Microbiology, 2021

3.4 • Unique Characteristics of Eukaryotic Cells 103
tumbles is decreased. This leads to chemotaxis: an overall directional movement toward the higher concentration of the attractant.
CHECK YOUR UNDERSTANDING
• What is the peptidoglycan layer and how does it differ between gram-positive and gram-negative bacteria?
• Compare and contrast monotrichous, amphitrichous, lophotrichous, and peritrichous flagella.
3.4 Unique Characteristics of Eukaryotic Cells
Learning Objectives
By the end of this section, you will be able to:
• Explain the distinguishing characteristics of eukaryotic cells
• Describe internal and external structures of eukaryotic cells in terms of their physical structure, chemical
structure, and function
• Identify and describe structures and organelles unique to eukaryotic cells
• Compare and contrast similar structures found in prokaryotic and eukaryotic cells
• Describe the processes of eukaryotic mitosis and meiosis, and compare to prokaryotic binary fission
Eukaryotic organisms include protozoans, algae, fungi, plants, and animals. Some eukaryotic cells are
independent, single-celled microorganisms, whereas others are part of multicellular organisms. The cells of
eukaryotic organisms have several distinguishing characteristics. Above all, eukaryotic cells are defined by the
presence of a nucleus surrounded by a complex nuclear membrane. Also, eukaryotic cells are characterized by
the presence of membrane-bound organelles in the cytoplasm. Organelles such as mitochondria, the
endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and peroxisomes are held in place by the
cytoskeleton, an internal network that supports transport of intracellular components and helps maintain cell
shape (Figure 3.35). The genome of eukaryotic cells is packaged in multiple, rod-shaped chromosomes as
opposed to the single, circular-shaped chromosome that characterizes most prokaryotic cells. Table 3.2
compares the characteristics of eukaryotic cell structures with those of bacteria and archaea.