Biology Chapter 5: Prokaryotes and Their Functions

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Questions and Answers

What distinguishes exotoxins from endotoxins?

Endotoxins are produced continuously without triggers.

Exotoxins are only released upon bacterial death.

Endotoxins cause disease regardless of bacterial presence.

Exotoxins are secreted and can cause disease without the bacteria being present. (correct)

Which organism is commonly used in gene cloning due to its properties?

Staphylococcus

Clostridium tetani

Salmonella

E. coli (correct)

What is one application of the CRISPR-Cas9 system mentioned?

Enhancing bacterial resistance to antibiotics.

Developing vaccines for bacterial diseases.

Creating synthetic toxins for research.

Research on treating HIV infection. (correct)

What type of biopolymer can bacteria synthesize for biodegradable plastics?

Polyhydroxyalkanoates Signup and view all the answers

What role do prokaryotes play in bioremediation?

They are primarily responsible for removing pollutants from the environment. Signup and view all the answers

What role do prokaryotes play in the recycling of chemical elements in ecosystems?

They function as decomposers. Signup and view all the answers

Which of the following statements about prokaryotes is true?

Prokaryotes can increase the availability of nitrogen and phosphorus. Signup and view all the answers

What contributes to the rapid genetic diversity observed in prokaryotes?

Genetic recombination and rapid evolution. Signup and view all the answers

Which statement best describes the importance of prokaryotes to life on Earth?

They play crucial roles in the biosphere's functioning. Signup and view all the answers

How do prokaryotes affect human activities?

They can have both beneficial and harmful impacts. Signup and view all the answers

What distinguishes Gram-positive bacteria from Gram-negative bacteria?

They have a large amount of peptidoglycan. Signup and view all the answers

Which bacterium is known to cause anthrax?

Bacillus anthracis Signup and view all the answers

What is the function of fimbriae in prokaryotic cells?

To allow attachment to substrates. Signup and view all the answers

What structure often covers many prokaryotes and can be made of polysaccharides or proteins?

Capsule Signup and view all the answers

Which type of bacteria is often associated with antibiotic resistance?

Gram-positive bacteria Signup and view all the answers

What term is used to describe the slimy extracellular matrix that often contains bacterial cells?

Biofilm Signup and view all the answers

How can flagella be characterized in terms of their distribution on the bacterial cell?

Scattered or concentrated at one or both ends. Signup and view all the answers

Which of these bacteria is typically not considered pathogenic?

Mycoplasmas Signup and view all the answers

What primarily limits the size of prokaryotic cells compared to eukaryotic cells?

The lack of a well-developed cytoskeleton Signup and view all the answers

Why do small cells have a greater surface area relative to volume?

Surface area increases by a factor of $n^2$ Signup and view all the answers

What function does the cell wall provide to prokaryotic cells?

Prevent the cell from lysing Signup and view all the answers

How do some prokaryotes compensate for their small size?

By having highly folded plasma membranes Signup and view all the answers

What is a disadvantage of lacking a well-developed cytoskeleton in prokaryotic cells?

Inability to support large cell volumes Signup and view all the answers

What happens to the surface area and volume of a cell as it increases in size?

Volume increases faster than surface area Signup and view all the answers

Which statement reflects the relationship between cell size and surface area-to-volume ratio?

As cells get smaller, their surface area-to-volume ratio increases Signup and view all the answers

What does the presence of a cell wall in prokaryotes indicate about their environment?

They are likely exposed to fluctuating external conditions Signup and view all the answers

What function do Rhizobium bacteria serve in leguminous plants?

They convert atmospheric nitrogen to ammonia. Signup and view all the answers

Which of the following best describes the process of nitrogen fixation?

Conversion of atmospheric nitrogen to ammonia. Signup and view all the answers

What characteristic is common among pathogens mentioned in the provided content?

They live within animal cells. Signup and view all the answers

Which statement is true about the cyanobacterium Anabaena?

It has specialized nitrogen-fixing cells called heterocysts. Signup and view all the answers

What is a significant health impact of pathogenic bacteria according to the content?

They are responsible for about half of all human diseases. Signup and view all the answers

Which bacterium is known to cause Lyme disease?

Borrelia burgdorferi Signup and view all the answers

Which bacterial group is involved in the conversion of NH4+ to NO2–?

Nitrosomonas Signup and view all the answers

What is the role of cooperation between prokaryotes as described?

It allows them to utilize environmental resources more effectively. Signup and view all the answers

What is the primary role of the F plasmid in bacterial conjugation?

