,
,
,
,OpenStax Concepts of Biology Instructor Answer Guide
Concepts of Biology
Unit 1. The Cellular Foundation of Life
Chapter 2: Chemistry of Life
Art Connection Questions
1. Figure 2.3. How many neutrons do (K) potassium-39 and potassium-40 have, respectively?
Answer
Potassium-39 has twenty neutrons. Potassium-40 has twenty one neutrons.
Review Questions
2. Magnesium has an atomic number of 12. Which of the following statements is true of a neutral
magnesium atom?
Answer
A. It has 12 protons, 12 electrons, and 12 neutrons.
3. Which type of bond represents a weak chemical bond?
Answer
A. hydrogen bond
4. An isotope of sodium (Na) has a mass number of 22. How many neutrons does it have?
Answer
, OpenStax Concepts of Biology Instructor Answer Guide
A. 11
5. Which of the following statements is not true?
Answer
D. Water is the most abundant atom in Earth’s atmosphere.
6. Using a pH meter, you find the pH of an unknown solution to be 8.0. How would you describe
this solution?
Answer
C. weakly basic
7. The pH of lemon juice is about 2.0, whereas tomato juice's pH is about 4.0. Approximately
how much of an increase in hydrogen ion concentration is there between tomato juice and lemon
juice?
Answer
C. 100 times
8. An example of a monosaccharide is ________.
Answer
D. all of the above (fructose, glucose, galactose)
9. Cellulose and starch are examples of ________.
Answer
D. polysaccharides
10. Phospholipids are important components of __________.
Answer
A. the plasma membrane of cells
11. The monomers that make up proteins are called _________.
Answer
C. amino acids
Critical Thinking Questions
12. Why are hydrogen bonds and van der Waals interactions necessary for cells?
Answer
Hydrogen bonds and van der Waals interactions form weak associations between different
molecules. They provide the structure and shape necessary for proteins and DNA within cells so
that they function properly. Hydrogen bonds also give water its unique properties, which are
necessary for life.
13. Why can some insects walk on water?
Answer
Some insects can walk on water, although they are heavier (denser) than water, because of the
surface tension of water. Surface tension results from cohesion, or the attraction between water
molecules at the surface of the body of water [the liquid-air (gas) interface].
14. Explain why water is an excellent solvent.
Answer
Water molecules are polar, meaning they have separated partial positive and negative charges.
Because of these charges, water molecules are able to surround charged particles created when a
substance dissociates. The surrounding layer of water molecules stabilizes the ion and keeps
differently charged ions from reassociating, so the substance stays dissolved.
15. Explain at least three functions that lipids serve in plants and/or animals.
Answer
,
,
,OpenStax Concepts of Biology Instructor Answer Guide
Concepts of Biology
Unit 1. The Cellular Foundation of Life
Chapter 2: Chemistry of Life
Art Connection Questions
1. Figure 2.3. How many neutrons do (K) potassium-39 and potassium-40 have, respectively?
Answer
Potassium-39 has twenty neutrons. Potassium-40 has twenty one neutrons.
Review Questions
2. Magnesium has an atomic number of 12. Which of the following statements is true of a neutral
magnesium atom?
Answer
A. It has 12 protons, 12 electrons, and 12 neutrons.
3. Which type of bond represents a weak chemical bond?
Answer
A. hydrogen bond
4. An isotope of sodium (Na) has a mass number of 22. How many neutrons does it have?
Answer
, OpenStax Concepts of Biology Instructor Answer Guide
A. 11
5. Which of the following statements is not true?
Answer
D. Water is the most abundant atom in Earth’s atmosphere.
6. Using a pH meter, you find the pH of an unknown solution to be 8.0. How would you describe
this solution?
Answer
C. weakly basic
7. The pH of lemon juice is about 2.0, whereas tomato juice's pH is about 4.0. Approximately
how much of an increase in hydrogen ion concentration is there between tomato juice and lemon
juice?
Answer
C. 100 times
8. An example of a monosaccharide is ________.
Answer
D. all of the above (fructose, glucose, galactose)
9. Cellulose and starch are examples of ________.
Answer
D. polysaccharides
10. Phospholipids are important components of __________.
Answer
A. the plasma membrane of cells
11. The monomers that make up proteins are called _________.
Answer
C. amino acids
Critical Thinking Questions
12. Why are hydrogen bonds and van der Waals interactions necessary for cells?
Answer
Hydrogen bonds and van der Waals interactions form weak associations between different
molecules. They provide the structure and shape necessary for proteins and DNA within cells so
that they function properly. Hydrogen bonds also give water its unique properties, which are
necessary for life.
13. Why can some insects walk on water?
Answer
Some insects can walk on water, although they are heavier (denser) than water, because of the
surface tension of water. Surface tension results from cohesion, or the attraction between water
molecules at the surface of the body of water [the liquid-air (gas) interface].
14. Explain why water is an excellent solvent.
Answer
Water molecules are polar, meaning they have separated partial positive and negative charges.
Because of these charges, water molecules are able to surround charged particles created when a
substance dissociates. The surrounding layer of water molecules stabilizes the ion and keeps
differently charged ions from reassociating, so the substance stays dissolved.
15. Explain at least three functions that lipids serve in plants and/or animals.
Answer
