Prokaryotic Cell Structure and Function

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Questions and Answers

What is the primary function of fimbriae in prokaryotes?

To stick to their substrate or other individuals in a colony (correct)

To propel themselves by flagella

To allow for the exchange of DNA

To enable movement towards or away from a stimulus

Which of the following is NOT a factor contributing to genetic diversity in prokaryotes?

Rapid reproduction

Mutation

Binary fission (correct)

Genetic recombination

What is the name of the movement towards or away from a chemical stimulus?

Phototaxis

Flagellated movement

Taxis

Chemotaxis (correct)

What is the structure composed of a motor, hook, and filament that propels motile bacteria?

Flagella Signup and view all the answers

What is the term for the ability of bacteria to move towards or away from a stimulus?

Taxis Signup and view all the answers

What is the name of the region within prokaryotic cells where the circular chromosome is located?

Nucleoid region Signup and view all the answers

Which of the following is a characteristic of prokaryotic reproduction?

Binary fission Signup and view all the answers

What is the term for the metabolically inactive structures formed by some prokaryotes that can remain viable in harsh conditions?

Endospores Signup and view all the answers

Which of the following archaea thrive in very hot environments?

Extreme thermophiles (Clade Crenarchaeota) Signup and view all the answers

What is the primary function of chemoheterotrophic prokaryotes in ecosystems?

To break down dead organisms and waste products Signup and view all the answers

Which of the following bacteria are photoautotrophs that generate oxygen?

Cyanobacteria Signup and view all the answers

Which of the following is a characteristic of methanogens?

They are strict anaerobes and are poisoned by O2 Signup and view all the answers

What is the primary function of prokaryotes in the recycling of chemical elements?

To increase the availability of nitrogen, phosphorus, and potassium Signup and view all the answers

Which of the following bacteria are helical heterotrophs?

Spirochetes Signup and view all the answers

Which of the following is an example of symbiosis?

Chlamydia living within animal cells Signup and view all the answers

What is the primary function of gram-positive bacteria such as Actinomycetes?

To decompose organic matter Signup and view all the answers

What is the process by which a prokaryotic cell takes up and incorporates foreign DNA from the surrounding environment?

Transformation Signup and view all the answers

Which of the following statements is true about conjugation in prokaryotes?

A donor cell attaches to a recipient by a pilus, pulls it closer, and transfers DNA Signup and view all the answers

What is the term for the movement of genes between bacteria by bacteriophages?

Transduction Signup and view all the answers

What is the term for the process by which some prokaryotes convert atmospheric nitrogen to ammonia?

Nitrogen fixation Signup and view all the answers

Which of the following modes of nutrition is characterized by the requirement of CO2 as a carbon source?

Autotrophs Signup and view all the answers

Which of the following statements is true about obligate anaerobes?

They are poisoned by O2 and use fermentation or anaerobic respiration Signup and view all the answers

What is the term for the exchange of metabolic products between photosynthetic cells and nitrogen-fixing cells in the cyanobacterium Anabaena?

Exchange of metabolic products Signup and view all the answers

Which of the following is a characteristic of facultative anaerobes?

They can survive with or without O2 Signup and view all the answers

What is the primary function of the capsule in bacterial structure?

To enable binding to surfaces and evade phagocytosis Signup and view all the answers

Which bacterial structure is composed of a phospholipid bilayer with hydrophilic and hydrophobic regions?

Plasma membrane Signup and view all the answers

What is the main difference between gram-positive and gram-negative bacteria?

The composition of the cell wall Signup and view all the answers

What is the function of pili in bacterial structure?

To attach to surfaces and contribute to disease-causing ability Signup and view all the answers

What is the composition of the cell wall in bacterial structure?

Peptidoglycan Signup and view all the answers

What is the characteristic of gram-positive bacteria that enables binding to cell walls or recognition by macrophages?

Lipoteichoic acid Signup and view all the answers

What is the site of protein synthesis in bacterial cells?

Ribosomes Signup and view all the answers

What is the characteristic of bacterial DNA?

Circular and double-stranded Signup and view all the answers

What is the primary reason antibiotics have been effective in saving millions of lives from infections?

They target the specific bacteria that cause infection Signup and view all the answers

What is a consequence of using antibiotics in animal feed and water?

Evolution of resistant bacteria in animal populations that can spread to humans Signup and view all the answers

What is the main consequence of the overuse of antibiotics?