It produces pili that facilitate DNA transfer. Signup and view all the answers

Which type of prokaryote requires oxygen for cellular respiration?

Obligate aerobes Signup and view all the answers

In which nutritional mode do organisms require an organic nutrient for carbon?

Chemoheterotrophy Signup and view all the answers

What characterizes a facultative anaerobe?

It can survive with or without oxygen. Signup and view all the answers

Which of the following describes mutualism in ecological interactions?

Both organisms benefit from the relationship. Signup and view all the answers

Which type of bacteria is known to be poisoned by oxygen?

Obligate anaerobes Signup and view all the answers

What is a significant impact of taking antibiotics on gut microbes?

They can disrupt the balance of gut microbiota. Signup and view all the answers

What type of bacteria carries genes that provide resistance to antibiotics?

R plasmids Signup and view all the answers

What defines photoautotrophy among prokaryotes?

Utilizing light energy to convert carbon dioxide into organic compounds. Signup and view all the answers

What is true about symbiosis in ecology?

It includes various types of relationships, such as mutualism and parasitism. Signup and view all the answers

Study Notes

Bacteria (Prokaryotes)

Bacteria are a domain of prokaryotic organisms.
They display diverse shapes, including spheres (cocci), rods (bacilli), and spirals.
Bacteria range in size from 0.5-5µm (prokaryotes). Eukaryotic cells are 10µm-100µm.

Bacteria: Taxonomy

Comparisons of ribosomal RNA sequences show a three-domain tree of life, making the term 'prokaryote' obsolete.
Domains include Bacteria, Archaea, and Eukarya.

Bacteria: Generalizations

Archaea have unique rRNA sequences, cell walls, and phospholipids in their plasma membranes.
Most prokaryotes are microscopic but some form colonies.
Bacteria can thrive nearly everywhere, even environments inhospitable to most other organisms.
Earth's first organisms were likely prokaryotes.

Bacteria: Size

A cell's volume increases faster than its surface area as it grows.
Small cells have a greater surface area to volume ratio.
Prokaryotic cells are small to accommodate the needs of their cell structure (lack of cytoskeleton).

Bacteria: Membranes

Some prokaryotes have highly folded plasma membranes to compensate for lack of organelles.
These specialized membranes perform metabolic functions similar to the endomembrane system in eukaryotes.

Bacteria: Cell Surface Structures

Nearly all prokaryotic cells possess a cell wall, maintaining cell shape and protecting against hypotonic environments.
Bacterial cell walls contain peptidoglycan, a network of sugar polymers.
Archaea cell walls lack peptidoglycan, containing polysaccharides and proteins instead.
Eukaryotic cell walls are made of cellulose (plants) or chitin (fungi).
Gram staining categorizes bacteria based on cell wall composition.

Bacteria: Gram -ve

Gram-negative bacteria have less peptidoglycan and an outer membrane.
Some gram-negative bacteria are known for producing toxic substances.
Examples of gram-negative bacteria: Chlamydias, Cyanobacteria, Spirochetes.

Bacteria: Gram +ve

Gram-positive bacteria have simpler walls with a high amount of peptidoglycan.
Examples of gram-positive bacteria: Streptomyces, Bacillus anthracis, Staphylococcus aureus, Mycoplasmas

Bacteria: Cell Surface Structures (Further)

A capsule, a polysaccharide or protein layer, surrounds many prokaryotes, aiding in attachment and protection.
Fimbriae are hairlike appendages that enable prokaryotes to stick to substances.
Biofilms are protective extracellular matrixes coating many bacterial cells, composed of polysaccharides, proteins, lipids, and DNA.
Flagella are appendages facilitating movement.

Bacteria: Endospores

Some prokaryotes form endospores, which are metabolically inactive structures inside the cell that can endure harsh conditions for considerable time periods.

Bacteria: Brainstorm Questions

Can a strain of Neisseria gonorrhoeae that lacks fimbriae still cause disease?
Why are Clostridium difficile infections in hospitals concerning?

Bacteria: Ecological Success

Prokaryotes exhibit considerable genetic variation due to rapid reproduction, mutations, and genetic recombination.
They have evolved a diversity of nutritional and metabolic adaptations.
Prokaryotes have branched into a wide range of lineages.
They play major roles in the biosphere and have both positive and negative interactions with humans.

Bacteria: Rapid Reproduction & Mutation

Binary fission is the primary method of reproduction for prokaryotes, producing identical offspring.
Prokaryotic mutation rates, though low, can lead to rapid accumulation of mutations and rapid evolution due to high reproduction rates.

