2 questions, one for each idea where we can. Answer them, then see which ideas to fix.
Question 1 of 2
Which statement correctly describes what happens when a polymer is hydrolyzed?
Answer and reasoning
AHydrogen bonds between monomers are broken, which splits the polymer into smaller molecules. A student who thinks monomers are held together by hydrogen bonds picks this. The bonds that join monomers, and that hydrolysis breaks, are covalent bonds.
BThe polymer dissolves, and its monomers drift apart without any bonds being broken. A student who thinks dissolving separates a polymer into monomers picks this. Dissolving leaves molecules intact; hydrolysis breaks covalent bonds.
CCovalent bonds between monomers are broken, splitting the polymer into smaller molecules.Correct Hydrolysis cleaves the covalent bonds that join monomers, adding the H and OH of a water molecule to the two products, so the polymer is broken down into smaller molecules.
DMonomers are linked into a longer chain, and a water molecule is released for each bond formed. A student who swaps the names of the two reactions picks this. Joining monomers and releasing water describes dehydration synthesis, the reverse of hydrolysis.
The diagram represents a reaction between two monomers, labeled 1 and 2. The atoms in the dashed boxes take part in the reaction. Which statement correctly identifies and describes the reaction shown?
Answer and reasoning
AHydrolysis, which releases water as a covalent bond forms to join two monomers A student who swaps the names of the two reactions picks this. Hydrolysis uses water to break a bond between monomers; joining them and releasing water is dehydration synthesis.
BDehydration synthesis, which releases water as a covalent bond joins monomersCorrect The diagram shows the OH of monomer 1 and the H of monomer 2 leaving as H₂O while the two monomers become joined through an O atom. Joining two monomers by a covalent bond with the loss of the equivalent of a water molecule is dehydration synthesis.
CHydrogen bonding, which holds the two separate monomers together by weak attractions A student who thinks monomers are held together by hydrogen bonds picks this. The H and OH leave the monomers entirely, as water, and the monomers are joined by a covalent bond through the O atom.
DHydration, which adds a whole water molecule between the two monomers to join them A student who thinks water is added to join monomers picks this. In the diagram, H₂O is a product: it is released, not added.
In preparation: 0 of 2 sections compiled and reviewed. The rest show key terms and common mistakes from our question bank until they are.
1.3.A.1 Hydrolysis Fix
Hydrolysis
A reaction that breaks a covalent bond between monomers by adding water. The hydrogen ion from the water is added to one monomer and the hydroxyl group to the other, splitting the molecule into smaller molecules.
Hydroxyl group
An –OH group: an oxygen atom covalently bonded to a hydrogen atom. In hydrolysis, the hydroxyl group from water becomes part of one of the products.
Isotope tracer (¹⁸O)
A heavy isotope of oxygen that behaves chemically like ordinary oxygen, so supplying it in water shows which product the oxygen atom of the water ends up in.
Students often think In hydrolysis, water only surrounds the molecule as a solvent; it does not take part in the reaction. In fact No. In hydrolysis, a water molecule reacts: its H is added to one monomer and its OH to the other, so its atoms become part of the products.
Students often think Hydrolysis splits water molecules into hydrogen gas (H₂) and oxygen gas (O₂). In fact No. In hydrolysis, water is split into an H and an OH, which are added to the two products. No hydrogen or oxygen gas is released.
1.3.A.2 Monomer Fix
Monomer
A small molecule that can be joined to other similar molecules by covalent bonds to form a polymer.
Polymer
A large molecule made of many monomers joined in a chain by covalent bonds.
Covalent bond
A bond in which two atoms share a pair of electrons. Monomers in a polymer are joined by covalent bonds, which are much stronger than hydrogen bonds.
Dehydration synthesis
A reaction that joins two smaller molecules by a covalent bond. A hydrogen ion (H) is removed from one monomer and a hydroxyl group (OH) from the other, so the equivalent of a water molecule is lost from the reactants.
Polymerization
The joining of many monomers into a polymer, one dehydration synthesis at a time. Joining n monomers into an unbranched chain forms n − 1 bonds and releases n − 1 water molecules.
Students often think Hydrolysis is the reaction that joins monomers and releases water, and dehydration synthesis is the reaction that splits them apart. In fact No. The reaction that joins monomers and releases the equivalent of a water molecule is dehydration synthesis. Hydrolysis is the reverse: it uses water to break the bond between monomers.
Students often think Monomers in a polymer are held together by hydrogen bonds or other weak attractions. In fact No. Monomers in a polymer are joined by covalent bonds formed in dehydration synthesis. Hydrogen bonds are much weaker attractions between molecules or between parts of a large molecule.
5 more questions. Every wrong answer here is a real mistake students make, and you see why it is wrong as soon as you answer.
Question 1 of 5
The model shows a dimer of two monomers, A and B, and the bond that is broken when the dimer is hydrolyzed. A student hydrolyzes the dimer in water in which every water molecule contains the heavy oxygen isotope ¹⁸O. Which result should the student predict immediately after the reaction?
Answer and reasoning
A¹⁸O is in a whole water molecule added to monomer A, but not B A student who thinks a whole water molecule is attached to one monomer picks this. The water is split: its H goes to monomer A and its OH, carrying the ¹⁸O, goes to monomer B, so A gains no ¹⁸O.
B¹⁸O remains only in the water, as water is just the solvent A student who thinks water is only a solvent in hydrolysis picks this. Water is a reactant: its atoms are added to the two products, so its ¹⁸O ends up in monomer B.
