Question 1

Which of the following best describes an isotope of an element?

Accepted Answer

An atom with the same number of protons but a different number of neutrons.

Question 2

A sodium atom (Na) reacts with a chlorine atom (Cl) to form sodium chloride (NaCl). What type of bond is formed, and what happens to the electrons?

Accepted Answer

An ionic bond is formed; an electron is transferred from Na to Cl.

Question 3

Which of the following statements about water is TRUE and explains its importance in biological systems?

Accepted Answer

Water is cohesive due to hydrogen bonding, allowing it to have surface tension and act as a solvent.

Question 4

Which equation correctly expresses the relationship between pH and hydrogen ion concentration?

Accepted Answer

$pH = -\log[H^+]$

Question 5

A solution has a hydrogen ion concentration of $1 	imes 10^{-4}$ M. What is its pH?

Accepted Answer

$pH = 4$

Question 6

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

Accepted Answer

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

Question 7

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

Accepted Answer

A peptide bond forms between the carboxyl group of one amino acid and the amino group of another by dehydration synthesis.

Question 8

Which of the following best describes the difference between a saturated and an unsaturated fatty acid?

Accepted Answer

Saturated fatty acids have only single bonds between carbon atoms; unsaturated fatty acids have one or more double bonds.

Question 9

Which of the following is NOT a function of carbohydrates in cells?

Accepted Answer

Catalyzing chemical reactions

Question 10

A scientist is analyzing a macromolecule and finds it contains carbon, hydrogen, oxygen, nitrogen, and phosphorus. Which type of macromolecule is it most likely to be?

Accepted Answer

Nucleic acid

Question 11

Which of the following best explains why phospholipids are essential for cell membrane structure?

Accepted Answer

They have both hydrophilic and hydrophobic regions, forming a bilayer in water.

Question 12

Which of the following is a property of water that is critical for maintaining temperature stability in living organisms?

Accepted Answer

Water can absorb significant amounts of energy without a large change in temperature.

Question 13

Which of the following best describes a buffer in biological systems?

Accepted Answer

A buffer prevents drastic changes in pH by absorbing or releasing H$^+$ ions.

Question 14

Which of the following is true about the secondary structure of proteins?

Accepted Answer

It involves hydrogen bonding between the backbone atoms, forming alpha helices and beta sheets.

Question 15

Which of the following best explains why DNA strands are described as antiparallel?

Accepted Answer

The two strands have complementary sequences and run in opposite 5' to 3' directions.

Question 16

A patient is found to have a blood pH of 7.1. Which of the following best describes this condition?

Accepted Answer

The blood is acidic.

Question 17

Which of the following best describes the difference between DNA and RNA?

Accepted Answer

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

Question 18

Which of the following is a real-life example of an exergonic reaction in biological systems?

Accepted Answer

ATP hydrolysis to ADP and inorganic phosphate

Question 19

Which of the following best describes the role of functional groups in organic molecules?

Accepted Answer

Functional groups are responsible for the specific chemical properties and reactivity of organic molecules.

Chapter 2: Chemical Principles – Foundations for Microbiology

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