necessary for cells?

27) Discuss how buffers help prevent drastic swings in pH.

28) Why can some insects walk on water?

29) What property of carbon makes it essential for organic life?

30) Compare and contrast saturated and unsaturated triglycerides.

31) Why are carbon, nitrogen, oxygen, and hydrogen the most abundant elements in living matter and, therefore, considered macronutrients?

32) Identify the functional group in each of the depicted structural formulas.

33) What are monosaccharides, disaccharides, and polysaccharides?

34) Describe the structure of a typical phospholipid. Are these molecules polar or nonpolar?

### Critical Thinking

35) The structural formula shown corresponds to penicillin G, a narrow-spectrum antibiotic that is given intravenously or intramuscularly as a treatment for several bacterial diseases. The antibiotic is produced by fungi of the genus Penicillium. (a) Identify three major functional groups in this molecule that each comprise two simpler functional groups. (b) Name the two simpler functional groups composing each of the major functional groups identified in (a).

36) The figure depicts the structural formulas of glucose, galactose, and fructose. (a) Circle the functional groups that classify the sugars either an aldose or a ketose, and identify each sugar as one or the other. (b) The chemical formula of these compounds is the same, although the structural formula is different. What are such compounds called?

37) Structural diagrams for the linear and cyclic forms of a monosaccharide are shown. (a) What is the molecular formula for this monosaccharide? (Count the C, H and O atoms in each to confirm that these two molecules have the same formula, and report this formula.) (b) Identify which hydroxyl group in the linear structure undergoes the ring-forming reaction with the carbonyl group.

38) The term “dextrose” is commonly used in medical settings when referring to the biologically relevant isomer of the monosaccharide glucose. Explain the logic of this alternative name.

39) Microorganisms can thrive under many different conditions, including high-temperature environments such as hot springs. To function properly, cell membranes have to be in a fluid state. How do you expect the fatty acid content (saturated versus unsaturated) of bacteria living in high-temperature environments might compare with that of bacteria living in more moderate temperatures?

40) Heating a protein sufficiently may cause it to denature. Considering the definition of denaturation, what does this statement say about the strengths of peptide bonds in comparison to hydrogen bonds?

41) The image shown represents a tetrapeptide. (a) How many peptide bonds are in this molecule? (b) Identify the side groups of the four amino acids composing this peptide.

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