The term heterotroph refers to an organism that
uses C02, for its carbon source.
must obtain organic compounds for its carbon needs.
gets energy by oxidizing inorganic compounds.
gets energy from sunlight.
does not need a carbon source.
The Correct Answer is B
A. uses CO₂ for its carbon source: Organisms that use carbon dioxide as their carbon source are called autotrophs, not heterotrophs. Autotrophs can synthesize organic compounds from inorganic carbon, whereas heterotrophs rely on preformed organic molecules.
B. must obtain organic compounds for its carbon needs: Heterotrophs cannot fix carbon dioxide into organic compounds, so they rely on consuming organic molecules such as carbohydrates, lipids, or proteins from other organisms. This dependency on external organic carbon distinguishes heterotrophs from autotrophs.
C. gets energy by oxidizing inorganic compounds: Organisms that derive energy from the oxidation of inorganic substances are chemolithotrophs. While some heterotrophs may also utilize chemical energy, the defining feature of a heterotroph is its requirement for organic carbon, not the energy source.
D. gets energy from sunlight: Organisms that capture energy from sunlight are phototrophs. While some phototrophs are autotrophs, heterotrophs rely on organic compounds for carbon and may use chemical energy rather than sunlight.
E. does not need a carbon source: All organisms require a carbon source to build cellular structures and macromolecules. Heterotrophs, in particular, must obtain organic carbon from their environment to survive and grow.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. Halophile: Halophiles are organisms that thrive in high-salt environments. The description of temperature-based growth does not indicate a preference for saline conditions, so this term would not apply to the observed growth pattern.
B. Anaerobe: Anaerobes are organisms that grow in the absence of oxygen. The scenario focuses on temperature preferences, not oxygen requirements.
C. Mesophile: Mesophiles grow optimally at moderate temperatures, typically between 20°C and 45°C, with 37°C being ideal for many human-associated mesophilic bacteria. Because this species did not grow at 37°C or 50°C, it does not fit the definition of a mesophile.
D. Psychrophile: Psychrophiles are organisms that thrive at cold temperatures, usually with optimal growth at 0–15°C and survival at temperatures below 20°C. The abundant growth in the refrigerator and minimal growth at room temperature, with no growth at 37°C or higher, indicates that this species is adapted to cold environments, fitting a psychrophile definition.
E. Capnophile: Capnophiles require elevated levels of carbon dioxide for optimal growth. The growth pattern described is based on temperature rather than carbon dioxide levels, so this term is not applicable.
Correct Answer is C
Explanation
A. Membrane-bound nucleus: Prokaryotic cells lack a true nucleus. Their genetic material exists in a nucleoid, an irregularly shaped region within the cytoplasm that is not enclosed by a membrane. This structural simplicity means that processes like transcription and translation can occur almost simultaneously, unlike in eukaryotic cells.
B. 80S ribosomes: Prokaryotic ribosomes are 70S, composed of 50S and 30S subunits, which are smaller than the 80S ribosomes (60S + 40S) found in eukaryotic cells. This distinction is medically important because many antibiotics, such as tetracyclines and aminoglycosides, target 70S ribosomes, inhibiting bacterial protein synthesis without affecting eukaryotic ribosomes.
C. Lack of membrane-bound organelles: A defining feature of prokaryotes is the absence of membrane-bound organelles like mitochondria, endoplasmic reticulum, Golgi apparatus, or lysosomes. Cellular processes such as energy production, protein synthesis, and metabolic reactions occur in the cytoplasm or at the plasma membrane. This simplicity allows rapid growth and replication but limits compartmentalization and regulation compared to eukaryotic cells.
D. Multiple chromosomes: Most prokaryotic cells contain a single circular chromosome, which carries essential genetic information. Some may have plasmids, but these are not considered true chromosomes. The presence of multiple linear chromosomes is characteristic of eukaryotes and allows complex regulation and redundancy in genetic material, which prokaryotes lack.
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