Question 1

Which of the following best describes why electrons remain in orbit around the nucleus of an atom instead of flying off, despite moving at high speeds?

Accepted Answer

Electrons are held by the electrostatic attraction between their negative charge and the positive charge of protons in the nucleus.

Question 2

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have different numbers of neutrons.

Question 3

A sodium atom (Na) has an atomic number of 11 and an atomic mass of 23. How many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 4

Which of the following best explains why water is an excellent solvent for many substances?

Accepted Answer

Water molecules are polar, allowing them to surround and separate ions and polar molecules.

Question 5

Which type of chemical bond is primarily responsible for the secondary structure (e.g., alpha helices and beta sheets) of proteins?

Accepted Answer

Hydrogen bonds

Question 6

A dehydration synthesis reaction between two monosaccharides results in which of the following?

Accepted Answer

A disaccharide and water

Question 7

Which of the following best describes the difference between a polar covalent bond and a nonpolar covalent bond?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons due to differences in electronegativity, while nonpolar covalent bonds involve equal sharing.

Question 8

Why do the cell membranes of microbes living in Arctic water likely contain more unsaturated fatty acids than those of microbes living in hot springs?

Accepted Answer

Unsaturated fatty acids increase membrane fluidity at low temperatures, preventing the membrane from becoming too rigid.

Question 9

Which of the following is NOT a function of proteins in living organisms?

Accepted Answer

Long-term energy storage

Question 10

Which of the following statements about DNA and RNA is correct?

Accepted Answer

DNA is usually double-stranded, while RNA is usually single-stranded.

Question 11

Which of the following best explains why decomposition reactions are exothermic?

Accepted Answer

They release energy as bonds in larger molecules are broken to form smaller, more stable products.

Question 12

Which of the following is a correct representation of the neutralization reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH)?

Accepted Answer

$$\mathrm{HCl} + \mathrm{NaOH} \rightarrow \mathrm{NaCl} + \mathrm{H}_2\mathrm{O}$$

Question 13

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers prevent drastic changes in internal pH.

Question 14

Which of the following is a property of water that is critical for life?

Accepted Answer

Water remains liquid across a wide range of temperatures.

Question 15

Which of the following statements about the structure of DNA is correct?

Accepted Answer

Cytosine pairs with guanine via three hydrogen bonds.

Question 16

Which of the following best explains why salts are important in biological systems?

Accepted Answer

Salts dissociate into electrolytes that help create electrical differences across cell membranes.

Question 17

Which of the following is a correct description of a phospholipid?

Accepted Answer

A molecule with a hydrophilic head and two hydrophobic fatty acid tails.

Question 18

Which of the following is a correct statement about the formation of peptide bonds?

Accepted Answer

Peptide bonds are formed by dehydration synthesis reactions between amino acids.

Question 19

Which of the following best describes the difference between a monomer and a polymer?

Accepted Answer

A monomer is a single building block, while a polymer is a large molecule made of repeating monomers.

The Chemistry of Microbiology: Essential Concepts and Macromolecules

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