Bacteria: Genetic Recombination

Genetic recombination, combining DNA from two sources, contributes to genetic diversity in prokaryotes.
Horizontal gene transfer – movement of genes among different species – results through processes like transformation, transduction, and conjugation.

Bacteria: Transformation

Transformation is the process where a prokaryotic cell takes up and incorporates foreign DNA from the environment.

Bacteria: Transduction

Transduction is the movement of genes between bacteria through the action of bacteriophages (viruses).

Bacteria: Conjugation

Conjugation is the process where genetic material is transferred between prokaryotic cells.
A pilus is a protein tube linking two bacteria, facilitating the transfer of DNA.
Many bacteria including E. coli carry plasmids. F plasmids are responsible for the production of pili. R plasmids often encode antibiotic resistance genes.

Bacteria: Nutritional Modes

Bacteria have four major modes of nutrition involving combinations of energy and carbon source types: photoautotrophs, chemoautotrophs, photoheterotrophs, and chemoheterotrophs.
Phototrophs get energy from light while chemotrophs are nourished by chemical compounds.
Autotrophs use carbon dioxide while heterotrophs require organic compounds.

Bacteria: Roles of Oxygen

Bacterial metabolic responses to oxygen vary.
Obligate aerobes require oxygen for cellular respiration.
Obligate anaerobes are killed by oxygen and utilize fermentation or anaerobic respiration.
Facultative anaerobes can survive in presence or absence of oxygen.

Bacteria: Ecological Interactions

Symbiosis involves close contact between two species: host and symbiont.
Mutualism benefits both symbiotic organisms.
Commensalism benefits one organism without significant effect on the other.
Parasitism benefits one organism (parasite) while harming the other.
Pathogens are parasites that result in disease in the host.

Bacteria: Mutualistic Symbiosis

Many bacteria in the human intestine perform mutualistic roles breaking down undigested food.
The bacteria in the gut are significantly more than the human cells.
Antibiotics can have an impact on the health of the gut flora.
Nitrogen is essential to producing amino acids and nucleic acids. Prokaryotes play key roles in nitrogen fixation (nitrogen converted to ammonia).

Bacteria: Nitrogen Cycle

Prokaryotes crucial in nutrient cycling. Important functions include: • nitrogen fixation, converting atmospheric nitrogen to ammonia; • decomposition, breaking down dead organic matter; • nitrification, transforming ammonia into nitrite and nitrate.

Bacteria: Electron Transfer

Microorganisms play essential roles in converting one chemical compound to another by transferring electrons from one substance to another.
Electron donors are molecules losing electrons; electron acceptors gain electrons.

Bacteria: Cyanobacteria

Cooperation between different prokaryotic cells allows for greater adaptation and resources usage.
Some cyanobacteria have cells specializing in photosynthesis and nitrogen fixation.

Bacteria: Pathogens

Many bacterial species are pathogens.
Examples: Campylobacter, Helicobacter pylori, Chlamydia trachomatis, Treponema pallidum, Borrelia burgdorferi.
Some bacterial pathogens produce toxins (exotoxins and endotoxins).

Bacteria: Toxins

Exotoxins are produced and secreted by bacteria, even when bacteria are not present.
Endotoxins are released during bacteria cell death and are lipids part of the outer membrane of certain types of bacteria.

Bacteria: Tetanus

Tetanus is a disease caused by exotoxin produced by Clostridium tetani, also known as tetanus bacteria.

Bacteria: Salmonella

LPS activates complement system in Salmonella infection.

Bacteria: Research and Technology

Prokaryotes are instrumental in developing new applications in DNA technology (E. coli), DNA polymerase (Pyrococcus furiosus), CRISPR-Cas9, and in producing natural plastics such as polyhydroxyalkanoates and polylactic acid. Bacteria are used for bioremediation removing pollutants.

Bacteria: Biosphere

Prokaryotes play essential roles in ecosystems, particularly in recycling chemicals and decomposing dead organic matter.

Bacteria: Nutrient Availability

Prokaryotic organisms often impact nutrient availability for plants. These microorganisms can increase (e.g. nitrogen, phosphorus, potassium) or decrease (immobilize) nutrient availability in the soil.

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Description

Test your knowledge on prokaryotes, their roles in ecosystems, and their significance to human life in this comprehensive quiz. Explore topics ranging from exotoxins and gene cloning to biopolymer synthesis and antibiotic resistance. Determine how these microorganisms contribute to bioremediation and the recycling of chemical elements.