1 question, one for each idea where we can. Answer them, then see which ideas to fix.
Question 1 of 1
Which statement correctly describes the relationship between monosaccharides and polysaccharides?
Answer and reasoning
AA polysaccharide is a polymer of many monosaccharides joined to one another by covalent bonds.Correct Monosaccharides (simple sugars) are the monomers of polysaccharides (complex carbohydrates); each unit is joined to the next by a covalent bond formed by dehydration synthesis.
BA polysaccharide is many monosaccharides held to one another by hydrogen bonds, not covalent bonds. A student who thinks the units of a polysaccharide are held by hydrogen bonds picks this. The units are joined by covalent bonds; hydrogen bonds are weaker attractions that can form between chains.
CA polysaccharide is just one long, unbranched chain of monosaccharides joined end to end. A student who thinks polymers must be unbranched picks this. Polysaccharides may be linear or branched.
DPolysaccharides are carbohydrates, but monosaccharides are simple sugars and not carbohydrates. A student who thinks only complex carbohydrates are carbohydrates picks this. Monosaccharides are carbohydrates too; they are the monomers from which polysaccharides are built.
In preparation: 0 of 1 sections compiled and reviewed. The rest show key terms and common mistakes from our question bank until they are.
1.4.A.1 Carbohydrate Fix
Carbohydrate
A biological molecule, usually made only of carbon, hydrogen and oxygen, that includes simple sugars (monosaccharides) and the polymers built from them (polysaccharides).
Monosaccharide
A simple sugar; the monomer from which polysaccharides are built. Glucose is an example.
Polysaccharide (complex carbohydrate)
A polymer made of many monosaccharides joined by covalent bonds. A polysaccharide may be linear (an unbranched chain) or branched.
Linear and branched polysaccharides
In a linear polysaccharide, each monosaccharide is joined to at most two others, forming one unbranched chain. In a branched polysaccharide, some monosaccharides are joined to three others, so side chains grow out from the main chain. Branching gives a molecule more chain ends.
Covalent bond between monosaccharides
The bond, formed by dehydration synthesis, that joins one monosaccharide to the next in a polysaccharide, both along a chain and at a branch point. Hydrolysis of each such bond uses one water molecule.
Starch
A polysaccharide that plants use to store glucose; some of its molecules are linear and others are branched.
Glycogen
A highly branched polysaccharide built from glucose that animals and fungi use to store glucose.
Cellulose
A linear polysaccharide built from glucose that is the main structural component of plant cell walls.
Students often think The monosaccharides of a polysaccharide, or at least its branches, are held on by hydrogen bonds rather than covalent bonds. In fact No. Every monosaccharide in a polysaccharide, along the main chain and at the branch points, is joined to the next by a covalent bond formed by dehydration synthesis. Hydrogen bonds can form between chains, but they do not join the units of a chain.
Students often think A polysaccharide is always one unbranched chain of monosaccharides, so a branched molecule is not a polysaccharide. In fact No. Monosaccharides can be connected to form polymers that are either linear or branched; both are polysaccharides.
6 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 6
The diagram shows models of three molecules, X, Y and Z. Each hexagon represents one monosaccharide unit, and each line joining two hexagons represents a bond between them. X and Y are simplified: each real molecule contains many more units than are drawn. Which statement correctly describes the three molecules?
Answer and reasoning
AX is a polysaccharide, but Y is not, because a polysaccharide cannot be branched. A student who thinks polysaccharides must be unbranched picks this. Monosaccharides can be connected into branched as well as linear polymers, so Y is a polysaccharide.
BX and Y are carbohydrates, but Z is not, because a simple sugar is not a carbohydrate. A student who thinks simple sugars are not carbohydrates picks this. Z, a monosaccharide, is a carbohydrate and is the monomer from which X and Y are built.
CX and Y are both polysaccharides, and each is a polymer of molecules like Z.Correct Z is a single monosaccharide. X is a linear chain and Y a branched chain of such units; both are polysaccharides, because polysaccharides may be linear or branched.
DY is one polysaccharide whose branch is held to the main chain by a hydrogen bond. A student who thinks the branches of a polysaccharide are held on by hydrogen bonds picks this. Y is one polysaccharide, but every unit in it, including the first unit of the branch, is joined to its neighbor by a covalent bond.
The model represents one molecule of a branched polysaccharide. Each hexagon is one monosaccharide unit, and each line joining two hexagons is a bond between them. How many water molecules are used when this molecule is hydrolyzed completely into monosaccharides?
Answer and reasoning
A17 A student who thinks the side chains are held on by hydrogen bonds picks this: 11 + 3 + 3, leaving out the 2 bonds that attach the side chains. Those bonds are covalent and are hydrolyzed like the others.
B10 A student who thinks each water molecule frees two monosaccharides picks this: 20 ÷ 2. Each water molecule breaks one bond, and the 20 units are joined by 19 bonds.
C20 A student who counts one water molecule per monosaccharide picks this. Water is used per bond, and 20 units in one connected molecule are joined by 19 bonds.
D19Correct Each bond between two units is broken by one water molecule. The 20 units are joined by 19 bonds: 11 along the main row, 3 within each side chain, and 1 attaching each side chain to the row.
