Prokaryotic cells are much smaller than eukaryotic cells. What is their comparative size?

NVS Staff Nurse - 2022

Applied Microbiology & Infection control

Easy

Appeared in: NVS Staff Nurse - 2022

Explanation

Prokaryotic cells are significantly smaller than eukaryotic cells, with a typical diameter ranging from 0.1 to 5.0 micrometers (µm).
This range is comprehensive, including some of the smallest bacteria like Mycoplasma (around 0.1-0.2 µm) as well as more common, larger bacteria.
Eukaryotic cells, by contrast, are much larger, typically measuring between 10 and 100 µm.
The provided source confirms that prokaryotes are small, with a size of less than or equal to 5 µm.

Option B: The upper limit of 6.0 µm is generally considered outside the typical size range for most prokaryotic cells, which is usually capped at 5.0 µm.
Option C: This range is very close to correct and represents many common bacteria. However, it is less inclusive than the 0.1 - 5.0 µm range, as it excludes the smallest known bacteria which are around 0.1 µm.
Option D: This option is identical to option B. The upper limit of 6.0 µm is generally considered outside the typical size range for most prokaryotic cells.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Comparative size of prokaryotic and eukaryotic cells as background academic context rather than a clinical decision trigger.
Understanding the vast size difference is fundamental in microbiology. The small size and simple structure of prokaryotic bacteria allow for rapid multiplication, which is why bacterial infections can progress so quickly.
This size and structural difference is a key target for antibiotics. Many drugs are designed to attack features unique to smaller, simpler prokaryotic cells (like 70S ribosomes or the cell wall) while leaving larger eukaryotic host cells unharmed.
What if? If bacteria were the size of eukaryotic cells, their rate of reproduction and metabolism would be much slower. This would likely make bacterial infections less acute, giving the host's immune system more time to respond and making the infections easier to manage.

How to Approach the Question

First, identify the key concept in the question, which is the size of prokaryotic cells.
Recall the fundamental differences between prokaryotic and eukaryotic cells, with size being a major one.
Access your knowledge of microbiology to remember the typical size range for bacteria, which are the most common prokaryotes. The range is on the micrometer (µm) scale.
Evaluate the given options. Compare each range (both lower and upper limits) to the known scientific standard.
Select the option that most accurately and inclusively represents the size of prokaryotic cells. The range 0.1-5.0 µm is the most comprehensive and correct answer.

Concept Tested & Keywords

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E6 Microbiology Applied AnjuDhir 3e Part 1 p. 57-59