AP Biology Unit 1: Chemistry of Life practice questions

Question 1

A cell loses water to its environment via osmosis. Which property of water makes it the solvent that drives this movement?

Accepted Answer

Water's polarity lets it hydrogen-bond, dissolve solutes and form osmotic gradients. Those gradients drive water movement across membranes.

Answer

Water's high heat of vaporization pulls it toward areas of high solute concentration

Answer

Cohesion between water molecules creates pressure that forces water out of the cell

Answer

Water's surface tension resists movement, so solute concentration has no effect

Question 2

A marathon runner sweats heavily during a race. Their core body temperature stays stable despite generating massive heat. Which property of water is responsible?

Accepted Answer

Water's high heat of vaporization drives evaporative cooling as sweat evaporates. Each gram of sweat carries away a large amount of heat as it leaves the skin.

Answer

Water's high specific heat capacity absorbs heat as it evaporates from the skin

Answer

Cohesion between water molecules on the skin surface pulls heat away from the body

Answer

Water's polarity allows it to bond with heat energy and release it into the air

Question 3

A water strider walks on the surface of a pond without breaking through. A drop of dish soap added nearby causes it to sink immediately. What property did the soap disrupt, and why?

Accepted Answer

Soap disrupted surface tension, which results from cohesion between water molecules. Hydrogen bonds between adjacent molecules form a film strong enough to support small loads.

Answer

Soap disrupted adhesion between water molecules and the insect's legs

Answer

Soap reduced water's specific heat capacity, making the surface less stable

Answer

Soap broke covalent bonds within water molecules, lowering the density of the surface

Question 4

An ocean retains warmth long after sunset while a nearby parking lot cools rapidly. Both absorbed the same solar energy during the day. What property of water explains the ocean's behavior?

Accepted Answer

Water's high specific heat capacity absorbs heat with little temperature change. Oceans store that heat by day and release it slowly after sunset.

Answer

Water's heat of vaporization traps thermal energy inside the ocean at night

Answer

Hydrogen bonds between water molecules generate heat energy as they re-form after dark

Answer

The large volume of the ocean increases adhesion, which retains thermal energy

Question 5

Your friend says carbon, hydrogen, and oxygen are enough to build any biological molecule. What critical element are they missing for building proteins specifically?

Accepted Answer

Sulfur — it forms the disulfide bridges that stabilize tertiary and quaternary protein structure. Carbon, hydrogen, and oxygen alone can't build those cross-links.

Answer

Phosphorus, because it forms the peptide bonds that link amino acids together

Answer

Nitrogen is the only additional element needed, and it alone accounts for all protein-specific chemistry

Answer

Iron, because it provides the charged side chains that fold the protein correctly

Question 6

Both phospholipids and nucleic acids contain phosphorus, but they use it in completely different ways. What role does phosphorus play in each?

Accepted Answer

In phospholipids, phosphorus forms the polar head group that faces aqueous environments. In nucleic acids, phosphorus forms the covalent backbone linking nucleotide monomers and defines the 5' end of each nucleotide.

Answer

Phosphorus stores energy in both molecules by forming the same high-energy phosphate bonds found in ATP

Answer

In both molecules, phosphorus forms hydrogen bonds that hold the polymer strands together

Answer

Phosphorus provides a hydrophobic region in nucleic acids just as it does in phospholipids

Question 7

Nitrogen is listed as an element of life, but it's not in carbohydrates or most lipids. Which macromolecule classes require nitrogen in their construction?

Accepted Answer

Nitrogen builds nucleic acids, in their nitrogenous bases, and proteins, in every amino group. Carbohydrates and most lipids contain none.

Answer

Nitrogen is needed only for nucleic acids; proteins are built entirely from carbon, hydrogen, and oxygen

Answer

Nitrogen is found in carbohydrates as part of the glycosidic bonds connecting glucose monomers

Answer

Nitrogen appears in all four macromolecule classes because it stabilizes covalent bonds

Question 8

Two amino acids are joined to form a dipeptide. A water molecule is not added — instead, one seems to disappear. Where did the water go, and what type of reaction occurred?

Accepted Answer

Dehydration synthesis joins them, removing an –H and an –OH to release one water molecule. That forms a covalent peptide bond between the two amino acids.

Answer

The water is added to stabilize the new bond — this is a hydrolysis reaction

Answer

No water is produced; the hydrogen and hydroxyl groups become part of the new peptide bond itself

Answer

Water evaporates passively as heat is released when any two molecules collide

AP Biology — Unit 1: Chemistry of Life

What AP Biology Unit 1 covers

AP Biology Unit 1 practice questions

Key terms in Unit 1

Drill all of Unit 1 with spaced repetition