Biology Chapter 4 Flashcards

Bacterial Appendages

• Bacterial cells can have various appendages for movement and attachment, including flagella, fimbriae, and sex pili; however, they do not have cilia.
• Spirochetes use periplasmic flagella for their twisting and flexing movement.
• Fimbriae are short and abundant appendages that help bacteria adhere to surfaces.
• Sex pili are tubular appendages used for genetic material transfer during bacterial conjugation.

Bacterial Structures and Functions

• Every bacterial cell contains a chromosome, which is organized within a region called the nucleoid.
• The presence of flagella allows bacteria to exhibit chemotaxis, directing movement toward chemicals in their environment.
• Capsules are protective structures that shield bacteria from being engulfed by immune cells.

Cell Wall Characteristics

• The Gram stain classification is based on differences in bacterial cell wall composition; gram-positive bacteria have thick peptidoglycan layers, while gram-negative bacteria have an outer membrane containing lipopolysaccharides.
• Peptidoglycan is a unique macromolecule found exclusively in bacterial cell walls, crucial for structural integrity.

Endospores

• Bacterial endospores serve as a protective mechanism for genetic material during adverse conditions; they are resistant to heat, radiation, and chemicals.
• Calcium dipicolinic acid presence indicates the presence of endospores, which are metabolically inactive during dormancy.

Shape and Arrangement of Bacteria

• Bacteria are classified by their shapes: cocci (spherical), rods (bacilli), spirilla (spiral), and specific arrangements like sarcinae (cuboidal packets).
• Coccobacillus refers to short and plump rod-shaped bacteria.

Biofilms and Evolution

• Biofilms are complex communities of microbes that cooperate and adapt, playing roles in ecological recycling and medical device colonization; they are difficult to eliminate with antimicrobials.
• The similarity in nitrogen base sequences of rRNA is an essential criterion for determining evolutionary relatedness among bacteria.

Phyla of Bacteria

• Bacterial phyla include Gracilicutes (gram-negative), Firmicutes (gram-positive), and Actinobacteria, which feature unique characteristics like waxy cell walls.
• Cyanobacteria are notable for their photosynthetic capabilities and presence of thylakoids for light absorption.

Miscellaneous Knowledge

• Lysozyme, found in tears, defends against bacteria by hydrolyzing peptidoglycan in cell walls.
• The mordant in Gram staining is iodine, which stabilizes the dye within the cell wall.
• Plasmids are crucial vectors in genetic engineering techniques due to their role in gene transfer among bacteria.
• Certain microorganisms thrive in extreme environments; for instance, Archaea can survive in highly acidic and hot habitats.

Mismatches in Classification

• Identifying mismatches in characteristics can clarify misconceptions; for example, Coxiella burnetti is associated with Q fever, not cowpox.
• Similarly, while Actinobacteria have waxy acid-fast walls, they differ from typical gram-positive structures.

Properties of Living Cells

• Living cells exhibit key characteristics such as boundary formation and ability to replicate; however, the presence of a nucleus is not a property exclusive to all living things, particularly in prokaryotic cells.