The evolution of antibiotic-resistant bacteria, or 'superbugs' Signup and view all the answers

Why should antibiotics be used judiciously?

To avoid driving the evolution of resistant bacteria Signup and view all the answers

What is the purpose of the Mega-Plate experiment?

To study how bacteria evolve resistance to antibiotics Signup and view all the answers

What is a limitation of using antibacterial chemicals in soaps and hand gels?

They can contribute to the problem of antibiotic resistance Signup and view all the answers

How do bacteria evolve resistance to antibiotics?

When bacteria with mutations that allow them to survive are the only ones left standing Signup and view all the answers

What did Alexander Fleming predict?

The development of antibiotic resistance Signup and view all the answers

What is the primary factor contributing to the rapid evolution of antibiotic resistance?

The fast reproduction rate of bacteria Signup and view all the answers

What is a key principle of responsible antibiotic use?

Using antibiotics to treat bacterial diseases only Signup and view all the answers

What is the outcome of the Mega-Plate experiment after 11 days?

The bacteria evolved from being susceptible to being highly resistant to antibiotics Signup and view all the answers

What is the primary function of the plasmid in bacterial genetics?

To encode for the sex pilus Signup and view all the answers

Which of the following processes involves the transfer of DNA from one bacterium to another through direct cell-to-cell contact?

Conjugation Signup and view all the answers

What is the term for the ability of bacteria to take up and incorporate foreign DNA from the environment?

Transformation Signup and view all the answers

Which of the following types of phages can give bacteria 'superpowers' such as the ability to produce exotoxins?

Lysogenic phages Signup and view all the answers

What is the primary function of the bacterial chromosome in bacterial genetics?

To store most of the bacterial DNA Signup and view all the answers

Which of the following processes involves the extraction of a small part of the bacterial chromosome to become a plasmid?

Transposition Signup and view all the answers

What is the term for the process by which a bacteriophage carrying its own DNA injects it into the bacterial DNA?

Transduction Signup and view all the answers

Which of the following bacteria are capable of taking up DNA from the environment and using it to gain new traits?

Streptococcus pneumoniae, H influenza, and Nesseria Signup and view all the answers

Which domain is characterized by the presence of histones, similar to Eukarya?

Archaea Signup and view all the answers

What is a common characteristic of Archaea and Eukarya during protein synthesis?

They use methionine as the start amino acid Signup and view all the answers

Which of the following is NOT a characteristic of domain Bacteria?

They are all extremophiles Signup and view all the answers

Which subgroup of Proteobacteria includes Rhizobium, which forms nodules on plant roots?

Alpha Proteobacteria Signup and view all the answers

What is the primary function of Cyanobacteria?

To produce their own sugar molecules using light and pigments Signup and view all the answers

Which of the following is a characteristic of Eukarya and Archaea?

They have similar RNA polymerase enzymes Signup and view all the answers

Which of the following is NOT a type of extremophile?

Phototrophs Signup and view all the answers

Which of the following domains is NOT closely related to Archaea?

Bacteria Signup and view all the answers

Study Notes

Prokaryotic Cell Structure and Function

Prokaryotes have fimbriae, which allow them to stick to their substrate or other individuals in a colony.
Pili (or sex pili) are longer than fimbriae and allow prokaryotes to exchange DNA.
Prokaryotes exhibit taxis, the ability to move toward or away from a stimulus, including chemotaxis, movement toward or away from a chemical stimulus.
Most motile bacteria propel themselves by flagella, which are composed of a motor, hook, and filament.

Prokaryotic Reproduction

Prokaryotes reproduce by binary fission, a process that takes 1-3 hours.
They have short generation times, which allows for rapid reproduction.
Many prokaryotes form metabolically inactive endospores, which can remain viable in harsh conditions for centuries.
Genetic diversity in prokaryotes arises from rapid reproduction, mutation, and genetic recombination.

Domain Bacteria

Proteobacteria are gram-negative bacteria that include photoautotrophs, chemoautotrophs, and heterotrophs.
Chlamydia are parasites that live only within animal cells.
Spirochetes are helical heterotrophs, some of which are parasites.
Cyanobacteria are photoautotrophs that generate O2.
Gram-positive bacteria include actinomycetes, Bacillus anthracis, Clostridium botulinum, and some Staphylococcus and Streptococcus.

