A holoenzyme is a combination of a protein and one or more substances called
apoenzymes.
catalysts.
cofactors.
substrates.
The Correct Answer is C
A. apoenzymes: An apoenzyme is the protein portion of an enzyme that is inactive on its own. It requires the binding of a cofactor or coenzyme to form a fully functional holoenzyme. Without this non-protein component, the apoenzyme cannot catalyze reactions efficiently.
B. catalysts: Catalysts are substances that speed up chemical reactions without being consumed in the process. While enzymes themselves act as biological catalysts, the term “catalyst” does not describe the non-protein component needed to form a holoenzyme.
C. cofactors: Cofactors are non-protein chemical substances, such as metal ions (e.g., Mg²⁺, Zn²⁺) or organic molecules (coenzymes), that bind to an apoenzyme to form a holoenzyme. The holoenzyme is the active enzyme capable of binding substrate and catalyzing a reaction, making cofactors essential for enzymatic activity.
D. substrates: Substrates are the molecules upon which enzymes act. They bind to the active site of the enzyme to undergo a chemical transformation. Substrates are not part of the enzyme structure and are not required to convert an apoenzyme into a holoenzyme.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. plasmids: Plasmids are small, circular, extrachromosomal DNA molecules found in many bacteria and some eukaryotes. They replicate independently of the main chromosome and often carry genes that provide selective advantages, such as antibiotic resistance, virulence factors, or metabolic capabilities.
B. chloroplast DNA: Chloroplasts in eukaryotic algae and plants contain their own circular DNA, encoding genes necessary for photosynthesis and other organelle-specific functions. This DNA is distinct from nuclear chromosomes and reflects the organelle’s prokaryotic origin through endosymbiosis.
C. All of the choices are correct: Microorganisms can possess multiple types of genetic material, including chromosomes, plasmids, and organelle DNA like mitochondrial or chloroplast DNA. This diversity enables adaptation, specialized functions, and horizontal gene transfer, making all the listed options accurate.
D. chromosomes: Chromosomes are the primary DNA structures that carry essential genetic information. Bacteria generally have a single circular chromosome, while eukaryotic microbes may have multiple linear chromosomes within a nucleus, encoding the majority of the organism’s genes.
E. mitochondrial DNA: Mitochondria in eukaryotic microorganisms contain their own circular DNA, coding for proteins and RNAs critical for oxidative phosphorylation and energy production. Like chloroplast DNA, mitochondrial DNA supports the endosymbiotic theory and allows semi-independent replication within the cell.
Correct Answer is D
Explanation
A. Lead: Lead is a heavy metal that has historical use in paints and plumbing but has limited antimicrobial properties. While toxic to humans and microbes at high concentrations, it is not commonly used as an effective antimicrobial agent in commercial products today due to safety concerns and poor efficacy compared with modern agents.
B. Carbohydrate: Carbohydrates serve primarily as nutrients and energy sources for organisms. They do not possess intrinsic antimicrobial properties and therefore are ineffective in killing microorganisms in commercial products.
C. Bacteriostatic: Bacteriostatic chemicals inhibit the growth and reproduction of microorganisms but do not directly kill them. These agents rely on the host immune system to eliminate the inhibited microbes. While useful, bacteriostatic agents are generally less immediately effective than bactericidal compounds when rapid microbial killing is desired.
D. Bactericidal: Bactericidal chemicals actively kill microorganisms by disrupting essential cellular structures or metabolic processes, such as the cell wall, cell membrane, or protein synthesis. Commercial products containing bactericidal agents, such as bleach, alcohol, and phenolic compounds, are more effective at eliminating microbial populations quickly and reducing the risk of infection.
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