Question

What is true for a prokaryotic cell? (a) They are smaller in size (b) Multiply much rapidly than eukaryotes (c) Greatly vary in shape and size (d) All of these

Short answer

The correct answer is (d): All of the statements are true for prokaryotic cells.

Step-by-step solution

Verification of Statement 1

Prokaryotic cells are indeed smaller in size than eukaryotes. This is verified by definitions and texts on biology, where the average size of prokaryotic cells is given as 0.2 to 2.0 micrometer in diameter, whereas eukaryotic cells are around 10 to 100 micrometers in diameter.

Verification of Statement 2

Prokaryotic cells multiply much more rapidly than eukaryotic cells. The reason for this lies in their simplified cell structure. For example, E. coli, a kind of prokaryote, can divide roughly every 20 minutes under optimal conditions. In contrast, eukaryotic cells take about 24 hours to complete a replication cycle.

Verification of Statement 3

Prokaryotic cells greatly vary in shape and size, which is typical for this group. Shapes can include spheres, rods, spirals and more complex structures.

Key concepts

Prokaryotic vs Eukaryotic Cells

Understanding the fundamental differences between prokaryotic and eukaryotic cells is crucial for students studying biology. Prokaryotic cells are unicellular organisms, such as bacteria and archaea, that lack a nucleus and other membrane-bound organelles. In contrast, eukaryotic cells, which make up plants, animals, and fungi, have a defined nucleus housing their genetic material.

Prokaryotic cells are generally more simplistic in structure. They usually carry their genetic material in a single, circular chromosome, while eukaryotic cells typically have multiple, linear chromosomes inside the nucleus. Prokaryotes also lack compartments like mitochondria and endoplasmic reticulum, making their ability to perform complex functions more limited but also enabling them to have faster reproduction rates.

Cell Size Comparison

When comparing the sizes of prokaryotic and eukaryotic cells, students can easily visualize the difference. Prokaryotic cells are significantly smaller, with a diameter of about 0.2 to 2.0 micrometers, resembling a speck under the microscope. On the other hand, eukaryotic cells are much larger, with diameters ranging from 10 to 100 micrometers. This size variation affects not only how these cells are studied but also influences their surface area to volume ratio, impacting nutrient uptake and waste expulsion, which is vital for cell survival and function.

Cell Division Rate

The rate of cell division is another key difference between prokaryotic and eukaryotic cells and is essential knowledge for students. Prokaryotic cells can reproduce at a remarkable rate; for example, under optimal conditions, E. coli can divide every 20 minutes. This rapid multiplication is due in part to the simplicity of their structure and their asexual reproduction method known as binary fission. Eukaryotic cells, however, usually have a cell cycle of approximately 24 hours, largely because they undergo more complex processes during cell division, including mitosis and cytokinesis.

It's important to note that this rapid division of prokaryotic cells is significant in different contexts, like bacterial infections, where their swift proliferation can present challenges in treatment.

Cell Shape and Structure

The diversity in cell shape and structure between prokaryotic and eukaryotic cells is vast and influences their functions. Prokaryotic cells are known to have a variety of shapes, including spherical (cocci), rod-shaped (bacilli), spiral, and even more complex structures. These variations can impact how prokaryotes move, attach to surfaces, and interact with their environment.

Eukaryotic cells, while often more complex internally, also show a broad range of shapes. This includes the elongated structure of nerve cells, the flattened shape of skin cells, and the malleable form of white blood cells. Their structure plays a critical part in enabling the multitude of specialized functions in multicellular organisms.