Microbiology Chapter 5 Quiz

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Questions and Answers

What is the major component of the cell wall in gram-positive bacteria?

Peptidoglycan (correct)

Teichoic acids

Braun lipoprotein

Lipopolysaccharide (LPS)

Which of the following is a characteristic of gram-negative bacteria's cell wall?

A single layer of peptidoglycan

A thick layer of peptidoglycan

The presence of teichoic acids

The presence of an outer membrane (correct)

What is the function of lysozyme?

Breaks down peptidoglycan (correct)

Prevents DNA replication

Synthesizes peptidoglycan

Inhibits protein synthesis

What is the toxic component of lipopolysaccharide (LPS) known as?

Lipid A (A) Signup and view all the answers

Which of the following is NOT considered a prokaryote that lacks a cell wall?

E. coli (C) Signup and view all the answers

What are the two main categories of morphology in prokaryotic cells?

Shape and Size (A) Signup and view all the answers

What is the size range for eukaryotic cells?

2 to >600 µm in diameter (C) Signup and view all the answers

What is the main function of the cytoplasmic membrane?

Selective permeability (C) Signup and view all the answers

What are the two main components of phospholipids?

Glycerol and phosphate (C) Signup and view all the answers

What is the name for the linkages in phospholipids of Archaea?

Ether (C) Signup and view all the answers

Which of the following is NOT a function of the cytoplasmic membrane?

Cell wall synthesis (D) Signup and view all the answers

What is the name of the rigid structure that surrounds bacterial cells?

Peptidoglycan (C) Signup and view all the answers

How do Gram-positive and Gram-negative bacteria differ in terms of their cell wall?

Gram-negative bacteria have an outer membrane (B), Gram-positive bacteria have a thicker peptidoglycan layer (C) Signup and view all the answers

Which of the following is NOT a function of capsules and slime layers?

Protection from osmotic lysis (B) Signup and view all the answers

What is a key characteristic of a capsule that distinguishes it from a slime layer?

Capsule is tightly attached to the cell wall, while slime layer is loosely adhered. (D) Signup and view all the answers

What is the unique characteristic of pseudomurein compared to peptidoglycan?

Pseudomurein is more resistant to lysozyme and penicillin than peptidoglycan. (B) Signup and view all the answers

Which type of pili is primarily associated with the exchange of genetic material between bacteria?

Conjugative pili (B) Signup and view all the answers

Which archaeal structure is responsible for forming biofilms through its barbed terminus?

Hamus (D) Signup and view all the answers

What is the primary mechanism by which bacteria move?

All of the above (D) Signup and view all the answers

Which of the following is NOT a characteristic of Archaella?

They are composed of flagellin. (C) Signup and view all the answers

Why do bacteria exhibit "run and tumble" behavior during chemotaxis?

To randomly explore their environment for favorable conditions. (D) Signup and view all the answers

What is the main difference between gliding and swimming motility?

Gliding motility requires surface contact, while swimming motility does not. (A) Signup and view all the answers

What does the nucleolus synthesize?

ribosomal RNA (A) Signup and view all the answers

Which of the following is an example of taxis?

A bacterium moving towards a higher concentration of glucose. (A) Signup and view all the answers

How do bacteria sense attractants and repellents during chemotaxis?

Using multiple chemoreceptors, each specialized for a specific attractant or repellent. (D) Signup and view all the answers

What is the function of cristae in mitochondria?

Enzymes needed for respiration and ATP production (B) Signup and view all the answers

Why is it important for bacteria to be able to sense spatial changes over time during chemotaxis?

Because bacteria are too small to detect absolute differences in concentration. (A) Signup and view all the answers

What is the major function of hydrogenosomes?

Oxidation of pyruvate to H2, CO2, and acetate (C) Signup and view all the answers

What is the main difference between eukaryotic and prokaryotic cells?

Eukaryotic cells have a nucleus, while prokaryotic cells do not. (A) Signup and view all the answers

What is the primary role of RubisCO in chloroplasts?

