Prokaryotic & Eukaryotic Cells: Videos & Practice Problems

Prokaryotic cells, including bacteria and archaea, lack a nucleus and membrane-bound organelles, featuring circular DNA located in a nucleoid. They are unicellular and smaller, with 70S ribosomes, dividing through binary fission. In contrast, eukaryotic cells possess a nucleus, linear DNA, and various organelles, can be unicellular or multicellular, and utilize larger 80S ribosomes, dividing via mitosis and cytokinesis. Both cell types share a cell membrane and essential biomolecules like carbohydrates and proteins, highlighting their fundamental biological roles.

Prokaryotic & Eukaryotic Cells

Prokaryotic and eukaryotic cells represent the two fundamental classifications of life, distinguished primarily by their structural characteristics. Prokaryotic cells encompass two domains: Bacteria and Archaea. These cells are defined by the absence of a nucleus, which is a key organelle found in eukaryotic cells. The term "prokaryotic" derives from the prefix "pro," meaning "before," and "karyo," which refers to the nucleus, indicating that these cells existed before the development of a nucleus.

In contrast, eukaryotic cells, which belong to the domain Eukarya, possess a well-defined nucleus and other membrane-bound organelles. The prefix "eu" means "good" or "true," suggesting that eukaryotic cells have a true nucleus. This distinction is crucial for understanding the complexity of cellular life.

A comparative analysis of prokaryotic and eukaryotic cells reveals several key differences:

• Domains of Life: Prokaryotic cells are classified under Bacteria and Archaea, while eukaryotic cells fall under Eukarya.
• Cell Type: Prokaryotic cells are unicellular, meaning they consist of a single cell, whereas eukaryotic cells can be unicellular or multicellular, with multicellular organisms, such as humans, being eukaryotic.
• Nucleus: Prokaryotic cells lack a nucleus, while eukaryotic cells have a nucleus.
• Organelles: Prokaryotic cells do not contain membrane-bound organelles, whereas eukaryotic cells do.
• Cell Size: Prokaryotic cells are generally much smaller, averaging around 1 micrometer in diameter, compared to eukaryotic cells, which can be up to 100 micrometers or more.

Understanding these differences is essential for studying cellular biology and the diversity of life forms. As we delve deeper into the subject, we will explore the various organelles present in eukaryotic cells and their functions, further highlighting the complexity and specialization of these cells.

Which domains of life are classified as prokaryotes?

• A. Bacteria & Eukarya.
• B. Archaea & Fungi.
• C. Bacteria & Archaea.
• D. Bacteria & Protista.

Answer: (C)

Features of Bacterial Cells

Bacterial cells are fascinating prokaryotic organisms that lack a nucleus and are recognized as the most abundant and diverse life forms on Earth. Their ancient lineage contributes to their prevalence. One of the defining characteristics of bacteria is their circular DNA, which is located in a specific region known as the nucleoid. This area is crucial as it houses the genetic material necessary for the cell's functions and reproduction.

Like all cells, bacteria contain ribosomes, which are essential for protein synthesis. However, bacterial ribosomes are notably smaller than those found in eukaryotic cells, specifically referred to as 70S ribosomes. The "S" denotes a unit of measurement related to the size of the ribosome, while the "70" indicates its specific size category. These ribosomes play a vital role in translating genetic information into proteins, which are fundamental for cellular processes.

When it comes to reproduction, bacteria utilize a straightforward method known as binary fission. This process allows a single bacterial cell to divide into two identical daughter cells, contrasting with the more complex division mechanisms seen in eukaryotic cells.

In summary, understanding the structure and function of bacterial cells, including their circular DNA, nucleoid region, and 70S ribosomes, provides insight into their unique biology and the fundamental differences between prokaryotic and eukaryotic cells. This foundational knowledge sets the stage for further exploration of cellular biology and the diverse roles that these microorganisms play in various ecosystems.

In bacteria, DNA will be found in _______________.

• A. A membrane-enclosed nucleus.
• B. Mitochondria.
• C. The nucleoid.
• D. Ribosomes.

Answer: (C)

Features of Eukaryotic Cells

Eukaryotic cells are distinct from prokaryotic cells in several key ways, primarily due to their complex structure. One of the most significant features of eukaryotic cells is the presence of a nucleus, which houses linear DNA. In contrast, prokaryotic cells lack a nucleus, and their DNA is circular and located in a region called the nucleoid. This fundamental difference highlights the organizational complexity of eukaryotic cells.

All cells, regardless of type, contain ribosomes, which are essential for protein synthesis. However, eukaryotic ribosomes are larger, classified as 80S, compared to the smaller 70S ribosomes found in prokaryotic cells. This size difference is indicative of the more intricate processes occurring within eukaryotic cells.

When it comes to cell division, eukaryotic cells undergo mitosis and cytokinesis, a more complex process than the binary fission seen in prokaryotic cells. This complexity allows for greater genetic diversity and cellular specialization.

Visually, eukaryotic cells are larger and contain numerous membrane-bound organelles, which facilitate various cellular functions. The presence of these organelles allows eukaryotic cells to perform more specialized tasks compared to their prokaryotic counterparts. The linear DNA within the nucleus and the larger ribosomes are critical components that contribute to the overall functionality and efficiency of eukaryotic cells.

As we continue to explore the features and functions of eukaryotic cells, understanding these distinctions will provide a solid foundation for further studies in cellular biology.

Which organelle packages the genetic/hereditary material in eukaryotes but not in prokaryotic cells?

