Biology Chapter 25: Bacteria and Archaea

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Questions and Answers

In which type of symbiotic relationship do both organisms derive benefits?

Competition

Mutualism (correct)

Parasitism

Commensalism

What characterizes commensalism in a symbiotic relationship?

Both organisms benefit

Neither organism benefits

One organism benefits and the other is unaffected (correct)

One organism benefits while the other is harmed

Which term describes a relationship where one organism harms but does not kill another?

Parasitism (correct)

Mutualism

Predation

Commensalism

What happens to the color of gram-negative bacteria after applying crystal violet?

The purple color is washed away, revealing red dye. Signup and view all the answers

How is the host affected in a parasitic relationship?

It is harmed by the parasite Signup and view all the answers

In mutualism, how do both organisms interact?

Both organisms benefit from each other Signup and view all the answers

Which statement accurately describes the outcome of staining with crystal violet in gram-negative bacteria?

Red dye is visible after crystal violet is rinsed away. Signup and view all the answers

What characteristic of gram-negative bacteria contributes to crystal violet being easily rinsed away?

Thin peptidoglycan layer. Signup and view all the answers

What distinguishes Archaea from Bacteria in terms of membrane composition?

Archaea possess cell membranes with unique branched isoprene chains. Signup and view all the answers

When staining gram-negative bacteria, what is observed after rinsing with crystal violet?

Visibility of red dye. Signup and view all the answers

Which dye becomes visible after the crystal violet is rinsed from gram-negative bacteria?

Safranin. Signup and view all the answers

Which of the following statements best describes the metabolic processes commonly found in Archaea?

Methanogenesis is a unique and prevalent metabolic process in Archaea. Signup and view all the answers

In terms of genetic structure, how do Archaea and Bacteria primarily differ?

Archaea have histones associated with their DNA, unlike Bacteria. Signup and view all the answers

Which of the following environments are Archaea most likely to thrive in?

High-salinity environments like salt lakes. Signup and view all the answers

Which cellular feature is NOT typically associated with Bacteria?

Introns present within genes. Signup and view all the answers

What is the primary method of reproduction in prokaryotes?

Binary fission Signup and view all the answers

How quickly can prokaryotes reproduce under optimal conditions?

Every 1–3 hours Signup and view all the answers

What is a characteristic feature of endospores formed by some prokaryotes?

They can survive in harsh conditions for centuries Signup and view all the answers

Which component is NOT typically associated with prokaryotic structures?

Mitochondria Signup and view all the answers

What is the significance of plasmids in prokaryotes?

They carry genes for antibiotic resistance Signup and view all the answers

What is the primary role of chemoheterotrophic prokaryotes in ecosystems?

Decomposing organic matter Signup and view all the answers

Which type of prokaryotes significantly contributes to the recycling of chemical elements?

Chemoheterotrophic prokaryotes Signup and view all the answers

What do decomposers mainly break down in ecosystems?

Corpses, dead vegetation, and waste products Signup and view all the answers

In the process of chemical cycling, what type of organic matter do saprophytes primarily target?

Animal and plant waste products Signup and view all the answers

Which of the following best describes the role of prokaryotes in the ecosystem?

Key players in nutrient cycling and decomposition Signup and view all the answers

What is a characteristic distinction between exotoxins and endotoxins?

Endotoxins are components of the gram-negative plasma membrane. Signup and view all the answers

Which component is exclusively associated with gram-positive bacteria?

Capsule Signup and view all the answers

Which structure in bacteria is primarily responsible for protein synthesis?

Ribosomes Signup and view all the answers

What is the primary function of the flagella in bacteria?

To facilitate locomotion Signup and view all the answers

Which of the following statements about the bacterial structure is false?

All bacteria possess a sex pilus. Signup and view all the answers

Study Notes

Chapter 25: Bacteria and Archaea

Prokaryotes are divided into two domains: bacteria and archaea
Most prokaryotes are unicellular, though some form colonies
Prokaryotic cells are typically 0.5-5 μm, significantly smaller than eukaryotic cells (10-100 μm)
Some bacteria are pathogens, causing disease; however, most bacteria are benign or beneficial to our bodies
Prokaryotic cells commonly exhibit three shapes: spheres (cocci), rods (bacilli), and spirals
Cocci are spherical prokaryotes; some cocci form chains called streptococci
Bacilli are rod-shaped; some can be threadlike or filamentous (e.g., E. coli)
Vibrio are curved rods (e.g., cholera)
Spirilla are short, rigid spirals; spirochetes are longer, flexible spirals (e.g., treponema pallidum, causing syphilis)
Several hundred bacterial species live on and in our bodies, aiding in functions like decomposing dead skin, producing vitamins, and preventing pathogenic organisms
Prokaryotes in soil decompose dead organisms sustaining chemical cycles
A key feature of prokaryotic cells is their cell wall, which maintains shape, provides protection, and prevents bursting in hypotonic environments
Eukaryotic cell walls are composed of cellulose or chitin
Bacterial cell walls contain peptidoglycan, a network of sugar polymers cross-linked by polypeptides
Gram stain categorizes bacteria into Gram-positive and Gram-negative groups based on cell wall composition
Gram-negative bacteria have less peptidoglycan, an outer membrane that may be toxic, and tend to be more antibiotic-resistant
Many antibiotics target peptidoglycan damaging bacterial cell walls
The prokaryotic genome is significantly smaller (one-thousandth of the size) compared to eukaryotic genomes
The prokaryotic genome is typically a single circular chromosome located in a nucleoid region
Some bacteria have smaller rings of DNA called plasmids
Prokaryotes reproduce asexually rapidly by binary fission, often every 1-3 hours
Many prokaryotes form endospores, metabolically inactive structures that remain dormant and viable in harsh conditions for centuries
Genetic diversity in prokaryotes is driven by rapid reproduction, mutation, and genetic recombination
Genetic recombination occurs via transformation (uptake of foreign DNA), transduction (gene transfer by bacteriophages, or viruses), and conjugation (DNA transfer between bacterial cells via sex pili)
F-factor, a piece of DNA, is needed to produce sex pili used in conjugation and may exist as a plasmid or within the chromosome; conjugation transfers this factor to other bacterial cells
R plasmids carry genes that provide antibiotic resistance
Nutritional diversity observed in prokaryotes manifests in varied energy and carbon sources (examples include phototrophs, chemoautotrophs, heterotrophs, photoheterotrophs and chemoheterotrophs)
Prokaryotes vary in their needs for Oxygen. A distinction is made between obligate aerobes, obligate anaerobes and facultative anaerobes
Prokaryotes such as nitrogen fixers play important roles in nitrogen fixation and recycling chemical elements in the biosphere
Symbiotic relationships among prokaryotes and other species are essential interactions within the biosphere; mutualism, commensalism, and parasitism are prevalent forms of symbiosis in which prokaryotes play an important role.
The presence of diverse toxins such as exotoxins and endotoxins influences the effect of pathogenic bacteria

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This quiz covers key concepts from Chapter 25 about prokaryotes, specifically bacteria and archaea. You will learn about their structures, shapes, and their roles in both health and disease. Test your understanding of how these microorganisms contribute to various biological processes.