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 typically unicellular and smaller, dividing through binary fission. In contrast, eukaryotic cells possess a nucleus, linear DNA, and various organelles, allowing for greater complexity. Eukaryotic cells can be unicellular or multicellular and divide via mitosis and cytokinesis. Both cell types share essential biomolecules and a cell membrane, highlighting their fundamental similarities despite significant structural differences.

Prokaryotic & Eukaryotic Cells

Prokaryotic and eukaryotic cells represent the two fundamental categories of life, distinguished primarily by their structural characteristics. Prokaryotic cells encompass two domains: bacteria and archaea. A defining feature of prokaryotic cells is the absence of a nucleus, which is a membrane-bound organelle that houses genetic material. In contrast, eukaryotic cells possess a nucleus and other membrane-bound organelles, allowing for more complex cellular functions.

The term "karyo" originates from the Greek word for "kernel," referring to the nucleus. The prefix "pro-" means "before," indicating that prokaryotic cells existed before the development of a nucleus. Conversely, the prefix "eu-" translates to "good" or "true," signifying that eukaryotic cells have a well-defined nucleus.

To further differentiate these cell types, consider the following characteristics:

• Domains of Life: Prokaryotic cells belong to the domains of bacteria and archaea, while eukaryotic cells are classified under the domain eukarya.
• Cell Type: Both bacteria and archaea are prokaryotic, whereas eukaryotic cells include a variety of organisms, including plants, animals, and fungi.
• Nucleus: Prokaryotic cells lack a nucleus, while eukaryotic cells have a nucleus.
• Organelles: Prokaryotic cells do not contain membrane-bound organelles, whereas eukaryotic cells are rich in various organelles that perform specialized functions.
• 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.
• Cellularity: Prokaryotic organisms are typically unicellular, meaning they consist of a single cell. Eukaryotic organisms can be unicellular or multicellular, with humans being a prime example of multicellular eukaryotes.

Understanding these distinctions is crucial as they lay the foundation for exploring the complexities of cellular biology. As we delve deeper into the study of cells, we will examine the various organelles found in eukaryotic cells and their functions, enhancing our comprehension of life at the cellular level.

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 organisms that belong to the prokaryotic category, meaning they lack a nucleus. They are the most abundant and diverse life forms on Earth, having existed for billions of years. One of the defining characteristics of bacteria is their circular DNA, which is located in a specific area known as the nucleoid. This region 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, classified as 70S ribosomes. The "S" refers to 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 necessary for various cellular processes.

When bacteria reproduce, they do so through a process called binary fission. This method is relatively straightforward compared to the more complex division processes seen in eukaryotic cells. During binary fission, a single bacterial cell divides into two identical daughter cells, allowing for rapid population growth.

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 evolutionary significance. As we continue to explore cellular biology, we will also compare these features with those of eukaryotic cells, enhancing our understanding of life at the cellular level.

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 ribosomes, compared to the smaller 70S ribosomes found in prokaryotic cells. This size difference is crucial for the various functions ribosomes perform within the cell.

When it comes to cell division, eukaryotic cells undergo a more intricate process known as mitosis and cytokinesis, unlike prokaryotic cells that divide through binary fission. Mitosis ensures that genetic material is accurately replicated and distributed to daughter cells, reflecting the complexity of eukaryotic cellular processes.

Visually, eukaryotic cells are characterized by numerous membrane-bound organelles, which facilitate various cellular functions. The larger size of eukaryotic cells allows for the accommodation of these organelles, making them more complex than their prokaryotic counterparts. The nucleus, depicted as a prominent circle in diagrams, contains the linear DNA, while ribosomes are represented as smaller blue circles throughout the cell.

In summary, the structural and functional differences between eukaryotic and prokaryotic cells underscore the advanced nature of eukaryotic cells, setting the stage for deeper exploration of their organelles and processes in future studies.

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 reflects their complexity; prokaryotic cells are generally smaller, ranging from 1 to 10 micrometers, compared to the larger eukaryotic cells, which measure between 10 to 100 micrometers. The size difference contributes to the overall complexity of these cells, with prokaryotic cells being less complex and exclusively unicellular, whereas eukaryotic cells can be either unicellular or multicellular, forming all multicellular organisms.

Another significant difference lies in the structure of their DNA. Prokaryotic cells contain circular DNA, while eukaryotic cells have linear DNA. Additionally, prokaryotic cells lack membrane-bound organelles, which are present in eukaryotic cells. The method of cell division also varies; prokaryotic cells undergo binary fission, a simpler process, whereas eukaryotic cells divide through mitosis and cytokinesis, which are more complex processes.

Ribosome size further distinguishes these two cell types. Prokaryotic cells have smaller ribosomes, referred to as 70S ribosomes, while eukaryotic cells contain larger 80S ribosomes. Despite these differences, both prokaryotic and eukaryotic cells share some similarities. They both possess a cell membrane, which is essential for maintaining cellular integrity, and they contain the major biomolecules necessary for life, including carbohydrates, proteins, nucleic acids, and lipids. This foundational knowledge of cell types will be essential as you continue to explore more complex biological concepts.

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?

Prokaryotic cells, such as bacteria and archaea, lack a nucleus and membrane-bound organelles. Their DNA is circular and located in a region called the nucleoid. They are typically unicellular and smaller, ranging from 1 to 10 micrometers, and divide through binary fission. In contrast, eukaryotic cells have a nucleus, linear DNA, and various organelles, allowing for greater complexity. Eukaryotic cells can be unicellular or multicellular and are larger, ranging from 10 to 100 micrometers. They divide via mitosis and cytokinesis. Both cell types share essential biomolecules and a cell membrane, highlighting their fundamental biological functions.

How do prokaryotic cells divide?

Prokaryotic cells divide through a process called binary fission. In binary fission, the cell's circular DNA replicates, and the cell grows in size. The DNA copies move to opposite ends of the cell, and the cell membrane pinches inwards, eventually splitting the cell into two genetically identical daughter cells. This process is simpler and faster than the division process in eukaryotic cells, which involves mitosis and cytokinesis.

What are the key features of bacterial cells?

Bacterial cells, which are prokaryotic, lack a nucleus and have circular DNA located in a region called the nucleoid. They possess small ribosomes (70S) for protein synthesis. Bacteria are unicellular and divide by binary fission. They are the most abundant and diverse organisms on Earth, partly due to their ancient origins. Bacterial cells also have a cell membrane and may have additional structures like cell walls, flagella, and pili for movement and attachment.

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 entry and exit of substances. They contain essential biomolecules such as carbohydrates, proteins, nucleic acids, and lipids. Additionally, both types of cells have ribosomes for protein synthesis, although prokaryotic ribosomes are smaller (70S) compared to eukaryotic ribosomes (80S). These shared features highlight their fundamental biological functions and evolutionary connections.

How do eukaryotic cells divide?

Eukaryotic cells divide through a more complex process involving mitosis and cytokinesis. During mitosis, the cell's linear DNA is replicated and evenly distributed into two daughter nuclei. This process includes several stages: prophase, metaphase, anaphase, and telophase. Following mitosis, cytokinesis occurs, where the cell's cytoplasm divides, resulting in two genetically identical daughter cells. This division process allows for growth, development, and tissue repair in multicellular organisms.