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Quizzes > Science > Biology

AP Bio Chapters 2-4 Quiz: Ace Atoms, Molecules & Compounds

Ready for your ap bio chapter 4 quiz? Challenge yourself with molecules & compounds questions!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art style illustration of atoms and molecules for an AP Biology quiz on chapters 2 to 4 on a golden yellow background

Calling all AP Biology enthusiasts! Dive into atoms, molecules & compounds with our AP Bio Chapter 2-4 Quiz, boosting your grasp of ap bio chapter 2 and key topics in ap bio chapter 4 quiz. Whether you're brushing up for an ap bio chapter 3 review or tackling ap bio review questions, this interactive challenge puts your skills to the test with an ap biology molecules quiz. Along the way, you'll master how ions form bonds, uncover water's unique properties, and unravel the role of macromolecules that power every living cell. Want more targeted practice? Check out our AP Biology Chapter 4 Quiz or hone your basics in the Atoms and Molecules Quiz. Ready to boost your bio mastery? Dive in now!

Which subatomic particle has a positive charge?
Proton
Neutron
Electron
Photon
Protons carry a positive charge and reside in the nucleus of an atom. Neutrons are neutral with no charge, and electrons are negatively charged. Photons are particles of light, not atomic constituents. source
What does the atomic number of an element represent?
Number of protons in the nucleus
Number of neutrons in the nucleus
Number of electrons in a neutral atom
Sum of protons and neutrons
The atomic number equals the number of protons in an atom’s nucleus and uniquely defines the element. Neutrons contribute to isotopes but do not affect the atomic number. In neutral atoms, the number of electrons equals the number of protons. source
Isotopes of an element differ in their number of which subatomic particle?
Protons
Neutrons
Electrons
Orbitals
Isotopes have the same atomic number (protons) but different numbers of neutrons, giving them different mass numbers. Electron count does not define isotopes. Orbitals describe electron locations, not isotope identity. source
Which of the following best defines a molecule?
Two or more atoms joined by chemical bonds
A single atom with a net charge
A substance composed of ions
A mixture of different elements
A molecule is formed when two or more atoms bond chemically, whether they are the same or different elements. A charged single atom is an ion, not a molecule. Mixtures and ionic compounds have distinct definitions from molecules. source
How does a compound differ from a molecule?
It contains two or more different elements
It only has ionic bonds
It is always a gas
It consists of isotopes
A compound is a molecule that contains atoms of at least two different elements bonded together. Molecules can be composed of the same element, like O2. Compounds aren’t defined by bond type or physical state. source
Ionic bonds form when electrons are:
Shared equally between atoms
Transferred from one atom to another
Shared unequally between atoms
Delocalized over several atoms
Ionic bonds result from the complete transfer of electrons from one atom to another, creating oppositely charged ions that attract. Equal or unequal sharing of electrons refers to covalent bonds. Delocalization occurs in metallic bonds. source
Water is considered a polar molecule because:
Oxygen has higher electronegativity than hydrogen
Hydrogen has more protons than oxygen
Electrons are shared equally
The molecule is symmetric
In water, oxygen attracts the shared electrons more strongly than hydrogen, creating a partial negative charge on oxygen and partial positive charges on hydrogens. This unequal sharing makes the molecule polar. Symmetry and equal sharing would make a molecule nonpolar. source
Which type of bond forms between adjacent water molecules?
Covalent bond
Ionic bond
Hydrogen bond
Peptide bond
Hydrogen bonds occur between the slightly positive hydrogen of one water molecule and the slightly negative oxygen of another. Covalent bonds hold the H and O within a single water molecule. Ionic and peptide bonds do not form between water molecules. source
A solution with pH 3 is classified as:
Neutral
Basic
Acidic
Alkaline
The pH scale runs from 0 to 14, with values below 7 being acidic, 7 neutral, and above 7 basic (alkaline). A pH of 3 indicates a high hydrogen ion concentration, characteristic of an acid. source
What role do biological buffers play in cells?
Catalyze metabolic reactions
Transport nutrients
Resist changes in pH
Increase reaction temperature
Buffers maintain a stable pH by absorbing excess H+ or OH- ions, preventing drastic pH shifts. They are not enzymes and do not transport materials or affect temperature. source
Electronegativity is best defined as:
Ability to lose electrons
Attraction for electrons in a bond
Measure of atomic mass
Strength of ionic bonds
Electronegativity measures how strongly an atom attracts bonding electrons. It is not about losing electrons or atomic mass. Ionic bond strength involves charge and distance, not directly electronegativity. source
Which pair represents structural isomers?
Glucose and fructose
D- and L-alanine
cis- and trans-2-butene
Carbon-12 and Carbon-14