Ecological Importance

Prokaryotes play a major role in the recycling of chemical elements between the living and nonliving components of ecosystems.
Chemoheterotrophic prokaryotes function as decomposers, breaking down dead organisms and waste products.
Prokaryotes can increase the availability of nitrogen, phosphorus, and potassium for plant growth.
Symbiosis is an ecological relationship in which two species live in close contact, including mutualism, commensalism, and parasitism.

Genetic Recombination

Genetic recombination in prokaryotes occurs through transformation, transduction, and conjugation.
Transformation is the process of taking up and incorporating foreign DNA from the surrounding environment.
Transduction is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria).
Conjugation is the process where genetic material is transferred between prokaryotic cells.

Metabolism and Nutrition

Prokaryotes can be categorized by how they obtain energy and carbon, including phototrophs, chemotrophs, autotrophs, and heterotrophs.
Energy and carbon sources are combined to give four major modes of nutrition.
Nitrogen is essential for the production of amino acids and nucleic acids, and some prokaryotes can fix atmospheric nitrogen (N2) to ammonia (NH3).
Prokaryotic metabolism varies with respect to O2, including obligate aerobes, obligate anaerobes, and facultative anaerobes.

Prokaryotic Diversity

Domain Archaea shares certain traits with bacteria and other traits with eukaryotes.
Some archaea live in extreme environments and are called extremophiles.
Methanogens are strict anaerobes and are poisoned by O2.
Domain Bacteria includes proteobacteria, chlamydia, spirochetes, cyanobacteria, and gram-positive bacteria.

Bacteria Structure

Bacteria are found everywhere and are the largest group of microorganisms with medical significance.
They occur in three main shapes: coccus (circular), bacillus (rod-shaped), and spiral.
Some bacteria have a capsule, a polysaccharide-containing layer that allows them to bind to surfaces and evade phagocytosis.

Bacterial Movement and Adhesion

Some bacteria have flagella, thin rigid filaments made of proteins that enable movement.
Bacteria can also possess hair-like appendages called fimbriae and pili, which help attach to surfaces and contribute to disease-causing ability.
Pili are involved in bacterial conjugation, the transfer of genetic material between bacteria.

Bacterial Layers

The outermost layer is the capsule, composed of polysaccharides, which enables binding to cell surfaces and avoids phagocytosis.
The plasma membrane is a semi-permeable membrane allowing transportation of substances in and out of the cell.
The plasma membrane is composed of a phospholipid bilayer, similar to those found in human cells, with hydrophilic and hydrophobic regions.
The cell wall is a semi-rigid structure between the capsule and plasma membrane, composed of peptidoglycan.

Gram-Positive and Gram-Negative Bacteria

Bacteria can be classified into two groups based on cell wall composition: gram-positive and gram-negative.
Gram-positive bacteria have a thick peptidoglycan layer and a cell membrane, while gram-negative bacteria have a thin peptidoglycan layer and an extra outer cell membrane.
Gram-positive bacteria have lipoteichoic acid, which enables binding to cell walls or recognition by macrophages.
Gram-negative bacteria have lipid-like structures on the outer cell membrane.

Cytoplasm and Genetic Material

Cytoplasm contains water, enzymes, ribosomes, and circular DNA.
Ribosomes are the site of protein synthesis and are found throughout the cytoplasm.
The circular DNA is the genetic material of bacteria, different from the linear DNA found in human cells.
Plasmids, small circular genetic information, are found in the cytoplasm and can be transferred between bacteria through conjugation.

Antibiotics and Bacteria

Antibiotics are natural substances produced by microbes to kill other microbes, and have been in use for billions of years
Alexander Fleming discovered penicillin in 1928, leading to the development of antibiotics that revolutionized medicine and saved millions of lives from infections

The Problem with Antibiotics

Commercial antibiotics are "shock and awe" weapons, killing both bad and good bacteria in the gut
Overuse of antibiotics creates antibiotic-resistant bacteria, or "superbugs"
Misuse of antibiotics leads to the evolution of resistant bacteria

The Mega-Plate Experiment

Scientists created a giant petri dish, the Mega-Plate, to study how bacteria evolve resistance to antibiotics
The experiment showed that E.coli bacteria can evolve from being susceptible to highly resistant to antibiotics in just 11 days

How Antibiotic Resistance Evolves

Mutations in bacteria allow them to survive antibiotic exposure, and these mutants reproduce to create a population of super-resistant bugs
Fast reproduction rate of bacteria, such as E.coli, allows antibiotic resistance to evolve rapidly

