AP Biology Unit 1 Practice Questions: Chemistry of Life MCQs and FRQs

Which property of water best explains why water molecules stick to one another at the surface?

1. A. Denaturation
2. B. Cohesion
3. C. Hydrolysis
4. D. Translation

Which property of water best explains why large bodies of water resist rapid temperature changes?

1. A. High specific heat
2. B. Hydrophobic exclusion
3. C. Low heat of vaporization
4. D. Low surface tension

Water is an effective solvent for many ionic and polar substances primarily because:

1. A. It is nonpolar and cannot form hydrogen bonds
2. B. It has no partial charges on its atoms
3. C. It repels all charged particles in solution
4. D. It is a polar molecule that forms favorable interactions with solutes

Water moving upward in plant xylem against gravity relies most strongly on:

1. A. Cohesion among water molecules and adhesion to tube walls
2. B. Hydrolysis of cellulose in leaves
3. C. Translation of mRNA in roots
4. D. Denaturation of transport proteins

Ice is less dense than liquid water primarily because:

1. A. Covalent bonds within each water molecule weaken when water freezes
2. B. Hydrogen bonds in ice form a lattice that spaces molecules farther apart
3. C. Hydrogen bonds do not exist in solid water
4. D. Ice molecules have a smaller molar mass than liquid water molecules

Which set lists the six most common elements found in living organisms (CHNOPS)?

1. A. Helium, neon, argon, krypton, xenon, radon
2. B. Carbon, silicon, arsenic, selenium, iodine, fluorine
3. C. Carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur
4. D. Sodium, chlorine, iron, gold, copper, zinc

Carbon's central role in the diversity of organic molecules is mainly due to:

1. A. Its ability to form four covalent bonds and build chains, branches, and rings
2. B. Its inability to bond with hydrogen or oxygen
3. C. Its tendency to exist only as a monatomic gas in cells
4. D. Its role as a fully charged ion in all macromolecules

Phosphorus is especially important in living systems because it is a key component of:

1. A. Pure hydrocarbon tails of triglycerides only
2. B. Amino acid R groups in all proteins
3. C. Alpha-glucose units in cellulose only
4. D. Nucleotides, ATP, and phospholipids

Sulfur contributes to protein structure primarily by allowing:

1. A. Glycosidic bonds between glucose monomers
2. B. Disulfide bridges between cysteine side chains
3. C. Peptide bonds between every adjacent amino acid
4. D. Phosphodiester bonds in DNA

A monomer is best defined as:

1. A. A small repeating subunit that can join to form a polymer
2. B. A large macromolecule made of many different elements only
3. C. A lipid bilayer surrounding the nucleus
4. D. An enzyme that always breaks polymers apart

Which monomer–polymer pairing is correct?

1. A. Monosaccharides build DNA
2. B. Fatty acids build starch
3. C. Nucleotides build triglycerides
4. D. Amino acids build proteins

Which statement about lipids and polymers is most accurate?

1. A. Lipids are polymers of nucleotides that store genetic information
2. B. Lipids are long chains of amino acids joined by peptide bonds
3. C. Lipids always form polysaccharides when dehydrated
4. D. Lipids are not usually true polymers of identical repeating monomers

Changing the order of monomers in a biological polymer most often:

1. A. Has no effect because only polymer length matters
2. B. Only affects lipids, not proteins or nucleic acids
3. C. Changes the structure and function of the polymer
4. D. Converts the polymer entirely into water

Dehydration synthesis reactions:

1. A. Break polymers using water and release only heat
2. B. Join monomers to build polymers and release water
3. C. Occur only when ice melts into liquid water
4. D. Always denature proteins at high temperature

Hydrolysis reactions:

1. A. Never require enzymes in living cells
2. B. Build polymers without using or releasing water
3. C. Form hydrogen bonds only between water molecules
4. D. Break polymers into monomers by adding water

When two amino acids link to begin a polypeptide chain, the reaction is:

1. A. Dehydration synthesis with water released
2. B. Denaturation caused only by pH change
3. C. Complementary base pairing in DNA
4. D. Hydrolysis with water added to break a bond

Digesting starch into glucose in the small intestine primarily involves:

1. A. Semiconservative replication of DNA
2. B. Dehydration synthesis that removes water while building starch
3. C. Hydrolysis reactions that add water to break glycosidic bonds
4. D. Translation of mRNA on ribosomes

The four major classes of biological macromolecules in cells are:

1. A. ATP, enzymes, DNA, and mRNA as unrelated non-macromolecules
2. B. Carbohydrates, lipids, proteins, and nucleic acids
3. C. Water, salts, noble gases, and metals only
4. D. Monomers, polymers, ions, and isotopes

Most enzymes are:

1. A. Proteins that speed up specific chemical reactions
2. B. Nucleic acids that make up the plasma membrane bilayer
3. C. Carbohydrates that store genetic information
4. D. Lipids that form the sugar-phosphate backbone of DNA

Genetic information in cells is primarily stored in:

1. A. Triglycerides in chromosomes
2. B. Starch granules in the cytoplasm
3. C. Lipid bilayers of the plasma membrane
4. D. Nucleic acids such as DNA

Which statement best connects macromolecule structure to function?