Converting CO2 to organics (B) Signup and view all the answers

What is the endosymbiotic hypothesis?

The theory that mitochondria and chloroplasts originated from free-living bacteria (A) Signup and view all the answers

What is the difference between mitosis and meiosis?

Mitosis produces genetically identical daughter cells, while meiosis produces genetically diverse daughter cells. (C) Signup and view all the answers

What is the role of histones in the nucleus?

They help to package and organize DNA. (C) Signup and view all the answers

Which of the following is a characteristic of eukaryotic cells that distinguishes them from prokaryotic cells?

Presence of a nucleus (B) Signup and view all the answers

What is the primary function of the smooth endoplasmic reticulum (SER)?

Lipid and carbohydrate metabolism (A) Signup and view all the answers

Which of the following cytoskeletal components is primarily responsible for maintaining cell shape and positioning organelles?

Intermediate filaments (C) Signup and view all the answers

What is the primary function of the Golgi complex in eukaryotic cells?

Modification and packaging of proteins for secretion (A) Signup and view all the answers

Which of the following structures is involved in the movement of chromosomes during cell division?

Microtubules (A) Signup and view all the answers

Which of the following statements about cilia and flagella is TRUE?

Cilia and flagella use ATP to drive their movement. (B) Signup and view all the answers

Study Notes

Microbial Cell Structure and Function

Prokaryotic cells have a cell wall, plasma membrane, ribosomes, mesosome, capsule, plasmid, nucleoid, pili, fimbriae, and flagellum.

Cell Morphology

Morphology describes the shape of an organism.
Prokaryotic cells can be spherical/ovoid, cylindrical, or curved/spiral.
After cell division, prokaryotes can exist in various forms, such as cocci, diplococci, streptococci, tetrads, staphylococci, sarcinae, bacilli, diplobacilli, streptobacilli, trichomes, palisade, coccobacilli, vibrio, spirilla, spirochaetes, arcula, filaments, mycelia, and appendaged and pleomorphic bacteria.

Size

Prokaryotic cells range from 0.2 µm to over 700 µm in diameter.
Eukaryotic cells range from 2 µm to over 600 µm in diameter.
The small size of prokaryotes optimizes nutrient uptake, waste elimination, and accelerates growth.

Cytoplasmic Membrane

The cytoplasmic membrane has a main function of selective permeability, is 8-10 nm wide, and has embedded proteins and fatty acids.
The membrane is composed of a phospholipid bilayer with hydrophilic regions facing outward and hydrophobic regions facing inward.
Integral and peripheral membrane proteins are embedded within the membrane and play various roles.

Comparisons of Cytoplasmic Membranes

Linkages in phospholipids differ between archaea (ether linkages) and bacteria/eukaryotes (ester linkages).
Archaea use isoprenes instead of fatty acids.
The cytoplasmic membrane serves as a permeability barrier, holds transport proteins, and is involved in energy conservation through the generation of a proton motive force.

Cell Walls: Peptidoglycan

Gram-staining distinguishes between gram-positive and gram-negative bacteria based on cell wall structure.
Gram-negative cell walls have an outer membrane (LPS layer) and a peptidoglycan layer. Gram-positive cell walls primarily consist of peptidoglycan.
Peptidoglycan is a rigid layer that gives structure and is a target for antibiotics like penicillin.
Lysozyme (enzymes found in human secretions) can disrupt the peptidoglycan, weakening bacterial cell walls.

Cell Walls (Archaea)

Archaea cell walls do not contain peptidoglycan.
The common cell wall type is S-layers—paracrystalline structures.
Pseudomurein is a polysaccharide similar to peptidoglycan.
Archaea cell walls are resistant to lysozyme and penicillin.