Working The molecule has 12 + 4 + 4 = 20 monosaccharide units. Bonds: 11 along the main row, 3 within each side chain, and 1 joining each side chain to the main row, so 11 + (3 + 1) + (3 + 1) = 19 bonds (n − 1 = 20 − 1 = 19 for any connected molecule of n units). Hydrolysis uses one water molecule per bond, so 19 water molecules. Distractors: two monosaccharides per water, 20/2 = 10; side chains not joined covalently, 17; one water per unit, 20.
In a hypothetical species of yeast, enzyme E catalyzes the dehydration synthesis reaction involving a storage polysaccharide. A mutation makes enzyme E nonfunctional; the yeast's other enzymes are unaffected. Which outcome is most likely in the mutant cells?
Answer and reasoning
AThe polysaccharide builds up in the cells, because the cells stop breaking it down. A student who swaps dehydration synthesis and hydrolysis thinks enzyme E breaks the polysaccharide down, so predicts that it builds up. Enzyme E builds the polysaccharide; without it, no new polysaccharide is made.
BMonosaccharides that would have been stored build up, and no new polysaccharide is made.Correct Without the enzyme, monosaccharides are not joined by covalent bonds into the polysaccharide, so none is made, and monosaccharides that would have been stored are left free in the cell.
CThe polysaccharide is still made, its units held by hydrogen bonds that need no enzyme. A student who thinks monosaccharides can be held in a polysaccharide by hydrogen bonds picks this. A polysaccharide's units are joined by covalent bonds, which in these cells form only by the enzyme-catalyzed reaction.
DExtra monosaccharides are instead converted into energy, so they do not build up in the cell. A student who thinks sugar can be turned into energy picks this. Matter is not converted into energy; sugars broken down for energy leave their atoms in products such as carbon dioxide and water.
Equal masses of two polysaccharides, B (branched) and L (linear), both built from the same monosaccharide, were each mixed with an enzyme that removes monosaccharides one at a time from the free ends of chains. The graph shows the mass of monosaccharide released over 30 minutes. Which statement correctly describes the data?
Answer and reasoning
AB released monosaccharide faster than L did over the first 10 minutes.Correct In the first 10 minutes B released 70 mg and L only 16 mg. A branched molecule has more chain ends from which the enzyme can remove units, which fits B's faster early release.
BB released monosaccharide faster than L did from 25 to 30 minutes. A student who reads the higher line as the faster rate picks this. From 25 to 30 minutes B's line is flat (100 mg at both times), so its rate was zero, while L rose from 40 to 48 mg.
CB released monosaccharide at one constant rate throughout the 30 minutes. A student who assumes a constant rate picks this. B released 40 mg in the first 5 minutes but 0 mg in the last 5; its curve rises steeply and then levels off.
DB contained more monosaccharide units than L, as its curve is higher at 30 minutes. A student who thinks branching adds monosaccharides picks this. The two samples had equal masses of the same monosaccharide; B's curve is higher at 30 minutes only because L's release was slower and not yet complete.
A student adds an enzyme solution to a solution of a polysaccharide and measures the concentration of monosaccharide in the mixture after 30 minutes. The student wants to check that the monosaccharide detected came from the polysaccharide and was not already present in the enzyme solution. Which control is most appropriate?
Answer and reasoning
APolysaccharide solution with water added in place of enzyme, measured after 30 minutes A student who thinks the control must always leave out the enzyme picks this. This tube tests whether the polysaccharide breaks down without the enzyme, but it contains no enzyme solution, so it cannot show whether the enzyme solution contains monosaccharide.
BEnzyme solution in water with no polysaccharide, measured after 30 minutesCorrect If the enzyme solution itself contained monosaccharide, this tube would show it. It keeps the enzyme solution and the timing the same and leaves out only the polysaccharide.
CA second tube of enzyme solution and polysaccharide, measured after 30 minutes A student who confuses a replicate with a control picks this. A repeat of the experimental tube shows how much results vary but cannot separate monosaccharide from the polysaccharide from monosaccharide in the enzyme solution.
DWater alone, with no enzyme solution and no polysaccharide, measured after 30 minutes A student who thinks a control should contain nothing added picks this. Without the enzyme solution, this tube cannot reveal any monosaccharide that the enzyme solution brings with it.
Glycogen and cellulose are both built from glucose monomers. Glycogen molecules are highly branched, while cellulose molecules are linear. A student claims that, because they are built from the same monomer, glycogen and cellulose must be the same molecule. Which response to the claim is correct?
Answer and reasoning
AIt is correct: polymers built from the same monomer are the same molecule, whatever their size or shape. A student who thinks the monomer alone defines a polymer picks this. Glycogen is branched and cellulose linear, so the same monomer has been connected in different ways.
BIt is incorrect, because glycogen's branches are held on by hydrogen bonds, not covalent ones. A student who thinks the branches of a polysaccharide are held on by hydrogen bonds picks this. Every glucose unit in glycogen, including those at branch points, is joined by a covalent bond; the two polymers differ in how their units are connected, not in the kind of bond that joins them.
CIt is incorrect: these two polymers of one monomer differ in how their glucose monomers are connected.Correct A polysaccharide is defined by its monomers and by how they are connected. Glycogen's glucose units are connected into branched molecules and cellulose's into linear chains, so they are different polymers even though their monomer is the same.
DIt is incorrect, because glycogen is branched and so is not truly a polysaccharide molecule. A student who thinks polysaccharides must be unbranched picks this. Monosaccharides can form branched polymers; glycogen is a branched polysaccharide.
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