The Impact of Antibiotic Misuse

Antibiotics are used in animal feed and water to prevent livestock disease, leading to the evolution of resistant bacteria in animal populations
Resistant bacteria in animal populations can spread to humans, exacerbating the problem of antibiotic resistance
Alexander Fleming predicted the problem of antibiotic resistance due to overuse

The Need for Responsible Antibiotic Use

Antibiotics should only be used to treat bacterial diseases, not viral diseases
Antibiotics should be used judiciously to avoid driving the evolution of resistant bacteria
Alternative approaches, such as antibacterial chemicals in soaps and hand gels, are not always effective and can contribute to the problem of antibiotic resistance

Bacterial Genetics

Bacterial DNA consists of two parts: the large, complex bacterial chromosome containing most of the DNA, and the smaller, independent bacterial plasmid containing a small part of the DNA.

Transposition

Transposition involves the extraction of a small part of the bacterial chromosome to form a plasmid, or the reintegration of a plasmid into the bacterial chromosome.
This process is related to plasmids, which are smaller and more accessible.

Conjugation

Conjugation occurs between bacteria with a sex pilus (F+ bacteria) and those without (F- bacteria).
The sex pilus is encoded by the bacterial plasmid, not the bacterial chromosome.
During conjugation, F+ bacteria create a copy of their plasmid and transfer it to F- bacteria, resulting in both bacteria having a plasmid that encodes for a sex pilus.

Transformation

Transformation, also known as competence, is the ability of bacteria to take up naked genomes or DNA from the environment and utilize it.
This process occurs exclusively in Streptococcus pneumoniae, H influenza, and Nesseria.
Through transformation, bacteria can acquire new traits, such as antibiotic resistance, by taking up DNA from their environment.

Transduction

Transduction is the process in which a bacteriophage (bacterial virus) carrying its own DNA injects it into bacterial DNA.
The viral DNA integrates into the bacterial DNA and begins replicating the virus.
There are two types of bacteriophages: lytic phages, which result in bacterial death, and lysogenic phages, which do not.
Lysogenic phages can grant bacteria new abilities, such as the production of exotoxins, effectively giving them "superpowers".

Phylogenetic Tree of Life

The phylogenetic tree represents three main domains of life: Eukarya, Archaea, and Bacteria.
Eukarya and Archaea share a common ancestor, making them sister taxa.
Bacteria is not closely related to Archaea, despite both being prokaryotic.

Similarities between Archaea and Eukarya

Both have similar RNA polymerase enzymes.
Both have methionine as the start amino acid during protein synthesis.
Both have histones, which organize DNA.

Domain Archaea

Archaea are extremophiles, thriving in extreme environments.
Examples of extremophiles include:
- Halophiles, found in high-salinity environments like the Dead Sea and Great Salt Lake.
- Thermofoils, found in high-temperature environments like hot springs and Yellowstone National Park.
- Methanogens, found in oxygen-absent environments.

Domain Bacteria

Bacteria are a widely diverse group found in many environments.
They perform beneficial functions for the environment and humans.
Some members of domain Bacteria cause diseases.
Subdivisions of domain Bacteria include:
- Proteobacteria (gram-negative), a wide variety of microbes.
- Chlamydia (gram-negative), mostly parasites that live within animal cells.
- Spirochetes (gram-negative), helical-shaped bacteria responsible for diseases like Lyme disease.
- Cyanobacteria, filamentous bacteria that produce sugar molecules using light and pigments like chlorophyll.
- Gram-positive bacteria, including many examples like Bacillus, Clostridium, and Staphylococcus.

Proteobacteria

Subgroups of Proteobacteria include:
- Alpha Proteobacteria, including Rhizobium, which forms nodules on plant roots.
- Beta Proteobacteria, including Nitrosomonas, a nitrogen-fixing bacterium.
- Gamma Proteobacteria, including Pseudomonas fluorescens, a heterotroph.
- Delta Proteobacteria, including bacteria that attack and destroy other bacteria.
- Epsilon Proteobacteria, including Helicobacter pylori, associated with stomach ulcers.

Other Bacteria

Chlamydia trachomatis is responsible for non-gonococcal urethritis, a common sexually transmitted disease.
Spirochetes have a helical shape and are responsible for diseases like Lyme disease.
Cyanobacteria include filamentous bacteria like Oscillatoria.
Gram-positive bacteria include Bacillus, Clostridium, and Staphylococcus, responsible for various diseases and having different characteristics.

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Description

This quiz covers the structure and function of prokaryotic cells, including fimbriae, pili, taxa, and flagella.