1. A. Only water molecules show structure–function relationships in cells
2. B. All macromolecules share identical shapes and therefore identical functions
3. C. Function depends only on whether a molecule is polar, not on its 3D structure
4. D. The shape and chemical arrangement of a macromolecule help determine what job it performs

Glucose is classified as a:

1. A. Nucleotide
2. B. Monosaccharide
3. C. Polypeptide
4. D. Phospholipid

Which polysaccharide is the main short-term energy storage molecule in animals?

1. A. DNA
2. B. Chitin in plant cell walls
3. C. Glycogen
4. D. Cellulose

Cellulose is structurally important in plants because it:

1. A. Stores genetic information in roots
2. B. Forms strong fibrils that reinforce plant cell walls
3. C. Catalyzes peptide bond formation in ribosomes
4. D. Creates amphipathic bilayers around the nucleus

Starch, glycogen, and cellulose are all polymers of glucose, but they differ mainly in:

1. A. Whether they are classified as lipids rather than carbohydrates
2. B. How glucose monomers are linked and branched, which affects function
3. C. Whether they contain nitrogenous bases instead of sugars
4. D. Their roles as enzymes that replicate DNA

A key property shared by most lipids is that they are:

1. A. Highly soluble because they carry many ionic groups on long hydrocarbon tails
2. B. Hydrophobic and insoluble in water
3. C. Built from amino acid monomers linked by peptide bonds
4. D. Polar polymers of nucleotides

The primary lipid component of cell membranes is:

1. A. Messenger RNA
2. B. Glycogen
3. C. Phospholipid
4. D. Cellulose

Phospholipids form bilayers in aqueous environments because they are:

1. A. Polymers of amino acids that repel water
2. B. Made only of saturated fatty acids with no phosphate group
3. C. Amphipathic, with hydrophilic heads and hydrophobic tails
4. D. Entirely nonpolar and unable to interact with water

Which statement about lipids is FALSE?

1. A. Many lipids store energy efficiently in C–H bonds
2. B. Steroids are lipids based on four fused carbon rings
3. C. Lipids are always long polymers of identical monomers joined by peptide bonds
4. D. Fatty acids in triglycerides may be saturated or unsaturated

The monomers that build proteins are:

1. A. Fatty acids only
2. B. Monosaccharides
3. C. Amino acids
4. D. Nucleotides

The covalent bond that joins two amino acids in a polypeptide is a:

1. A. Glycosidic bond
2. B. Phosphodiester bond
3. C. Hydrogen bond only
4. D. Peptide bond

Heating a protein until it loses its native shape and function is called:

1. A. Denaturation
2. B. Semiconservative replication
3. C. Dehydration synthesis
4. D. Hydrolysis of peptide bonds only

A mutation changes one amino acid in an enzyme's active site and the enzyme no longer binds its substrate. This best illustrates:

1. A. Structure affects function
2. B. Water is nonpolar
3. C. Carbohydrates always form DNA
4. D. Lipids store genetic information

The primary structure of a protein is:

1. A. Alpha helices and beta pleated sheets only
2. B. The overall 3D shape of one polypeptide
3. C. The arrangement of multiple polypeptide subunits
4. D. The linear sequence of amino acids

The monomers that build nucleic acids are:

1. A. Fatty acids
2. B. Amino acids
3. C. Nucleotides
4. D. Monosaccharides

Each nucleotide in a nucleic acid contains:

1. A. Glucose units linked by glycosidic bonds only
2. B. A sugar, a phosphate group, and a nitrogenous base
3. C. Only a fatty acid and glycerol
4. D. Two amino acids joined by a peptide bond

The repeating backbone of DNA and RNA is made of:

1. A. Amino acids linked by peptide bonds
2. B. Alternating sugar and phosphate groups
3. C. Fatty acid tails and steroid rings
4. D. Only nitrogenous bases with no sugars

The part of a nucleic acid that stores hereditary information is:

1. A. The hydrophobic tails of phospholipids
2. B. The R groups of amino acids only
3. C. The glycosidic bonds in cellulose
4. D. The sequence of nitrogenous bases

Hydrophobic lipid tails facing inward while polar heads face water in a membrane best demonstrates:

1. A. That proteins store genetic information in their R groups
2. B. That water is nonpolar and cannot hydrogen bond
3. C. That all macromolecules are identical polymers
4. D. How molecular structure determines membrane organization and function

Which statement best summarizes AP Biology Unit 1: Chemistry of Life?

1. A. Chemical structure and properties of molecules help explain how living systems work
2. B. Biology does not depend on chemistry or molecular interactions
3. C. All macromolecules have the same shape and function
4. D. Water is nonpolar and cannot support life processes