Structural isomers share the same molecular formula but differ in atom connectivity; glucose and fructose are classic examples (C6H12O6). D- and L-alanine are enantiomers, cis/trans are geometric isomers, and isotopes differ in neutron number. source
Which functional group characterizes alcohols?
Amino group
Carbonyl group
Hydroxyl group
Carboxyl group
Alcohols contain a hydroxyl (-OH) group attached to a carbon atom. Amino groups define amines, carbonyl groups appear in ketones/aldehydes, and carboxyl groups characterize acids. source
Dehydration synthesis reactions involve:
Addition of a water molecule to break a bond
Removal of water to form a bond
Breaking polymers into monomers
Oxidation of organic molecules
Dehydration synthesis, or condensation, removes a water molecule to link monomers into polymers. The reverse, hydrolysis, adds water to break bonds. It is not an oxidation reaction. source
When NaCl dissolves in water, Na+ and Cl- ions are separated due to:
Hydrogen bonding between ions
Ionic attractions in water
Hydration shells formed by water molecules
Covalent interactions with water
Water molecules surround and stabilize Na+ and Cl– ions through their dipole moments, creating hydration shells that pull the ions apart. This is not due to covalent interactions or hydrogen bonds between the ions themselves. source
Water’s high specific heat capacity is mainly a result of:
Ionic bonds in water
Weak Van der Waals forces
Extensive hydrogen-bond network
High molecular mass of water
Hydrogen bonds between water molecules require significant energy to break, giving water a high specific heat. Its molecular mass is low, and ionic or Van der Waals forces are not the main contributors. source
Cohesion in water refers to:
Water sticking to other substances
Water molecules sticking to each other
Water dissolving ionic compounds
Water undergoing phase change
Cohesion is the attraction between water molecules via hydrogen bonding. Adhesion describes water sticking to other surfaces. Dissolution and phase changes are different phenomena. source
Which buffer system is most important for maintaining blood pH in humans?
Phosphate buffer
Bicarbonate buffer
Ammonia buffer
Acetate buffer
The bicarbonate buffer system (H2CO3/HCO3–) is the primary regulator of blood pH in humans. Phosphate plays a minor role intracellularly, and ammonia and acetate buffers are not major blood buffers. source
Carbon’s ability to form four covalent bonds allows it to:
Form only linear molecules
Build complex and diverse organic structures
Create only small molecules
Bond exclusively with metals
With four valence electrons available for bonding, carbon can form tetravalent structures, leading to a vast array of complex molecules including rings, chains, and branches essential to life. It does not bond exclusively with metals. source
Enantiomers are molecules that are:
Different structural isomers
Mirror images that cannot be superimposed
Geometric isomers with cis/trans differences
Identical molecules in different conformations
Enantiomers are non-superimposable mirror-image stereoisomers. They have identical connectivity but differ in three-dimensional arrangement, affecting optical activity. Geometric isomers differ by bond rotation restrictions. source
The dipole moment of a molecule depends on:
Number of protons in each atom
Only the molecular mass
Bond polarity and molecular geometry
Presence of ionic bonds
Dipole moment arises from differences in electronegativity between atoms (bond polarity) and the spatial arrangement of those bonds (geometry). Mass and ionic bonds alone do not determine dipole moments. source
Trace elements such as iron often function as:
Primary energy sources
Cofactors in enzymatic reactions
Structural components of lipids
Genetic information carriers
Trace elements like iron and zinc serve as cofactors that assist enzymes in catalyzing reactions by stabilizing structures or participating in redox chemistry. They are not energy sources or genetic materials. source
Van der Waals interactions contribute to protein structure by:
Forming strong covalent cross-links
Creating permanent ionic bonds
Providing weak, transient attractions between nonpolar regions
Establishing hydrogen bonds with water
Van der Waals interactions are weak attractions between transient dipoles in nonpolar side chains that help stabilize tertiary protein structure. They are not covalent or ionic bonds, nor hydrogen bonds with water. source
The pKa of an amino acid side chain indicates:
Temperature at which the side chain denatures
The pH at which the side chain is half protonated
Its maximum buffering capacity
Its solubility in water
pKa is the pH at which a functional group is 50% protonated and 50% deprotonated, critical for understanding ionization states in proteins. It does not directly indicate temperature or solubility. source
The distinction between alpha and beta glycosidic bonds in polysaccharides lies in:
The type of monosaccharides joined
Orientation of the hydroxyl group on the anomeric carbon
Number of carbons in the sugar
Presence of nitrogen atoms
Alpha and beta linkages differ by the position of the ?OH group at the anomeric carbon: alpha has the group below the ring plane, beta above. This orientation alters digestibility and polymer shape. source
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Study Outcomes