C¹⁸O is released in O₂ gas as the water molecules are split apart A student who thinks hydrolysis splits water into H₂ and O₂ picks this. Hydrolysis splits water into H and OH, which are added to the products; no oxygen gas is released.
D¹⁸O is in the OH group added to monomer B, but not in monomer ACorrect The bond broken is between the O atom and monomer B, so monomer A keeps that O atom and gains an H from the water, while monomer B gains the water's OH group. The water's oxygen, ¹⁸O, therefore ends up in monomer B only.
In a cell, 10 molecules of a hypothetical monomer, each with a molar mass of 180 g/mol, are joined into one unbranched chain by dehydration synthesis. The molar mass of water is 18 g/mol. What is the molar mass of the polymer formed?
Answer and reasoning
A1800 g/mol A student who thinks a polymer's mass equals the total mass of its monomers picks this. Each of the 9 bonds formed releases a water molecule, so the polymer is 162 g/mol lighter than the monomers together.
B1620 g/mol A student who links one water molecule to each monomer picks this: 1800 − 10 × 18. Water is released per bond, and 10 monomers in a chain form only 9 bonds.
C1638 g/molCorrect Ten monomers in an unbranched chain are joined by 9 bonds, and each bond formed releases one water molecule: 10 × 180 − 9 × 18 = 1800 − 162 = 1638 g/mol.
D1962 g/mol A student who thinks water is added to join monomers picks this: 1800 + 9 × 18. In dehydration synthesis the water is released, so its mass is subtracted.
Working An unbranched chain of 10 monomers has 10 − 1 = 9 bonds, and each bond formed releases one water molecule. Mass of the monomers = 10 × 180 = 1800 g/mol. Mass of water released = 9 × 18 = 162 g/mol. Polymer = 1800 − 162 = 1638 g/mol. Distractors: no water lost, 1800 g/mol; one water per monomer, 1800 − 10 × 18 = 1620 g/mol; water added instead of released, 1800 + 162 = 1962 g/mol.
The seeds of a hypothetical plant store a polymer made of sugar monomers. During germination, an enzyme in the seed hydrolyzes this stored polymer. Which is the most likely effect on the seedling of a mutation that makes this enzyme nonfunctional?
Answer and reasoning
AThe stored polymer is not broken down, so the seedling is short of the monomers it needs to grow.Correct Without the enzyme, hydrolysis of the stored polymer does not occur at a useful rate, so its covalent bonds stay intact and the seedling receives few monomers for energy or for building new molecules; its growth is reduced.
BThe seedling uses the stored polymer whole, as it is, so its growth is not affected. A student who thinks stored polymers can be used without being broken down picks this. The seedling uses the monomers, which must first be released by hydrolysis.
CWater taken up by the seed breaks the polymer down by itself, so its growth is not affected. A student who thinks that placing a polymer in water separates its monomers picks this. Water does not break the covalent bonds of the polymer at a useful rate without the enzyme.
DThe seedling cannot join monomers into the polymer, so more free monomers are available to it. A student who confuses hydrolysis with dehydration synthesis picks this. The enzyme breaks the polymer down; without it, fewer monomers, not more, are available.
A student placed equal amounts of a polymer in two tubes of water. An enzyme that hydrolyzes the polymer was added to tube 1 only. The graph shows the concentration of monomers in each tube over 60 minutes. Which statement correctly describes the data?
Answer and reasoning
AIn tube 1, monomers were released fastest between 40 and 60 minutes, when their concentration was highest. A student who reads the highest point as the fastest rate picks this. The concentration was highest after 40 minutes, but it did not change then, so the rate was zero.
BIn tube 1, monomers were released at a single constant rate throughout all 60 minutes of the experiment. A student who assumes reactions proceed at a constant rate picks this. The increases in successive 10-minute intervals were 5.0, 3.0, 1.5, 0.5, 0 and 0 mM, so the rate fell.
CIn tube 2, monomers were also released, though more slowly than they were released in tube 1. A student who thinks water alone separates a polymer into monomers picks this. Tube 2's monomer concentration stayed at 0 throughout; without the enzyme, no hydrolysis was detected.
DIn tube 1, monomers were released fastest in the first 10 minutes, and release had stopped by 40 minutes.Correct Tube 1's monomer concentration rose by 5.0 mM in the first 10 minutes, then by 3.0, 1.5 and 0.5 mM in the next three 10-minute intervals, and did not change after 40 minutes. Tube 2 shows no monomers at any time.
In a cell, one reaction builds a polymer from monomers while another reaction breaks a different polymer into its monomers. Which statement correctly compares the role of water in the two reactions?
Answer and reasoning
ABuilding the polymer uses water; breaking the other polymer down releases water. A student who swaps hydrolysis and dehydration synthesis picks this. Synthesis releases water; hydrolysis uses it.
BBuilding the polymer releases water; breaking the other one down uses water.Correct Building a polymer joins monomers by dehydration synthesis, which releases the equivalent of a water molecule for each bond. Breaking a polymer down is hydrolysis, which uses one water molecule for each bond broken.
CBuilding the polymer uses water, and breaking the other polymer down also uses water. A student who thinks water is added to join monomers picks this. Hydrolysis does use water, but dehydration synthesis releases it.
DNeither reaction uses or releases water; in both, water serves only as the solvent. A student who thinks water is only a solvent in these reactions picks this. Water is a product of dehydration synthesis and a reactant in hydrolysis.
Compiled from the AP Biology Course and Exam Description (effective Fall 2025) and our question bank · Specialist review in progress. How these pages are made · Free, no account
