Question 1

Refer to the first image. When table salt (NaCl) dissolves in water, what is the primary reason the ions separate and remain dissolved?

Accepted Answer

Water is a polar solvent, so its molecules surround and stabilize the Na⁺ and Cl⁻ ions, preventing them from re-forming a crystal.

Question 2

Based on the second image, which of the following best explains why ice is less dense than liquid water?

Accepted Answer

Hydrogen bonds in ice form a rigid, open lattice that spaces water molecules farther apart than in liquid water.

Question 3

Refer to the third image. If the pH of a solution changes from 7 to 5, by what factor does the hydrogen ion concentration change?

Accepted Answer

It increases by a factor of 100.

Question 4

Using the fourth image, which process is being illustrated and what is its biological significance?

Accepted Answer

Hydrolysis; it is how cells break down carbohydrates into simple sugars for energy.

Question 5

Refer to the fifth image. What is the main difference between the process shown here and the previous image?

Accepted Answer

This image shows dehydration synthesis, which builds carbohydrates from simple sugars, while the previous image shows hydrolysis, which breaks them down.

Question 6

Based on the sixth and seventh images, what type of reaction forms sucrose from glucose and fructose, and what is a byproduct?

Accepted Answer

Dehydration synthesis; water is produced.

Question 7

Refer to the eighth image. What is the structural difference between ribose and deoxyribose, and why is this important for nucleic acids?

Accepted Answer

Ribose has one more oxygen atom than deoxyribose, which makes RNA less stable than DNA.

Question 8

Refer to the ninth and tenth images. What is the main structural difference between saturated and unsaturated fatty acids?

Accepted Answer

Unsaturated fatty acids have double bonds, causing kinks in the chain.

Question 9

Refer to the eleventh image. What property of phospholipids makes them essential for cell membrane structure?

Accepted Answer

They have both hydrophilic (polar) heads and hydrophobic (nonpolar) tails, allowing them to form bilayers in water.

Question 10

Refer to the twelfth, thirteenth, and fourteenth images. Which levels of protein structure are illustrated, and what stabilizes each?

Accepted Answer

Secondary (alpha helix and beta sheet) and quaternary; secondary is stabilized by hydrogen bonds, quaternary by interactions between polypeptide chains.

Question 11

Refer to the fifteenth image. What is the role of enzymes in biochemical reactions, as shown in the diagram?

Accepted Answer

Enzymes lower the activation energy, speeding up reactions without being consumed.

Question 12

Refer to the sixteenth image. Which components are found in a nucleotide, and which is unique to nucleic acids?

Accepted Answer

A phosphate group, a sugar, and a nitrogenous base; the combination of all three is unique to nucleic acids.

Question 13

Refer to the seventeenth image. What happens when ATP is hydrolyzed in the cell?

Accepted Answer

ATP is converted to ADP and a phosphate group, releasing energy for cellular work.

The Chemistry of Living Things: Water, pH, and Organic Molecules

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