CLEP-BIOLOGY Sample Questions & Answers
Free CLEP Biology practice questions with worked answers and explanations. See how the ExamJungle simulator prepares you — then jump into the full test.
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- Question 1Intermediate
Molecular and Cellular Biology · Inhibition and regulation
An enzymologist evaluates an enzyme-catalyzed reaction in the presence of a chemical inhibitor. Increasing the substrate concentration progressively overcomes the inhibition, allowing the reaction to reach its original maximum velocity (Vmax), but the apparent Michaelis constant (Km) is increased.
flowchart LR A["Free Enzyme + Substrate"] --> B["ES Complex"] B --> C["Free Enzyme + Product"] D["Reversible Inhibitor"] -.->|Competes for Catalytic Active Site| AShow answer & explanation
Correct answer: B
Competitive inhibitors bind reversibly to the active site, increasing apparent Km without changing Vmax because excess substrate outcompetes the inhibitor.
- Question 2Beginner
Molecular and Cellular Biology · Inorganic cofactors
While organic non-protein helper molecules derived from vitamins are classified as coenzymes, essential inorganic ions such as magnesium (Mg2+) or zinc (Zn2+) required for optimal enzyme catalytic activity are classified as _____.
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Correct answer: C
Inorganic ions that assist enzyme function are termed cofactors, whereas organic non-protein helper molecules are called coenzymes.
- Question 3Intermediate
Molecular and Cellular Biology · Glycolysis, cellular respiration, aerobic and anaerobic pathways
During complete aerobic respiration of a glucose molecule in eukaryotic cells, which metabolic stage produces the greatest amount of ATP by coupling electron transport to chemiosmosis?
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Correct answer: D
Oxidative phosphorylation harnesses the proton gradient across the inner mitochondrial membrane via ATP synthase, producing about 90% of cellular ATP via chemiosmosis.
- Question 4Advanced
Molecular and Cellular Biology · Photosynthesis
In oxygenic photosynthetic electron transport, what is the immediate role of electrons extracted from water during photolysis at the oxygen-evolving complex of Photosystem II?
flowchart TD H2O["H2O Photolysis at PS II"] -->|Electrons| P680["Oxidized P680 Reaction Center"] P680 -->|Light Excitation| ETC["Thylakoid Electron Transport Chain"] ETC -->|Electrons| P700["Photosystem I P700"] P700 -->|Light Excitation| NADP["NADP+ Reductase to NADPH"]Show answer & explanation
Correct answer: D
Water photolysis at PS II generates O2, protons, and electrons that replenish the photo-oxidized P680 reaction center chlorophyll, sustaining non-cyclic electron transport.
- Question 5AdvancedSelect 2
Molecular and Cellular Biology · DNA replication
During DNA replication in Escherichia coli, which TWO of the following enzymes are directly required to remove RNA primers and join adjacent Okazaki fragments into a continuous DNA strand? (Select TWO)
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Correct answers: D, E
DNA pol I removes RNA primers and fills the gaps with deoxyribonucleotides, while DNA ligase seals nicked phosphodiester backbones between adjacent Okazaki fragments.
- Question 6Advanced
Molecular and Cellular Biology · Control of protein synthesis: transcription, translation, and post-transcriptional processing
A molecular biology research team investigates an engineered bacterial strain displaying constitutive expression of an inducible operon. In wild-type cells, transcription of the structural genes is strongly repressed unless a specific small-molecule inducer is present in the culture medium. In the mutant strain, however, the structural enzymes are continuously synthesized at maximal levels even in the complete absence of the inducer.
Genetic sequencing of the mutant reveals a missense mutation in the regulatory gene coding for the repressor protein. In vitro biochemical binding assays show that the mutant repressor protein is properly folded and stably expressed, but it exhibits zero binding affinity for the operator sequence of the operon.
Which molecular mechanism best accounts for the continuous transcription of the operon in this bacterial strain?
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Correct answer: D
When a mutation disables repressor binding to the operator, RNA polymerase transcribes the structural genes constitutively without negative regulation.
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