Biology Chapter 1.3: Prokaryotes and Their Diversity

Questions and Answers

What characteristic distinguishes gram-negative bacteria from gram-positive bacteria?

Absence of an outer membrane

Presence of a thick layer of peptidoglycan

Ability to absorb crystal violet stain

Presence of lipopolysaccharides in the outer membrane (correct)

How does penicillin affect gram-positive bacteria?

It directly damages the bacterial DNA

It disrupts the cell membrane

It prevents cross-linking of peptidoglycan (correct)

It stimulates the immune response

What is the function of flagella in bacteria?

To aid in nutrient absorption

To store genetic information

To synthesize proteins

To provide propulsion for movement (correct)

What is the potential role of lipoteichoic acid in gram-positive bacteria?

It may activate the human immune system Signup and view all the answers

What structural component of flagella is responsible for its motility?

Basal body Signup and view all the answers

Why are certain bacteria still sensitive to penicillin despite widespread resistance?

They have not developed resistance mechanisms Signup and view all the answers

What type of DNA structure can confer advantages like antibiotic resistance in prokaryotes?

Plasmids Signup and view all the answers

What type of cell wall structure does a gram-positive bacterium primarily contain?

Thick layer of peptidoglycan Signup and view all the answers

What is chemotaxis in bacteria?

Movement towards or away from chemical stimuli Signup and view all the answers

Which component of the cell wall is primarily responsible for triggering an immune response in humans for gram-negative bacteria?

Lipopolysaccharides Signup and view all the answers

What size are prokaryotic ribosomes compared to eukaryotic ribosomes?

Smaller and less complex Signup and view all the answers

Which is a similarity between archaea and bacteria regarding flagella?

They can contain flagella but have different structures Signup and view all the answers

What role does the cytoplasmic membrane play in prokaryotes?

It functions for ATP generation and transport chain Signup and view all the answers

What is a characteristic feature of prokaryotes?

Single circular molecule of DNA Signup and view all the answers

Which two domains specifically contain prokaryotes?

Archaea and Bacteria Signup and view all the answers

What distinguishes Archaea from Bacteria?

Similarities in metabolic pathways to eukaryotes Signup and view all the answers

Why is understanding the diversity of prokaryotes essential in medicine?

Incorrect identification can lead to ineffective treatment Signup and view all the answers

Historically, where were Archaea commonly isolated from?

Harsh environments with extreme conditions Signup and view all the answers

What type of energy sources can some Archaea utilize?

Inorganic compounds including sulfur and nitrogen Signup and view all the answers

What hypothesis exists regarding the origin of eukaryotes?

Eukaryotes and Archaea share a common origin Signup and view all the answers

What was the previous classification of Archaea and Bacteria?

Kingdom Monera Signup and view all the answers

Which statement accurately describes the DNA structure in Archaea?

It is associated with histones. Signup and view all the answers

What is one way antibiotics differentiate between bacteria and eukaryotes?

By targeting the bacterial ribosome. Signup and view all the answers

Which type of bacteria requires oxygen for metabolism?

Obligate aerobes Signup and view all the answers

What characterizes mutualistic bacteria in the human gut?

They provide essential nutrients like vitamin K. Signup and view all the answers

What type of bacterium can switch between using oxygen for metabolism and not using it?

Facultative anaerobes Signup and view all the answers

Which classification describes spherical bacteria?

Cocci Signup and view all the answers

What is true about the cell wall of gram-negative bacteria?

It is more resistant to antibiotics than gram-positive cell walls. Signup and view all the answers

Which type of bacteria is known to cause Lyme disease?

Borrelia burgdorferi Signup and view all the answers

What do we call bacteria that are unable to use oxygen for metabolism and are harmed by its presence?

Obligate anaerobes Signup and view all the answers

What is one of the primary functions of bacterial flagella?

For motility. Signup and view all the answers

What is a characteristic of obligate anaerobes?

They cannot survive in an oxygenated environment. Signup and view all the answers

Bacteria that both benefit from and assist humans are known as?

Symbiotes Signup and view all the answers

What does the Gram staining process help determine?

The structural classification of bacteria. Signup and view all the answers

What is a major distinction between prokaryotes and eukaryotes?

Prokaryotes have no nucleus. Signup and view all the answers

Study Notes

Prokaryotes Overview

Simplest organisms, primarily consisting of bacteria.
Do not possess membrane-bound organelles.
Genetic material is a single circular DNA molecule located in the nucleoid region.

Importance in Medicine

Prokaryotic diversity is crucial for understanding infections.
Knowledge of bacterial structure aids in appropriate antibiotic selection.

Prokaryotic Domains

Life classified into three domains: Archaea, Bacteria, and Eukarya.
Prokaryotes are found in Archaea and Bacteria, previously grouped under Monera.

Archaea Characteristics

Single-celled organisms resembling bacteria, with genes more similar to eukaryotes.
Initially viewed as extremophiles but now found in diverse environments, including humans.
Can utilize alternative energy sources: some are photosynthetic, while many are chemosynthetic.

Comparison with Eukaryotes

Eukaryotes and Archaea share similar RNA polymerases, start translation with methionine, and associate DNA with histones.
Archaea have a single circular chromosome and reproduce by binary fission or budding.

Bacteria Characteristics

Comprise a cell membrane and cytoplasm; some have flagella or fimbriae.
Antibiotics can target structures unique to bacteria, such as ribosomes and flagella.

Bacteria Functions

Essential for human health, such as vitamin K production.
Newborns lack gut bacteria and receive a vitamin K injection to aid clotting until colonization occurs.
Approximately 5 × 10^30 bacteria exist on Earth, outnumbering all plants and animals.

Relationships with Humans

Some bacteria are mutualistic (e.g., gut bacteria producing vitamins), while others are pathogenic (e.g., Chlamydia trachomatis, Clostridium tetani).

Bacterial Classification by Shape

Cocci: spherical; examples include Streptococcus pyogenes.
Bacilli: rod-shaped; examples include Escherichia coli.
Spirilli: spiral-shaped; include Treponema pallidum (syphilis).

Bacteria Oxygen Requirements

Obligate aerobes require oxygen; anaerobes do not.
Obligate anaerobes can’t survive in oxygen; facultative anaerobes can switch metabolic processes.

Prokaryotic Cell Structure

Lack a nucleus and membrane-bound organelles; live as single-celled organisms.
Cell envelope consists of a cell wall and membrane.

Cell Wall Types

Gram-positive: thick peptidoglycan layer; appears purple when stained.
Gram-negative: thin peptidoglycan, with an outer membrane; appears pink-red when stained.

Antibiotic Interaction

Penicillin disrupts peptidoglycan cross-linking in gram-positive bacteria, leaving them susceptible to osmotic damage.

Flagella Structure

Composed of a filament, basal body, and hook; aids in bacterial movement and chemotaxis.

Genetic Material in Prokaryotes

DNA primarily in a single circular chromosome; may carry plasmids that confer advantages (e.g., antibiotic resistance).
Ribosomes in prokaryotes (30S and 50S subunits) differ in size from eukaryotic ribosomes (40S and 60S), allowing for antibiotic targeting.

Miscellaneous

No mitochondria in prokaryotes; instead, ATP generation occurs at the cell membrane.
Primitive cytoskeleton is present but simpler than in eukaryotic cells.

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Description

This quiz delves into the characteristics and diversity of prokaryotes, emphasizing their role in medicine. Understand the structure, function, and importance of these simple organisms, particularly in relation to infections and antibiotics. Test your knowledge on the fascinating world of bacteria and other prokaryotes.