College BiologyFree College-Level Biology Practice practice test

Correct answer: D. Ionic bond

An ionic bond results from the electrostatic attraction between oppositely charged ions. Covalent bonds involve electron sharing between atoms. Hydrogen bonds involve attraction between a partially positive hydrogen and an electronegative atom — these are between uncharged but polarized molecules, not fully charged ions.

Correct answer: A. Base

According to Brønsted-Lowry definitions, a base accepts protons while an acid donates them. A buffer resists changes in pH but does not simply accept protons. A polar molecule describes charge distribution, not proton behavior.

Correct answer: E. Amino acid

Each codon is a triplet of nucleotides that corresponds to one specific amino acid. A sequence of codons along an mRNA collectively encodes an entire protein, but each individual codon only specifies one amino acid.

Correct answer: E. Cannot be determined without knowing the organism from which the enzyme was isolated

Restriction enzymes are named after their organism of origin, not after the sequence or gene they cut. For example, EcoRI derives its name from Escherichia coli. Without knowing the host bacterium, you cannot construct a proper name — unlike most enzymes, which are named after their substrate using the -ase suffix.

Correct answer: B. Attached ribosome and rough endoplasmic reticulum

Ribosomes are classified as free (floating in the cytoplasm) or attached (bound to the ER membrane). When ribosomes are attached to the ER, that region is called the rough ER. Smooth ER, by definition, lacks ribosomes. Therefore, a ribosome on the ER surface means it is an attached ribosome associated with rough ER.

Correct answer: D. Transparency to visible light

Water's transparency arises because its electrons are not excited by wavelengths in the visible spectrum — this is a quantum electronic property unrelated to polarity. The other properties all stem from hydrogen bonding, which is a direct result of water's polar O–H bonds: hydrogen bonding raises the boiling point, increases specific heat, creates strong surface tension, and forces ice into a hexagonal lattice.

Correct answer: E. They include glucose, fructose, sucrose, and cellulose

Glucose and fructose are genuine monosaccharides, but sucrose is a disaccharide formed by linking glucose and fructose, while cellulose is a large polysaccharide made of repeating glucose units. Including sucrose and cellulose in a list of monosaccharides makes that statement false.

Correct answer: C. Water boiling and converting to steam

A chemical reaction requires the formation or breaking of chemical bonds to produce new substances. Boiling converts liquid water to water vapor but no new molecules are formed — it is a physical phase change driven by added thermal energy. By contrast, rusting forms iron oxide, burning produces CO₂ and water, egg decomposition generates hydrogen sulfide from amino acids, and mixing baking soda and vinegar releases CO₂ gas.

Correct answer: C. Cell walls are exclusive to the plant kingdom and are absent in all other organisms

Cell walls are not unique to plants. Bacteria also possess cell walls (composed of peptidoglycan rather than cellulose), and fungi have walls made of chitin. The remaining statements accurately describe plant cell walls, which provide rigidity to the organism, store water, consist of cellulose and lignin, and allow most molecules to pass through.

Correct answer: E. A single gene typically spans across multiple separate chromatin segments

A gene may span many nucleosomes, but it is contained within a single continuous segment of chromatin — it does not jump across separate chromatin regions. Chromatin is indeed made of DNA coiled around histones, organized into nucleosomes, and it compacts into visible chromosomes at the onset of mitosis.