Cell Surface Structures

Capsules and slime layers are polysaccharide layers outside the cell wall.
Capsules are organized and tightly attached, increasing the cell's adherence to surfaces.
Slime layers are loosely attached and enhance adherence.
Both capsules and slime layers can help protect bacteria from the host's immune system and contribute to biofilm formation.
Fimbriae and pili are filamentous protein structures helping organisms attach to surfaces.
Fimbriae are shorter and more numerous; pili are longer and fewer.
Conjugative pili facilitate genetic exchange between cells.
Type IV pili enable twitching motility and attachment to host tissues.
Hamus are grappling hooks used for attachment and biofilm formation.

Cell Inclusions

Inclusions function as energy reserves, carbon reservoirs, or play other specific functions.
Inclusions are often enclosed by thin membranes, reducing osmotic stress.
Common examples of inclusion bodies are carbon storage polymers (e.g., polyhydroxyalkanoates), inorganic phosphate (polyphosphate granules), sulfur globules, carbonate minerals (allowing for magnetotaxis), and magnetosomes.

Gas Vesicles

Gas vesicles are conical-shaped, gas-filled structures made of protein.
These structures are impermeable to water and solutes.
Gas vesicles help prokaryotes to regulate buoyancy.

Endospores

Endospores are highly differentiated, resistant structures formed during endosporulation (sporulation).
They are survival structures that allow cells to endure harsh conditions.
Endospores are dormant stages of the bacterial life cycle, ideal for dispersal.
Endospores feature multiple layers (exosporium, spore coat, cortex, core), dipicolinic acid and high calcium concentration, helping them to resist harsh conditions.
Endospores are formed when growth ceases because of essential nutrient lack.

Eukaryotic Cell Structures

Eukaryotic cells contain a membrane-enclosed nucleus, numerous organelles such as mitochondria, Golgi complex, lysosomes, endoplasmic reticulum, cytoskeletal elements (microtubules, microfilaments, intermediate filaments, and cilia), smooth/rough ER.
The nucleus houses the chromosomes (DNA wound around histones)).
Specialized cell division mechanisms occur, such as mitosis (producing identical diploid cells) and meiosis (producing unique haploid gametes).

Mitochondria, Hydrogenosomes, and Chloroplasts

Mitochondria and hydrogenosomes are involved in energy metabolism.
Mitochondria are located in aerobic eukaryotes and have two membranes, including the inner membrane that forms cristae (foldings).
Mitochondria contain enzymes for respiration and ATP production.
Hydrogenosomes are found in anaerobic eukaryotes and lack TCA cycle and cristae.
Chloroplasts are involved in energy metabolism in photosynthetic eukaryotes. They have two membranes and inner membrane-surrounded stroma that contain RubisCO enzymes for CO₂ conversion to organic compounds.
Chloroplasts have thylakoids, membrane discs containing chlorophyll for light energy capture.

Other Eukaryotic Cell Structures

Endoplasmic reticulum (ER) is a network of membranes continuous with the nuclear membrane.
Rough ER has ribosomes to synthesize proteins, and smooth ER synthesizes lipids and carbohydrates.
Golgi complex modifies and sorts ER products for secretion. Lysosomes contain digestive enzymes, degrading cellular components, while other eukaryotic structures perform various roles in cell structure, motility and storage.
The cytoskeleton contains elements like microtubules (a- and ẞ-tubulin), microfilaments (actin), and intermediate filaments (keratin) supporting the cell's structure.
Flagella/cilia are organelles responsible for movement, with microtubules arranged in specific bundles and a special protein (dynein) enabling movement by rotating or beating.

Chemotaxis and Other Taxes

Taxis is directed movement in response to chemical or physical gradients.
Chemotaxis is movement in response to chemical gradients.
Phototaxis is movement in response to light gradients.
Aerotaxis is movement in response to oxygen gradients.
Osmotaxis and hydrotaxis are movements in response to osmotic and water concentration gradients, respectively.

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Description

Test your knowledge on the structural components of prokaryotic and eukaryotic cells with this quiz focused on microbial cell walls and membranes. You will explore the distinctions between Gram-positive and Gram-negative bacteria, as well as the functions of various cellular structures. Ideal for students studying microbiology at any level.