Question 1

Which of the following statements best explains why isotopes of an element have nearly identical chemical properties?

Accepted Answer

Because isotopes have the same number of protons and electrons, which determine chemical behavior.

Question 2

A solution is prepared by dissolving 18 grams of NaCl in 2 liters of water. What is the weight-volume proportion of NaCl in this solution?

Accepted Answer

$$9\ \mathrm{g/L}$$

Question 3

Which type of chemical bond is primarily responsible for the structure of water and its ability to dissolve many substances?

Accepted Answer

Hydrogen bonds between water molecules and polar solutes

Question 4

A patient receives an intravenous solution labeled as 0.9% saline. How many grams of NaCl are present in 500 mL of this solution?

Accepted Answer

$$4.5\ \mathrm{g}$$

Question 5

Which of the following best describes an amphipathic molecule?

Accepted Answer

A molecule that contains both hydrophilic and hydrophobic regions

Question 6

Which of the following is a correct formula for calculating the pH of a solution?

Accepted Answer

$$\mathrm{pH} = -\log [\mathrm{H}^+]$$

Question 7

Which of the following best explains why saturated fatty acids are solid at room temperature, while unsaturated fatty acids are liquid?

Accepted Answer

Saturated fatty acids lack double bonds, allowing tight packing; unsaturated fatty acids have double bonds that create kinks, preventing tight packing.

Question 8

A scientist is studying a bacterial cell wall component that is toxic and found only in Gram-negative bacteria. Which molecule is she most likely investigating?

Accepted Answer

Lipopolysaccharide (LPS)

Question 9

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

Accepted Answer

DNA nucleotides contain deoxyribose and thymine; RNA nucleotides contain ribose and uracil.

Question 10

Which of the following functional groups is present in all amino acids and is responsible for their acidic properties?

Accepted Answer

Carboxyl group ($$-\mathrm{COOH})$$

Question 11

A protein's tertiary structure is stabilized by which of the following interactions?

Accepted Answer

Hydrogen bonds, ionic bonds, van der Waals interactions, and disulfide bridges

Question 12

Which of the following best describes a dehydration synthesis reaction?

Accepted Answer

A reaction that joins two molecules together by removing a molecule of water

Question 13

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, forming the basis of cell membranes

Question 14

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

Accepted Answer

$$4$$

Question 15

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

Accepted Answer

Water molecules have polar covalent bonds, allowing them to form hydrogen bonds with other polar molecules.

Question 16

Which of the following is a correct match between a polysaccharide and its biological function?

Accepted Answer

Cellulose: structural component of plant and algal cell walls

Question 17

Which of the following best describes the primary structure of a protein?

Accepted Answer

The linear sequence of amino acids in a polypeptide chain

Question 18

Which of the following molecules is classified as an organic molecule?

Accepted Answer

Glucose ($$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6)$$

Question 19

Which of the following best describes the role of ATP in cells?

Accepted Answer

ATP is a ribonucleotide that serves as a primary energy source for cellular processes.

Question 20

A scientist is analyzing a molecule with a long hydrocarbon chain and a carboxylic acid group. Which type of molecule is this most likely to be?

Accepted Answer

Fatty acid

Biochemistry Basics for Microbiology

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