  1. Identify Atomic Structure -

    Recognize and label the subatomic particles and their arrangement within atoms, including protons, neutrons, and electrons, to build a strong foundation in ap bio chapter 2 concepts.

  2. Explain Chemical Bonding -

    Describe how ionic, covalent, and hydrogen bonds form and determine the stability and properties of molecules and compounds in biological systems.

  3. Distinguish Molecule Types -

    Differentiate between simple molecules, complex compounds, and macromolecules, and understand their roles in cellular structure and function.

  4. Calculate Molecular Mass -

    Perform basic calculations of molecular weight using atomic masses, enabling you to predict reaction outcomes and stoichiometry in biochemical processes.

  5. Analyze Molecular Interactions -

    Evaluate how intermolecular forces like Van der Waals interactions, dipole - dipole interactions, and hydrogen bonding affect molecular behavior and biological activity.

  6. Apply Knowledge to Quiz Scenarios -

    Use instant feedback from quiz questions to reinforce learning, identify knowledge gaps, and prepare effectively for ap bio chapter 3 review and chapter 4 quizzes.

Cheat Sheet

  1. Atomic Structure Fundamentals -

    In ap bio chapter 2 you'll learn that atoms consist of protons, neutrons, and electrons, where the atomic number (Z) equals the number of protons and the mass number (A) equals protons plus neutrons (A=Z+N). A handy mnemonic is "PEN" (Protons, Electrons, Neutrons) to recall subatomic particles and their charges. Universities like MIT and Khan Academy confirm this foundational concept for molecular biology.

  2. Isotopes and Radioactivity -

    Isotopes vary in neutron number but share atomic number; for example, carbon-12 and carbon-14 both have six protons but differ in neutrons (6 vs. 8). Carbon-14's radioactive decay underpins radiometric dating, a technique covered in research sources like the US Geological Survey. Remember "Iso-same, top-diff" (same atomic number, different mass) to distinguish isotopes.

  3. Covalent vs. Ionic Bonds -

    Covalent bonds form when atoms share electron pairs (e.g., H2O), while ionic bonds involve electron transfer creating charged ions like Na+ and Cl− in NaCl. Use the electronegativity difference rule: ΔEN > 1.7 for ionic and < 1.7 for covalent, as detailed in Chemistry LibreTexts. A useful tip is "Share for friends, give for charges."

  4. Unique Properties of Water -

    Water's polarity and hydrogen bonding result in high cohesion, adhesion, specific heat, and solvent abilities - the "CAPES" mnemonic helps recall Cohesion, Adhesion, Polarity, Excellent solvent, and Surface tension. These properties are critical for temperature regulation in organisms and are highlighted in research from the National Science Foundation. Practicing polarity diagrams for H-O-H angles (104.5°) makes the concept stick.

  5. Macromolecule Synthesis via Dehydration Reactions -

    Monomers link to form polymers through dehydration synthesis, releasing water (e.g., amino acids form polypeptides, monosaccharides form polysaccharides). The reverse process is hydrolysis, where water splits bonds, as explained in the "Campbell Biology" 11th Edition. Use the mnemonic "Dehydrate to build, hydrate to break" when reviewing ap bio chapter 2 concepts moving into chapters 3 and 4.

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