• A. Nucleus.
• B. Mitochondria.
• C. Chloroplasts.
• D. Nucleolus.

Answer: (A)

Recap: Prokaryotic vs. Eukaryotic Cells

Understanding the differences between prokaryotic and eukaryotic cells is fundamental in biology. Prokaryotic cells are characterized by the absence of a nucleus, while eukaryotic cells possess a defined nucleus. This distinction is crucial as it highlights the complexity of eukaryotic cells, which are generally larger, ranging from 10 to 100 micrometers, compared to the much smaller prokaryotic cells, which measure between 1 to 10 micrometers.

Prokaryotic cells are exclusively unicellular, meaning they consist of a single cell, whereas eukaryotic cells can be either unicellular or multicellular, with all multicellular organisms classified as eukaryotic. The structure of DNA also differs significantly; prokaryotic cells contain circular DNA, while eukaryotic cells have linear DNA. Additionally, prokaryotic cells lack membrane-bound organelles, which are present in eukaryotic cells, contributing to their greater complexity.

When it comes to cell division, prokaryotic cells undergo binary fission, a simpler process, while eukaryotic cells divide through mitosis and cytokinesis, which are more intricate processes. Another notable difference lies in ribosome size; prokaryotic cells have smaller 70S ribosomes, whereas eukaryotic cells contain larger 80S ribosomes.

Despite these differences, prokaryotic and eukaryotic cells share some similarities. Both types of cells possess a cell membrane, which serves as a barrier and regulates the movement of substances in and out of the cell. Furthermore, they both utilize essential biomolecules, including carbohydrates, proteins, nucleic acids, and lipids, which are vital for various cellular functions.

This overview of prokaryotic and eukaryotic cells lays the groundwork for further exploration of cellular biology, emphasizing the importance of understanding these fundamental concepts as we progress in our studies.

Which of the following is/are a primary difference(s) between all prokaryotes and eukaryotic cells?

• A. Prokaryotes have DNA that floats freely in the cytoplasm.
• B. Prokaryotes are significantly smaller than eukaryotic cells.
• C. Prokaryotes do not have ribosomes like eukaryotic cells.
• D. a and b.
• E. a, b, and c

Answer: (D)

Which of the following is not a common feature shared by all types of cells?

• A. Contains DNA as the genetic material.
• B. Contains a protective cell wall or cell membrane.
• C. Contains a fluid-like portion called the cytoplasm.
• D. Contains a nucleus that stores the genetic material.

Answer: (D)

You isolate a cell with the following characteristics: (1) no nucleus, (2) a cell wall, and the cell is (3) 2 μm in size. This cell could be a/an:

• A. Bacterium.
• B. Plant cell.
• C. Animal cell.
• D. Bacterial cell or a plant cell.
• E. Plant cell or an animal cell.

Answer: (A)

Here’s what students ask on this topic:

What are the main differences between prokaryotic and eukaryotic cells?

The main differences between prokaryotic and eukaryotic cells include the presence of a nucleus, cell size, complexity, and organelles. Prokaryotic cells, such as bacteria and archaea, lack a nucleus and membrane-bound organelles, featuring circular DNA located in a nucleoid. They are unicellular and smaller, with 70S ribosomes, and divide through binary fission. In contrast, eukaryotic cells possess a nucleus, linear DNA, and various organelles. They can be unicellular or multicellular, utilize larger 80S ribosomes, and divide via mitosis and cytokinesis. These differences highlight the complexity and diversity of eukaryotic cells compared to the simpler structure of prokaryotic cells.

How do prokaryotic cells divide?

Prokaryotic cells divide through a process called binary fission. During binary fission, the circular DNA of the prokaryotic cell replicates, and the cell grows in size. The cell then divides into two identical daughter cells, each containing a copy of the original DNA. This process is simpler and faster than the division process in eukaryotic cells, which involves mitosis and cytokinesis. Binary fission allows prokaryotic cells to reproduce quickly, contributing to their abundance and diversity.

What are the similarities between prokaryotic and eukaryotic cells?

Despite their differences, prokaryotic and eukaryotic cells share several similarities. Both cell types have a cell membrane that regulates the movement of substances in and out of the cell. They also contain essential biomolecules such as carbohydrates, proteins, nucleic acids, and lipids. Additionally, both prokaryotic and eukaryotic cells have ribosomes, which are responsible for protein synthesis. These shared features highlight the fundamental biological roles that both cell types play in living organisms.

What is the function of ribosomes in prokaryotic and eukaryotic cells?

Ribosomes are essential organelles found in both prokaryotic and eukaryotic cells, responsible for protein synthesis. In prokaryotic cells, ribosomes are smaller (70S) and float freely in the cytoplasm. In eukaryotic cells, ribosomes are larger (80S) and can be found either free in the cytoplasm or attached to the endoplasmic reticulum, forming rough ER. Ribosomes translate mRNA into polypeptide chains, which then fold into functional proteins. Despite the size difference, the fundamental role of ribosomes in protein synthesis is conserved across both cell types.

What are the characteristics of bacterial cells?

Bacterial cells, which are prokaryotic, have several distinct characteristics. They lack a nucleus, with their circular DNA located in a region called the nucleoid. Bacteria have small ribosomes (70S) for protein synthesis. They are unicellular and can reproduce quickly through binary fission. Bacterial cells also have a cell membrane and often a cell wall for structural support. Some bacteria have additional structures like flagella for movement and pili for attachment to surfaces. These features contribute to their adaptability and diversity in various environments.