chapter 16 - prokaryotes

Comprehensive vocabulary flashcards covering Chapters 16, 24, 6, 7, 5, and 21 from Campbell Biology: Concepts & Connections (10th Edition) for Biology Exam 2 preparation.

Prokaryotic cell

A cell without a nucleus or membrane-bound organelles. Bacteria and Archaea are prokaryotes.

Main structures of a prokaryotic cell

The plasma membrane controls what enters and leaves; cytoplasm is where reactions occur; ribosomes make proteins; DNA stores genetic information; and the cell wall provides support. Some prokaryotes also have capsules, pili, and flagella.

DNA in prokaryotes

DNA is found in the nucleoid region, which is not surrounded by a membrane. Some prokaryotes also contain small DNA circles called plasmids.

Binary fission

Asexual reproduction in which one prokaryotic cell copies its DNA and divides into two cells.

Prokaryote shapes and Gram staining

Cocci are spherical, bacilli are rod-shaped, and spirilla are spiral-shaped. Gram-positive bacteria have thick peptidoglycan walls and stain purple; Gram-negative bacteria have thinner peptidoglycan walls, an outer membrane, and stain pink or red.

Bacteria vs. Archaea

Both are prokaryotes, but they differ in cell chemistry and genetics. Bacterial cell walls usually contain peptidoglycan; archaeal cell walls do not. Archaea share important molecular and genetic features with eukaryotes.

Prokaryotic energy and carbon sources

Phototrophs obtain energy from light; chemotrophs obtain energy from chemicals. Autotrophs use $CO_2$ or another inorganic carbon source to make organic molecules; heterotrophs obtain carbon from organic molecules. These categories can be combined, such as photoautotrophs and chemoheterotrophs.

Oxygen requirements

Aerobes require oxygen for their energy-producing processes. Anaerobes do not require oxygen; some are harmed or killed by it.

Temperature adaptations

Psychrophiles grow best in cold environments; mesophiles grow best at moderate temperatures; thermophiles grow best at high temperatures.

Extreme archaea

Halophiles thrive in high-salt environments; thermophiles thrive in hot environments; methanogens produce methane and live in oxygen-free environments.

Biofilms and quorum sensing

Biofilms are communities of microbes attached to a surface and protected by a surrounding material, making them difficult to eliminate. Quorum sensing is chemical communication that helps bacteria coordinate group behaviors based on how many nearby cells are present.

Helpful roles of bacteria

Bacteria help decompose waste, treat wastewater, break down pollutants through bioremediation, and support digestion and health as part of the gut microbiome.

Pathogenic bacteria and Koch’s postulates

Pathogens cause disease. Mycobacterium tuberculosis causes tuberculosis; Staphylococcus aureus can cause skin infections and other illnesses. Koch’s postulates are traditional criteria for linking a microorganism to a disease by finding it in diseased hosts, isolating it, testing whether it causes disease, and recovering it again.

Exotoxins vs. endotoxins

Exotoxins are harmful substances released by certain bacteria. Endotoxin refers to LPS in the outer membrane of Gram-negative bacteria; its lipid A portion can trigger strong inflammation.

Antibiotics, resistance, and viruses

Antibiotics kill bacteria or stop their growth but do not directly treat viruses. Antibiotic resistance occurs when bacteria survive medicines that would normally kill them or stop their growth. Viruses are noncellular agents containing DNA or RNA in a protein coat; they require host cells to reproduce and are generally not considered alive. In the lytic cycle, new viruses are made and released; in the lysogenic cycle, viral genetic material persists with the host’s genetic material and may later enter the lytic cycle.